draft-ietf-issll-is802-svc-mapping-02.txt   draft-ietf-issll-is802-svc-mapping-03.txt 
Internet Draft M. Seaman Internet Draft M. Seaman
Expires February 1999 3Com Expires May 1999 3Com Corp.
draft-ietf-issll-is802-svc-mapping-02.txt A. Smith draft-ietf-issll-is802-svc-mapping-03.txt A. Smith
Extreme Networks Standards Track Extreme Networks
E. Crawley E. Crawley
Argon Networks Argon Networks
J. Wroclawski J. Wroclawski
MIT LCS MIT LCS
August 1998 November 1998
Integrated Service Mappings on IEEE 802 Networks Integrated Service Mappings on IEEE 802 Networks
Status of this Memo Status of this Memo
This document is an Internet Draft. Internet Drafts are working This document is an Internet Draft. Internet Drafts are working
documents of the Internet Engineering Task Force (IETF), its Areas, documents of the Internet Engineering Task Force (IETF), its Areas, and
and its Working Groups. Note that other groups may also distribute its Working Groups. Note that other groups may also distribute working
working documents as Internet Drafts. documents as Internet Drafts.
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months. Internet Drafts may be updated, replaced, or obsoleted by Internet Drafts may be updated, replaced, or obsoleted by other
other documents at any time. It is not appropriate to use Internet documents at any time. It is not appropriate to use Internet Drafts as
Drafts as reference material or to cite them other than as a "working reference material or to cite them other than as a "working draft" or
draft" or "work in progress." "work in progress."
To view the entire list of current Internet-Drafts, please check the To learn the current status of any Internet-Draft, please check the
"1id-abstracts.txt" listing contained in the Internet-Drafts Shadow "1id-abstracts.txt" listing contained in the Internet-Drafts Shadow
Directories on ftp.is.co.za (Africa), ftp.nordu.net (Europe), Directories on ftp.ietf.org (US East Coast), nic.nordu.net (Europe),
munnari.oz.au (Pacific Rim), ftp.ietf.org (US East Coast), or ftp.isi.edu (US West Coast), or munnari.oz.au (Pacific Rim).
ftp.isi.edu (US West Coast).
This document is a product of the IS802 subgroup of the ISSLL working This document is a product of the IS802 subgroup of the ISSLL working
group of the Internet Engineering Task Force. Comments are solicited group of the Internet Engineering Task Force. Comments are solicited
and should be addressed to the working group's mailing list at and should be addressed to the working group's mailing list at
issll@mercury.lcs.mit.edu and/or the authors. Copyright (C) The issll@mercury.lcs.mit.edu and/or the authors.
Internet Society (1998). All Rights Reserved.
Abstract A revised version of this draft document will be submitted to the RFC
editor as a Proposed Standard for the Internet Community. Discussion
and suggestions for improvement are requested. This document will
expire before February 1999. Distribution of this draft is unlimited.
This document describes mappings of IETF Integrated Services over Copyright (C) The Internet Society (1998). All Rights Reserved.
LANs built from IEEE 802 network segments which may be interconnected
by IEEE 802.1 MAC Bridges (switches) [1][2].
9 Abstract
9 Seaman,Smith,Crawley,Wroclawski. Expires February 1999 This document describes mappings of IETF Integrated Services over LANs
It describes parameter mappings for supporting Controlled Load [6] built from IEEE 802 network segments which may be interconnected by IEEE
and Guaranteed Service [7] using the inherent capabilities of 802.1 MAC Bridges (switches) [1][2]. It describes parameter mappings
relevant IEEE 802 technologies and, in particular, 802.1D-1998 for supporting Controlled Load [6] and Guaranteed Service [7] using the
queuing features in switches [2]. inherent capabilities of relevant IEEE 802 technologies and, in
particular, 802.1D-1998 queuing features in switches [2].
These mappings are one component of the Integrated Services over IEEE These mappings are one component of the Integrated Services over IEEE
802 LANs framework described in [5]. 802 LANs framework described in [5].
1. Introduction 1. Introduction
The IEEE 802.1 Interworking Task Group has developed a set of The IEEE 802.1 Interworking Task Group has developed a set of
enhancements to the basic MAC Service provided in Bridged Local Area enhancements to the basic MAC Service provided in Bridged Local Area
Networks (a.k.a. "switched LANs"). As a supplement to the original Networks (a.k.a. "switched LANs"). As a supplement to the original IEEE
IEEE MAC Bridges standard, IEEE 802.1D-1990 [1], the updated IEEE MAC Bridges standard, IEEE 802.1D-1990 [1], the updated IEEE 802.1D-1998
802.1D-1998 [2] proposes differential traffic class queuing in [2] proposes differential traffic class queuing in switches and extends
switches and extends the capabilities of Ethernet/802.3 media to the capabilities of Ethernet/802.3 media to carry a traffic class
carry a traffic class indicator, or "user_priority" field, within indicator, or "user_priority" field, within data frames [8].
data frames [8].
The availability of this differential traffic queuing, together with The availability of this differential traffic queuing, together with
additional mechanisms to provide admission control and signaling, additional mechanisms to provide admission control and signaling, allows
allows IEEE 802 networks to support a close approximation of the IEEE 802 networks to support a close approximation of the IETF-defined
IETF-defined Integrated Services capabilities [6][7]. This document Integrated Services capabilities [6][7]. This document describes methods
describes methods for mapping the service classes and parameters of for mapping the service classes and parameters of the IETF model into
the IETF model into IEEE 802.1D network parameters. A companion IEEE 802.1D network parameters. A companion document [10] describes a
document [10] describes a signaling protocol for use with these signaling protocol for use with these mappings. It is recommended that
mappings. It is recommended that readers be familiar with the readers be familiar with the overall framework in which these mappings
overall framework in which these mappings and signaling protocol are and signaling protocol are expected to be used; this framework is
expected to be used; this framework is described fully in [5]. described fully in [5].
Within this document, Section 2 describes the method by which end Within this document, Section 2 describes the method by which end
systems and routers bordering the IEEE Layer-2 cloud learn what systems and routers bordering the IEEE Layer-2 cloud learn what traffic
traffic class should be used for each data flow's packets. Section 3 class should be used for each data flow's packets. Section 3 describes
describes the approach recommended to map IP-level traffic flows to the approach recommended to map IP-level traffic flows to IEEE traffic
IEEE traffic classes within the Layer 2 network. Section 4 describes classes within the Layer 2 network. Section 4 describes the computation
the computation of Characterization Parameters by the layer 2 of Characterization Parameters by the layer 2 network. The remaining
network. The remaining sections discuss some particular issues with sections discuss some particular issues with the use of the RSVP/SBM
the use of the RSVP/SBM signaling protocols, and describe the signaling protocols, and describe the applicability of all of the above
applicability of all of the above to different layer 2 network to different layer 2 network topologies.
topologies.
