draft-ietf-issll-atm-mapping-00.txt   draft-ietf-issll-atm-mapping-01.txt 
INTERNET-DRAFT Marty Borden, INTERNET-DRAFT Mark W. Garrett,
Bay Networks, Bellcore
Mark W. Garrett,
Bellcore. Marty Borden,
September, 1996. New Oak, Inc.
November, 1996.
Interoperation of Controlled-Load and Guaranteed-Service with ATM Interoperation of Controlled-Load and Guaranteed-Service with ATM
<draft-ietf-issll-atm-mapping-00.txt> <draft-ietf-issll-atm-mapping-01.txt>
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
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and its working groups. Note that other groups may also distribute and its working groups. Note that other groups may also distribute
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Abstract Abstract
Service mappings are an important aspect of effective interoperation Service mappings are an important aspect of effective interoperation
between Internet Integrated Services and ATM networks. Both Internet between Internet Integrated Services and ATM networks. Both Internet
and ATM technologies have well-defined service architectures. In and ATM technologies have well-defined service architectures. These
each, a small number of services are identified, with behavioral include definitions of several services and associated parameters
descriptions and related parameters to quantify network traffic and which quantify source traffic and Quality of Service (QoS)
Quality of Service (QoS). requirements.
This draft provides mappings between the services of each technology, This draft provides mappings between IP and ATM services which will
in order to facilitate effective end-to-end Quality of Service in the facilitate effective end-to-end Quality of Service for IP networks
case where ATM subnetwork technology occurs in the path between containing ATM subnetworks. We discuss the various features of
Internet end systems. Specifically, it identifies the types of ATM Guaranteed Service and Controlled Load Service, and identify
Virtual Circuits (VCs) which can be utilized for each of the two appropriate mechanisms in ATM Virtual Circuits (VCs), which
currently defined IP services. A detailed discussion is given of the facilitate these services.
accompanying parameters and options, and the interactions between the
two models. Some of the text may be considered preliminary 0.0 What's New in This Version
discussion and is expected to be refined as this draft evolves into a
proper specification. Section 3.2 on use of AdSpec in Guaranteed Service.
Expanded Section 2.5 on traffic descriptor mapping.
Placeholder Section 3.1 on handling of excess traffic
Mention of new I.356 version, which changes ITU QoS class definitions.
General cleanup of text.
1.0 Introduction 1.0 Introduction
We consider the problem of providing IP Integrated Services [RFC1633] We consider the problem of providing IP Integrated Services [1] with
with an ATM subnetwork. We assume the use of the rsvp protocol an ATM subnetwork. This document is intended to be consistent with
[RSVP] for IP-level resource reservation. In the ATM network, we the rsvp protocol [2] for IP-level resource reservation (although it
consider ATM Forum UNI Signaling, versions 3.0, 3.1 and 4.0 [UNI3.0, is independent of rsvp to the extent that GS and CLS services could
UNI3.1, UNI4.0]. The latter uses the more complete service model of be supported through another mechanism). In the ATM network, we
The ATM Forum's TM 4.0 specification [TM40, ATMsvc]. consider ATM Forum UNI Signaling, versions 3.0, 3.1 and 4.0 [3, 4,
5]. The latter uses the more complete service model of The ATM
Forum's TM 4.0 specification [6, 7].
This is a complex problem with many facets. In this draft, we focus This is a complex problem with many facets. In this draft, we focus
on the service types, parameters and signalling elements needed for on the service types, parameters and signalling elements needed for
service interoperation. The resulting service mappings can be used service interoperation. The resulting service mappings can be used
to provide effective end-to-end Quality of Service (QoS) for IP to provide effective end-to-end Quality of Service (QoS) for IP
traffic that traverses ATM networks. traffic that traverses ATM networks.
The IP services considered are Guaranteed Service [GS] and Controlled The IP services considered are Guaranteed Service (GS) [8] and
Load Service [CLS]. We also treat the default Best Effort Service Controlled Load Service (CLS) [9]. We also treat the default Best
(BE) in parallel with these. Our recommendations for BE are intended Effort Service (BE) in parallel with these. Our recommendations for
to be consistent with RFC 1755 [RFC1755], which defines how ATM VCs BE are intended to be consistent with RFC 1755 [10], and its revision
can be used in support of normal BE IP service. The ATM services we (still in progress) [11], which defines how ATM VCs can be used in
consider are: support of normal BE IP service. The ATM services we consider are:
CBR Constant Bit Rate CBR Constant Bit Rate
rtVBR Real-time Variable Bit Rate rtVBR Real-time Variable Bit Rate
nrtVBR Non-real-time Variable Bit Rate nrtVBR Non-real-time Variable Bit Rate
UBR Unspecified Bit Rate UBR Unspecified Bit Rate
ABR Available Bit Rate ABR Available Bit Rate
In the case of UNI 3.0 and 3.1 signaling, where these service are not (Note, Appendix 1 provides definitions for all abbreviations.) In
the case of UNI 3.0 and 3.1 signaling, where these service are not
all clearly distinguishable, we identify equivalent services where all clearly distinguishable, we identify equivalent services where
possible. possible.
The service mappings which follow most naturally from their The service mappings which follow most naturally from the service
definitions are as follows: definitions are as follows:
Guaranteed Service -> CBR or rtVBR Guaranteed Service -> CBR or rtVBR
Controlled Load -> nrtVBR or ABR (with a minimum cell rate) Controlled Load -> nrtVBR or ABR (with a minimum cell rate)
Best Effort -> UBR or ABR Best Effort -> UBR or ABR
However, for completeness we provide detailed mappings for all For completeness we provide detailed mappings for all service
service combinations and identify how each meets or fails to meet the combinations and identify how each meets or fails to meet the
requirements of the higher level IP services. A number of details, requirements of the higher level IP services. The reason for not
such as treatment of packets in excess of the flow traffic restricting mappings to the most obvious or natural ones is that we
descriptor, make service mapping a complicated subject, which cannot cannot assume now that these services will always be ubiquitously
be expressed briefly and accurately at the same time. available. A number of details, such as treatment of packets in
excess of the flow traffic descriptor, make service mapping a
complicated subject, which cannot be expressed briefly and accurately
at the same time.
The remainder of this introduction provides a general discussion of The remainder of this introduction provides a general discussion of
the system configuration and other assumptions. Section 2 considers the system configuration and other assumptions. Section 2 considers
the relevant ATM protocol elements and their effects as related to the relevant ATM protocol elements and their effects as related to
Guaranteed, Controlled Load and Best Effort services (the latter Guaranteed, Controlled Load and Best Effort services (the latter
being the default "service"). Section 3 discusses a number of being the default "service"). Section 3 discusses a number of
important features of the IP services and how they can be handled on important features of the IP services and how they can be handled on
an ATM subnetwork. Section 4 gives detailed VC setup parameters for an ATM subnetwork. Section 4 addresses a few miscellaneous problems
Guaranteed Service, and considers the effect of using each of the ATM which are neither distinctly IP nor ATM. Section 5 gives detailed VC
service categories. Section 5 provides a similar treatment for setup parameters for Guaranteed Service, and considers the effect of
Controlled Load Service. Section 6 considers Best Effort service. using each of the ATM service categories. Section 6 provides a
similar treatment for Controlled Load Service. Section 7 considers
Best Effort service.
This document is only a part of the total solution to providing the This document is only a part of the total solution to providing the
interworking of IP integrated services with ATM subnetworks. We do interworking of IP integrated services with ATM subnetworks. The
not consider the important issues of when ATM VCs should be created important issue of VC management, including flow aggregation, is
or destroyed, how they should be used or coordinated, or of how considered in [12]. We do not consider how routing -- QoS sensitive
routing -- QoS sensitive or not -- interacts with the use of VCs, or not -- interacts with the use of VCs, especially in the case of
especially in the case of multicast (or point-to-multipoint) flows. multicast (or point-to-multipoint) flows. We expect that a
considerable degree of implementation latitude will exist, even
within the guidelines presented here. Many aspects of interworking
between IP and ATM will depend on economic factors, and will not be
subject to standardization.
