draft-ietf-issll-diffserv-rsvp-02.txt   draft-ietf-issll-diffserv-rsvp-03.txt 
Y. Bernet, Microsoft Y. Bernet, Microsoft
R. Yavatkar, Intel R. Yavatkar, Intel
P. Ford, Microsoft P. Ford, Microsoft
F. Baker, Cisco F. Baker, Cisco
L. Zhang, UCLA L. Zhang, UCLA
M. Speer, Sun Microsystems M. Speer, Sun Microsystems
R. Braden, ISI R. Braden, ISI
B. Davie, Cisco B. Davie, Cisco
John Wroclawski, MIT LCS
E. Felstaine, Allot Communications
Internet Draft Internet Draft
Expires: December, 1999 Expires: March, 2000
Document: draft-ietf-issll-diffserv-rsvp-02.txt June, 1999 Document: draft-ietf-issll-diffserv-rsvp-03.txt September, 1999
Integrated Services Operation Over Diffserv Networks A Framework For Integrated Services Operation Over Diffserv Networks
Status of this Memo Status of this Memo
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Copyright (C) The Internet Society (1999). All Rights Reserved.
1. Abstract 1. Abstract
The Integrated Services architecture provides a means for the The Integrated Services architecture provides a means for the
delivery of end-to-end QoS to applications over heterogeneous delivery of end-to-end QoS to applications over heterogeneous
networks. To support this end-to-end model, the Intserv architecture networks. To support this end-to-end model, the Intserv architecture
must be supported over a wide variety of different types of network must be supported over a wide variety of different types of network
elements. In this context, a network that supports Differentiated elements. In this context, a network that supports Differentiated
Services (Diffserv) may be viewed as a network element in the total Services (Diffserv) may be viewed as a network element in the total
end-to-end path. This document describes a framework by which end-to-end path. This document describes a framework by which
Integrated Services may be supported over Diffserv networks. Integrated Services may be supported over Diffserv networks.
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2. Introduction 2. Introduction
Work on QoS-enabled IP networks has led to two distinct approaches: Work on QoS-enabled IP networks has led to two distinct approaches:
the Integrated Services architecture (intserv)[10] and its the Integrated Services architecture (Intserv)[10] and its
accompanying signaling protocol, RSVP [1], and the Differentiated accompanying signaling protocol, RSVP [1], and the Differentiated
Services architecture (diffserv)[8]. This document describes ways in Services architecture (Diffserv)[8]. This document describes ways in
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which a Diffserv network can be used in the context of the Intserv which a Diffserv network can be used in the context of the Intserv
architecture to support the delivery of end-to-end QOS. architecture to support the delivery of end-to-end QOS.
2.1 Integrated Services Architecture 2.1 Integrated Services Architecture
The integrated services architecture defined a set of extensions to The integrated services architecture defined a set of extensions to
the traditional best effort model of the Internet with the goal of the traditional best effort model of the Internet with the goal of
allowing end-to-end QOS to be provided to applications. One of the allowing end-to-end QOS to be provided to applications. One of the
key components of the architecture is a set of service definitions; key components of the architecture is a set of service definitions;
the current set of services consists of the controlled load and the current set of services consists of the controlled load and
guaranteed services. The architecture assumes that some explicit guaranteed services. The architecture assumes that some explicit
setup mechanism is used to convey information to routers so that setup mechanism is used to convey information to routers so that
they can provide requested services to flows that require them. they can provide requested services to flows that require them.
While RSVP is the most widely known example of such a setup While RSVP is the most widely known example of such a setup
mechanism, the intserv architecture is designed to accommodate other mechanism, the Intserv architecture is designed to accommodate other
mechanisms. mechanisms.
Intserv services are implemented by _network elements_. While it is Intserv services are implemented by _network elements_. While it is
common for network elements to be individual nodes such as routers common for network elements to be individual nodes such as routers
or links, more complex entities, such as ATM _clouds_ or 802.3 or links, more complex entities, such as ATM _clouds_ or 802.3
networks may also function as network elements. As discussed in more networks may also function as network elements. As discussed in more
detail below, a Diffserv network (or _cloud_) may be viewed as a detail below, a Diffserv network (or _cloud_) may be viewed as a
network element within a larger intserv network. network element within a larger Intserv network.
2.3 RSVP 2.3 RSVP
RSVP is a signaling protocol that applications may use to request RSVP is a signaling protocol that applications may use to request
resources from the network. The network responds by explicitly resources from the network. The network responds by explicitly
admitting or rejecting RSVP requests. Certain applications that have admitting or rejecting RSVP requests. Certain applications that have
quantifiable resource requirements express these requirements using quantifiable resource requirements express these requirements using
intserv parameters as defined in the appropriate intserv service Intserv parameters as defined in the appropriate Intserv service
specification. As noted above, RSVP and intserv are separable. RSVP specification. As noted above, RSVP and Intserv are separable. RSVP
is a signaling protocol which may carry intserv information. Intserv is a signaling protocol which may carry Intserv information. Intserv
defines the models for expressing service types, quantifying defines the models for expressing service types, quantifying
resource requirements and for determining the availability of the resource requirements and for determining the availability of the
requested resources at relevant network elements (admission requested resources at relevant network elements (admission
control). control).
The current prevailing model of RSVP usage is based on a combined The current prevailing model of RSVP usage is based on a combined
RSVP/intserv architecture. In this model, RSVP signals per-flow RSVP/Intserv architecture. In this model, RSVP signals per-flow
resource requirements to network elements, using Intserv parameters. resource requirements to network elements, using Intserv parameters.
These network elements apply Intserv admission control to signaled These network elements apply Intserv admission control to signaled
requests. In addition, traffic control mechanisms on the network requests. In addition, traffic control mechanisms on the network
element are configured to ensure that each admitted flow receives element are configured to ensure that each admitted flow receives
the service requested in strict isolation from other traffic. To the service requested in strict isolation from other traffic. To
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this end, RSVP signaling configures microflow (MF) [8] packet this end, RSVP signaling configures microflow (MF) [8] packet
classifiers in intserv capable routers along the path of the traffic classifiers in Intserv capable routers along the path of the traffic
flow. These classifiers enable per-flow classification of packets flow. These classifiers enable per-flow classification of packets
based on IP addresses and port numbers. based on IP addresses and port numbers.
The following factors have impeded deployment of RSVP (and the The following factors have impeded deployment of RSVP (and the
intserv architecture) in the Internet at large: Intserv architecture) in the Internet at large:
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1. The use of per-flow state and per-flow processing raises 1. The use of per-flow state and per-flow processing raises
scalability concerns for large networks. scalability concerns for large networks.
2. Only a small number of hosts currently generate RSVP signaling. 2. Only a small number of hosts currently generate RSVP signaling.
While this number is expected to grow dramatically, many While this number is expected to grow dramatically, many
applications may never generate RSVP signaling. applications may never generate RSVP signaling.
3. The necessary policy control mechanisms -- access control, 3. The necessary policy control mechanisms -- access control,
authentication, and accounting _- have only recently become authentication, and accounting _- have only recently become
available [17]. available [17].
2.4 Diffserv 2.4 Diffserv
The market is pushing for immediate deployment of a QoS solution The market is pushing for immediate deployment of a QoS solution
that addresses the needs of the Internet as well as enterprise that addresses the needs of the Internet as well as enterprise
networks. This push led to the development of diffserv. In contrast networks. This push led to the development of Diffserv. In contrast
to the per-flow orientation of RSVP, diffserv networks classify to the per-flow orientation of RSVP, Diffserv networks classify
packets into one of a small number of aggregated flows or 'classes', packets into one of a small number of aggregated flows or 'classes',
based on the diffserv codepoint (DSCP) in the packet's IP header. based on the Diffserv codepoint (DSCP) in the packet's IP header.
This is known as behavior aggregate (BA) classification [8]. At each This is known as behavior aggregate (BA) classification [8]. At each
diffserv router, packets are subjected to a 'per-hop behaviour' Diffserv router, packets are subjected to a 'per-hop behavior'
(PHB), which is invoked by the DSCP. The primary benefit of diffserv (PHB), which is invoked by the DSCP. The primary benefit of Diffserv
is its scalability. Diffserv eliminates the need for per-flow state is its scalability. Diffserv eliminates the need for per-flow state
and per-flow processing and therefore scales well to large networks. and per-flow processing and therefore scales well to large networks.
2.5 Roles of Intserv, RSVP and Diffserv 2.5 Roles of Intserv, RSVP and Diffserv
We view intserv, RSVP and diffserv as complementary technologies in We view Intserv, RSVP and Diffserv as complementary technologies in
the pursuit of end-to-end QoS. Together, these mechanisms can the pursuit of end-to-end QoS. Together, these mechanisms can
facilitate deployment of applications such as IP-telephony, video- facilitate deployment of applications such as IP-telephony, video-
on-demand, and various non-multimedia mission-critical applications. on-demand, and various non-multimedia mission-critical applications.
Intserv enables hosts to request per-flow, quantifiable resources, Intserv enables hosts to request per-flow, quantifiable resources,
along end-to-end data paths and to obtain feedback regarding along end-to-end data paths and to obtain feedback regarding
admissibility of these requests. Diffserv enables scalability across admissibility of these requests. Diffserv enables scalability across
large networks. large networks.
2.6 Components of Intserv, RSVP and Diffserv 2.6 Components of Intserv, RSVP and Diffserv
Before proceeding, it is helpful to identify the following Before proceeding, it is helpful to identify the following
components of the QoS technologies described: components of the QoS technologies described:
RSVP signaling - This term refers to the standard RSVP signaling RSVP signaling - This term refers to the standard RSVP signaling
protocol. RSVP signaling is used by hosts to signal application protocol. RSVP signaling is used by hosts to signal application
resource requirements to the network (and to each other). Network resource requirements to the network (and to each other). Network
elements use RSVP signaling to return an admission control decision
to hosts. RSVP signaling may or may not carry intserv parameters.
Admission control at a network element may or may not be based on
the intserv model.
Bernet, ed. et al. 3 Bernet, ed. et al. 3
Integrated Services Operation Over Diffserv Networks June, 1999 Integrated Services Operation Over Diffserv Networks June, 1999
elements use RSVP signaling to return an admission control decision
to hosts. RSVP signaling may or may not carry Intserv parameters.
Admission control at a network element may or may not be based on
the Intserv model.
MF traffic control - This term refers to traffic control which is MF traffic control - This term refers to traffic control which is
applied independently to individual traffic flows and therefore applied independently to individual traffic flows and therefore
requires recognizing individual traffic flows via MF classification. requires recognizing individual traffic flows via MF classification.
Aggregate traffic control - This term refers to traffic control Aggregate traffic control - This term refers to traffic control
which is applied collectively to sets of traffic flows. These sets which is applied collectively to sets of traffic flows. These sets
of traffic flows are recognized based on BA (DSCP) classification. of traffic flows are recognized based on BA (DSCP) classification.
In this draft, we use the terms 'aggregate traffic control' and In this draft, we use the terms 'aggregate traffic control' and
'diffserv' interchangeably. 'Diffserv' interchangeably.
Aggregate RSVP. While the existing definition of RSVP supports only Aggregate RSVP. While the existing definition of RSVP supports only
per-flow reservations, extensions to RSVP are being developed to per-flow reservations, extensions to RSVP are being developed to
enable RSVP reservations to be made for aggregated traffic, i.e. enable RSVP reservations to be made for aggregated traffic, i.e.
sets of flows that may be recognized by BA classification. This use sets of flows that may be recognized by BA classification. This use
of RSVP may be useful in controlling the allocation of bandwidth in of RSVP may be useful in controlling the allocation of bandwidth in
Diffserv networks. Diffserv networks.