9
9 Seaman,Smith,Crawley,Wroclawski. Expires February 1999
2. Flow Identification and Traffic Class Selection 2. Flow Identification and Traffic Class Selection
One model for supporting integrated services over specific link One model for supporting integrated services over specific link layers
layers treats layer-2 devices very much as a special case of routers. treats layer-2 devices very much as a special case of routers. In this
In this model, switches and other devices along the data path make model, switches and other devices along the data path make packet
packet handling decisions based on the RSVP flow and filter handling decisions based on the RSVP flow and filter specifications, and
specifications, and use these specifications to classify the use these specifications to classify the corresponding data packets. The
corresponding data packets. The specifications could either be used specifications could either be used directly, or could be used
directly, or could be used indirectly by mapping each RSVP session indirectly by mapping each RSVP session onto a layer-2 construct such as
onto a layer-2 construct such as an ATM virtual circuit. an ATM virtual circuit.
This approach is inappropriate for use in the IEEE 802 environment. This approach is inappropriate for use in the IEEE 802 environment.
Filtering to the per-flow level becomes expensive with increasing Filtering to the per-flow level becomes expensive with increasing switch
switch speed; devices with such filtering capabilities are likely to speed; devices with such filtering capabilities are likely to have a
have a very similar implementation complexity to IP routers, and may very similar implementation complexity to IP routers, and may not make
not make use of simpler mechanisms such as 802.1D user priority. use of simpler mechanisms such as 802.1D user priority.
The Integrated Services over IEEE 802 LANs framework [5] and this The Integrated Services over IEEE 802 LANs framework [5] and this
document use an "aggregated flow" approach based on use of layer 2 document use an "aggregated flow" approach based on use of layer 2
traffic classes. In this model, each arriving flow is assigned to one traffic classes. In this model, each arriving flow is assigned to one of
of the available layer-2 classes, and traverses the 802 cloud in this the available layer-2 classes, and traverses the 802 cloud in this
class. Traffic flows requiring similar service are grouped together class. Traffic flows requiring similar service are grouped together
into a single class, while the system's admission control and class into a single class, while the system's admission control and class
selection rules ensure that the service requirements for flows in selection rules ensure that the service requirements for flows in each
each of the classes are met. In many situations this is a viable of the classes are met. In many situations this is a viable
intermediate point between no QoS control and full router- type intermediate point between no QoS control and full router- type
integrated services. The approach can work effectively even with integrated services. The approach can work effectively even with
switches implementing only the simplest differential traffic switches implementing only the simplest differential traffic
classification capability specified in the 802.1D model. classification capability specified in the 802.1D model. In the
aggregated flow model, traffic arriving at the boundary of a layer-2
In the aggregated flow model, traffic arriving at the boundary of a cloud is tagged by the boundary device (end host or border router) with
layer 2 cloud is tagged by the boundary device (end host or border an appropriate traffic class, represented as an 802.1D "user_priority"
router) with an appropriate traffic class, represented as an 802.1D value. Two fundamental questions are "who determines the correspondence
"user_priority" value. Two fundamental questions are "who determines between IP-level traffic flows and link-level classes?" and "how is
the correspondence between IP-level traffic flows and link-level this correspondence conveyed to the boundary devices that must mark the
classes?" and "how is this correspondence conveyed to the boundary data frames?"
devices that must mark the data frames?"
One approach to answering these questions would be for the meanings One approach to answering these questions would be for the meanings of
of the classes to be universally defined. This document would then the classes to be universally defined. This document would then
standardise the meanings of a set of classes; e.g. 1 = best effort, 2 standardise the meanings of a set of classes; e.g. 1 = best effort, 2 =
= 100 ms peak delay target, 3 = 10 ms peak delay target, 4 = 1 ms 100 ms peak delay target, 3 = 10 ms peak delay target, 4 = 1 ms peak
peak delay target, etc. The meanings of these universally defined delay target, etc. The meanings of these universally defined classes
classes could then be encoded directly in end stations, and the could then be encoded directly in end stations, and the flow-to-class
flow-to-class mappings computed directly in these devices. mappings computed directly in these devices.
Seaman,Smith,Crawley,Wroclawski. Expires February 1999 [Page This universal definition approach would be simple to implement, but is
3] too rigid to map the wide range of possible user requirements onto the
This universal definition approach would be simple to implement, but limited number of available 802.1D classes. The model described in [5]
is too rigid to map the wide range of possible user requirements onto uses a more flexible mapping: clients ask "the network" which
the limited number of available 802.1D classes. The model described
in [5] uses a more flexible mapping: clients ask "the network" which
user_priority traffic class to use for a given traffic flow, as user_priority traffic class to use for a given traffic flow, as
categorised by its flow-spec and layer-2 endpoints. The network categorised by its flow-spec and layer-2 endpoints. The network provides
provides a value back to the requester that is appropriate a value back to the requester that is appropriate considering the
considering the current network topology, load conditions, other current network topology, load conditions, other admitted flows, etc.
admitted flows, etc. The task of configuring switches with this The task of configuring switches with this mapping (e.g. through network
mapping (e.g. through network management, a switch-switch protocol or management, a switch-switch protocol or via some network-wide QoS-
via some network-wide QoS-mapping directory service) is an order of mapping directory service) is an order of magnitude less complex than
magnitude less complex than performing the same function in end performing the same function in end stations. Also, when new services
stations. Also, when new services (or other network reconfigurations) (or other network reconfigurations) are added to such a network, the
are added to such a network, the network elements will typically be network elements will typically be the ones to be upgraded with new
the ones to be upgraded with new queuing algorithms etc. and can be queuing algorithms etc. and can be provided with new mappings at this
provided with new mappings at this time. time.
In this model, when a new session or "flow" requiring QoS support is In this model, when a new session or "flow" requiring QoS support is
created, a client must ask "the network" which user_priority traffic created, a client must ask "the network" which traffic class (IEEE 802
class to use for a given traffic flow, so that it can label the user_priority) to use for a given traffic flow, so that it can label the
packets of the flow as it places them into the network. A packets of the flow as it places them into the network. A
request/response protocol is needed between client and network to request/response protocol is needed between client and network to return
return this information. The request can be piggy-backed onto an this information. The request can be piggy-backed onto an admission
admission control request and the response can be piggy-backed onto control request and the response can be piggy-backed onto an admission
an admission control acknowledgment. This "one pass" assignment has control acknowledgment. This "one pass" assignment has the benefit of
the benefit of completing the admission control transaction in a completing the admission control transaction in a timely way and
timely way and reducing the exposure to changing conditions that reducing the exposure to changing conditions that could occur if clients
could occur if clients cached the knowledge for extensive periods. A cached the knowledge for extensive periods. A set of extensions to the
set of extensions to the RSVP protocol for communicating this RSVP protocol for communicating this information have been defined[10].
information have been defined[10].