1.1 General System Architecture 1.1 General System Architecture
The network architecture we consider is illustrated in Figure 1, We assume that the reader has a general working knowledge of IP, rsvp
below. An IP-attached host may send unicast datagrams to another and ATM protocols. The network architecture we consider is
host, or may use an IP multicast address to send packets to all of illustrated in Figure 1, below. An IP-attached host may send unicast
the hosts which have "joined" the multicast "tree". In either case, datagrams to another host, or may use an IP multicast address to send
any destination host may use RSVP to establish resource reservation packets to all of the hosts which have "joined" the multicast "tree".
in routers along the internet path for the data flow. In either case, a destination host may then use RSVP to establish
resource reservation in routers along the internet path for the data
flow.
An ATM network lies in the path (chosen by the IP routing), and An ATM network lies in the path (chosen by the IP routing), and
consists of one or many ATM switches. It uses VCs to provide both consists of one or many ATM switches. It uses VCs to provide both
resources and QoS within the ATM cloud. These connections are set resources and QoS within the ATM cloud. These connections are set
up, added to (in the case of multipoint trees), torn down, and up, added to (in the case of multipoint trees), torn down, and
controlled by the edge devices, which act as both IP routers and ATM controlled by the edge devices, which act as both IP routers and ATM
interfaces, capable of initiating and managing VCs across the ATM interfaces, capable of initiating and managing VCs across the ATM
user-to-network (UNI) interface. The edge devices are assumed to be user-to-network (UNI) interface. The edge devices are assumed to be
fully functional in both the IP int-serv/RSVP protocols and the ATM fully functional in both the IP int-serv/RSVP protocols and the ATM
UNI protocols, as well as translating between them. UNI protocols, as well as translating between them.
ATM Cloud ATM Cloud
------------------ ------------------
H ---\ ( ) /------- H H ---- ( ) /------- H
H ---- R -- R -- E --( ATM SW -- ATM SW ) -- E -- R -- R -- H H ---- R -- R -- E --( ATM Sw -- ATM Sw ) -- E -- R -- R -- H
H ---/ | ( ) \ H ----/ | ( ) (
| ------------------ ------- H | ------------------ ------- H
H ----------R H ----------R
Figure 1: Network Architecture with hosts (H), Figure 1: Network Architecture with hosts (H),
Routers (R) and Edge Devices (E). Routers (R) and Edge Devices (E).
The edge devices may be considered part of the IP internet or part of The edge devices may be considered part of the IP internet or part of
the ATM cloud, or both. This is not an issue since they must provide the ATM cloud, or both. This is not an issue since they must provide
capabilities of both environments. The edge devices have normal RSVP capabilities of both environments. The edge devices have normal RSVP
capability to process RSVP messages, reserve resources, and maintain capability to process RSVP messages, reserve resources, and maintain
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into ATM VC (UNI) semantics. into ATM VC (UNI) semantics.
A range of VC management policies are possible, which determine A range of VC management policies are possible, which determine
whether a flow should initiate a new VC or join an existing one. VCs whether a flow should initiate a new VC or join an existing one. VCs
are managed according to a combination of standards and local policy are managed according to a combination of standards and local policy
rules, which are specific to either the implementation (equipment) or rules, which are specific to either the implementation (equipment) or
the operator (network service provider). Point-to-multipoint the operator (network service provider). Point-to-multipoint
connections within the ATM cloud can be used to support general IP connections within the ATM cloud can be used to support general IP
multicast flows. In ATM, a point to multipoint connection can be multicast flows. In ATM, a point to multipoint connection can be
controlled by the source (or root) node, or a leaf initiated join controlled by the source (or root) node, or a leaf initiated join
(LIJ) feature in ATM may be used. (Note, a longer section on VC (LIJ) feature in ATM may be used. Note, the topic of VC management
management will be written, either in as part of this draft or and mapping of flows onto VCs is considered at length in another
another one from the issll working group at some point. issll working group draft [12].
will be written, either in as part of this draft or another one from
the issll working group at some point.
Figure 2 shows the functions of an edge device, summarizing the work Figure 2 shows the functions of an edge device, summarizing the work
not part of IP or ATM abstractly as an InterWorking Function (IWF), not part of IP or ATM abstractly as an InterWorking Function (IWF),
and segregating the control and data planes. (Note: for expositional and segregating the control and data planes. (Note: for expositional
convenience, policy control and other control functions are included convenience, policy control and other control functions are included
as part of the admission control in the diagram.) as part of the admission control in the diagram.)
IP ATM IP ATM
____________________ ____________________
| IWF | | IWF |
| | | |
admission <--> | service mapping | <--> ATM admission <--> | service mapping | <--> ATM
control | VC management | signalling & control | VC management | signalling &
| address resolution | admission | address resolution | admission
|....................| control |....................| control
| | | |
classification/ | ATM Adaption Layer | cell classification/ |ATM Adaptation Layer| cell
policing & <--> | Segmentation and | <--> scheduling/ policing & <--> | Segmentation and | <--> scheduling/
scheduling | Reassembly | shaping scheduling | Reassembly | shaping
| Buffering | | Buffering |
____________________ ____________________
Figure 2: Edge Device Functions showing the IWF Figure 2: Edge Device Functions showing the IWF
In the logical view of Figure 2, some functions, such as scheduling, In the logical view of Figure 2, some functions, such as scheduling,
are shown separately, since these functions are required of both the are shown separately, since these functions are required of both the
IP and ATM sides. However it may be possible in an integrated IP and ATM sides. However it may be possible in an integrated
implementation to combine such functions. implementation to combine such functions.
It is not possible to completely separate the service mapping and VC It is not possible to completely separate the service mapping and VC
management functions. Several illustrative examples come to mind: management functions. Several illustrative examples come to mind:
(i) Multiple integrated-services flows may be aggregated to use one (i) Multiple integrated-services flows may be aggregated to use one
point-to-multipoint VC. In this case, we assume the IP flows are of point-to-multipoint VC. In this case, we assume the IP flows are of
the same service type and their parameters have been merged the same service type and their parameters have been merged
appropriately. (ii) The VC management function may choose to appropriately. (ii) The VC management function may choose to
allocate extra resources in anticipation of further reservations or allocate extra resources in anticipation of further reservations or
based on an empiric of changing TSpecs. In this case we can assume based on an empiric of changing TSpecs. (iii) There must exist a
that the additional resources are still specifiable in the form of a path for best effort flows and for sending the rsvp control messages.
TSpec, which can be mapped using the same algorithm. (iii) There How this interacts with the establishment of VCs for QoS traffic may
must exist a path for best effort flows and for sending the rsvp alter the characteristics required of those VCs. See [12] for
control messages. How this interacts with the establishment of VCs further details on VC management.
for QoS traffic may alter the characteristics required of those VCs.
Therefore, in discussing the service-mapping problem, we will assume Therefore, in discussing the service-mapping problem, we will assume
that the VC management function of the IWF can always express its that the VC management function of the IWF can always express its
result in terms of an IP-level service with some QoS and TSpec. The result in terms of an IP-level service with some QoS and TSpec. The
service mapping algorithm, which is the subject of this draft, can service mapping algorithm, which is the subject of this draft, can
then identify the appropriate VC parameters, whether the resulting then identify the appropriate VC parameters, whether the resulting
action is initiation of a new VC, the addition/deletion of a leaf to action is initiation of a new VC, the addition/deletion of a leaf to
an existing multipoint tree, or the modification of an existing VC to an existing multipoint tree, or the modification of an existing VC to
one of another description. one of another description.
1.2 Related documents 1.2 Related Documents
Earlier ATM Forum documents were called UNI 3.0 and UNI 3.1. The 3.1 Earlier ATM Forum documents were called UNI 3.0 and UNI 3.1. The 3.1
release was used to correct errors and fix alignment with the ITU. release was used to correct errors and fix alignment with the ITU.
Unfortunately UNI 3.0 and 3.1 are incompatible. However this is in Unfortunately UNI 3.0 and 3.1 are incompatible. However this is in
terms of actual codepoints, not semantics. Therefore, descriptions terms of actual codepoints, not semantics. Therefore, descriptions
of parameter values can generally be used for both. of parameter values can generally be used for both.