Per-flow RSVP. The conventional usage of RSVP to perform resource Per-flow RSVP. The conventional usage of RSVP to perform resource
reservations for individual microflows. reservations for individual microflows.
RSVP/Intserv - This term is used to refer to the prevailing model of RSVP/Intserv - This term is used to refer to the prevailing model of
RSVP usage which includes RSVP signaling with intserv parameters, RSVP usage which includes RSVP signaling with Intserv parameters,
intserv admission control and per-flow traffic control at network Intserv admission control and per-flow traffic control at network
elements. elements.
Diffserv Region. A set of contiguous routers which support BA Diffserv Region. A set of contiguous routers which support BA
classification and traffic control. While such a region may also classification and traffic control. While such a region may also
support MF classification, the goal of this document is to describe support MF classification, the goal of this document is to describe
how such a region may be used in delivery of end-to-end QOS when how such a region may be used in delivery of end-to-end QOS when
only BA classification is performed inside the diffserv region. only BA classification is performed inside the Diffserv region.
Intserv Region. The portions of the network outside the diffserv Non-Diffserv Region. The portions of the network outside the
region. We assume MF classification and traffic control is available Diffserv region. Such a region may also offer a variety of different
in such regions. Such a region may also offer BA classification and types of classification and traffic control.
traffic control.
Note that, for the purposes of this document, the key distinction Note that, for the purposes of this document, the defining features
between an Intserv and a Diffserv region is the type of of a Diffserv region is the type of classification and traffic
classification and traffic control that is used for the delivery of control that is used for the delivery of end-to-end QOS for a
end-to-end QOS for a particular application. Thus, while it may not particular application. Thus, while it may not be possible to
be possible to identify a certain region as _purely Diffserv_ or identify a certain region as _purely Diffserv_ with respect to all
_purely Intserv_ with respect to all traffic flowing through the traffic flowing through the region, it is possible to define it in
region, it is possible to make these distinctions from the this way from the perspective of the treatment of traffic from a
perspective of the treatment of traffic from a single application. single application.
2.7 The Framework 2.7 The Framework
In the framework we present, end-to-end, quantitative QoS is
provided by coupling Intserv regions at the periphery of the network
with diffserv regions in the core of the network. The diffserv
regions may, but are not required to, participate in end-to-end RSVP
Bernet, ed. et al. 4 Bernet, ed. et al. 4
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signaling for the purpose of optimizing resource allocation and In the framework we present, end-to-end, quantitative QoS is
supporting admission control. provided by applying the Intserv model end-to-end across a network
containing one or more Diffserv regions. The Diffserv regions may,
but are not required to, participate in end-to-end RSVP signaling
for the purpose of optimizing resource allocation and supporting
admission control.
From the perspective of Intserv, diffserv regions of the network are From the perspective of Intserv, Diffserv regions of the network are
treated as virtual links connecting Intserv capable routers or hosts treated as virtual links connecting Intserv capable routers or hosts
(much as an 802.1p network region is treated as a virtual link in (much as an 802.1p network region is treated as a virtual link in
[5]). Within the diffserv regions of the network routers implement [5]). Within the Diffserv regions of the network routers implement
specific PHBs (aggregate traffic control). The total amount of specific PHBs (aggregate traffic control). The total amount of
traffic that is admitted into the diffserv region that will receive traffic that is admitted into the Diffserv region that will receive
a certain PHB may be limited by policing at the edge. As a result a certain PHB may be limited by policing at the edge. As a result
we expect that the diffserv regions of the network will be able to we expect that the Diffserv regions of the network will be able to
support the intserv style services requested from the periphery. As support the Intserv style services requested from the periphery.
such, we often refer to the Intserv network regions as 'customers' In our framework, we address the support of end-to-end Integrated
of the diffserv network regions. Services over the Diffserv regions of the network. Our goal is to
enable seamless inter-operation. As a result, the network
In our framework, we address the inter-operability between the administrator is free to choose which regions of the network act as
Intserv regions of the network and the diffserv regions of the Diffserv regions. In one extreme the Diffserv region is pushed all
network. Our goal is to enable seamless inter-operation. As a the way to the periphery, with hosts alone having full Intserv
result, the network administrator is free to choose which regions of capability. In the other extreme, Intserv is pushed all the way to
the network act as Intserv regions and which act as diffserv the core, with no Diffserv region.
regions. In one extreme the diffserv region is pushed all the way to
the periphery, with hosts alone comprising the Intserv regions of
the network. In the other extreme, Intserv is pushed all the way to
the core, with no diffserv region.
2.8 Contents 2.8 Contents
In section 3 we discuss the benefits that can be realized by using In section 3 we discuss the benefits that can be realized by using
the aggregate traffic control provided by diffserv network regions the aggregate traffic control provided by Diffserv network regions
in the broader context of the Intserv architecture. In section 4, we in the broader context of the Intserv architecture. In section 4, we
present the framework and the reference network. Section 5 details present the framework and the reference network. Section 5 details
two possible realizations of the framework. Section 6 discusses the two possible realizations of the framework. Section 6 discusses the
implications of the framework for diffserv. Appendix A contains a implications of the framework for Diffserv. Section 7 presents some
list of some important terms used in this document. issues specific to multicast flows.
Though the primary goal of this draft is to describe a framework
for inter-operation of Intserv network regions and diffserv network
regions, the draft currently does not address the issues specific to
IP multicast flows.
3. Benefits of Using Intserv with Diffserv 3. Benefits of Using Intserv with Diffserv
The primary benefit of diffserv aggregate traffic control is its The primary benefit of Diffserv aggregate traffic control is its
scalability. In this section, we discuss the benefits that scalability. In this section, we discuss the benefits that
interoperation with Intserv can bring to a diffserv network region. interoperation with Intserv can bring to a Diffserv network region.
Note that this discussion is in the context of servicing Note that this discussion is in the context of servicing
quantitative QoS applications specifically. By this we mean those quantitative QoS applications specifically. By this we mean those
applications that are able to quantify their traffic and QoS applications that are able to quantify their traffic and QoS
requirements. requirements.
3.1 Resource Based Admission Control 3.1 Resource Based Admission Control
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In Intserv networks, quantitative QoS applications use an explicit In Intserv networks, quantitative QoS applications use an explicit
setup mechanism (e.g. RSVP) to request resources from the network. setup mechanism (e.g. RSVP) to request resources from the network.
The network may accept or reject these requests in response. This is The network may accept or reject these requests in response. This is
'explicit admission control'. Explicit admission control helps to 'explicit admission control'. Explicit admission control helps to
assure that network resources are optimally used. To further assure that network resources are optimally used. To further
understand this issue, consider a diffserv network region providing
only aggregate traffic control with no signaling. In the diffserv Bernet, ed. et al. 5
Integrated Services Operation Over Diffserv Networks June, 1999
understand this issue, consider a Diffserv network region providing
only aggregate traffic control with no signaling. In the Diffserv
network region, admission control is applied implicitly by network region, admission control is applied implicitly by
provisioning policing parameters at network elements. For example, a provisioning policing parameters at network elements. For example, a
network element at the ingress to a diffserv network region could be network element at the ingress to a Diffserv network region could be
provisioned to accept only 50 Kbps of traffic for the EF DSCP. provisioned to accept only 50 Kbps of traffic for the EF DSCP.
While such implicit admission control does protect the network to While such implicit admission control does protect the network to
some degree, it can be quite ineffective. For example, consider that some degree, it can be quite ineffective. For example, consider that
there may be 10 IP telephony sessions originating outside the there may be 10 IP telephony sessions originating outside the
diffserv network region, each requiring 10 Kbps of EF service from Diffserv network region, each requiring 10 Kbps of EF service from
the diffserv network region. Since the network element protecting the Diffserv network region. Since the network element protecting
the diffserv network region is provisioned to accept only 50 Kbps of the Diffserv network region is provisioned to accept only 50 Kbps of
traffic for the EF DSCP, it will discard half the offered traffic. traffic for the EF DSCP, it will discard half the offered traffic.
This traffic will be discarded from the aggregation of traffic This traffic will be discarded from the aggregation of traffic
marked EF, with no regard to the microflow from which it originated. marked EF, with no regard to the microflow from which it originated.
As a result, it is likely that of the ten IP telephony sessions, As a result, it is likely that of the ten IP telephony sessions,
none will obtain satisfactory service when in fact, there are none will obtain satisfactory service when in fact, there are
sufficient resources available in the diffserv network region to sufficient resources available in the Diffserv network region to
satisfy five sessions. satisfy five sessions.
In the case of explicit admission control, the network will signal In the case of explicit admission control, the network will signal
rejection in response to requests for resources that would exceed rejection in response to requests for resources that would exceed
the 50 Kbps limit. As a result, upstream network elements (including the 50 Kbps limit. As a result, upstream network elements (including
originating hosts) and applications will have the information they originating hosts) and applications will have the information they
require to take corrective action. The application might respond by require to take corrective action. The application might respond by
refraining from transmitting, or by requesting admission for a refraining from transmitting, or by requesting admission for a
lesser traffic profile. The host operating system might respond by lesser traffic profile. The host operating system might respond by
marking the application's traffic for the DSCP that corresponds to marking the application's traffic for the DSCP that corresponds to
best-effort service. Upstream network elements might respond by re- best-effort service. Upstream network elements might respond by re-
marking packets on the rejected flow to a lower service level. In marking packets on the rejected flow to a lower service level. In
some cases, it may be possible to reroute traffic over alternate some cases, it may be possible to reroute traffic over alternate
paths or even alternate networks (e.g. the PSTN for voice calls). In paths or even alternate networks (e.g. the PSTN for voice calls). In
any case, the integrity of those flows that were admitted would be any case, the integrity of those flows that were admitted would be
preserved, at the expense of the flows that were not admitted. Thus, preserved, at the expense of the flows that were not admitted. Thus,
by appointing an Intserv-conversant admission control agent for the by appointing an Intserv-conversant admission control agent for the
diffserv region of the network it is possible to enhance the service Diffserv region of the network it is possible to enhance the service
that the network can provide to quantitative QoS applications. that the network can provide to quantitative QoS applications.
3.2 Policy Based Admission Control 3.2 Policy Based Admission Control
In network regions where RSVP is used, resource requests can be In network regions where RSVP is used, resource requests can be
intercepted by RSVP-aware network elements and can be reviewed intercepted by RSVP-aware network elements and can be reviewed
against policies stored in policy databases. These resource requests against policies stored in policy databases. These resource requests
securely identify the user and the application for which the securely identify the user and the application for which the
resources are requested. Consequently, the network element is able resources are requested. Consequently, the network element is able
to consider per-user and/or per-application policy when deciding to consider per-user and/or per-application policy when deciding
whether or not to admit a resource request. So, in addition to
optimizing the use of resources in a Diffserv network region (as
discussed in 3.1) RSVP conversant admission control agents can be
used to apply specific customer policies in determining the specific
customer traffic flows entitled to use the Diffserv network region's
Bernet, ed. et al. 6 Bernet, ed. et al. 6
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whether or not to admit a resource request. So, in addition to
optimizing the use of resources in a diffserv network region (as
discussed in 3.1) RSVP conversant admission control agents can be
used to apply specific customer policies in determining the specific
customer traffic flows entitled to use the diffserv network region's
resources. Customer policies can be used to allocate resources to resources. Customer policies can be used to allocate resources to
specific users and/or applications. specific users and/or applications.