The network (i.e. the first network element encountered downstream
from the client) must then answer the following questions:
1. Which of the available traffic classes would be appropriate for The network (i.e. the first network element encountered downstream from
this flow? the client) must then answer the following questions:
In general, a newly arriving flow might be assigned to a number
of classes. For example, if 10ms of delay is acceptable, the
flow could potentially be assigned to either a 10ms delay class
or a 1ms delay class. This packing problem is quite difficult to
solve if the target parameters of the classes are allowed to
change dynamically as flows arrive and depart. It is quite
simple if the target parameters of each class is held fixed, and
the class table is simply searched to find a class appropriate
Seaman,Smith,Crawley,Wroclawski. Expires February 1999 [Page 1. Which of the available traffic classes would be appropriate for this
4] flow?
for the arriving flow. This document adopts the latter approach. In general, a newly arriving flow might be assigned to a number of
classes. For example, if 10ms of delay is acceptable, the flow could
potentially be assigned to either a 10ms delay class or a 1ms delay
class. This packing problem is quite difficult to solve if the
target parameters of the classes are allowed to change dynamically
as flows arrive and depart. It is quite simple if the target
parameters of each class is held fixed, and the class table is
simply searched to find a class appropriate for the arriving flow.
This document adopts the latter approach.
2. Of the appropriate traffic classes, which if any have enough 2. Of the appropriate traffic classes, which if any have enough capacity
capacity available to accept the new flow? available to accept the new flow?
This is the admission control problem. It is necessary to This is the admission control problem. It is necessary to compare
compare the level of traffic currently assigned to each class the level of traffic currently assigned to each class with the
with the available level of network resources (bandwidth, available level of network resources (bandwidth, buffers, etc), to
buffers, etc), to ensure that adding the new flow to the class ensure that adding the new flow to the class will not cause the
will not cause the class's performance to go below its target class's performance to go below its target values. This problem is
values. This problem is compounded because in a priority queuing compounded because in a priority queuing system adding traffic to a
system adding traffic to a higher-priority class can affect the higher-priority class can affect the performance of lower-priority
performance of lower-priority classes. The admission control classes. The admission control algorithm for a system using the
algorithm for a system using the default 802 priority behavior default 802 priority behavior must be reasonably sophisticated to
must be reasonably sophisticated to provide acceptable results. provide acceptable results.
If an acceptable class is found, the network returns the chosen If an acceptable class is found, the network returns the chosen
user_priority value to the client. user_priority value to the client.
Note that the client may be an end station, a router at the edge Note that the client may be an end station, a router at the edge of the
of the layer 2 network, or a first switch acting as a proxy for layer 2 network, or a first switch acting as a proxy for a device that
a device that does not participate in these protocols for does not participate in these protocols for whatever reason. Note also
whatever reason. Note also that a device e.g. a server or router that a device e.g. a server or router may choose to implement both the
may choose to implement both the "client" as well as the "client" as well as the "network" portion of this model so that it can
"network" portion of this model so that it can select its own select its own user_priority values. Such an implementation would
user_priority values. Such an implementation would generally be generally be discouraged unless the device has a close tie-in with the
discouraged unless the device has a close tie-in with the network topology and resource allocation policies. It may, however, work
network topology and resource allocation policies. It may, acceptably in cases where there is known over-provisioning of resources.
however, work acceptably in cases where there is known over-
provisioning of resources.
3. Choosing a flow's IEEE 802 user_priority class 3. Choosing a flow's IEEE 802 user_priority class
This section describes the method by which IP-level flows are mapped This section describes the method by which IP-level flows are mapped
into appropriate IEEE user_priority classes. The IP-level services into appropriate IEEE user_priority classes. The IP-level services
considered are Best Effort, Controlled Load, and Guaranteed Service. considered are Best Effort, Controlled Load, and Guaranteed Service.
The major issue is that admission control requests and application The major issue is that admission control requests and application
requirements are specified in terms of a multidimensional vector of requirements are specified in terms of a multidimensional vector of
parameters e.g. bandwidth, delay, jitter, service class. This parameters e.g. bandwidth, delay, jitter, service class. This
multidimensional space must be mapped onto a set of traffic classes multidimensional space must be mapped onto a set of traffic classes
whose default behaviour in L2 switches is unidimensional (i.e. strict whose default behaviour in L2 switches is unidimensional (i.e. strict
priority default queuing). This priority queuing alone can provide priority default queuing). This priority queuing alone can provide only
only relative ordering between traffic classes. It can neither relative ordering between traffic classes. It can neither enforce an
absolute (quantifiable) delay bound for a traffic class, nor can it
Seaman,Smith,Crawley,Wroclawski. Expires February 1999 [Page discriminate amongst Int-Serv flows within the aggregate in a traffic
5] class. Therefore, it cannot provide the absolute control of packet loss
enforce an absolute (quantifiable) delay bound for a traffic class, and delay required for individual Int-Serv flows.
nor can it discriminate amongst Int-Serv flows within the aggregate
in a traffic class. Therefore, it cannot provide the absolute control
of packet loss and delay required for individual Int-Serv flows.
To provide absolute control of loss and delay three things must To provide absolute control of loss and delay three things must occur:
occur:
(1) The amount of bandwidth available to the QoS-controlled flows (1) The amount of bandwidth available to the QoS-controlled flows
must be known, and the number of flows admitted to the network must be known, and the number of flows admitted to the network
(allowed to use the bandwidth) must be limited. (allowed to use the bandwidth) must be limited.
(2) A traffic scheduling mechanism is needed to give preferential (2) A traffic scheduling mechanism is needed to give preferential
service to flows with lower delay targets. service to flows with lower delay targets.
(3) Some mechanism must ensure that best-effort flows and QoS (3) Some mechanism must ensure that best-effort flows and QoS
controlled flows that are exceeding their Tspecs do not damage controlled flows that are exceeding their Tspecs do not damage
the quality of service delivered to in-Tspec QoS controlled the quality of service delivered to in-Tspec QoS controlled
flows. This mechanism could be part of the traffic scheduler, or flows. This mechanism could be part of the traffic scheduler, or
it could be a separate policing mechanism. it could be a separate policing mechanism.
For IEEE 802 networks, the first function (admission control) is For IEEE 802 networks, the first function (admission control) is
provided by a Subnet Bandwidth Manager, as discussed below. We provided by a Subnet Bandwidth Manager, as discussed below. We use the
use the link-level user_priority mechanism at each switch and link-level user_priority mechanism at each switch and bridge to
bridge to implement the second function (preferential service to implement the second function (preferential service to flows with lower
flows with lower delay targets). Because a simple priority delay targets). Because a simple priority scheduler cannot provide
scheduler cannot provide policing (function three), policing for policing (function three), policing for IEEE networks is generally
IEEE networks is generally implemented at the edge of the implemented at the edge of the network by a layer-3 device. When this
network by a layer-3 device. When this policing is performed policing is performed only at the edges of the network it is of
only at the edges of the network it is of necessity approximate. necessity approximate. This issue is discussed further in [5].
This issue is discussed further in [5].
3.1. Context of admission control and delay bounds 3.1. Context of admission control and delay bounds
As described above, it is the combination of priority-based As described above, it is the combination of priority-based scheduling
scheduling and admission control that creates quantified delay and admission control that creates quantified delay bounds. Thus, any
bounds. Thus, any attempt to quantify the delay bounds expected by a attempt to quantify the delay bounds expected by a given traffic class
given traffic class has to made in the context of the admission has to made in the context of the admission control elements. Section 6
control elements. Section 6 of the framework [5] provides for two of the framework [5] provides for two different models of admission
different models of admission control - centralized or distributed control - centralized or distributed Bandwidth Allocators.