After 3.1, the ATM Forum decided to release documents separately for After 3.1, the ATM Forum decided to release documents separately for
each technical subcommittee. The Traffic Management and Signalling each technical working group. The Traffic Management and Signalling
4.0 documents are available publically at ftp.atmforum.com/pub. We 4.0 documents are available publically at ftp.atmforum.com/pub. We
refer to the combination of traffic management and signalling as refer to the combination of traffic management and signalling as
TM/UNI 4.0, although specific references may be made to the TM 4.0 TM/UNI 4.0, although specific references may be made to the TM 4.0
specification or the UNI SIG 4.0 specification. specification or the UNI SIG 4.0 specification.
Within the IETF area, related material includes: Within the IETF area, related material includes the work of the rsvp
[2], int-serv [1, 8, 9, 13, 14] and ion working groups [10, 11] of
RSVP functional specification, the IETF. Rsvp defines the resource reservation protocol (which is
Guaranteed Service specification, analogous to signaling in ATM). Int-serv defines the behavior and
Controlled Load service specification, semantics of particular services (analogous e.g., to the Traffic
Int-serv data encoding specification, Management working group in the ATM Forum). Ion defines interworking
RFC 1577, of IP and ATM for traditional Best Effort service, and covers all
RFC 1755, issues related to routing and addressing.
RFC 1821,
draft-crawley-rsvp-over-atm,
draft-birman-ipatm-rsvpatm,
draft-onvural-srinivasan-rsvp-atm.
1.3 Abbreviations
ABR Available Bit Rate RFC 1821 [15], represent an early discussions of issues involved with
BCOB Broadband Connection-Oriented Bearer Capability interoperating IP and ATM protocols for integrated services and QoS.
BCOB-{A,C,X} Bearer Class A, C, or X
BE Best Effort
BT Burst Tolerance
CBR Constant Bit Rate
CDV Cell Delay Variation
CDVT Cell Delay Variation Tolerance
CLS Controlled Load Service
CLP Cell Loss Priority (bit)
CLR Cell Loss Ratio
CTD Cell Transfer Delay
GS Guaranteed Service
IWF Interworking Function
MBS Maximum Burst Size
MCR Minimum Cell Rate
PCR Peak Cell Rate
SCR Sustained Cell Rate
UBR Unspecified Bit Rate
VBR Variable Bit Rate
nrtVBR Non-real-time VBR
rtVBR Real-time VBR
2.0 Discussion of Relevant ATM Protocol Features 2.0 Discussion of ATM Protocol Features
In this section, we discuss each of the items that must be specified In this section, we discuss each of the items that must be specified
in the setup of an ATM VC. For each of these we discuss which in the setup of an ATM VC. For each of these we discuss which
specified items and values may be most appropriate for each of the specified items and values may be most appropriate for each of the
integrated services. three integrated services.
The ATM Call Setup is sent by the edge device to the ATM network to The ATM Call Setup is sent by the edge device to the ATM network to
establish end-to-end [ATM] service. This setup contains the establish end-to-end (ATM) service. This setup contains the
following information. following information.
Service Category/Broadband Bearer Capability Service Category/Broadband Bearer Capability
AAL Parameters AAL Parameters
Broadband Low Layer Information Broadband Low Layer Information
Calling and Called Party Addressing Information Calling and Called Party Addressing Information
Traffic Descriptors Traffic Descriptors
QoS Parameters QoS Parameters
Additional Parameters of TM/UNI 4.0 Additional Parameters of TM/UNI 4.0
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we require -- see below) it can be used interchangeably and we require -- see below) it can be used interchangeably and
consistently with the above two capabilities. consistently with the above two capabilities.
In TM/UNI 4.0 the service categories are: In TM/UNI 4.0 the service categories are:
Constant Bit Rate (CBR) Constant Bit Rate (CBR)
Real-time Variable Bit Rate (rtVBR) Real-time Variable Bit Rate (rtVBR)
Non-real-time Variable Bit Rate (nrtVBR) Non-real-time Variable Bit Rate (nrtVBR)
Unspecified Bit Rate (UBR) Unspecified Bit Rate (UBR)
Available Bit Rate (ABR) Available Bit Rate (ABR)
The first two of these are real-time services, so that rtVBR is new The first two of these are real-time services, so that rtVBR is new
to TM/UNI 4.0. The ABR service is also new to TM/UNI 4.0. UBR to TM/UNI 4.0. The ABR service is also new to TM/UNI 4.0. UBR
exists in all specifications, except perhaps in name, through the exists in all specifications, except perhaps in name, through the
``best effort'' indication flag and/or the QoS Class 0. ``best effort'' indication flag and/or the QoS Class 0.
The encoding used in 4.0 is consistent with the earlier versions. The encoding used in 4.0 is consistent with the earlier versions.
For example, the Service Category is indicated solely by the For example, the Service Category is indicated solely by the
combination of the Bearer Capabilty and the Best Effort indication combination of the Bearer Capability and the Best Effort indication
flag. flag.
In principle, it is possible to support any forseeable service In principle, it is possible to support any foreseeable service
through the use of BCOB-A/CBR. This is because the CBR service is through the use of BCOB-A/CBR. This is because the CBR service is
equivalent to having a ``pipe'' with specified bandwidth/timing. equivalent to having a ``pipe'' with specified bandwidth/timing.
However, it may be desirable to make better use of the ATM network's However, it may be desirable to make better use of the ATM network's
resources by using other, less demanding, services when available. resources by using other, less demanding, services when available.
(See RFC 1821 for a discussion of this.) (See RFC 1821 for a discussion of this [15].)
2.1.1 Service Categories for Guaranteed Service 2.1.1 Service Categories for Guaranteed Service
There are two possible mappings for GS: There are two possible mappings for GS:
CBR (BCOB-A) CBR (BCOB-A)
rtVBR rtVBR
GS requires real-time support, that is, timing is required. Thus in GS requires real-time support, that is, timing is required. Thus in
UNI 3.x, the bearer class BCOB-A (or an equivalent BCOB-X UNI 3.x, the bearer class BCOB-A (or an equivalent BCOB-X
formulation) must be used. In TM/UNI 4.0 either of CBR or rtVBR is formulation) must be used. In TM/UNI 4.0 either CBR or rtVBR is
appropriate, the latter allowing the network to possibly take appropriate. In both cases, GS would use a value of CLR
advantage of the statistical multiplexing gain of variable rate flows appropriately low for the link (i.e., such that congestion losses are
and to use tagging (see section 2.2). dominated by losses due to bit errors). The use of rtVBR may
encourage recovery of allocated bandwidth left unused by a source.
It also accomm odates more bursty sources with a larger bucket
parameter, and permits the use of tagging for excess traffic (see
Section 2.2).
Neither the BCOB-C bearer class, nor nrtVBR, UBR, ABR are matches for Neither the BCOB-C bearer class, nor nrtVBR, UBR, ABR are good
the GS service. These provide no delay estimates and one cannot matches for the GS service. These provide no delay estimates and
expect low, predictable, or consistent delays. cannot guarantee consistently low delay for every packet.
Specification of BCOB-A or CBR requires specification of a PCR. The Specification of BCOB-A or CBR requires specification of a PCR. The
PCR should be specified as the the token bucket rate parameter, with PCR should be specified as the the token bucket rate parameter, with
appropriate conversion from bytes to cells (accounting for overhead), appropriate conversion from bytes to cells (accounting for overhead),
of the GS TSpec. For both of these, the network provides a nominal of the GS TSpec. For both of these, the network provides a nominal
clearing rate of PCR with jitter toleration (bucket size) CDVT, clearing rate of PCR with jitter toleration (bucket size) CDVT,
specified in a network specific manner (see below). specified in a network specific manner (see below).
Specification of rtVBR requires the specification of two rates, SCR Specification of rtVBR requires the specification of two rates, SCR
and PCR. This models bursty traffic with specified peak and average and PCR. This models bursty traffic with specified peak and average
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simply allocate a fixed-rate ``pipe'', which should be ubiquitously simply allocate a fixed-rate ``pipe'', which should be ubiquitously
supported in ATM networks. However unless this is the only choice supported in ATM networks. However unless this is the only choice
available, this will probably be wasteful of network resources. available, this will probably be wasteful of network resources.