By comparison, in diffserv network regions without RSVP signaling, By comparison, in Diffserv network regions without RSVP signaling,
policies are typically applied based on the diffserv customer policies are typically applied based on the Diffserv customer
network from which traffic originates, not on the originating user network from which traffic originates, not on the originating user
or application within the customer network. or application within the customer network.
3.3 Assistance in Traffic Identification/Classification 3.3 Assistance in Traffic Identification/Classification
Within diffserv network regions, traffic is allotted service based Within Diffserv network regions, traffic is allotted service based
on the DSCP marked in each packet's IP header. Thus, in order to on the DSCP marked in each packet's IP header. Thus, in order to
obtain a particular level of service within the diffserv network obtain a particular level of service within the Diffserv network
region, it is necessary to effect the marking of the correct DSCP in region, it is necessary to effect the marking of the correct DSCP in
packet headers. There are two mechanisms for doing so, host marking packet headers. There are two mechanisms for doing so, host marking
and router marking. In the case of host marking, the host operating and router marking. In the case of host marking, the host operating
system marks the DSCP in transmitted packets. In the case of router system marks the DSCP in transmitted packets. In the case of router
marking, routers in the network are configured to identify specific marking, routers in the network are configured to identify specific
traffic (typically based on MF classification) and to mark the DSCP traffic (typically based on MF classification) and to mark the DSCP
as packets transit the router. There are advantages and as packets transit the router. There are advantages and
disadvantages to each scheme. Regardless of the scheme used, disadvantages to each scheme. Regardless of the scheme used,
explicit signaling offers significant benefits. explicit signaling offers significant benefits.
skipping to change at line 382 skipping to change at line 379
decision than the network. Furthermore, if IPSEC encryption is used, decision than the network. Furthermore, if IPSEC encryption is used,
the host may be the only device in the network that is able to make the host may be the only device in the network that is able to make
a meaningful determination of the appropriate marking for each a meaningful determination of the appropriate marking for each
packet. packet.
Host marking requires that the host be aware of the interpretation Host marking requires that the host be aware of the interpretation
of DSCPs by the network. This information can be configured into of DSCPs by the network. This information can be configured into
each host. However, such configuration imposes a management burden. each host. However, such configuration imposes a management burden.
Alternatively, hosts can use an explicit signaling protocol such as Alternatively, hosts can use an explicit signaling protocol such as
RSVP to query the network to obtain a suitable DSCP or set of DSCPs RSVP to query the network to obtain a suitable DSCP or set of DSCPs
to apply to packets for which a certain intserv service has been to apply to packets for which a certain Intserv service has been
requested. An example of how this can be achieved is described in requested. An example of how this can be achieved is described in
[14]. [14].
3.3.2 Router Marking 3.3.2 Router Marking
Bernet, ed. et al. 7
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In the case of router marking, MF classification criteria must be In the case of router marking, MF classification criteria must be
configured in the router. This may be done dynamically, by request configured in the router. This may be done dynamically, by request
from the host operating system, or statically via manual from the host operating system, or statically via manual
configuration or via automated scripts. configuration or via automated scripts.
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Integrated Services Operation Over Diffserv Networks June, 1999
There are significant difficulties in doing so statically. There are significant difficulties in doing so statically.
Typically, it is desirable to allot service to traffic based on the Typically, it is desirable to allot service to traffic based on the
application and/or user originating the traffic. At times it is application and/or user originating the traffic. At times it is
possible to identify packets associated with a specific application possible to identify packets associated with a specific application
by the IP port numbers in the headers. It may also be possible to by the IP port numbers in the headers. It may also be possible to
identify packets originating from a specific user by the source IP identify packets originating from a specific user by the source IP
address. However, such classification criteria may change address. However, such classification criteria may change
frequently. Users may be assigned different IP addresses by DHCP. frequently. Users may be assigned different IP addresses by DHCP.
Applications may use transient ports. To further complicate matters, Applications may use transient ports. To further complicate matters,
multiple users may share an IP address. These factors make it very multiple users may share an IP address. These factors make it very
skipping to change at line 423 skipping to change at line 420
draft, RSVP signaling is ideally suited for this task. In addition draft, RSVP signaling is ideally suited for this task. In addition
to enabling dynamic and accurate updating of MF classification to enabling dynamic and accurate updating of MF classification
criteria, RSVP signaling enables classification of IPSEC [13] criteria, RSVP signaling enables classification of IPSEC [13]
packets (by use of the SPI) which would otherwise be unrecognizable. packets (by use of the SPI) which would otherwise be unrecognizable.
3.4 Traffic Conditioning 3.4 Traffic Conditioning
Intserv-capable network elements are able to condition traffic at a Intserv-capable network elements are able to condition traffic at a
per-flow granularity, by some combination of shaping and/or per-flow granularity, by some combination of shaping and/or
policing. Pre-conditioning traffic in this manner before it is policing. Pre-conditioning traffic in this manner before it is
submitted to the diffserv region of the network is beneficial. In submitted to the Diffserv region of the network is beneficial. In
particular, it enhances the ability of the diffserv region of the particular, it enhances the ability of the Diffserv region of the
network to provide quantitative services using aggregate traffic network to provide quantitative services using aggregate traffic
control. control.
4. The Framework 4. The Framework
In the general framework we envision an Internet in which the In the general framework we envision an Internet in which the
Integrated Services architecture is used to deliver end-to-end QOS Integrated Services architecture is used to deliver end-to-end QOS
to applications. The network includes some combination of Intserv to applications. The network includes some combination of Intserv
regions (in which MF classification and per-flow traffic control is capable nodes (in which MF classification and per-flow traffic
applied) and diffserv regions (in which aggregate traffic control is control is applied) and Diffserv regions (in which aggregate traffic
applied). Individual routers may or may not participate in RSVP control is applied). Individual routers may or may not participate
signaling regardless of the type of network region in which they in RSVP signaling regardless of where in the network they reside.
reside.
We will consider two specific realizations of the framework. In the We will consider two specific realizations of the framework. In the
first, resources within the diffserv regions of the network are first, resources within the Diffserv regions of the network are
statically provisioned and these regions include no RSVP aware statically provisioned and these regions include no RSVP aware
devices. In the second, resources within the diffserv region of the devices. In the second, resources within the Diffserv region of the
network are dynamically provisioned and select devices within the
Diffserv network regions participate in RSVP signaling.
4.1 Reference Network
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network are dynamically provisioned and select devices within the
diffserv network regions participate in RSVP signaling.
4.1 Reference Network
The two realizations of the framework will be discussed in the The two realizations of the framework will be discussed in the
context of the following reference network: context of the following reference network:
/ \ / \ / \ / \ / \ / \
/ \ / \ / \ / \ / \ / \
|---| | |---| |---| |---| |---| | |---| |---| | |---| |---| |---| |---| | |---|
|Tx |-| |ER1|---|BR1| |BR2|---|ER2| |-|Rx | |Tx |-| |ER1|---|BR1| |BR2|---|ER2| |-|Rx |
|---| | |-- | |---| |---| |---| | |---| |---| | |-- | |---| |---| |---| | |---|
\ / \ / \ / \ / \ / \ /
\______ / \___ _________ / \__ _____/ \______ / \___ _________ / \__ _____/
Intserv region Diffserv region Intserv region Non-Diffserv region Diffserv region Non-Diffserv region
Figure 1: Sample Network Configuration Figure 1: Sample Network Configuration
The reference network includes a diffserv region interconnecting two The reference network includes a Diffserv region in the middle of a
Intserv regions. The diffserv region contains a mesh of routers, at larger network supporting Intserv end-to-end. The Diffserv region
least some of which provide aggregate traffic control. The Intserv contains a mesh of routers, at least some of which provide aggregate
regions contain meshes of routers and attached hosts, at least some traffic control. The regions outside the Diffserv region (non-
of which support the Integrated Services architecture. Diffserv regions) contain meshes of routers and attached hosts, at
least some of which support the Integrated Services architecture.
In the interest of simplicity we consider a single QoS sender, Tx in In the interest of simplicity we consider a single QoS sender, Tx
one of the Intserv network regions and a single QoS receiver, Rx in communicating across this network with a single QoS receiver, Rx.
the other. The edge routers (ER1, ER2) within the Intserv regions The edge routers (ER1, ER2) which are adjacent to the Diffserv
interface to the border routers (BR1, BR1) within the diffserv region interface to the border routers (BR1, BR2) within the
regions. Diffserv region.
From an economic viewpoint, we may consider that the diffserv region From an economic viewpoint, we may consider that the Diffserv region
sells service to the Intserv regions, which provide service to sells service to the network outside the Diffserv region, which in
hosts. Thus, we may think of the Intserv regions as customers of turn provides service to hosts. Thus, we may think of the non-
the diffserv region. In the following, we use the term 'customer' Diffserv regions as customers of the Diffserv region. In the
for the Intserv regions. Note that the boundaries of the regions may following, we use the term 'customer' for the non-Diffserv regions.
or may not align with administrative domain boundaries, and that a Note that the boundaries of the regions may or may not align with
single region might contain multiple administrative domains. administrative domain boundaries, and that a single region might
contain multiple administrative domains.
We now define the major components of the reference network. We now define the major components of the reference network.
4.1.1 Hosts 4.1.1 Hosts
We assume that both sending and receiving hosts use RSVP to We assume that both sending and receiving hosts use RSVP to
communicate the quantitative QoS requirements of QoS-aware communicate the quantitative QoS requirements of QoS-aware
applications running on the host. In principle, other mechanisms may applications running on the host. In principle, other mechanisms may
be used to establish resource reservations in an Intserv region, but be used to establish resource reservations in Intserv-capable nodes,
RSVP is clearly the prevalent mechanism for this purpose. but RSVP is clearly the prevalent mechanism for this purpose.
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Typically, a QoS process within the host operating system generates Typically, a QoS process within the host operating system generates
RSVP signaling on behalf of applications. This process may also RSVP signaling on behalf of applications. This process may also
invoke local traffic control. invoke local traffic control.
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As discussed above, traffic control in the host may mark the DSCP in As discussed above, traffic control in the host may mark the DSCP in
transmitted packets, and shape transmitted traffic to the transmitted packets, and shape transmitted traffic to the
requirements of the intserv service in use. Alternatively, the requirements of the Intserv service in use. Alternatively, the first
first-hop router within the Intserv network regions may provide Intserv-capable router downstream from the host may provide these
these traffic control functions. traffic control functions.
4.1.2 End-to-End RSVP Signaling 4.1.2 End-to-End RSVP Signaling
We assume that RSVP signaling messages travel end-to-end between We assume that RSVP signaling messages travel end-to-end between
hosts Tx and Rx to support RSVP/intserv reservations in the Intserv hosts Tx and Rx to support RSVP/Intserv reservations outside the
network regions. We require that these end-to-end RSVP messages are Diffserv network region. We require that these end-to-end RSVP
carried across the diffserv region. Depending on the specific messages are at least carried across the Diffserv region. Depending
realization of the framework, these messages may be processed by on the specific realization of the framework, these messages may be
none, some or all of the routers in the diffserv region. processed by none, some or all of the routers in the Diffserv
region.