Bandwidth Allocators.
It is important to note that in this approach it is the admission It is important to note that in this approach it is the admission
Seaman,Smith,Crawley,Wroclawski. Expires February 1999 [Page
6]
control algorithm that determines which of the Int-Serv services is control algorithm that determines which of the Int-Serv services is
being offered. Given a set of priority classes with delay targets, a being offered. Given a set of priority classes with delay targets, a
relatively simple admission control algorithm can place flows into relatively simple admission control algorithm can place flows into
classes so that the bandwidth and delay behavior experienced by each classes so that the bandwidth and delay behavior experienced by each
flow corresponds to the requirements of the Controlled-Load service, flow corresponds to the requirements of the Controlled-Load service, but
but cannot offer the higher assurance of the Guaranteed service. To cannot offer the higher assurance of the Guaranteed service. To offer
offer the Guaranteed service, the admission control algorithm must be the Guaranteed service, the admission control algorithm must be much
much more stringent in its allocation of resources, and must also more stringent in its allocation of resources, and must also compute the
compute the C and D error terms required of this service. C and D error terms required of this service.
A delay bound can only be realized at the admission control element A delay bound can only be realized at the admission control element
itself so any delay numbers attached to a traffic class represent the itself so any delay numbers attached to a traffic class represent the
delay that a single element can allow for. That element may delay that a single element can allow for. That element may represent a
represent a whole L2 domain or just a single L2 segment. whole L2 domain or just a single L2 segment.
With either admission control model, the delay bound has no scope With either admission control model, the delay bound has no scope
outside of a L2 domain. The only requirement is that it be understood outside of a L2 domain. The only requirement is that it be understood by
by all Bandwidth Allocators in the L2 domain and, for example, be all Bandwidth Allocators in the L2 domain and, for example, be exported
exported as C and D terms to L3 devices implementing the Guaranteed as C and D terms to L3 devices implementing the Guaranteed Service.
Service. Thus, the end-to-end delay experienced by a flow can only be Thus, the end-to-end delay experienced by a flow can only be
characterized by summing along the path using the usual RSVP characterized by summing along the path using the usual RSVP mechanisms.
mechanisms.
3.2. Default service mappings 3.2. Default service mappings
Table 1 presents the default mapping from delay targets to IEEE 802.1 Table 1 presents the default mapping from delay targets to IEEE 802.1
user_priority classes. However, these mappings must be viewed as user_priority classes. However, these mappings must be viewed as
defaults, and must be changeable. defaults, and must be changeable.
In order to simplify the task of changing mappings, this mapping In order to simplify the task of changing mappings, this mapping table
table is held by *switches* (and routers if desired) but generally is held by *switches* (and routers if desired) but generally not by end-
not by end-station hosts. It is a read-write table. The values station hosts. It is a read-write table. The values proposed below are
proposed below are defaults and can be overridden by management defaults and can be overridden by management control so long as all
control so long as all switches agree to some extent (the required switches agree to some extent (the required level of agreement requires
level of agreement requires further analysis). further analysis).
In future networks this mapping table might be adjusted dynamically In future networks this mapping table might be adjusted dynamically and
and without human intervention. It is possible that some form of without human intervention. It is possible that some form of network-
network-wide lookup service could be implemented that serviced wide lookup service could be implemented that serviced requests from
requests from clients e.g. traffic_class = getQoSbyName("H.323 clients e.g. traffic_class = getQoSbyName("H.323 video") and notified
video") and notified switches of what traffic categories they were switches of what traffic categories they were likely to encounter and
likely to encounter and how to allocate those requests into traffic how to allocate those requests into traffic classes. Alternatively, the
classes. Alternatively, the network's admission control mechanisms network's admission control mechanisms might directly adjust the mapping
might directly adjust the mapping table to maximize the utilization table to maximize the utilization of network resources. Such mechanisms
are for further study.
Seaman,Smith,Crawley,Wroclawski. Expires February 1999 [Page The delay bounds numbers proposed in Table 1 are for per-Bandwidth
7] Allocator element delay targets and are derived from a subjective
of network resources. Such mechanisms are for further study. analysis of the needs of typical delay-sensitive applications e.g.
voice, video. See Annex H of [2] for further discussion of the selection
of these values. Although these values appear to address the needs of
current video and voice technology, it should be noted that there is no
requirement to adhere to these values and no dependence of IEEE 802.1 on
these values.
user_priority Service user_priority Service
0 Default, assumed to be Best Effort 0 Default, assumed to be Best Effort
1 reserved, "less than" Best Effort 1 reserved, "less than" Best Effort
2 reserved 2 reserved
3 reserved 3 reserved
4 Delay Sensitive, no bound 4 Delay Sensitive, no bound
5 Delay Sensitive, 100ms bound 5 Delay Sensitive, 100ms bound
6 Delay Sensitive, 10ms bound 6 Delay Sensitive, 10ms bound
7 Network Control 7 Network Control
Table 1 - Example user_priority to service mappings Table 1 - Example user_priority to service mappings
skipping to change at page 9, line ? skipping to change at page 8, line 18
1 reserved, "less than" Best Effort 1 reserved, "less than" Best Effort
2 reserved 2 reserved
3 reserved 3 reserved
4 Delay Sensitive, no bound 4 Delay Sensitive, no bound
5 Delay Sensitive, 100ms bound 5 Delay Sensitive, 100ms bound
6 Delay Sensitive, 10ms bound 6 Delay Sensitive, 10ms bound
7 Network Control 7 Network Control
Table 1 - Example user_priority to service mappings Table 1 - Example user_priority to service mappings
The delay bounds numbers proposed above are for per-Bandwidth
Allocator element delay targets and are derived from a subjective
analysis of the needs of typical delay-sensitive applications e.g.
voice, video. See Annex H of [2] for further discussion of the
selection of these values. Although these values appear to address
the needs of current video and voice technology, it should be noted
that there is no requirement to adhere to these values and no
dependence of IEEE 802.1 on these values.
Note: These mappings are believed to be useful defaults but further Note: These mappings are believed to be useful defaults but further
implementation and usage experience is required. The mappings may be implementation and usage experience is required. The mappings may be
refined in future editions of this document. refined in future editions of this document.
With this example set of mappings, delay-sensitive, admission With this example set of mappings, delay-sensitive, admission controlled
controlled traffic flows are mapped to user_priority values in traffic flows are mapped to user_priority values in ascending order of
ascending order of their delay bound requirement. Note that the their delay bound requirement. Note that the bounds are targets only -
bounds are targets only - see [5] for a discussion of the effects of see [5] for a discussion of the effects of other non-conformant flows on
other non-conformant flows on delay bounds of other flows. Only by delay bounds of other flows. Only by applying admission control to
applying admission control to higher-priority classes can any higher-priority classes can any promises be made to lower-priority
promises be made to lower-priority classes. classes.
This set of mappings also leaves several classes as reserved for This set of mappings also leaves several classes as reserved for future
future definition. definition.