The ABR category with a positive MCR aligns with the CLS idea of The ABR category with a positive MCR aligns with the CLS idea of
``best effort with floor.'' The ATM network agrees to forward cells ``best effort with floor.'' The ATM network agrees to forward cells
with a rate of at least MCR, which should be directly converted from with a rate of at least MCR, which should be directly converted from
the token bucket rate of the TSpec. The bucket size parameter the token bucket rate of the TSpec. The bucket size parameter
measures approximately the amount of buffer required at the IWF. measures approximately the amount of buffer required at the IWF.
The nrtVBR/BCOB-C category can also be used. It does introduce some The nrtVBR/BCOB-C category can also be used. The rtVBR category can
unaligned complexity in the conformance definition (see section 2.2) be used, although the edge device must choose a value for CTD and CDV
by the use of two leaky buckets. The CLS rate parameter would as a matter of local policy.
correspond to the SCR, while the PCR should be set to the line rate,
as for Guaranteed Service.
The remaining service categories are inappropriate for CLS. The The UBR category does not provide enough capability for Controlled
rtVBR category adds complexity without providing useful features: Load. The point of CLS is to allow an allocation of resources, which
there is no need for tightly constrained delays, and the double-rate is facilitated by the token bucket traffic descriptor, and is
traffic description is not needed. The UBR category does not provide unavailable in UBR.
enough capability for Controlled Load. The point of CLS is to allow
an allocation of resources, which is facilitated by the token bucket
traffic descriptor, and is unavailable in UBR.
2.1.3 Service Categories for Best Effort 2.1.3 Service Categories for Best Effort
Any of the service categories has the capability to carry Best Effort Any of the service categories has the capability to carry Best Effort
service, but the natural service category is UBR (or, in UNI 3.x, service, but the natural service category is UBR (or, in UNI 3.x,
BCOB-C or BCOB-X, with the best effort indicator flag). A CBR or BCOB-C or BCOB-X, with the best effort indicator flag). A CBR or
rtVBR clearly could be used, and since the service is not real-time, rtVBR clearly could be used, and since the service is not real-time,
a nrtVBR connection could also be used. In these cases the rate a nrtVBR connection could also be used. In these cases the rate
parameter used reflects a bandwidth allocation in support of the edge parameter used reflects a bandwidth allocation in support of the edge
device's best effort connectivity to the far edge router. It would device's best effort connectivity to the far edge router. It would
skipping to change at page 10, line 34 skipping to change at page 10, line 15
are not necessarily identified or accounted for. CBR may be a are not necessarily identified or accounted for. CBR may be a
preferred solution in the case where best effort traffic is preferred solution in the case where best effort traffic is
sufficiently highly aggregated that a simple fixed-rate pipe is sufficiently highly aggregated that a simple fixed-rate pipe is
efficient. An ABR connection could similarly be used to support Best efficient. An ABR connection could similarly be used to support Best
Effort traffic. This is the purpose for which ABR was specifically Effort traffic. This is the purpose for which ABR was specifically
designed. It is conceivable that a separate ABR connection would be designed. It is conceivable that a separate ABR connection would be
made for different IP flows, although the normal case would probably made for different IP flows, although the normal case would probably
have all IP Best Effort traffic with a common exit router sharing a have all IP Best Effort traffic with a common exit router sharing a
single ABR connection. single ABR connection.
See specifications from the IETF ion working group [10, 11] for
related work on support of Best Effort service with ATM.
2.2 Cell Loss Priority Bit, Tagging and Conformance Definitions 2.2 Cell Loss Priority Bit, Tagging and Conformance Definitions
An ATM header carries the Cell Loss Priority (CLP) bit. Cells with An ATM header carries the Cell Loss Priority (CLP) bit. Cells with
bit CLP=1 are said to have been tagged and have lower priority. This bit CLP=1 are said to have been tagged and have lower priority. This
tagging may have been done by the source or an upstream switch. tagging may have been done by the source or an upstream switch.
Options involving the use of tagging are decided at call setup time. Options involving the use of tagging are decided at call setup time.
A Conformance Definition is a rule that determines whether a cell is A Conformance Definition is a rule that determines whether a cell is
conforming to the traffic descriptor of the VC. The conformance conforming to the traffic descriptor of the VC. The conformance
definition is given in terms of a Generic Cell Rate Algorithm (GCRA), definition is given in terms of a Generic Cell Rate Algorithm (GCRA),
skipping to change at page 11, line 15 skipping to change at page 10, line 45
network supports the tagging option. When congestion occurs, a network supports the tagging option. When congestion occurs, a
switch must attempt to discard tagged cells in preference to the switch must attempt to discard tagged cells in preference to the
discarding of CLP=0 cells. However, the mechanism for doing this is discarding of CLP=0 cells. However, the mechanism for doing this is
completely implementation specific. Tagged cells are treated with a completely implementation specific. Tagged cells are treated with a
behavior which is Best Effort in the sense that they are transported behavior which is Best Effort in the sense that they are transported
when bandwidth is available, queued when buffers are available, and when bandwidth is available, queued when buffers are available, and
dropped when the resources are overcommitted. dropped when the resources are overcommitted.
Since GS and CLS services require excess traffic to be treated as Since GS and CLS services require excess traffic to be treated as
Best Effort, the tagging option should always be chosen (if Best Effort, the tagging option should always be chosen (if
supported) in the VC setup as a means of ``downgrading'' supported) in the VC setup as a means of ``downgrading'' non-
nonconformant cells. However, we wish to point out that the term conformant cells. However, we wish to point out that the term ``best
``best effort'' seems to be used with two distinguishable meanings in effort'' seems to be used with two distinguishable meanings in the
the int-serv specs. The first interpretation is that of a service int-serv specs. The first interpretation is that of a service class
class that, in some typical scheduler implementations, would that, in some typical scheduler implementations, would correspond to
correspond to a separate queue. Placing excess traffic in best a separate queue. Placing excess traffic in best effort in this
effort in this sense would be giving it lower delay priority. The sense would be giving it lower delay priority. The other sense is
other sense is more generic, meaning that the network would make a more generic, meaning that the network would make a best effort to
best effort to transport the traffic. A reasonable expectation is transport the traffic. A reasonable expectation is that a network
that a network with no contending traffic would transport the packet, with no contending traffic would transport the packet, while a very
while a very congested network would drop the packet. A packet that congested network would drop the packet. A packet that could be
could be tagged with lower loss priority (such as the ATM CLP bit) tagged with lower loss priority (such as the ATM CLP bit) would be
would be more likely to be dropped, but would not normally be more likely to be dropped, but would not normally be transported out
transported out of order with respect to the conforming portion of of order with respect to the conforming portion of the flow. Such a
the flow. Such a mechanism would agree with the latter definition of mechanism would agree with the latter definition of best effort, but
best effort, but not the former. not the former.
In TM/UNI 4.0 tagging does not apply to the CBR or ABR services. In TM/UNI 4.0 tagging does not apply to the CBR or ABR services.
However, there are three conformance definitions of VBR service (for However, there are three conformance definitions of VBR service (for
both rtVBR and nrtVBR) to consider. In VBR, only the conformance both rtVBR and nrtVBR) to consider. In VBR, only the conformance
definition VBR.3 supports tagging and applies the GCRA with PCR to definition VBR.3 supports tagging and applies the GCRA with PCR to
the aggregate CLP=0+1 cells, and another GCRA with SCR to the CLP=0 the aggregate CLP=0+1 cells, and another GCRA with SCR to the CLP=0
cells. Thus this conformance definition should always be used in cells. Thus this conformance definition should always be used in
support of IP integrated services. For UBR service, conformance support of IP integrated services. For UBR service, conformance
definition UBR.2 supports the use of tagging, but a CLP=1 cell does definition UBR.2 supports the use of tagging, but a CLP=1 cell does
not imply non-conformance; it may be a hint of network congestion. not imply non-conformance; it may be a hint of network congestion.
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one direction for point-to-multipoint connections, which are one direction for point-to-multipoint connections, which are
unidirectional. When more than one flow aggregated into a single VC, unidirectional. When more than one flow aggregated into a single VC,
the TSpecs are merged to yield the largest packet size. In no case the TSpecs are merged to yield the largest packet size. In no case
can this exceed 65535 (or, of course, the MTU of the link). can this exceed 65535 (or, of course, the MTU of the link).