4.1.3 Edge Routers 4.1.3 Edge Routers
ER1 and ER2 are edge routers, residing in the Intserv network ER1 and ER2 are edge routers, residing adjacent to the Diffserv
regions. The functionality of the edge routers varies depending on network regions. The functionality of the edge routers varies
the specific realization of the framework. In the case in which the depending on the specific realization of the framework. In the case
diffserv network region is RSVP unaware, edge routers act as in which the Diffserv network region is RSVP unaware, edge routers
admission control agents to the diffserv network. They process act as admission control agents to the Diffserv network. They
signaling messages from both Tx and Rx, and apply admission control process signaling messages from both Tx and Rx, and apply admission
based on resource availability within the diffserv network region control based on resource availability within the Diffserv network
and on customer defined policy. In the case in which the diffserv region and on customer defined policy. In the case in which the
network region is RSVP aware, the edge routers apply admission Diffserv network region is RSVP aware, the edge routers apply
control based on local resource availability and on customer defined admission control based on local resource availability and on
policy. In this case, the border routers act as the admission customer defined policy. In this case, the border routers act as the
control agent to the diffserv network region. admission control agent to the Diffserv network region.
We will later describe the functionality of the edge routers in We will later describe the functionality of the edge routers in
greater depth for each of the two realizations of the framework. greater depth for each of the two realizations of the framework.
4.1.4 Border Routers 4.1.4 Border Routers
BR1 and BR2 are border routers, residing in the diffserv network BR1 and BR2 are border routers, residing in the Diffserv network
region. The functionality of the border routers varies depending on region. The functionality of the border routers varies depending on
the specific realization of the framework. In the case in which the the specific realization of the framework. In the case in which the
diffserv network region is RSVP-unaware, these routers act as pure Diffserv network region is RSVP-unaware, these routers act as pure
diffserv routers. As such, their sole responsibility is to police Diffserv routers. As such, their sole responsibility is to police
submitted traffic based on the service level specified in the DSCP submitted traffic based on the service level specified in the DSCP
and the agreement negotiated with the customer (aggregate traffic and the agreement negotiated with the customer (aggregate traffic
control). In the case in which the diffserv network region is RSVP- control). In the case in which the Diffserv network region is RSVP-
aware, the border routers participate in RSVP signaling and act as aware, the border routers participate in RSVP signaling and act as
admission control agents for the diffserv network region. admission control agents for the Diffserv network region.
We will later describe the functionality of the border routers in We will later describe the functionality of the border routers in
greater depth for each of the two realizations of the framework. greater depth for each of the two realizations of the framework.
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4.1.5 Intserv Network Regions 4.1.5 Diffserv Network Region
Each Intserv network region consists of Intserv capable hosts and
some number of routers. These routers may reasonably be assumed to
be Intserv capable, although this might not be required in the case
of a small, over-provisioned network region. Even if they are not
Intserv capable, we assume that they will pass RSVP messages
unhindered. Routers in the Intserv network region are not precluded
from providing aggregate traffic control to some subset of the
traffic passing through them.
4.1.6 Diffserv Network Region
The diffserv network region supports aggregate traffic control and The Diffserv network region supports aggregate traffic control and
is assumed not to be capable of MF classification. Depending on the is assumed not to be capable of MF classification. Depending on the
specific realization of the framework, some number of routers within specific realization of the framework, some number of routers within
the diffserv region may be RSVP aware and therefore capable of per- the Diffserv region may be RSVP aware and therefore capable of per-
flow signaling and admission control. If devices in the diffserv flow signaling and admission control. If devices in the Diffserv
region are not RSVP aware, they will pass RSVP messages region are not RSVP aware, they will pass RSVP messages
transparently with negligible performance impact (see [6]). transparently with negligible performance impact (see [6]).
The diffserv network region provides two or more levels of service The Diffserv network region provides two or more levels of service
based on the DSCP in packet headers. It may include sub-regions based on the DSCP in packet headers. It may be a single
managed as different administrative domains. administrative domain or may span multiple domains.
4.1.5 Non-Diffserv Network Regions
The network outside of the Diffserv region consists of Intserv
capable hosts and other network elements. Other elements may include
routers and perhaps various types of network (e.g. 802, ATM, etc.).
These network elements may reasonably be assumed to support Intserv,
although this might not be required in the case of over-
provisioning. Even if these elements are not Intserv capable, we
assume that they will pass RSVP messages unhindered. Routers outside
of the Diffserv network region are not precluded from providing
aggregate traffic control to some subset of the traffic passing
through them.
4.2 Service Mapping 4.2 Service Mapping
Intserv service requests specify an intserv service type and a set Intserv service requests specify an Intserv service type and a set
of quantitative parameters known as a 'flowspec'. At each hop in an of quantitative parameters known as a 'flowspec'. At each hop in an
intserv network, the Intserv service requests are interpreted in a Intserv network, the Intserv service requests are interpreted in a
form meaningful to the specific link layer medium. For example at form meaningful to the specific link layer medium. For example at
an 802.1 hop, the intserv parameters are mapped to an appropriate an 802.1 hop, the Intserv parameters are mapped to an appropriate
802.1p priority level [5]. 802.1p priority level [5].
In our framework, diffserv regions of the network are analogous to In our framework, Diffserv regions of the network are analogous to
the 802.1p capable switched segments described in [5]. Requests for the 802.1p capable switched segments described in [5]. Requests for
Intserv services must be mapped onto the underlying capabilities of Intserv services must be mapped onto the underlying capabilities of
the Diffserv network region. Aspects of the mapping include: the Diffserv network region. Aspects of the mapping include:
- selecting an appropriate PHB, or set of PHBs, for the requested - selecting an appropriate PHB, or set of PHBs, for the requested
service; service;
- performing appropriate policing (including, perhaps, shaping or - performing appropriate policing (including, perhaps, shaping or
remarking) at the edges of the Diffserv region; remarking) at the edges of the Diffserv region;
- exporting Intserv parameters from the Diffserv region (e.g. for - exporting Intserv parameters from the Diffserv region (e.g. for
the updating of ADSPECs); the updating of ADSPECs);
- performing admission control on the Intserv requests that takes - performing admission control on the Intserv requests that takes
into account the resource availability in the Diffserv region. into account the resource availability in the Diffserv region.
Exactly how these functions are performed will be a function of the
way bandwidth is managed inside the Diffserv network region, which
is a topic we discuss in Section 4.3.
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Exactly how these functions are performed will be a function of the
way bandwidth is managed inside the Diffserv network region, which
is a topic we discuss in Section 4.3.
When the PHB (or set of PHBs) has been selected for a particular When the PHB (or set of PHBs) has been selected for a particular
Intserv flow, it may be necessary to communicate the choice of DSCP Intserv flow, it may be necessary to communicate the choice of DSCP
for the flow to other network elements. Two schemes may be used to for the flow to other network elements. Two schemes may be used to
achieve this end, as discussed below. achieve this end, as discussed below.
4.2.1 Default Mapping 4.2.1 Default Mapping
In this scheme, there is some standard, well-known mapping from In this scheme, there is some standard, well-known mapping from
intserv service type to a DSCP that will invoke the appropriate Intserv service type to a DSCP that will invoke the appropriate
behavior in the diffserv network. behavior in the Diffserv network.
4.2.2 Network Driven Mapping 4.2.2 Network Driven Mapping
In this scheme, RSVP conversant routers in the diffserv network In this scheme, RSVP conversant routers in the Diffserv network
region (perhaps at its edge) may override the well-known mapping region (perhaps at its edge) may override the well-known mapping
described in 4.2.1. In the case that DSCPs are marked at the ingress described in 4.2.1. In the case that DSCPs are marked at the ingress
to the Diffserv region, the DSCPs can simple be remarked at the to the Diffserv region, the DSCPs can simply be remarked at the
boundary routers. However, in the case that DSCP marking occurs boundary routers. However, in the case that DSCP marking occurs
upstream of the Diffserv region, either in a host or a router, then upstream of the Diffserv region, either in a host or a router, then
the appropriate mapping needs to be communicated Upstream, to the the appropriate mapping needs to be communicated upstream, to the
marking device. This may be accomplished using RSVP, as described marking device. This may be accomplished using RSVP, as described
in [14]. in [14].
The decision regarding where to mark DSCP and whether to override The decision regarding where to mark DSCP and whether to override
the well-known service mapping is a mater of policy to be decided by the well-known service mapping is a mater of policy to be decided by
the administrator of the diffserv network region in cooperation with the administrator of the Diffserv network region in cooperation with
the administrator of the intserv network region. the administrator of the network adjacent to the Diffserv region.
4.2.3 Microflow Separation 4.2.3 Microflow Separation
Boundary routers residing at the edge of the Diffserv region will Boundary routers residing at the edge of the Diffserv region will
typically police traffic submitted from the Intserv region in order typically police traffic submitted from the outside the Diffserv
to protect resources within the Diffserv region. This policing will region in order to protect resources within the Diffserv region.
be applied on an aggregate basis, with no regard for the individual This policing will be applied on an aggregate basis, with no regard
microflows making up each aggregate. As a result, it is possible for for the individual microflows making up each aggregate. As a result,
a misbehaving microflow to claim more than its fair share of it is possible for a misbehaving microflow to claim more than its
resources within the aggregate, thereby degrading the service fair share of resources within the aggregate, thereby degrading the
provided to other microflows. This problem may be addressed by: service provided to other microflows. This problem may be addressed
by:
1. Providing per microflow policing at the edge routers - this is 1. Providing per microflow policing at the edge routers - this is
generally the most appropriate location for microflow policing, generally the most appropriate location for microflow policing,
since it pushes per-flow work to the edges of the network, where it since it pushes per-flow work to the edges of the network, where it
scales better. In addition, since the intserv region is responsible scales better. In addition, since Intserv-capable routers outside
for providing microflow service to its customers and the diffserv the Diffserv region are responsible for providing microflow service
region is responsible for providing aggregate service to its to their customers and the Diffserv region is responsible for
customers, this distribution of functionality mirrors the providing aggregate service to its customers, this distribution of
distribution of responsibility. functionality mirrors the distribution of responsibility.
2. Providing per microflow policing at the border routers - this
approach tends to be less scalable than the previous approach. It
also imposes a management burden on the diffserv region of the
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2. Providing per microflow policing at the border routers - this
approach tends to be less scalable than the previous approach. It
also imposes a management burden on the Diffserv region of the
network. However, it may be appropriate in certain cases, for the network. However, it may be appropriate in certain cases, for the
diffserv boundary routers to offer per microflow policing as a Diffserv boundary routers to offer per microflow policing as a
value-add to its intserv customers. value-add to its Intserv customers.
3. Relying on upstream shaping and policing - in certain cases, the 3. Relying on upstream shaping and policing - in certain cases, the
customer may trust the shaping of certain groups of hosts customer may trust the shaping of certain groups of hosts
sufficiently to not warrant reshaping or policing at the boundary sufficiently to not warrant reshaping or policing at the boundary of
between the intserv and diffserv regions. Note that, even if the the Diffserv region. Note that, even if the hosts are shaping
hosts are shaping microflows properly, these shaped flows may become microflows properly, these shaped flows may become distorted as they
distorted as they transit through the intserv region of the network. transit through the non-Diffserv region of the network. Depending on
Depending on the degree of distortion, it may be necessary to the degree of distortion, it may be necessary to somewhat over-
somewhat over-provision the aggregate capacities in the diffserv provision the aggregate capacities in the Diffserv region, or to re-
region, or to re-police using either 1 or 2 above. police using either 1 or 2 above.