Note: this mapping does not dictate what mechanisms or algorithms a Note: this mapping does not dictate what mechanisms or algorithms a
network element (e.g. an Ethernet switch) must perform to implement network element (e.g. an Ethernet switch) must perform to implement
these mappings: this is an implementation choice and does not matter these mappings: this is an implementation choice and does not matter
so long as the requirements for the particular service model are met. so long as the requirements for the particular service model are
met.
Note: these mappings apply primarily to networks constructed from Note: these mappings apply primarily to networks constructed from
devices that implement the priority-scheduling behavior defined as devices that implement the priority-scheduling behavior defined as
Seaman,Smith,Crawley,Wroclawski. Expires February 1999 [Page
8]
the default in 802.1D. Some devices may implement more complex the default in 802.1D. Some devices may implement more complex
scheduling behaviors not based only on priority. In that circumstance scheduling behaviors not based only on priority. In that
these mappings might still be used, but other, more specialized circumstance these mappings might still be used, but other, more
mappings may be more appropriate. specialized mappings may be more appropriate.
3.3. Discussion 3.3. Discussion
The recommendation of classes 4, 5 and 6 for Delay Sensitive, The recommendation of classes 4, 5 and 6 for Delay Sensitive, Admission
Admission Controlled flows is somewhat arbitrary; any classes with Controlled flows is somewhat arbitrary; any classes with priorities
priorities greater than that assigned to Best Effort can be used. greater than that assigned to Best Effort can be used. Those proposed
Those proposed here have the advantage that, for transit through here have the advantage that, for transit through 802.1D switches with
802.1D switches with only two-level strict priority queuing, all only two-level strict priority queuing, all delay-sensitive traffic gets
delay-sensitive traffic gets "high priority" treatment (the 802.1D "high priority" treatment (the 802.1D default split is 0-3 and 4-7 for a
default split is 0-3 and 4-7 for a device with 2 queues). device with 2 queues).
The choice of the delay bound targets is tuned to an average expected The choice of the delay bound targets is tuned to an average expected
application mix, and might be retuned by a network manager facing a application mix, and might be retuned by a network manager facing a
widely different mix of user needs. The choice is potentially very widely different mix of user needs. The choice is potentially very
significant: wise choice can lead to a much more efficient allocation significant: wise choice can lead to a much more efficient allocation of
of resources as well as greater (though still not very good) resources as well as greater (though still not very good) isolation
isolation between flows. between flows.
Placing Network Control traffic at class 7 is necessary to protect Placing Network Control traffic at class 7 is necessary to protect
important traffic such as route updates and network management. important traffic such as route updates and network management.
Unfortunately, placing this traffic higher in the user_priority Unfortunately, placing this traffic higher in the user_priority ordering
ordering causes it to have a direct effect on the ability of devices causes it to have a direct effect on the ability of devices to provide
to provide assurances to QoS controlled application traffic. assurances to QoS controlled application traffic. Therefore, an estimate
Therefore, an estimate of the amount of Network Control traffic must of the amount of Network Control traffic must be made by any device that
be made by any device that is performing admission control (e.g. is performing admission control (e.g. SBMs). This would be in terms of
SBMs). This would be in terms of the parameters that are normally the parameters that are normally taken into account by the admission
taken into account by the admission control algorithm. This estimate control algorithm. This estimate should be used in the admission control
should be used in the admission control decisions for the lower decisions for the lower classes (the estimate is likely to be a
classes (the estimate is likely to be a configuration parameter of configuration parameter of SBMs).
SBMs).
A traffic class such as class 1 for "less than best effort" might be A traffic class such as class 1 for "less than best effort" might be
useful for devices that wish to dynamically "penalty tag" all of the useful for devices that wish to dynamically "penalty tag" all of the
data of flows that are presently exceeding their allocation or Tspec. data of flows that are presently exceeding their allocation or Tspec.
This provides a way to isolate flows that are exceeding their service This provides a way to isolate flows that are exceeding their service
limits from flows that are not, to avoid reducing the QoS delivered limits from flows that are not, to avoid reducing the QoS delivered to
to flows that are within their contract. Data from such tagged flows flows that are within their contract. Data from such tagged flows might
might also be preferentially discarded by an overloaded downstream also be preferentially discarded by an overloaded downstream device.
device.
9
9 Seaman,Smith,Crawley,Wroclawski. Expires February 1999 A somewhat simpler approach would be to tag only the portion of a flow's
A somewhat simpler approach would be to tag only the portion of a packets that actually exceed the Tspec at any given instant as low
flow's packets that actually exceed the Tspec at any given instant as priority. However, it is often considered to be a bad idea to treat
low priority. However, it is often considered to be a bad idea to flows in this way as it will likely cause significant re-ordering of the
treat flows in this way as it will likely cause significant re- flow's packets, which is not desirable. Note that the default 802.1D
ordering of the flow's packets, which is not desirable. Note that the treatment of user_priorities 1 and 2 is "less than" the default class 0.
default 802.1D treatment of user_priorities 1 and 2 is "less than"
the default class 0.
4. Computation of integrated services characterization parameters by 4. Computation of integrated services characterization parameters by
IEEE 802 devices IEEE 802 devices
The integrated service model requires that each network element that The integrated service model requires that each network element that
supports integrated services compute and make available certain supports integrated services compute and make available certain
"characterization parameters" describing the element's behavior. "characterization parameters" describing the element's behavior. These
These parameters may be either generally applicable or specific to a parameters may be either generally applicable or specific to a
particular QoS control service. These parameters may be computed by particular QoS control service. These parameters may be computed by
calculation, measurement, or estimation. When a network element calculation, measurement, or estimation. When a network element cannot
cannot compute its own parameters (for example, a simple link), we compute its own parameters (for example, a simple link), we assume that
assume that the device sending onto or receiving data from the link the device sending onto or receiving data from the link will compute the
will compute the link's parameters as well as it's own. link's parameters as well as it's own. The accuracy of calculation of
these parameters may not be very critical; in some cases loose estimates
The accuracy of calculation of these parameters may not be very are all that is required to provide a useful service. This is important
critical; in some cases loose estimates are all that is required to in the IEEE 802 case, where it will be virtually impossible to compute
provide a useful service. This is important in the IEEE 802 case, parameters accurately for certain topologies and switch technologies.
where it will be virtually impossible to compute parameters Indeed, it is an assumption of the use of this model by relatively
accurately for certain topologies and switch technologies. Indeed, it simple switches (see [5] for a discussion of the different types of
is an assumption of the use of this model by relatively simple switch functionality that might be expected) that they merely provide
switches (see [5] for a discussion of the different types of switch values to describe the device and admit flows conservatively. The
functionality that might be expected) that they merely provide values discussion below presents a general outline for the computation of these
to describe the device and admit flows conservatively. parameters, and points out some cases where the parameters must be
computed accurately. Further specification of how to export these
The discussion below presents a general outline for the computation parameters is for further study.
of these parameters, and points out some cases where the parameters
must be computed accurately. Further specification of how to export
these parameters is for further study.