2.4 Broadband Low Layer Information 2.4 Broadband Low Layer Information
The B-LLI Information Element is transferred transparently by the ATM The B-LLI Information Element is transferred transparently by the ATM
network between the edge devices and is used to specify the network between the edge devices and is used to specify the
encapsulation method. Multiple B-LLI IEs may be sent as part of encapsulation method. Multiple B-LLI IEs may be sent as part of
negotiation. The default encapsulation LLC/SNAP must be supported as negotiation. The default encapsulation LLC/SNAP [16] must be
specified in RFC 1577 and RFC 1755. Additional encapsulations are supported as specified in RFC 1577 and RFC 1755. Additional
discussed in RFC 1755 and we refer to the discussion there. encapsulations are discussed in RFC 1755 and we refer to the
discussion there.
2.5 Traffic Descriptor 2.5 Traffic Descriptors
The ATM traffic descriptor always contains specification of a peak The ATM traffic descriptor always contains specification of a peak
cell rate (PCR) (in each direction). For variable rate services it cell rate (PCR) (in each direction). For variable rate services it
also contains specification of a sustainable cell rate (SCR) and also contains specification of a sustainable cell rate (SCR) and
maximum burst size (MBS). maximum burst size (MBS). The SCR and MBS form a leaky bucket pair
(rate, depth), while the bucket depth parameter for PCR is CDVT.
Note that CDVT is not signaled explicitly, but is determined by the
network operator, and serves as a measure of the jitter imposed by
the network.
The Best Effort indicators and Tagging indicators are also part of Since CDVT is not signaled, and is presumed to be small, the leaky
the traffic descriptors in the signalling sense. In UNI SIG 4.0 bucket traffic descriptor (TSpec) of the Internet service cannot
there is an additional parameter, the Frame Discard indicator in the always be directly mapped into PCR/CDVT parameters. Additional
traffic descriptor. The latter is used to indicate the request that buffering is needed at the IWF to account for the depth of the
if a cell is to be dropped, then all subsequent cells of a frame be bucket.
dropped up to the End of Message (EOM) cell (AAL 5); see section 2.7.
In ATM UNI SIG 4.0 there are also the notions of Alternative Traffic The Burst Tolerance is related to MBS (see TM 4.0 for details).
Roughly, they are both expressions of the bucket depth parameter that
goes with SCR. The units of BT is time while the units of MBS is
cells. Since both SCR and MBS are signalled, they can be computed
directly from the IP layer traffic description. The specific manner
in which resources are allocated from the traffic description is
implementation specific. Note that when translating the traffic
parameters, the segmentation overhead and minimum policed unit need
to be taken into account (see Section 4.2 below).
In ATM UNI SIG 4.0 there are the notions of Alternative Traffic
Descriptors and Minimal Traffic Descriptors. Alternative Traffic Descriptors and Minimal Traffic Descriptors. Alternative Traffic
Descriptors enumerate other acceptable choices for traffic Descriptors enumerate other acceptable choices for traffic
descriptors and do not seem to be relevant here. Minimal Traffic descriptors and are not considered here. Minimal Traffic Descriptors
Descriptors are used in ``negotiation,'' a term which when are used in ``negotiation,'' which refers to the specific way in
interpreted colloquially will lead to confusion. Very roughly it which an ATM connection is set up. Very roughly it works like this,
works like this, e.g., for PCR. A minimal PCR and a requested PCR are taking PCR as an example: A minimal PCR and a requested PCR are
signalled, the requested PCR being the usual item signalled, and the signalled, the requested PCR being the usual item signalled, and the
minimal PCR being the absolute minimum that the source edge device minimal PCR being the absolute minimum that the source edge device
will accept. When sensing the existence of both minimal and requested will accept. When sensing the existence of both minimal and
parameters, intermediate switches along the path may reduce the requested parameters, the intermediate switches along the path may
requested PCR to a comfortable level. If at any point the requested reduce the requested PCR to a ``comfortable'' level. This choice is
PCR falls below the minimal PCR then the call is cleared. This is a part of admission control, and is therefore implementation dependent.
very rough sketch, but we do see potential to make use of Minimal If at any point the requested PCR falls below the minimal PCR then
Traffic Descriptors in future versions of this draft in order to the call is cleared. Minimal Traffic Descriptors can be used to
present an acceptable range for parameters and have higher liklihood present an acceptable range for parameters and ensure a higher
of call admission. Minimal Traffic Descriptors are not explored likelihood of call admission. Whether anything more specific about
further in this version of the draft. Minimal Traffic Descriptors needs to be said here is left for further
study (FFS). In general, our discussion of connection parameters
assumes the values resulting from successful connection setup.
The Traffic Management viewpoint, which we examine next, is more The Best Effort indicator (used only with UBR) and Tagging indicators
concerned with the value of the PCR, SCR and MBS parameters after are also part of the signaled information element (IE) containing the
call setup. traffic descriptor. In the UNI SIG 4.0 traffic descriptor IE there
is an additional parameter, the Frame Discard indicator (see Section
2.7).
PCR and CDVT are used in the CBR and VBR conformance definitions as 2.5.1 Translating Traffic Descriptors for Guaranteed Service
parameters for a leaky bucket. However CDVT is not signalled and is
determined by the network operator as a measure of the ``clumping''
done by the network. This makes it difficult to map any leaky bucket
description of a TSpec to the PCR-CDVT leaky bucket. Additional
buffering will be needed at the IWF to account for the depth of the
bucket.
The SCR and MBS are used with the VBR services. They are used in an For Guaranteed Service there is a peak rate, p, a source Tspec rate,
implementation specific manner to allocate resources. The Burst r_s, a receiver Tspec rate r_r, and an Rspec rate, R. The two Tspec
Tolerance (BT) is derived from MBS (see TM 4.0) to be used in a rates are intended to support receiver heterogeneity, in the sense
second SCR-BT leaky bucket. Since both parameters are available to that different receivers can accept different rates representing
be signalled, this leaky bucket has the potential to be used in the subsets of the sender's traffic. In this document we leave this
same way as the integrated services bucket. Note that the feature for further study (FFS), and assume the two Tspec rates are
segmentation overhead and minimum policed unit need to be taken into always identical. The Tspec rate describes the traffic itself, and
account when translating the bucket parameters. is used for policing, while the Rspec rate (which cannot be smaller)
is the allocated service rate. A receiver increases R over r to
reduce the delay.
For Guaranteed Service there is a bucket rate, r and a service rate, When mapping Guaranteed Service onto a rtVBR VC, the ATM traffic
R. The bucket rate describes the traffic, and can be used for descriptor parameters (PCR, SCR, MBS) can be set within the following
policing, while the service rate (which cannot be smaller) is the bounds:
allocated service rate. When mapping Guaranteed Service onto a rtVBR
VC, the mapping is straightforward. The bucket rate maps to the SCR
and the peak rate maps to PCR. The bucket depth parameter maps to
MBS. The minimum policed unit may need to be taken into account when
translating the leaky bucket parameters. Note that due to cell
segmentation, the ATM traffic parameters will increase due to the
additional headers. The minimum packet size can be used to identify
the worst case situation.
For GS over CBR, the bucket rate can be mapped to the PCR parameter. R <= PCR <= min(p, line rate)
As noted above, the edge device may need to ensure that adequate r <= SCR <= PCR
buffering exists at the ATM network ingress to accommodate the TSpec b <= MBS.
bucket depth. If the available buffering is not sufficient, then a
VC may have to be set up using the IP peak rate parameter mapping to
PCR. It is probably inadvisable to try to set the PCR to a value
between the bucket rate and the peak rate, since such a value would
depend on assumptions about the statistical properties of the source.