The choice of one mechanism or another is a matter of policy to be The choice of one mechanism or another is a matter of policy to be
decided by the administrator of the intserv network region. decided by the administrator of the network outside the Diffserv
region.
4.3 Resource Management in Diffserv Regions 4.3 Resource Management in Diffserv Regions
A variety of options exist for management of resources (e.g., A variety of options exist for management of resources (e.g.,
bandwidth) in the Diffserv network regions to meet the needs of end- bandwidth) in the Diffserv network regions to meet the needs of end-
to-end Intserv flows. These options include: to-end Intserv flows. These options include:
- statically provisioned resources; - statically provisioned resources;
- resources dynamically provisioned by RSVP; - resources dynamically provisioned by RSVP;
- resources dynamically provisioned by other means (e.g., a form of - resources dynamically provisioned by other means (e.g., a form of
Bandwidth Broker). Bandwidth Broker).
Some of the details of using each of these different approaches are Some of the details of using each of these different approaches are
discussed in the following section. discussed in the following section.
5. Detailed Examples of the Operation of Intserv over Diffserv Regions 5. Detailed Examples of the Operation of Intserv over Diffserv Regions
In this section we provide detailed examples of our framework in In this section we provide detailed examples of our framework in
action. We discuss two examples, one in which the diffserv network action. We discuss two examples, one in which the Diffserv network
region is RSVP unaware, the other in which the diffserv network region is RSVP unaware, the other in which the Diffserv network
region is RSVP aware. region is RSVP aware.
5.1 Statically Provisioned Diffserv Network Region 5.1 Statically Provisioned Diffserv Network Region
In this example, no devices in the diffserv network region are RSVP In this example, no devices in the Diffserv network region are RSVP
aware. The diffserv network region is statically provisioned. The aware. The Diffserv network region is statically provisioned. The
owner(s) of the Intserv network regions and the owner of the customer(s) of the Diffserv network regions and the owner of the
diffserv network region have negotiated a static contract (service Diffserv network region have negotiated a static contract (service
level specification, or SLS) for the transmit capacity to be level specification, or SLS) for the transmit capacity to be
provided to the customer at each of a number of standard diffserv provided to the customer at each of a number of standard Diffserv
service levels. The _transmit capacity_ may be simply an amount of service levels. The _transmit capacity_ may be simply an amount of
bandwidth or it could be a more complex _profile_ involving a number
of factors such as burst size, peak rate, time of day etc.
It is helpful to consider each edge router in the customer network
as consisting of two halves, a standard Intserv half, which
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interfaces to the customer's Intserv network regions and a diffserv bandwidth or it could be a more complex _profile_ involving a number
half which interfaces to the diffserv network region. The Intserv of factors such as burst size, peak rate, time of day etc.
half is able to identify and process traffic on per-flow
granularity.
The diffserv half of the router can be considered to consist of a It is helpful to consider each edge router in the customer network
number of virtual transmit interfaces, one for each diffserv service as consisting of two halves, a standard Intserv half, which
interfaces to the customer's network regions and a Diffserv half
which interfaces to the Diffserv network region. The Intserv half is
able to identify and process traffic on per-flow granularity.
The Diffserv half of the router can be considered to consist of a
number of virtual transmit interfaces, one for each Diffserv service
level negotiated in the SLS. The router contains a table that level negotiated in the SLS. The router contains a table that
indicates the transmit capacity provisioned, per the SLS at each indicates the transmit capacity provisioned, per the SLS at each
diffserv service level. This table, in conjunction with the default Diffserv service level. This table, in conjunction with the default
mapping described in 4.2.1, is used to perform admission control mapping described in 4.2.1, is used to perform admission control
decisions on intserv flows which cross the diffserv network region. decisions on Intserv flows which cross the Diffserv network region.
5.1.1 Sequence of Events in Obtaining End-to-end QoS 5.1.1 Sequence of Events in Obtaining End-to-end QoS
The following sequence illustrates the process by which an The following sequence illustrates the process by which an
application obtains end-to-end QoS when RSVP is used within the application obtains end-to-end QoS when RSVP is used by the hosts.
Intserv region.
1. The QoS process on the sending host Tx generates an RSVP PATH 1. The QoS process on the sending host Tx generates an RSVP PATH
message that describes the traffic offered by the sending message that describes the traffic offered by the sending
application. application.
2. The PATH message is carried toward the receiving host, Rx. In the 2. The PATH message is carried toward the receiving host, Rx. In the
Intserv network region to which the sender is attached, standard network region to which the sender is attached, standard
RSVP/intserv processing is applied at capable network elements. RSVP/Intserv processing is applied at capable network elements.
3. At the edge router ER1, the PATH message is subjected to standard 3. At the edge router ER1, the PATH message is subjected to standard
RSVP processing and PATH state is installed in the router. The PATH RSVP processing and PATH state is installed in the router. The PATH
message is sent onward to the diffserv network region. message is sent onward to the Diffserv network region.
4. The PATH message is ignored by routers in the diffserv network 4. The PATH message is ignored by routers in the Diffserv network
region and then processed at ER2 according to standard RSVP region and then processed at ER2 according to standard RSVP
processing rules. processing rules.
5. When the PATH message reaches the receiving host Rx, the 5. When the PATH message reaches the receiving host Rx, the
operating system generates an RSVP RESV message, indicating interest operating system generates an RSVP RESV message, indicating interest
in offered traffic of a certain intserv service type. in offered traffic of a certain Intserv service type.
6. The RESV message is carried back towards the diffserv network 6. The RESV message is carried back towards the Diffserv network
region and the sending host. Consistent with standard RSVP/intserv region and the sending host. Consistent with standard RSVP/Intserv
processing, it may be rejected at any RSVP node in the Intserv processing, it may be rejected at any RSVP-capable node in the path
network region if resources are deemed insufficient to carry the if resources are deemed insufficient to carry the traffic requested.
traffic requested.
7. At ER2, the RESV message is subjected to standard RSVP/intserv 7. At ER2, the RESV message is subjected to standard RSVP/Intserv
processing. It may be rejected if resources on the downstream processing. It may be rejected if resources on the downstream
interface of ER2 are deemed insufficient to carry the resources interface of ER2 are deemed insufficient to carry the resources
requested. If it is not rejected, it will be carried transparently requested. If it is not rejected, it will be carried transparently
through the diffserv network region, arriving at ER1. through the Diffserv network region, arriving at ER1.
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8. In ER1, the RESV message triggers admission control processing. 8. In ER1, the RESV message triggers admission control processing.
ER1 compares the resources requested in the RSVP/intserv request to ER1 compares the resources requested in the RSVP/Intserv request to
the resources available in the diffserv network region at the the resources available in the Diffserv network region at the
corresponding diffserv service level. The corresponding service corresponding Diffserv service level. The corresponding service
level is determined by the intserv to diffserv mapping discussed level is determined by the Intserv to Diffserv mapping discussed
previously. The availability of resources is determined by the previously. The availability of resources is determined by the
capacity provisioned in the SLS. ER1 may also apply a policy capacity provisioned in the SLS. ER1 may also apply a policy
decision such that the resource request may be rejected based on the decision such that the resource request may be rejected based on the
customer's specific policy criteria, even though the aggregate customer's specific policy criteria, even though the aggregate
resources are determined to be available per the SLS. resources are determined to be available per the SLS.
9. If ER1 approves the request, the RESV message is admitted and is 9. If ER1 approves the request, the RESV message is admitted and is
allowed to continue upstream towards the sender. If it rejects the allowed to continue upstream towards the sender. If it rejects the
request, the RESV is not forwarded and the appropriate RSVP error request, the RESV is not forwarded and the appropriate RSVP error
messages are sent. If the request is approved, ER1 updates its messages are sent. If the request is approved, ER1 updates its
internal tables to indicate the reduced capacity available at the internal tables to indicate the reduced capacity available at the
admitted service level on its transmit interface. admitted service level on its transmit interface.
10. The RESV message proceeds through the Intserv network region to 10. The RESV message proceeds through the network region to which
which the sender is attached. Any RSVP node in this region may the sender is attached. Any RSVP node in this region may reject the
reject the reservation request due to inadequate resources or reservation request due to inadequate resources or policy. If the
policy. If the request is not rejected, the RESV message will arrive request is not rejected, the RESV message will arrive at the sending
at the sending host, Tx. host, Tx.
11. At Tx, the QoS process receives the RESV message. It interprets 11. At Tx, the QoS process receives the RESV message. It interprets
receipt of the message as indication that the specified traffic flow receipt of the message as indication that the specified traffic flow
has been admitted for the specified intserv service type (in the has been admitted for the specified Intserv service type (in the
Intserv network regions) and for the corresponding diffserv service Intserv-capable nodes). It may also learn the appropriate DSCP
level (in the diffserv network regions). It may also learn the marking to apply to packets for this flow from information provided
appropriate DSCP marking to apply to packets for this flow from in the RESV.
information provided in the RESV.
12. Tx may mark the DSCP in the headers of packets that are 12. Tx may mark the DSCP in the headers of packets that are
transmitted on the admitted traffic flow. The DSCP may be the transmitted on the admitted traffic flow. The DSCP may be the
default value which maps to the intserv service type specified in default value which maps to the Intserv service type specified in
the admitted RESV message, or it may be a value explicitly provided the admitted RESV message, or it may be a value explicitly provided
in the RESV.. in the RESV.
In this manner, we obtain end-to-end QoS through a combination of In this manner, we obtain end-to-end QoS through a combination of
networks that support RSVP/Intserv and networks that support networks that support RSVP/Intserv and networks that support
diffserv. Diffserv.
5.2 RSVP-Aware Diffserv Network Region 5.2 RSVP-Aware Diffserv Network Region
In this example, the customer's edge routers are standard RSVP In this example, the customer's edge routers are standard RSVP
routers. The border router, BR1 is RSVP aware. In addition, there routers. The border router, BR1 is RSVP aware. In addition, there
may be other routers within the diffserv network region which are may be other routers within the Diffserv network region which are
RSVP aware. Note that although these routers are able to participate RSVP aware. Note that although these routers are able to participate
in some form of RSVP signaling, they classify and schedule traffic in some form of RSVP signaling, they classify and schedule traffic
in aggregate, based on DSCP, not on the per-flow classification in aggregate, based on DSCP, not on the per-flow classification
criteria used by standard RSVP/Intserv routers. It can be said that criteria used by standard RSVP/Intserv routers. It can be said that
their control-plane is RSVP while their data-plane is diffserv. This their control-plane is RSVP while their data-plane is Diffserv. This
Bernet, ed. et al. 15 Bernet, ed. et al. 15
Integrated Services Operation Over Diffserv Networks June, 1999 Integrated Services Operation Over Diffserv Networks June, 1999
approach exploits the benefits of RSVP signaling while maintaining approach exploits the benefits of RSVP signaling while maintaining
much of the scalability associated with diffserv. much of the scalability associated with Diffserv.