4.1. General characterization parameters 4.1. General characterization parameters
There are some general parameters [9] that a device will need to use There are some general parameters [9] that a device will need to use
and/or supply for all service types: and/or supply for all service types:
* Ingress link * Ingress link
Seaman,Smith,Crawley,Wroclawski. Expires February 1999 [Page * Egress links and their MTUs, framing overheads and minimum packet
10] sizes (see media-specific information presented above).
* Egress links and their MTUs, framing overheads and minimum
packet sizes (see media-specific information presented above).
* available path bandwidth: updated hop-by-hop by any device along * Available path bandwidth: updated hop-by-hop by any device along the
the path of the flow. path of the flow.
* minimum latency * Minimum latency
Of these parameters, the MTU and minimum packet size information Of these parameters, the MTU and minimum packet size information must be
must be reported accurately. Also, the "break bits" must be set reported accurately. Also, the "break bits" must be set correctly, both
correctly, both the overall bit that indicates the existence of the overall bit that indicates the existence of QoS control support and
QoS control support and the individual bits that specify support the individual bits that specify support for a particular scheduling
for a particular scheduling service. The available bandwidth
should be reported as accurately as possible, but very loose service. The available bandwidth should be reported as accurately as
estimates are acceptable. The minimum latency parameter should possible, but very loose estimates are acceptable. The minimum latency
be determined and reported as accurately as possible if the parameter should be determined and reported as accurately as possible if
element offers Guaranteed service, but may be loosely estimated the element offers Guaranteed service, but may be loosely estimated or
or reported as zero if the element offers only Controlled-Load reported as zero if the element offers only Controlled-Load service.
service.
4.2. Parameters to implement Guaranteed Service 4.2. Parameters to implement Guaranteed Service
A network element supporting the Guaranteed Service must be able to A network element supporting the Guaranteed Service must be able to
determine the following parameters [7]: determine the following parameters [7]:
* Constant delay bound through this device (in addition to any * Constant delay bound through this device (in addition to any value
value provided by "minimum latency" above) and up to the provided by "minimum latency" above) and up to the receiver at the
receiver at the next network element for the packets of this next network element for the packets of this flow if it were to be
flow if it were to be admitted. This includes any access admitted. This includes any access latency bound to the outgoing
latency bound to the outgoing link as well as propagation delay link as well as propagation delay across that link. This value is
across that link. This value is advertised as the "C" parameter advertised as the 'C' parameter of the Guaranteed Service.
of the Guaranteed Service.
* Rate-proportional delay bound through this device and up to the * Rate-proportional delay bound through this device and up to the
receiver at the next network element for the packets of this receiver at the next network element for the packets of this flow if
flow if it were to be admitted. This value is advertised as the it were to be admitted. This value is advertised as the 'D'
"D" parameter of the Guaranteed Service. parameter of the Guaranteed Service.
* Receive resources that would need to be associated with this * Receive resources that would need to be associated with this flow
flow (e.g. buffering, bandwidth) if it were to be admitted and (e.g. buffering, bandwidth) if it were to be admitted and not suffer
not suffer packet loss if it kept within its supplied packet loss if it kept within its supplied Tspec/Rspec. These values
Tspec/Rspec. These values are used by the admission control are used by the admission control algorithm to decide whether a new
algorithm to decide whether a new flow can be accepted by the flow can be accepted by the device.
device.
Seaman,Smith,Crawley,Wroclawski. Expires February 1999 [Page * Transmit resources that would need to be associated with this flow
11] (e.g. buffering, bandwidth, constant- and rate-proportional delay
* Transmit resources that would need to be associated with this bounds) if it were to be admitted. These values are used by the
flow (e.g. buffering, bandwidth, constant- and rate-proportional admission control algorithm to decide whether a new flow can be
delay bounds) if it were to be admitted. These values are used accepted by the device.
by the admission control algorithm to decide whether a new flow
can be accepted by the device.
The exported characterization parameters for this service should be The exported characterization parameters for this service should be
reported as accurately as possible. If estimations or approximations reported as accurately as possible. If estimations or approximations are
are used, they should err in whatever direction causes the user to used, they should err in whatever direction causes the user to receive
receive better performance than requested. For example, the C and D better performance than requested. For example, the C and D error terms
error terms should overestimate delay, rather than underestimate it. should overestimate delay, rather than underestimate it.
4.3. Parameters to implement Controlled Load 4.3. Parameters to implement Controlled Load
A network element implementing the Controlled Load service must be A network element implementing the Controlled Load service must be able
able to determine the following [6]: to determine the following [6]:
* Receive resources that would need to be associated with this * Receive resources that would need to be associated with this flow
flow (e.g. buffering) if it were to be admitted. These values (e.g. buffering) if it were to be admitted. These values are used by
are used by the admission control algorithm to decide whether a the admission control algorithm to decide whether a new flow can be
new flow can be accepted by the device. accepted by the device.
* Transmit resources that would need to be associated with this * Transmit resources that would need to be associated with this flow
flow (e.g. buffering) if it were to be admitted. These values (e.g. buffering) if it were to be admitted. These values are used by
are used by the admission control algorithm to decide whether a the admission control algorithm to decide whether a new flow can be
new flow can be accepted by the device. accepted by the device.
The Controlled Load service does not export any service-specific The Controlled Load service does not export any service-specific
characterization parameters. Internal resource allocation estimates characterization parameters. Internal resource allocation estimates
should ensure that the service quality remains high when considering should ensure that the service quality remains high when considering the
the statistical aggregation of Controlled Load flows into 802 traffic statistical aggregation of Controlled Load flows into 802 traffic
classes. classes.
4.4. Parameters to implement Best Effort 4.4. Parameters to implement Best Effort
For a network element that implements only best effort service there For a network element that implements only best effort service there are
are no explicit parameters that need to be characterized. Note that no explicit parameters that need to be characterized. Note that an
an integrated services aware network element that implements only integrated services aware network element that implements only best
best effort service will set the "break bit" described in [11]. effort service will set the "break bit" described in [11].
Seaman,Smith,Crawley,Wroclawski. Expires February 1999 [Page
12]
5. Merging of RSVP/SBM objects 5. Merging of RSVP/SBM objects
Where reservations that use the SBM protocol's TCLASS object [10] Where reservations that use the SBM protocol's TCLASS object [10] need
need to be merged, an algorithm needs to be defined that is to be merged, an algorithm needs to be defined that is consistent with
consistent with the mappings to individual user_priority values in the mappings to individual user_priority values in use in the Layer-2
use in the network. cloud. A merged reservation must receive at least as good a service as
the best of the component reservations.
A merged reservation must receive at least as good a service as the There is no single merging rule that can prevent all of the following
best of the component reservations. In the circumstances considered side-effects:
here, this translates into placing the merged reservation into the
lowest delay class of those that could be used for the individual
reservations.
For the example mappings proposed in this document, the merging * If a merger were to demote the existing branch of the flow into a
device should merge to the "highest" priority value of the values higher-delay traffic class then this is a denial of service to the
received in TCLASS objects of the PATH/RESV messages where "highest" existing flow which would likely receive worse service than before.
is defined as follows:
Lowest -------> Highest * If a merger were to promote the existing branch of the flow into a
1, 2, 0, 3, 4, 5, 6, 7 new, lower-delay, traffic class, this might then suffer either
admission control failures or may cost more in some sense than the
already-admitted flow. This can also be considered as a denial-of-
service attack.