Controlled Load service has a single bucket rate and corresponding Note that a receiver can choose R > p to lower the delay. This
depth parameter. The minimum policed unit and maximum packet size leaves the first equation somewhat subject to interpretation. If a
play the same roles in mapping parameters as for Guaranteed Service. receiver chooses R > line rate, it seems clear that the admission
When using nrtVBR, the bucket rate and depth map to SCR and MBS, control would simply reject the reservation.
while the PCR parameter can be set to the line rate as a worst case
value. For ABR VCs, the bucket rate would be used to set the minimum The edge device has a buffer preceding the ATM network which must be
cell rate (MCR) parameter. The bucket depth parameter does not map sufficient to absorb bursts arriving faster than they can be admitted
directly to a signalled ATM parameter, but the edge device should into the ATM network. For example, parameters may be set as PCR = R,
check that the buffering at the ATM ingress is sufficient to account SCR = r, MBS = b. The edge device buffer of size b would absorb a
for the size of bursts allowed by that parameter. Finally for CBR, burst sent at any IP-level peak rate. Although this buffer exists,
the bucket rate sets the PCR, and again, the available buffering in the ATM network must accept bursts at rate PCR, at least R, to ensure
the edge device must be adequate to accommodate possible bursts. that the edge device delay is no greater than b/R. Since this buffer
is not in the ATM network, its delay is not included in D_ATM.
For GS over CBR, the service rate is mapped to the PCR parameter,
using the same constraint for PCR given above. The edge device again
requires adequate buffering to accommodate the TSpec bucket depth and
ensure delay before entering the ATM network of no more than b/R. If
PCR is greater than R, the buffer requirement may be relaxed
accordingly.
2.5.2 Translating Traffic Descriptors for Controlled Load Service
Controlled Load service has a peak rate, p, a Tspec rate, r, and a
corresponding bucket depth parameter, b. The ATM traffic parameters
for nrtVBR service category are constrained by
r <= SCR <= PCR <= min(p, line rate)
b <= MBS.
For ABR VCs, the Tspec rate would be used to set the minimum cell
rate (MCR) parameter. The bucket depth parameter does not map
directly to a signalled ATM parameter, so the edge device must have a
buffer of at least b bytes.
For CBR, the Tspec rate sets a lower bound on PCR, and again, the
available buffering in the edge device must be adequate to
accommodate possible bursts.
2.5.2 Translating Traffic Descriptors for Best Effort Service
For Best Effort service, there is no traffic description. The UBR For Best Effort service, there is no traffic description. The UBR
service category allows negotiation of PCR, simply to identify to the service category allows negotiation of PCR, simply to allow the
source the smallest physical bottleneck along the path. source to discover the smallest physical bottleneck along the path.
2.6 QoS Classes and Parameters 2.6 QoS Classes and Parameters
In TM/UNI 4.0 the three QoS parameters may be individually signalled. In TM/UNI 4.0 the three QoS parameters may be individually signalled.
These parameters are the Cell Loss Ratio (CLR), Cell Transfer Delay These parameters are the Cell Loss Ratio (CLR), Cell Transfer Delay
(CTD), and Cell Delay Variation (CDV). In UNI 3.x the setup message (CTD), and Cell Delay Variation (CDV). In UNI 3.x the setup message
includes only the QoS Class, which is essentially an index to a includes only the QoS Class, which is essentially an index to a
network specific table of values for these three parameters. A network specific table of values for these three parameters. A
network provider may choose to associate other parameters, such as network provider may choose to associate other parameters, such as
Severely Errored Cell Block Ratio, but these are less well understood Severely Errored Cell Block Ratio, but these are less well understood
and accepted compared to the basic loss, delay and jitter parameters and accepted compared to the basic loss, delay and jitter parameters
mentioned here. The ITU may include a standard set of parameter mentioned here. The ITU has recently included a standard set of
values for a number (probably four) of QoS classes. In that case, parameter values for a (small) number of QoS classes in the latest
the network provider could define further network-specific QoS version of Recommendation I.356, October 1996. The network provider
classes in addition. The problem of agreement between network may choose to define further network-specific QoS classes in addition
providers as to the definition of QoS classes is completely to these. The problem of agreement between network providers as to
unaddressed to date. We will adopt a convention expressed in UNI the definition of QoS classes is completely unaddressed to date. We
3.x, that assumes that QoS class 1 is appropriate for low-delay, will adopt a convention expressed in UNI 3.x, that assumes that QoS
low-loss CBR connections, and QoS class 3 is appropriate for variable class 1 is appropriate for low-delay, low-loss CBR connections, and
rate connections with loss and delay roughly appropriate for non- QoS class 3 is appropriate for variable rate connections with loss
real-time data applications. and delay roughly appropriate for non-real-time data applications.
Note that the QoS class definitions in the new I.356 version may not
align with this model.
Since no IP layer counterparts to these ATM QoS parameters exist in Since no IP layer counterparts to these ATM QoS parameters exist in
any of the IP services, they must be set by policy of the edge any of the IP services, they must be set by policy of the edge
device. The QoS classes can be chosen relatively easily. QoS class device. The QoS classes can be chosen relatively easily. QoS class
1 should be used with Guaranteed Service and QoS class 3 should be 1 should be used with Guaranteed Service and QoS class 3 should be
used with Controlled Load Service. Best Effort Service always gets used with Controlled Load Service. Best Effort Service always gets
QoS class 0, which is unspecified QoS by definition. There are two QoS class 0, which is unspecified QoS by definition. There are two
issues which amount to the same thing: First, the choice of issues which amount to the same thing: First, the choice of
individually signalled parameter values (under TM/UNI 4.0) for GS and individually signalled parameter values (under TM/UNI 4.0) for GS and
CLS is the edge device policy. The second issue is choosing CLS is the edge device policy. The second issue is choosing
skipping to change at page 15, line 32 skipping to change at page 16, line 14
2.7 Additional Parameters -- Frame Discard Mode 2.7 Additional Parameters -- Frame Discard Mode
In TM/UNI 4.0 ATM allows the user to choose a mode where a dropped In TM/UNI 4.0 ATM allows the user to choose a mode where a dropped
cell causes all cells up to the last remaining in the AAL5 PDU to be cell causes all cells up to the last remaining in the AAL5 PDU to be
also dropped. This improves efficiency and the behavior of end-to- also dropped. This improves efficiency and the behavior of end-to-
end protocols such as TCP, since the remaining cells of a damaged PDU end protocols such as TCP, since the remaining cells of a damaged PDU
are useless to the receiver. For IP over ATM, Frame Discard should are useless to the receiver. For IP over ATM, Frame Discard should
always be used in both directions, if available, for all services. always be used in both directions, if available, for all services.
3.0 Discussion of Miscellaneous Items 3.0 Discussion of IP-IS Protocol Features
3.1 Units Conversion 3.1 Handling of Excess Traffic
In the integrated services domain, buckets and rates are measured in (Placeholder for text.)
bytes and bytes/sec, respectively, whereas for ATM, they are measured
in cells and cells/sec. 3.2 Use of AdSpec in Guaranteed Service with ATM
The AdSpec is a feature of Guaranteed Service which allows a receiver
to calculate the worst-case delay associated with a GS flow. Three
quantities, C, D, and MPL, are accumulated (by simple addition of
components, one for each network element) in the PATH message from
source to receiver. The resulting values can be different for each
unique receiver. The maximum delay is then found by
delay <= b/R + C/R + D + MPL
The Maximum Path Latency (MPL) includes propagation delay and any
other unavoidable system delays. (We neglect the effect of maximum
packet size and peak rate here; see the GS specification [8] for the
more detailed equation.) The service rate requested by the receiver,
R, can be greater than the sender's Tspec rate, r. The effect of the
larger R is to allocate more bandwidth and, through this equation,
lower the packet delay. The burst size, b, is the leaky bucket
parameter from the Tspec, and is not changed by the receiver in the
Rspec.
The values of C and D which a router advertise will depend on both
the particular packet scheduling algorithm used in the router, and
the characteristics of the subnet attached to the router. We assume
here that each router (or the source host) takes responsibility for
its downstream subnet only. If the subnet is a simple point-to-point
link, then the subnet-specific parts of C and D will account for the
link transmission rate and MTU. An ATM subnet is more complex.
The edge router will always have an internal packet scheduler, which
will contribute to C and D. For this discussion we consider only the
ATM subnet-specific components. We further assume that the ATM
network will be represented as a "pure delay" element, contributing a
component to D, but not to C. The reason for this is that C would
depend on details of the cell scheduling algorithm inside the ATM
switches, which is not known by the edge device, where the AdSpec
parameters are accumulated. (In the special case where the edge
device does have enough information to modify C, it would not be
precluded.) Generally the delay behavior of the whole ATM cloud may
be expressed abstractly as a fixed constant D_ATM.