In the preceding example, there is no signaling between the Intserv In the preceding example, there is no signaling between the Diffserv
network regions and the diffserv network region. The negotiation of network region and network elements outside it. The negotiation of
an SLS is the only explicit exchange of resource availability an SLS is the only explicit exchange of resource availability
information between the two network regions. ER1 is configured with information between the two network regions. ER1 is configured with
the information represented by the SLS and as such, is able to act the information represented by the SLS and as such, is able to act
as an admission control agent for the diffserv network region. Such as an admission control agent for the Diffserv network region. Such
configuration does not readily support dynamically changing SLSs, configuration does not readily support dynamically changing SLSs,
since ER1 requires reconfiguration each time the SLS changes. It is since ER1 requires reconfiguration each time the SLS changes. It is
also difficult to make efficient use of the resources in the also difficult to make efficient use of the resources in the
diffserv network region. This is because admission control does not Diffserv network region. This is because admission control does not
consider the availability of resources in the diffserv network consider the availability of resources in the Diffserv network
region along the specific path that would be impacted. region along the specific path that would be impacted.
By contrast, when the diffserv network region is RSVP aware, the By contrast, when the Diffserv network region is RSVP aware, the
admission control agent is part of the diffserv network. As a admission control agent is part of the Diffserv network. As a
result, changes in the capacity available in the diffserv network result, changes in the capacity available in the Diffserv network
region can be indicated to the Intserv network regions via RSVP. By region can be indicated to the Intserv-capable nodes outside the
including routers interior to the diffserv network region in RSVP Diffserv region via RSVP. By including routers interior to the
signaling, it is possible to simultaneously improve the efficiency Diffserv network region in RSVP signaling, it is possible to
of resource usage within the diffserv region and to improve the simultaneously improve the efficiency of resource usage within the
level of confidence that the resources requested at admission Diffserv region and to improve the level of confidence that the
control are indeed available at this particular point in time. This resources requested at admission control are indeed available at
is because admission control can be linked to the availability of this particular point in time. This is because admission control can
resources along the specific path that would be impacted. We refer be linked to the availability of resources along the specific path
to this benefit of RSVP signaling as 'topology aware admission that would be impacted. We refer to this benefit of RSVP signaling
control'. A further benefit of supporting RSVP signaling within the as 'topology aware admission control'. A further benefit of
diffserv network region is that it is possible to effect changes in supporting RSVP signaling within the Diffserv network region is that
the provisioning of the diffserv network region (e.g., allocating it is possible to effect changes in the provisioning of the Diffserv
more or less bandwidth to the EF queue in a router) in response to network region (e.g., allocating more or less bandwidth to the EF
resource requests from the RSVP/intserv network regions. queue in a router) in response to resource requests from outside of
the Diffserv region.
Various mechanisms may be used within the diffserv network region to Various mechanisms may be used within the Diffserv network region to
support dynamic provisioning and topology aware admission control. support dynamic provisioning and topology aware admission control.
These include aggregated RSVP, per-flow RSVP and bandwidth brokers, These include aggregated RSVP, per-flow RSVP and bandwidth brokers,
as described in the following paragraphs. as described in the following paragraphs.
5.2.1 Aggregated or Tunneled RSVP 5.2.1 Aggregated or Tunneled RSVP
A number of drafts [3,6,15, 16] propose mechanisms for extending A number of drafts [3,6,15, 16] propose mechanisms for extending
RSVP to reserve resources for an aggregation of flows between edges RSVP to reserve resources for an aggregation of flows between edges
of a network. Border routers may interact with core routers and of a network. Border routers may interact with core routers and
other border routers using aggregated RSVP to reserve resources other border routers using aggregated RSVP to reserve resources
between edges of the diffserv network region. Initial reservation between edges of the Diffserv network region. Initial reservation
levels for each service level may be established between major levels for each service level may be established between major
border routers, based on anticipated traffic patterns. Border border routers, based on anticipated traffic patterns. Border
routers could trigger changes in reservation levels as a result of routers could trigger changes in reservation levels as a result of
the cumulative per-flow RSVP requests from peripheral RSVP/intserv the cumulative per-flow RSVP requests from the non-Diffserv regions
network regions reaching high or low-water marks. reaching high or low-water marks.
Bernet, ed. et al. 16 Bernet, ed. et al. 16
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In this approach, admission of per-flow RSVP requests from In this approach, admission of per-flow RSVP requests from nods
RSVP/intserv networks would be counted against the appropriate outside the Diffserv region would be counted against the appropriate
aggregate reservations for the corresponding service level. The size aggregate reservations for the corresponding service level. The size
of the aggregate reservations may or may not be dynamically adjusted of the aggregate reservations may or may not be dynamically adjusted
to deal with the changes in per-flow reservations. to deal with the changes in per-flow reservations.
The advantage of this approach is that it offers dynamic, topology The advantage of this approach is that it offers dynamic, topology
aware admission control to the diffserv network region without aware admission control to the Diffserv network region without
requiring the level of RSVP signaling processing that would be requiring the level of RSVP signaling processing that would be
required to support per-flow RSVP. required to support per-flow RSVP.
We note that resource management of a Diffserv region using
aggregated RSVP is most likely to be feasible only within a single
administrative domain, as each domain will probably choose its own
mechanism to manage its resources.
5.2.3 Per-flow RSVP 5.2.3 Per-flow RSVP
In this approach, described in [3], routers in the diffserv network In this approach, described in [3], routers in the Diffserv network
region respond to the standard per-flow RSVP signaling originating region respond to the standard per-flow RSVP signaling originating
from the Intserv network regions. This approach provides the from the Intserv-capable nodes outside the Diffserv region. This
benefits of the previous approach (dynamic, topology aware admission approach provides the benefits of the previous approach (dynamic,
control) without requiring aggregated RSVP support. Resources are topology aware admission control) without requiring aggregated RSVP
also used more efficiently as a result of the per-flow admission support. Resources are also used more efficiently as a result of the
control. However, the demands on RSVP signaling resources within the per-flow admission control. However, the demands on RSVP signaling
diffserv network region may be significantly higher than in an resources within the Diffserv network region may be significantly
aggregated RSVP approach. higher than in an aggregated RSVP approach.
Note that per-flow RSVP and aggregated RSVP are not mutually Note that per-flow RSVP and aggregated RSVP are not mutually
exclusive in a single diffserv region. It is possible to use per- exclusive in a single Diffserv region. It is possible to use per-
flow RSVP at the edges of the diffserv region and aggregation only flow RSVP at the edges of the Diffserv region and aggregation only
in some _core_ region within the diffserv region. in some _core_ region within the Diffserv region.
5.2.4 Granularity of Deployment of RSVP Aware Routers 5.2.4 Granularity of Deployment of RSVP Aware Routers
In 5.2.2 and 5.2.3 some subset of the routers within the diffserv In 5.2.2 and 5.2.3 some subset of the routers within the Diffserv
network is RSVP signaling aware (though traffic control is network is RSVP signaling aware (though traffic control is
aggregated as opposed to per-flow). The relative number of routers aggregated as opposed to per-flow). The relative number of routers
in the core that participate in RSVP signaling is a provisioning in the core that participate in RSVP signaling is a provisioning
decision that must be made by the network administrator. decision that must be made by the network administrator.
In one extreme case, only the border routers participate in RSVP In one extreme case, only the border routers participate in RSVP
signaling. In this case, either the diffserv network region must be signaling. In this case, either the Diffserv network region must be
extremely over-provisioned and therefore, inefficiently used, or extremely over-provisioned and therefore, inefficiently used, or
else it must be carefully and statically provisioned for limited else it must be carefully and statically provisioned for limited
traffic patterns. The border routers must enforce these patterns. traffic patterns. The border routers must enforce these patterns.
In the other extreme case, each router in the diffserv network In the other extreme case, each router in the Diffserv network
region might participate in RSVP signaling. In this case, resources region might participate in RSVP signaling. In this case, resources
can be used with optimal efficiency, but signaling processing can be used with optimal efficiency, but signaling processing
requirements and associated overhead increase. As noted above, RSVP requirements and associated overhead increase. As noted above, RSVP
aggregation is one way to limit the signaling overhead at the cost
of some loss of optimality in resource utilization.
It is likely that some network administrators will compromise by
enabling RSVP signaling on some subset of routers in the diffserv
network region. These routers will likely represent major traffic
Bernet, ed. et al. 17 Bernet, ed. et al. 17
Integrated Services Operation Over Diffserv Networks June, 1999 Integrated Services Operation Over Diffserv Networks June, 1999
aggregation is one way to limit the signaling overhead at the cost
of some loss of optimality in resource utilization.
It is likely that some network administrators will compromise by
enabling RSVP signaling on some subset of routers in the Diffserv
network region. These routers will likely represent major traffic
switching points with over-provisioned or statically provisioned switching points with over-provisioned or statically provisioned
regions of RSVP unaware routers between them. regions of RSVP unaware routers between them.
5.3 Dynamically Provisioned, Non-RSVP-aware Diffserv Region 5.3 Dynamically Provisioned, Non-RSVP-aware Diffserv Region
Border routers might not use any form of RSVP signaling within the Border routers might not use any form of RSVP signaling within the
diffserv network region but might instead use custom protocols to Diffserv network region but might instead use custom protocols to
interact with an 'oracle'. The oracle is a hypothetical agent that interact with an 'oracle'. The oracle is a hypothetical agent that
has sufficient knowledge of resource availability and network has sufficient knowledge of resource availability and network
topology to make admission control decisions. The set of RSVP aware topology to make admission control decisions. The set of RSVP aware
routers in the previous two examples can be considered collectively routers in the previous two examples can be considered collectively
as a form of distributed oracle. In various definitions of the as a form of distributed oracle. In various definitions of the
'bandwidth broker' [4], it is able to act as a centralized oracle. 'bandwidth broker' [4], it is able to act as a centralized oracle.
6. Implications of the Framework for Diffserv Network Regions 6. Implications of the Framework for Diffserv Network Regions
We have described a framework in which RSVP/intserv style QoS can be We have described a framework in which RSVP/Intserv style QoS can be
provided across end-to-end paths that include diffserv network provided across end-to-end paths that include Diffserv network
regions. This section discusses some of the implications of this regions. This section discusses some of the implications of this
framework for the diffserv network region. framework for the Diffserv network region.
6.1 Requirements from Diffserv Network Regions 6.1 Requirements from Diffserv Network Regions
A diffserv network region must meet the following requirements in A Diffserv network region must meet the following requirements in
order for it to support the framework described in this draft. order for it to support the framework described in this draft.
1. A diffserv network region must be able to provide support for the 1. A Diffserv network region must be able to provide support for the
standard intserv QoS services between its border routers. It must be standard Intserv QoS services between its border routers. It must be
possible to invoke these services by use of standard PHBs within the possible to invoke these services by use of standard PHBs within the
diffserv region and appropriate behavior at the edge of the diffserv Diffserv region and appropriate behavior at the edge of the Diffserv
region. region.
2. Diffserv network regions must provide admission control 2. Diffserv network regions must provide admission control
information to intserv network regions. This information can be information to their _customer_ (non-Diffserv) network regions.
provided by a dynamic protocol or through static service level This information can be provided by a dynamic protocol or through
agreements enforced at the edges of the diffserv region. static service level agreements enforced at the edges of the
Diffserv region.
3. Diffserv network regions must be able to pass RSVP messages, in 3. Diffserv network regions must be able to pass RSVP messages, in
such a manner that they can be recovered at the egress of the such a manner that they can be recovered at the egress of the
diffserv network region. The diffserv network region may, but is not Diffserv network region. The Diffserv network region may, but is not
required to, process these messages. Mechanisms for transparently required to, process these messages. Mechanisms for transparently
carrying RSVP messages across a transit network are described in carrying RSVP messages across a transit network are described in
[3,6,15, 16]. [3,6,15, 16].