Note: this counter-intuitive ordering is an artifact of the *default* * Promotion of the new branch may lead to rejection of the request
relative treatment of user_priority values in the IEEE 802.1D because it has been re-assigned to a traffic class that has not
specification (see Annex H of [2]). If a device has been configured enough resources to accommodate it.
to apply non-default treatment of user_priority values then it should
adjust this merging operation accordingly.
6. Applicability of these service mappings Therefore, such a merger is declared to be illegal and the usual SBM
admission control failure rules are applied. Traffic class selection is
performed based on the TSpec information. When the first RESV for a flow
arrives, a traffic class is chosen based on the request, an SBM TCLASS
object is inserted into the message and admission control for that
traffic class is done by the SBM. Reservation succeeds or fails as
usual.
Switches using layer-2-only standards (e.g. 802.1D-1990, 802.1D- When a second RESV for the same flow arrives at a different egress point
1998) need to inter-operate with routers and layer-3 switches. Wide of the Layer-2 cloud the process starts to repeat. Eventually the SBM-
deployment of such 802.1D-1998 switches will occur in a number of augmented RESV may hit a switch with an existing reservation in place
roles in the network: "desktop switches" provide dedicated 10/100 for the flow i.e. an L2 branch point for the flow. If so, the traffic
Mbps links to end stations and high speed core switches often act as class chosen for the second reservation is checked against the first. If
central campus switching points for layer-3 devices. Layer-2 devices they are the same, the RESV requests are merged and passed on towards
will have to operate in all of the following scenarios: the sender(s).
* every device along a network path is layer-3 capable and If the second TCLASS would have been different, an RSVP/SBM ResvErr
intrusive into the full data stream error is returned to the Layer-3 device that launched the second RESV
request into the Layer-2 cloud. This device will then pass on the
ResvErr to the original requester according to RSVP rules.
6. Applicability of these service mappings
Switches using layer-2-only standards (e.g. 802.1D-1990, 802.1D-1998)
need to inter-operate with routers and layer-3 switches. Wide deployment
of such 802.1D-1998 switches will occur in a number of roles in the
network: "desktop switches" provide dedicated 10/100 Mbps links to end
stations and high speed core switches often act as central campus
switching points for layer-3 devices. Layer-2 devices will have to
operate in all of the following scenarios:
* every device along a network path is layer-3 capable and intrusive
into the full data stream
* only the edge devices are pure layer-2 * only the edge devices are pure layer-2
Seaman,Smith,Crawley,Wroclawski. Expires February 1999 [Page
13]
* every alternate device lacks layer-3 functionality * every alternate device lacks layer-3 functionality
* most devices lack layer-3 functionality except for some key * most devices lack layer-3 functionality except for some key control
control points such as router firewalls, for example. points such as router firewalls, for example.
Where int-serv flows pass through equipment which does not support Where int-serv flows pass through equipment which does not support
Integrated Services or 802.1D traffic management and which places all Integrated Services or 802.1D traffic management and which places
packets through the same queuing and overload-dropping paths, it is all packets through the same queuing and overload-dropping paths, it
obvious that some of a flow's desired service parameters become more is obvious that some of a flow's desired service parameters become
difficult to support. In particular, the two integrated service more difficult to support. In particular, the two integrated service
classes studied here, Controlled Load and Guaranteed Service, both classes studied here, Controlled Load and Guaranteed Service, both
assume that flows will be policed and kept "insulated" from assume that flows will be policed and kept "insulated" from
misbehaving other flows or from best effort traffic during their misbehaving other flows or from best effort traffic during their
passage through the network. This cannot be done within an IEEE 802 passage through the network. This cannot be done within an IEEE 802
network using devices with the default user_priority function; in network using devices with the default user_priority function; in
this case policing must be approximated at the network edges. this case policing must be approximated at the network edges.
In addition, in order to provide a Guaranteed Service, *all* In addition, in order to provide a Guaranteed Service, *all*
switching elements along the path must participate in special switching elements along the path must participate in special
treatment for packets in such flows: where there is a "break" in treatment for packets in such flows: where there is a "break" in
guaranteed service, all bets are off. Thus, a network path that guaranteed service, all bets are off. Thus, a network path that
includes even a single switch transmitting onto a shared or half- includes even a single switch transmitting onto a shared or half-
duplex LAN segment is unlikely to be able to provide a very good duplex LAN segment is unlikely to be able to provide a very good
approximation to Guaranteed Service. For Controlled Load service, the approximation to Guaranteed Service. For Controlled Load service,
requirements on the switches and link types are less stringent the requirements on the switches and link types are less stringent
although it is still necessary to provide differential queueing and although it is still necessary to provide differential queueing and
buffering in switches for CL flows over best effort in order to buffering in switches for CL flows over best effort in order to
approximate CL service. Note that users receive indication of such approximate CL service. Note that users receive indication of such
breaks in the path through the "break bits" described in [11]. These breaks in the path through the "break bits" described in [11]. These
bits must be correctly set when IEEE 802 devices that cannot provide bits must be correctly set when IEEE 802 devices that cannot provide
a specific service exist in a network. a specific service exist in a network.
Other approaches might be to pass more information between switches Other approaches might be to pass more information between switches
about the capabilities of their neighbours and to route around non- about the capabilities of their neighbours and to route around non-
QoS-capable switches: such methods are for further study. And of QoS-capable switches: such methods are for further study. And of
course the easiest solution of all is to upgrade links and switches course the easiest solution of all is to upgrade links and switches
to higher capacities. to higher capacities.