Since the AdSpec values are incremented before any reservation is
made, the edge device must have some knowledge about the VC which
would be set up in case a reservation were made. This does not
really add to the complexity of the device, since it must also have
this information in order to make an intelligent VC setup request.
For example, the edge device may have a cached table with the
propagation delay and a reasonable additional delay budget, from
which it composes a value of CTD for the VC setup. The device may
learn such information through VC setup negotiation, and, indeed,
there may be no other way to obtain that information. However, it
seems reasonable that these values would be cached for later use when
new VCs to the same egress router need to be established.
Therefore, we will presume a table with values of MPL (which includes
propagation delay) and expected queueing delays for each possible
egress edge device. (How such a table is maintained is
implementation specific.) The latter quantity is simply D_ATM, the
value added to the AdSpec D term to account for the ATM network.
When a RESV message arrives, causing a VC to be set up, the requested
value for CTD should then be given by
CTD = D_ATM + MPL + S_ATM.
The last term, S_ATM is the portion of the slack term applied to the
ATM portion of the path. Recall that the slack term [8] is positive
when the receiver can afford more delay than that computed from the
AdSpec. The ATM edge device may take part (or all) of the slack term
to relax the delay constraint on the ATM VC. The distribution of
delay slack among the nodes and subnets is network specific.
An important detail to note is the relationship between the b/R term
of the (Internet) delay and the corresponding MBS/SCR in the ATM
network, when using a VBR VC. The term b/R accounts for the delay
experienced by the last byte of a burst, of size b, which encounters
a congested node. In the simple ideal case, where the scheduling
algorithm emulates a fixed rate server, at rate R, the delay of the
last byte is b/R. Once this occurs, the stream has been smoothed,
and such a delay will not occur at later congested nodes, as long as
they also serve at rate R. The form of the delay equation expresses
this ideal behavior with C and D acting as error terms. Now, since
the delay which smooths the burst can occur outside of the ATM cloud,
the b/R term cannot include any delay within the ATM cloud. However,
a burst of size MBS is permitted to enter the ATM network, and it may
be served at a rate no greater than SCR. We might reasonably expect
a queueing delay of MBS/SCR to occur at a congested ATM switch. If
the ATM network will impose this delay, then it must be included in
the value of D_ATM advertised. If the ATM network can increase its
bandwidth allocation (e.g., due to CTD being lower than MBS/SCR), to
decrease this delay, then this behavior should be reflected in the
value of D_ATM. So, the information from which the edge device
determines D_ATM must reflect an accurate abstraction of the actual
behavior of the ATM network. To the extent that D_ATM is approximate
(and it must be an upper bound on the actual delay), it reduces the
chance that the VC setup will succeed, and/or increases its cost.
4.0 Discussion of Miscellaneous Items
4.1 Units Conversion
In the integrated services domain, bucket sizes and rates are
measured in bytes and bytes/sec, respectively, whereas for ATM, they
are measured in cells and cells/sec.
Packets are segmented into 53 byte cells of which the first 5 bytes Packets are segmented into 53 byte cells of which the first 5 bytes
are header information. For are header information. For
B = number of Bytes, B = number of Bytes,
C = number of cells, C = number of cells,
a rough approximation between the token bucket parameters (rate and a rough approximation between the token bucket parameters (rate and
bucket depth) is bucket depth) is
C = B/48. C = B/48.
This is actually a lower bound on C and does not take into account This is actually a lower bound on C and does not take into account
the extra padding at the end of a partially filled cell, or the 8 the extra padding at the end of a partially filled cell, or the 8
byte trailer in the last cell of an AAL5 encoding. The actual byte trailer in the last cell of an AAL5 encoding. The actual
relationship between the number of cells and bytes of one packet is relationship between the number of cells and bytes of one packet is
C = 1 + int(B/48) + x,
C = 1 + int(B/48) + x,
where x = 1 if B mod 48 > 41 where x = 1 if B mod 48 > 41
0 otherwise. 0 otherwise.
where int() is the rounding down operation. The third term is 0 or where int() is the rounding down operation. The third term is 0 or
1 and is 1 only when the remainder of B/48 is 41 or more. (An 1 and is 1 only when the remainder of B/48 is 41 or more. (An
additional cell is needed because the 41 bytes plus 8 byte trailer additional cell is needed because the 41 bytes plus 8 byte trailer
will not fit in a cell.) will not fit in a cell.)
The above formula is not particularly amenable to engineering The above formula is not particularly amenable to engineering
considerations. By equating the number of bytes before and after considerations. By equating the number of bytes before and after
segmentation we have segmentation we have
48 C = B + 8 + A, 48 C = B + 8 + A,
where A is the additional padding used in the last 2 cells and has where A is the additional padding used in the last 2 cells and has
the range 0 <= A <= 47. From this we obtain a number of useful the range 0 <= A <= 47. From this we obtain a number of useful
observations. observations.
For example, if one believes that the packet lengths are uniformly For example, if one believes that the packet lengths are uniformly
distributed mod 48, then on average, 48 C = B + 8 + 47/2, or C = B/48 distributed mod 48, then on average, 48 C = B + 8 + 47/2, or C = B/48
+ .65625. + .65625.
We can also make use of the upper bound on A to state that 48 C <= B We can also make use of the upper bound on A to state that 48 C <= B
+ 55. This is true for any one packet. Considering the number of + 55. This is true for any one packet. Considering the number of
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the range 0 <= A <= 47. From this we obtain a number of useful the range 0 <= A <= 47. From this we obtain a number of useful
observations. observations.
For example, if one believes that the packet lengths are uniformly For example, if one believes that the packet lengths are uniformly
distributed mod 48, then on average, 48 C = B + 8 + 47/2, or C = B/48 distributed mod 48, then on average, 48 C = B + 8 + 47/2, or C = B/48
+ .65625. + .65625.
We can also make use of the upper bound on A to state that 48 C <= B We can also make use of the upper bound on A to state that 48 C <= B
+ 55. This is true for any one packet. Considering the number of + 55. This is true for any one packet. Considering the number of
bytes in a stream of P packets, we have bytes in a stream of P packets, we have
48 C <= B + 55 P. 48 C <= B + 55 P.
The number of packets P may not be a readily available quantity. The number of packets P may not be a readily available quantity.
However, in terms of the minimum policed unit m, we know that P * m However, in terms of the minimum policed unit m, we know that P * m
<= B. Hence P <= B/m and 48 C <= B ( 1 + 55/m). That is, <= B. Hence P <= B/m and 48 C <= B ( 1 + 55/m). That is,
C <= B/48 * (1 + 55/m). C <= B/48 * (1 + 55/m).
4.0 Guaranteed Service over ATM 5.0 Summary of ATM VC Setup Parameters for Guaranteed Service
This section describes how to create ATM VCs appropriately matched This section describes how to create ATM VCs appropriately matched
for Guaranteed Service. The key points differentiating among ATM for Guaranteed Service. The key points differentiating among ATM
choices are that real-time timing is required, that the data flow may choices are that real-time timing is required, that the data flow may
have a variable rate, and that demotion of non-conforming traffic to have a variable rate, and that demotion of non-conforming traffic to
best effort is desired. For this reason, we prefer a rtVBR service best effort is required to be in agreement with the definition of GS.
in which tagging is supported. Another good match is to use CBR with For this reason, we prefer an rtVBR service in which tagging is
special handling of any non-conforming traffic. supported. Another good match is to use CBR with special handling of
any non-conforming traffic.
The encodings assume a point-to-multipoint connection. For a unicast The encodings assume a point-to-multipoint connection. For a unicast
connection, the backward parameters would be equal to the forward connection, the backward parameters would be equal to the forward
parameters. parameters.