To meet these requirements, additional work is required in the areas
of:
1. Mapping intserv style service specifications to services that can
be provided by diffserv network regions.
Bernet, ed. et al. 18 Bernet, ed. et al. 18
Integrated Services Operation Over Diffserv Networks June, 1999 Integrated Services Operation Over Diffserv Networks June, 1999
To meet these requirements, additional work is required in the areas
of:
1. Mapping Intserv style service specifications to services that can
be provided by Diffserv network regions.
2. Definition of the functionality required in network elements to 2. Definition of the functionality required in network elements to
support RSVP signaling with aggregate traffic control (for network support RSVP signaling with aggregate traffic control (for network
elements residing in the diffserv network region). elements residing in the Diffserv network region).
3. Definition of mechanisms to efficiently and dynamically provision 3. Definition of mechanisms to efficiently and dynamically provision
resources in a diffserv network region (e.g. aggregated RSVP, resources in a Diffserv network region (e.g. aggregated RSVP,
tunneling, MPLS, etc.). This might include protocols by which an tunneling, MPLS, etc.). This might include protocols by which an
_oracle_ conveys information about resource availability within a _oracle_ conveys information about resource availability within a
diffserv region to border routers. Diffserv region to border routers.
6.2 Protection of Intserv Traffic from Other Traffic 6.2 Protection of Intserv Traffic from Other Traffic
Network administrators must be able to share resources in the Network administrators must be able to share resources in the
diffserv network region between three types of traffic: Diffserv network region between three types of traffic:
a. End-to-end Intserv traffic - this is typically traffic a. End-to-end Intserv traffic - this is typically traffic
associated with quantitative QoS applications. It requires a associated with quantitative QoS applications. It requires a
specific quantity of resources with a high degree of assurance. specific quantity of resources with a high degree of assurance.
b. Non-intserv traffic. The Diffserv region may allocate resources b. Non-Intserv traffic. The Diffserv region may allocate resources
to traffic that does not make use of intserv techniques to quantify to traffic that does not make use of Intserv techniques to quantify
its requirements, e.g. through the use of static provisioning and its requirements, e.g. through the use of static provisioning and
SLSs enforced at the edges of the region. Such traffic might be SLSs enforced at the edges of the region. Such traffic might be
associated with applications whose QoS requirements are not readily associated with applications whose QoS requirements are not readily
quantifiable but which require a 'better than best-effort' level of quantifiable but which require a 'better than best-effort' level of
service. service.
c. All other (best-effort) traffic c. All other (best-effort) traffic
These three classes of traffic must be isolated from each other by These three classes of traffic must be isolated from each other by
the appropriate configuration of policers and classifiers at ingress the appropriate configuration of policers and classifiers at ingress
points to the diffserv network region, and by appropriate points to the Diffserv network region, and by appropriate
provisioning within the diffserv network region. To provide provisioning within the Diffserv network region. To provide
protection for Intserv traffic in diffserv regions of the network, protection for Intserv traffic in Diffserv regions of the network,
we suggest that the DSCPs assigned to such traffic not overlap with we suggest that the DSCPs assigned to such traffic not overlap with
the DSCPs assigned to other traffic. the DSCPs assigned to other traffic.
7. Multicast 7. Multicast
The use of integrated services over Diffserv networks is
significantly more complex for multicast sessions than for unicast
sessions. With respect to a multicast connection, each participating
region has a single ingress router and zero, one or several egress
routers. The difficulties of multicast are associated with Diffserv
regions that contain several egress routers. (Support of multicast
functionality outside the Diffserv region is relatively
straightforward since every Intserv-capable router along the
multicast tree stores state for each flow.)
To be written. Bernet, ed. et al. 19
Integrated Services Operation Over Diffserv Networks June, 1999
Consider the following reference network:
Non-Diffserv region 2
________
/ \
| | |---|
________ _____________ | |-|Rx1|
/ \ / |--\ |---| | |---|
/ \ / /|BR2\-----\ER2| /
|---| | |---| |---| |--|/ |---| \--|____/
|Tx |-| |ER1|---|BR1|--|RR| | ________
|---| | |-- | |---| |--|\ |---| /--| \
\ / \ \|BR3/-----|ER3| | |---|
\________/ \__________|--/ |---| |-|Rx2|
| | |---|
Non-Diffserv region 1 Diffserv region \ /
\______/
Non-Diffserv region 3
Figure 2: Sample Multicast Network Configuration
The reference network is similar to that of Figure 1. However, in
Figure 2, copies of the packets sent by Tx are delivered to several
receivers outside of the Diffserv region, namely to Rx1 and Rx2.
Moreover, packets are copied within the Diffserv region in a _branch
point_ router RR. In the reference network BR1 is the ingress router
to the Diffserv region whereas BR2 and BR3 are the egress routers.
In the simplest case the receivers, Rx1 and Rx2 in the reference
network, require identical reservations. The Diffserv framework [18]
supports service level specifications (SLS) from an ingress router
to one, some or all of the egress routers. This calls for a _one to
many_ SLS within the Diffserv region, from BR1 to BR2 and BR3. Given
that the SLS is granted by the Diffserv region, the ingress router
BR1, or perhaps an upstream node such as ER1, marks packets entering
the Diffserv region with the appropriate DSCP. The packets are
routed to the egresses of the Diffserv domain using the original
multicast address.
The two major problems, explained in the following, are associated
with heterogeneous multicast trees containing branch points within
the Diffserv region, i.e. multicast trees where the level of
resource requirement is not uniform among all receivers. An example
of such a scenario in the network of Figure 2 is the case where both
Rx1 and Rx2 need to receive multicast data from Tx1 but only one of
the receivers has requested a level of service above best effort. We
consider such scenarios in the following paragraphs.
7.1 Remarking of packets in branch point routers
Bernet, ed. et al. 20
Integrated Services Operation Over Diffserv Networks June, 1999
In the above scenario, the packets that arrive at BR1 are marked
with an appropriate DSCP for the requested Intserv service and are
sent to RR. Packets arriving at the branch point must be sent
towards BR2 with the same DSCP otherwise the service to Rx1 is
degraded. However, the packets going from RR towards BR3 need not
maintain the high assurance level anymore. They may be demoted to
best effort so that the QoS provided to other packets along this
branch of the tree is not disrupted. Several problems can be
observed in the given scenario:
- In the Diffserv region, DSCP marking is done at edge routers
(ingress), whereas a branch point router might be a core
router, which does not mark packets.
- Being a core Diffserv router, RR classifies based on
aggregate traffic streams (BA) _ as opposed to per flow (MF)
classification. Hence, it does not necessarily have the
capability to distinguish those packets which belong to a
specific multicast tree and require demotion from the other
packets in the behavior aggregate, which carry the same DSCP.
- Since RR may be RSVP-unaware, it may not participate in the
admission control process, and would thus not store any per-
flow state about the reservations for the multicast tree.
Hence, even if RR were able to perform MF classification and
DSCP remarking, it would not know enough about downstream
reservations to remark the DSCP intelligently.
These problems can be tackled by the following mechanisms:
1. If some Intserv-capable routers are placed within the Diffserv
region, it might be possible to administer the network topology and
routing parameters so as to ensure that branch points occur only
within such routers. These routers would support MF classification
and remarking and hold per-flow state for the heterogeneous
reservations for which they are the branch point. Note that in this
case, branch point routers would have essentially the same
functionality as ingress routers of an RSVP-aware Diffserv domain.
2. Packets sent on the _non-reserved_ branch (from RR towards BR3)
are marked with the _wrong_ DSCP; that is, they are not demoted to
best effort but retain their DSCP. This in turn requires over
reservation of resources along that link or runs the risk of
degrading service to packets that legitimately bear the same DSCP
along this path. However, it allows the Diffserv routers to remain
free of per-flow state.
3. A combination of mechanism 1 and 2 may be an effective
compromise. In this case, there are some Intserv-capable routers in
the core of the network, but the network cannot be administered so
that ALL branch points fall at such routers.
Bernet, ed. et al. 21
Integrated Services Operation Over Diffserv Networks June, 1999
4. Administrators of Diffserv regions may decide not to enable
heterogeneous sub-trees in their domains. In the case of different
downstream reservations, a ResvErr message would be sent according
to the RSVP rules. This is similar to the approach taken for Intserv
over IEEE 802 Networks [2,5].
5. In [3], a scheme was introduced whereby branch point routers in
the interior of the aggregation region (i.e. the Diffserv region)
keep reduced state information regarding the reservations by using
measurement based admission control. Under this scheme, packets are
tagged by the more knowledgeable Intserv edges routers with
scheduling information that is used in place of the detailed Intserv
state. If the Diffserv region and branch point routers are designed
following that framework, demotion of packets becomes possible.
7.2 Multicast SLSs and Heterogeneous Trees
Multicast flows with heterogeneous reservations present some
challenges in the area of SLSs. For example, a common example of an
SLS is one where a certain amount of traffic is allowed to enter a
Diffserv region marked with a certain DSCP, and such traffic may be
destined to any egress router of that region. We call such an SLS a
homogeneous, or uniform, SLS. However, in a multicast environment, a
single packet that is admitted to the Diffserv region may consume
resources along many paths in the region as it is replicated and
forwarded towards many egress routers; alternatively, it may flow
along a single path. This situation is further complicated by the
possibility described above and depicted in Figure 2, in which a
multicast packet might be treated as best effort along some branches
while receiving some higher QOS treatment along others. We simply
note here that the specification of meaningful SLSs which meet the
needs of heterogeneous flows and which can be met be providers is
likely to be challenging.
Dynamic SLSs may help to address these issues. For example, by using
RSVP to signal the resources that are required along different
branches of a multicast tree, it may be possible to more closely
approach the goal of allocating appropriate resources only where
they are needed rather than overprovisioning or underprovisioning
along certain branches of a tree. This is essentially the approach
described in [15].
8. Security Considerations 8. Security Considerations
8.1 General RSVP Security 8.1 General RSVP Security
We are proposing that RSVP signaling be used to obtain resources in We are proposing that RSVP signaling be used to obtain resources in
both diffserv and Intserv regions of a network. Therefore, all RSVP both Diffserv and non-Diffserv regions of a network. Therefore, all
security considerations apply [9]. In addition, network RSVP security considerations apply [9]. In addition, network
Bernet, ed. et al. 22
Integrated Services Operation Over Diffserv Networks June, 1999
administrators are expected to protect network resources by administrators are expected to protect network resources by
configuring secure policers at interfaces with untrusted customers. configuring secure policers at interfaces with untrusted customers.
8.2 Host Marking 8.2 Host Marking
Bernet, ed. et al. 19
Integrated Services Operation Over Diffserv Networks June, 1999
Though it does not mandate host marking of the DSCP, our proposal Though it does not mandate host marking of the DSCP, our proposal
does allow it. Allowing hosts to set the DSCP directly may alarm does allow it. Allowing hosts to set the DSCP directly may alarm
network administrators. The obvious concern is that hosts may network administrators. The obvious concern is that hosts may
attempt to 'steal' resources. In fact, hosts may attempt to exceed attempt to 'steal' resources. In fact, hosts may attempt to exceed
negotiated capacity in diffserv network regions at a particular negotiated capacity in Diffserv network regions at a particular
service level regardless of whether they invoke this service level service level regardless of whether they invoke this service level
directly (by setting the DSCP) or indirectly (by submitting traffic directly (by setting the DSCP) or indirectly (by submitting traffic
that classifies in an intermediate marking router to a particular that classifies in an intermediate marking router to a particular
diff-serv DSCP). DSCP).