Seaman,Smith,Crawley,Wroclawski. Expires February 1999 [Page
14]
7. References 7. References
[1] "MAC Bridges", ISO/IEC 10038, ANSI/IEEE Std 802.1D-1993 [1] "MAC Bridges", ISO/IEC 10038, ANSI/IEEE Std 802.1D-1993
[2] "Information technology - Telecommunications and information [2] "Information technology - Telecommunications and information
exchange between systems - Local and metropolitan area networks exchange between systems - Local and metropolitan area networks -
- Common specifications - Part 3: Media Access Control (MAC) Common specifications - Part 3: Media Access Control (MAC) Bridges:
Bridges: Revision (Incorporating IEEE P802.1p: Traffic Class Revision (Incorporating IEEE P802.1p: Traffic Class Expediting and
Expediting and Dynamic Multicast Filtering", ISO/IEC Final CD Dynamic Multicast Filtering", ISO/IEC Final CD 15802-3 IEEE
15802-3 IEEE P802.1D/D15, November 1997
[3] Clark, D. et al. "Integrated Services in the Internet Architecture:
[3] Clark, D. et al. "Integrated Services in the Internet
[4] Braden, R., L. Zhang, S. Berson, S. Herzog, S. Jamin, "Resource [4] Braden, R., L. Zhang, S. Berson, S. Herzog, S. Jamin, "Resource
Reservation Protocol (RSVP) - Version 1 Functional Reservation Protocol (RSVP) - Version 1 Functional Specification",
Specification", RFC 2205, September 1997 RFC 2205, September 1997
[5] Ghanwani, A., Pace, W., Srinivasan, V., Smith, A., Seaman, M., [5] Ghanwani, A., Pace, W., Srinivasan, V., Smith, A., Seaman, M., "A
"A Framework for Providing Integrated Services Over Shared and Framework for Providing Integrated Services Over Shared and
Switched LAN Technologies", Internet Draft, March 1998 <draft- Switched LAN Technologies", Internet Draft, May 1998 <draft-ietf-
ietf-issll-is802-framework-04> issll-is802-framework-05>
[6] Wroclawski, J., "Specification of the Controlled-Load Network [6] Wroclawski, J., "Specification of the Controlled-Load Network
Element Service", RFC 2211, September 1997 Element Service", RFC 2211, September 1997
[7] Schenker, S., Partridge, C., Guerin, R., "Specification of [7] Schenker, S., Partridge, C., Guerin, R., "Specification of
Guaranteed Quality of Service", RFC 2212 September 1997 Guaranteed Quality of Service", RFC 2212 September 1997
[8] [8] "IEEE Standards for Local and Metropolitan Area Networks: for
"IEEE Standards for Local and Metropolitan Area Networks: for Virtual Bridged Local Area Networks", July 1998, IEEE Draft
Virtual Bridged Local Area Networks", March 1998, IEEE Draft Standard P802.1Q/D11
Standard P802.1Q/D10
[9] Shenker, S., Wroclawski, J., "General Characterization [9] Shenker, S., Wroclawski, J., "General Characterization Parameters
Parameters for Integrated Service Network Elements", RFC 2215, for Integrated Service Network Elements", RFC 2215, September 1997
September 1997
[10] Yavatkar, R., Hoffman, D., Bernet, Y., Baker, F., Speer, M., [10] Yavatkar, R., Hoffman, D., Bernet, Y., Baker, F., Speer, M., "SBM
"SBM (Subnet Bandwidth Manager): A Protocol for Admission (Subnet Bandwidth Manager): A Protocol for Admission Control over
Control over IEEE 802-style Networks", Internet Draft, March IEEE 802-style Networks", Internet Draft, March 1998 <draft-ietf-
1998 <draft-ietf-issll-sbm-06> issll-sbm-06>
[11] Wroclawski, J., "The use of RSVP with IETF Integrated Services", [11] Wroclawski, J., "The use of RSVP with IETF Integrated Services",
RFC 2210, September 1997. RFC 2210, September 1997.
Seaman,Smith,Crawley,Wroclawski. Expires February 1999 [Page
15]
8. Security Considerations 8. Security Considerations
Any use of QoS requires examination of security considerations Any use of QoS requires examination of security considerations because
because it leaves the possibility open for denial of service or theft it leaves the possibility open for denial of service or theft of service
of service attacks. This document introduces no new security issues attacks. This document introduces no new security issues on top of those
on top of those discussed in the companion ISSLL documents [5] and discussed in the companion ISSLL documents [5] and [10]. Any use of
[10]. Any use of these service mappings assumes that all requests these service mappings assumes that all requests for service are
for service are authenticated appropriately. authenticated appropriately.
9. Acknowledgments 9. Acknowledgments
This document draws heavily on the work of the ISSLL WG of the IETF This document draws heavily on the work of the ISSLL WG of the IETF and
and the IEEE P802.1 Interworking Task Group. the IEEE P802.1 Interworking Task Group.
9. Authors' Addresses 10. Authors' addresses
Mick Seaman Mick Seaman
3Com Corp. 3Com Corp.
5400 Bayfront Plaza 5400 Bayfront Plaza
Santa Clara CA 95052-8145 Santa Clara CA 95052-8145
USA USA
+1 (408) 764 5000 +1 (408) 764 5000
mick_seaman@3com.com mick_seaman@3com.com
Andrew Smith Andrew Smith
skipping to change at line 721 skipping to change at page 16, line 42
Cupertino CA 95014 Cupertino CA 95014
USA USA
+1 (408) 863 2821 +1 (408) 863 2821
andrew@extremenetworks.com andrew@extremenetworks.com
Eric Crawley Eric Crawley
Argon Networks Argon Networks
25 Porter Rd. 25 Porter Rd.
Littleton MA 01460 Littleton MA 01460
USA USA
+1 (978) 486 0665 +1 (508) 486 0665
esc@argon.com esc@argon.com
Seaman,Smith,Crawley,Wroclawski. Expires February 1999 [Page
16]
John Wroclawski John Wroclawski
MIT Laboratory for Computer Science MIT Laboratory for Computer Science
545 Technology Sq. 545 Technology Sq.
Cambridge, MA 02139 Cambridge, MA 02139
USA USA
+1 (617) 253 7885 +1 (617) 253 7885
jtw@lcs.mit.edu jtw@lcs.mit.edu
Table of Contents Table of Contents
1 Introduction ................................................. 2 1 Introduction .................................................... 2
2 Flow Identification and Traffic Class Selection .............. 3 2 Flow Identification and Traffic Class Selection ................. 3
3 Choosing a flow's IEEE 802 user_priority class ............... 5 3 Choosing a flow's IEEE 802 user_priority class .................. 5
3.1 Context of admission control and delay bounds .............. 6 3.1 Context of admission control and delay bounds ................. 6
3.2 Default service mappings ................................... 7 3.2 Default service mappings ...................................... 7
3.3 Discussion ................................................. 9 3.3 Discussion .................................................... 9
4 Computation of integrated services characterization 4 Computation of integrated services characterization parameters
parameters by IEEE 802 devices ............................ 10 by IEEE 802 devices .......................................... 10
4.1 General characterization parameters ........................ 10 4.1 General characterization parameters ........................... 10
4.2 Parameters to implement Guaranteed Service ................. 11 4.2 Parameters to implement Guaranteed Service .................... 11
4.3 Parameters to implement Controlled Load .................... 12 4.3 Parameters to implement Controlled Load ....................... 12
4.4 Parameters to implement Best Effort ........................ 12 4.4 Parameters to implement Best Effort ........................... 12
5 Merging of RSVP/SBM objects .................................. 13 5 Merging of RSVP/SBM objects ..................................... 12
6 Applicability of these service mappings ...................... 13 6 Applicability of these service mappings ......................... 13
7 References ................................................... 15 7 References ...................................................... 14
8 Security Considerations ...................................... 16 8 Security Considerations ......................................... 16
9 Authors' Addresses ........................................... 16 9 Acknowledgments ................................................. 16
10 Authors' addresses ............................................. 16
Seaman,Smith,Crawley,Wroclawski. Expires February 1999 [Page Copyright (C) The Internet Society (date). All Rights Reserved.
17]
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be revoked by the Internet Society or its successors or
assigns.
This document and the information contained herein is provided This document and the information contained herein is provided on
on
an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR
PURPOSE.
Seaman,Smith,Crawley,Wroclawski. Expires February 1999 [Page
18]
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