In either case, it will be necessary for each diffserv network In either case, it will generally be necessary for each Diffserv
region to protect its resources by policing to assure that customers network region to protect its resources by policing to assure that
do not use more resources than they are entitled to, at each service customers do not use more resources than they are entitled to, at
level (DSCP). If the sending host does not do the marking, the each service level (DSCP). The exception to this rule is when the
boundary router (or trusted intermediate routers) must provide MF host is known to be trusted, e.g. a server that is under the control
classification, mark and police. If the sending host does do the of the network administrators. If an untrusted sending host does not
marking, the boundary router needs only to provide BA classification perform DSCP marking, the boundary router (or trusted intermediate
and to police to ensure that the customer is not exceeding the routers) must provide MF classification, mark and police. If an
aggregate capacity negotiated for the service level. untrusted sending host does perform marking, the boundary router
needs only to provide BA classification and to police to ensure that
the customer is not exceeding the aggregate capacity negotiated for
the service level.
In summary, there are no additional security concerns raised by In summary, there are no additional security concerns raised by
marking the DSCP at the edge of the network since diffserv providers marking the DSCP at the edge of the network since Diffserv providers
will have to police at their boundaries anyway. Furthermore, this will have to police at their boundaries anyway. Furthermore, this
approach reduces the granularity at which border routers must approach reduces the granularity at which border routers must
police, thereby pushing finer grain shaping and policing police, thereby pushing finer grain shaping and policing
responsibility to the edges of the network, where it scales better. responsibility to the edges of the network, where it scales better
The larger diffserv network regions are thus focused on the task of and provides other benefits described in Section 3.3.1. The larger
protecting their networks, while the Intserv network regions are Diffserv network regions are thus focused on the task of protecting
focused on the task of shaping and policing their own traffic to be their networks, while the Intserv-capable nodes are focused on the
in compliance with their negotiated intserv parameters. task of shaping and policing their own traffic to be in compliance
with their negotiated Intserv parameters.
9. Acknowledgments 9. Acknowledgments
Authors thank the following individuals for their comments that led Authors thank the following individuals for their comments that led
to improvements to the previous version(s) of this draft: David to improvements to the previous version(s) of this draft: David
Oran, Andy Veitch, Curtis Villamizer, Walter Weiss, Francois le Oran, Andy Veitch, Curtis Villamizer, Walter Weiss, Francois le
Faucheur and Russell White. Faucheur and Russell White.
Many of the ideas in this document have been previously discussed in Many of the ideas in this document have been previously discussed in
the original intserv architecture document [10]. the original Intserv architecture document [10].
10. References 10. References
Bernet, ed. et al. 23
Integrated Services Operation Over Diffserv Networks June, 1999
[1] Braden, R., Zhang, L., Berson, S., Herzog, S. and Jamin, S., [1] Braden, R., Zhang, L., Berson, S., Herzog, S. and Jamin, S.,
"Resource Reservation Protocol (RSVP) Version 1 Functional "Resource Reservation Protocol (RSVP) Version 1 Functional
Specification", RFC 2205, Proposed Standard, September 1997 Specification", RFC 2205, Proposed Standard, September 1997
[2] Yavatkar, R., Hoffman, D., Bernet, Y., Baker, F. and Speer, M., [2] Yavatkar, R., Hoffman, D., Bernet, Y., Baker, F. and Speer, M.,
"SBM (Subnet Bandwidth Manager): A Protocol For RSVP-based "SBM (Subnet Bandwidth Manager): A Protocol For RSVP-based
Admission Control Over IEEE 802 Style Networks", Internet Draft, Admission Control Over IEEE 802 Style Networks", Internet Draft,
Bernet, ed. et al. 20
Integrated Services Operation Over Diffserv Networks June, 1999
[3] Berson, S. and Vincent, R., "Aggregation of Internet Integrated [3] Berson, S. and Vincent, R., "Aggregation of Internet Integrated
Services State", Internet Draft, draft-berson-rsvp-aggregation- Services State", Internet Draft, draft-berson-rsvp-aggregation-
00.txt, August 1998. 00.txt, August 1998.
[4] Nichols, K., Jacobson, V. and Zhang, L., "A Two-bit [4] Nichols, K., Jacobson, V. and Zhang, L., "A Two-bit
Differentiated Services Architecture for the Internet", Internet Differentiated Services Architecture for the Internet", RFC
Draft, draft-nichols-diff-svc-arch-01.txt, April 1999. 2638, July 1999.
[5] Seaman, M., Smith, A., Crawley, E., and Wroclawski, J., [5] Seaman, M., Smith, A., Crawley, E., and Wroclawski, J.,
"Integrated Service Mappings on IEEE 802 Networks", Internet "Integrated Service Mappings on IEEE 802 Networks", Internet
[6] Guerin, R., Blake, S. and Herzog, S.,"Aggregating RSVP based QoS [6] Guerin, R., Blake, S. and Herzog, S., "Aggregating RSVP based
QoS
Requests", Internet Draft, draft-guerin-aggreg-rsvp-00.txt, Requests", Internet Draft, draft-guerin-aggreg-rsvp-00.txt,
November 1997. November 1997.
[7] Nichols, Kathleen, et al., "Definition of the Differentiated [7] Nichols, Kathleen, et al., "Definition of the Differentiated
Services Field (DS Field) in the IPv4 and IPv6 Headers", RFC Services Field (DS Field) in the IPv4 and IPv6 Headers", RFC
2474, December 1998. 2474, December 1998.
[8] Blake, S., et al., "An Architecture for Differentiated [8] Blake, S., et al., "An Architecture for Differentiated
Services." RFC 2475, December 1998. Services." RFC 2475, December 1998.
skipping to change at line 1153 skipping to change at line 1325
[11] Garrett, M. W., and Borden, M., "Interoperation of Controlled- [11] Garrett, M. W., and Borden, M., "Interoperation of Controlled-
Load Service and Guaranteed Service with ATM", RFC2381, August Load Service and Guaranteed Service with ATM", RFC2381, August
1998. 1998.
[12] Weiss, Walter, Private communication, November 1998. [12] Weiss, Walter, Private communication, November 1998.
[13] Kent, S., Atkinson, R., "Security Architecture for the Internet [13] Kent, S., Atkinson, R., "Security Architecture for the Internet
Protocol", RFC 2401, November 1998. Protocol", RFC 2401, November 1998.
[14] Bernet, Y., "Usage and Format of the DCLASS Object with RSVP [14] Bernet, Y., "Usage and Format of the DCLASS Object with RSVP
Signaling", Internet Draft, draft-bernet-dclass-00.txt, Signaling", Internet Draft, draft-issll-dclass-00.txt, August
February 1999. 1999.
Bernet, ed. et al. 24
Integrated Services Operation Over Diffserv Networks June, 1999
[15] Baker, F., Iturralde, C., le Faucheur, F., and Davie, B. "RSVP [15] Baker, F., Iturralde, C., le Faucheur, F., and Davie, B. "RSVP
Reservation Aggregation", Internet Draft, draft-baker-rsvp- Reservation Aggregation", Internet Draft, draft-ietf-issll-
aggregation-00.txt, February 1999. aggregation-00.txt, September 1999.
[16] Terzis, A., Krawczyk, J., Wroclawski, J., Zhang, L., "RSVP [16] Terzis, A., Krawczyk, J., Wroclawski, J., Zhang, L., "RSVP
Operation Over IP Tunnels", Internet Draft, draft-ietf-rsvp- Operation Over IP Tunnels", Internet Draft, draft-ietf-rsvp-
tunnel-03.txt, April 1999. tunnel-04.txt, May 1999.
Bernet, ed. et al. 21
Integrated Services Operation Over Diffserv Networks June, 1999
[17] Boyle, J., Cohen, R., Durham, D., Herzog, S., Rajan, D., and [17] Boyle, J., Cohen, R., Durham, D., Herzog, S., Rajan, D., and
Sastry, A., _COPS Usage for RSVP_, Internet Draft, draft-ietf- Sastry, A., _COPS Usage for RSVP_, Internet Draft, draft-ietf-
rap-cops-rsvp-05.txt, June 1999. rap-cops-rsvp-05.txt, June 1999.
Author's Addresses: [18] Bernet, Y., et al., _A Framework for Differentiated Services_,
Internet draft, draft-ietf-diffserv-framework-02.txt, February
1999.
11. Author's Addresses:
Yoram Bernet Yoram Bernet
Microsoft Microsoft
One Microsoft Way, Redmond, WA 98052 One Microsoft Way, Redmond, WA 98052
Phone: (425) 936-9568 Phone: (425) 936-9568
Email: yoramb@microsoft.com Email: yoramb@microsoft.com
Raj Yavatkar Raj Yavatkar
Intel Corporation Intel Corporation
JF3-206 2111 NE 25th. Avenue, Hillsboro, OR 97124 JF3-206 2111 NE 25th. Avenue, Hillsboro, OR 97124
skipping to change at line 1207 skipping to change at line 1383
Lixia Zhang Lixia Zhang
UCLA UCLA
4531G Boelter Hall Los Angeles, CA 90095 4531G Boelter Hall Los Angeles, CA 90095
Phone: +1 310-825-2695 Phone: +1 310-825-2695
Email: lixia@cs.ucla.edu Email: lixia@cs.ucla.edu
Michael Speer Michael Speer
Sun Microsystems Sun Microsystems
901 San Antonio Road UMPK15-215 Palo Alto, CA 94303 901 San Antonio Road UMPK15-215 Palo Alto, CA 94303
Bernet, ed. et al. 25
Integrated Services Operation Over Diffserv Networks June, 1999
Phone: +1 650-786-6368 Phone: +1 650-786-6368
Email: speer@Eng.Sun.COM Email: speer@Eng.Sun.COM
Bob Braden Bob Braden
USC Information Sciences Institute USC Information Sciences Institute
4676 Admiralty Way Marina del Rey, CA 90292-6695 4676 Admiralty Way Marina del Rey, CA 90292-6695
Phone: 310-822-1511 Phone: 310-822-1511
Email: braden@isi.edu Email: braden@isi.edu
Bruce Davie Bruce Davie
Cisco Systems Cisco Systems
250 Apollo Drive, Chelmsford, MA 01824 250 Apollo Drive, Chelmsford, MA 01824
Phone: (978)-244-8000 Phone: (978)-244-8000
Email: bsd@cisco.com
Bernet, ed. et al. 22 Eyal Felstaine
Allot Communications
5 Hanagar St.
Neve Ne'eman B Hod- Hasharon.
45800 Israel.
Phone: +972-9-7443676/ext 202
Email: efelstaine@allot.com
John Wroclawski
MIT Laboratory for Computer Science
545 Technology Sq.
Cambridge, MA 02139
Phone: 617-253-7885
E-mail: jtw@lcs.mit.edu
12. Full Copyright Statement
Copyright (C) The Internet Society (1999). All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph
are included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
Bernet, ed. et al. 26
Integrated Services Operation Over Diffserv Networks June, 1999 Integrated Services Operation Over Diffserv Networks June, 1999
Email: bsd@cisco.com This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE."
This draft expires December, 1999 This draft expires March, 2000
Bernet, ed. et al. 23 Bernet, ed. et al. 27
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