4.1 Encoding GS as a real-time variable bit rate service 5.1 Encoding GS Using Real-Time VBR
AAL AAL
Type 5 Type 5
Forward CPCS-SDU Size parameter M of TSpec Forward CPCS-SDU Size parameter M of TSpec
Backward CPCS-SDU Size 0 Backward CPCS-SDU Size 0
Mode 1 (Message mode) Note 1 Mode 1 (Message mode) Note 1
SSCS Type 0 (Null SSCS) SSCS Type 0 (Null SSCS)
Traffic Descriptor Traffic Descriptor
Forward PCR CLP=0+1 From TSpec peak rate Forward PCR CLP=0+1 Note 6
Backward PCR CLP=0+1 0 Backward PCR CLP=0+1 0
Forward SCR CLP=0 From TSpec token bucket rate Forward SCR CLP=0 Note 6
Backward SCR CLP=0 0 Backward SCR CLP=0 0
Forward MBS (CLP=0) From TSpec bucket size param Forward MBS (CLP=0) Note 6
Backward MBS (CLP=0) 0 Backward MBS (CLP=0) 0
BE indicator NOT included BE indicator NOT included
Forward Frame Discard bit 1 Note 2 Forward Frame Discard bit 1 Note 2
Backward Frame Discard bit 1 Note 2 Backward Frame Discard bit 1 Note 2
Tagging Forward bit 1 (Tagging requested) Note 2 Tagging Forward bit 1 (Tagging requested) Note 2
Tagging Backward bit 0 (No Tagging) Note 2 Tagging Backward bit 0 (No Tagging) Note 2
Broadband Bearer Capability Broadband Bearer Capability
Bearer Class 16 (BCOB-X) Note 3 Bearer Class 16 (BCOB-X) Note 3
ATM Transfer Capability 9 Note 2 ATM Transfer Capability 9 Note 2
skipping to change at page 17, line 45 skipping to change at page 20, line 46
Broadband Low Layer Information Broadband Low Layer Information
Layer 2 protocol 12 (ISO 8802/2) Layer 2 protocol 12 (ISO 8802/2)
Layer 3 protocol 204 (ISO/IEC TR 9577) Layer 3 protocol 204 (ISO/IEC TR 9577)
QoS Class QoS Class
QoS Class Forward 1 Note 4 QoS Class Forward 1 Note 4
QoS Class Backward 1 Note 4 QoS Class Backward 1 Note 4
QoS Parameters QoS Parameters
Transit Delay 100ms Notes 2,5 Transit Delay 100ms Notes 2,5
Forward CLR (CLP=0) 1.0e-6 Notes 2,5 Forward CLR (CLP=0) 1.0e-9 Notes 2,5,7
Backward CLR (CLP=0) 1.0e-6 Notes 2,5 Backward CLR (CLP=0) 1.0e-9 Notes 2,5,7
Forward CDV 30ms Notes 2,5 Forward CDV 30ms Notes 2,5
Backward CDV 30ms Notes 2,5 Backward CDV 30ms Notes 2,5
Note 1: Only included for UNI 3.0. Note 1: Only included for UNI 3.0.
Note 2: Only included in TM/UNI 4.0. Note 2: Only included in TM/UNI 4.0.
Note 3: Value 1 (BCOB-A) can also be used. Note 3: Value 1 (BCOB-A) can also be used.
Note 4: Optional in TM/UNI 4.0. Note 4: Optional in TM/UNI 4.0. Cf ITU I.365 (Oct 1996) for new definition.
Note 5: Values chosen to initiate discussion. Note 5: Values chosen to initiate discussion. May be network specific.
Note 6: See discussion on AdSpec, Section 3.2.
Note 7: CLR should include physical link errors with no queueing loss.
4.2 Encoding GS as a constant bit rate service 5.2 Encoding GS Using CBR
It is also possible to support GS using a CBR ``pipe.'' The It is also possible to support GS using a CBR ``pipe.'' The
advantage of this is that CBR is probably supported; the disadvantage advantage of this is that CBR is probably supported; the disadvantage
is that data flows may not fill the pipe (utilization loss) and there is that data flows may not fill the pipe (utilization loss) and there
is no tagging option available. is no tagging option available.
AAL AAL
Type 5 Type 5
Forward CPCS-SDU Size parameter M of TSpec Forward CPCS-SDU Size parameter M of TSpec
Backward CPCS-SDU Size parameter M of TSpec Backward CPCS-SDU Size parameter M of TSpec
Mode 1 (Message mode) Note 1 Mode 1 (Message mode) Note 1
SSCS Type 0 (Null SSCS) SSCS Type 0 (Null SSCS)
Traffic Descriptor Traffic Descriptor
Forward PCR 0+1 From TSpec token bucket rate Forward PCR 0+1 Note 6
Backward PCR 0+1 0 Backward PCR 0+1 0
BE indicator NOT included BE indicator NOT included
Forward Frame Discard bit 1 Note 2 Forward Frame Discard bit 1 Note 2
Backward Frame Discard bit 1 Note 2 Backward Frame Discard bit 1 Note 2
Tagging Forward bit 0 (No Tagging) Note 2 Tagging Forward bit 0 (No Tagging) Note 2
Tagging Backward bit 0 (No Tagging) Note 2 Tagging Backward bit 0 (No Tagging) Note 2
Broadband Bearer Capability Broadband Bearer Capability
Bearer Class 16 (BCOB-X) Note 3 Bearer Class 16 (BCOB-X) Note 3
ATM Transfer Capability 7 Note 2 ATM Transfer Capability 7 Note 2
skipping to change at page 19, line 5 skipping to change at page 22, line 8
Broadband Low Layer Information Broadband Low Layer Information
Layer 2 protocol 12 (ISO 8802/2) Layer 2 protocol 12 (ISO 8802/2)
Layer 3 protocol 204 (ISO/IEC TR 9577) Layer 3 protocol 204 (ISO/IEC TR 9577)
QoS Class QoS Class
QoS Class Forward 1 Note 4 QoS Class Forward 1 Note 4
QoS Class Backward 1 Note 4 QoS Class Backward 1 Note 4
QoS Parameters QoS Parameters
Transit Delay 100ms Notes 2,5 Transit Delay 100ms Notes 2,5
Forward CLR (CLP=0) 1.0e-6 Notes 2,5 Forward CLR (CLP=0) 1.0e-9 Notes 2,5,7
Backward CLR (CLP=0) 1.0e-6 Notes 2,5 Backward CLR (CLP=0) 1.0e-9 Notes 2,5,7
Forward CDV 30ms Notes 2,5 Forward CDV 30ms Notes 2,5
Backward CDV 30ms Notes 2,5 Backward CDV 30ms Notes 2,5
Note 1: Only included for UNI 3.0. Note 1: Only included for UNI 3.0.
Note 2: Only included in TM/UNI 4.0. Note 2: Only included in TM/UNI 4.0.
Note 3: Value 1 (BCOB-A) can also be used. Note 3: Value 1 (BCOB-A) can also be used.
Note 4: Optional in TM/UNI 4.0. Note 4: Optional in TM/UNI 4.0. Cf ITU I.365 (Oct 1996) for new definition.
Note 5: Values chosen to initiate discussion. Note 5: Values chosen to initiate discussion. May be network specific.
Note 6: See discussion on AdSpec, Section 3.2.
Note 7: CLR should include physical link errors with no queueing loss.
4.3 Encoding GS as a non-real-time variable bit rate service 5.3 Encoding GS Using Non-Real-Time VBR
The remaining ATM service categories, including nrtVBR, do not The remaining ATM service categories, including nrtVBR, do not
provide delay guarantees and cannot be recommended as the best fits. provide delay guarantees and cannot be recommended as the best fits.
However in some circumstances, the best fits may not be available. However in some circumstances, the best fits may not be available.
If nrtVBR is used, no hard delay can be given. However by using a If nrtVBR is used, no hard delay can be given. However by using a
variable rate service with low utilization, delay may be variable rate service with low utilization, delay may be
`reasonable', but not controlled. The encoding of GS as nrtVBR is `reasonable', but not controlled. The encoding of GS as nrtVBR is
the same as that for CL using nrtVBR, except that the Forward PCR the same as that for CLS using nrtVBR, except that the Forward PCR
would be derived from the Tspec peak rate. See section 5.2 below. would be derived from the Tspec peak rate. See Section 6.2 below.
4.4 Encoding GS as an ABR service 5.4 Encoding GS Using ABR
The authors feel that this is a very unlikely combination. The The authors feel that this is a very unlikely combination. The
objective of the ABR service is to provide `low' loss rates which, objective of the ABR service is to provide `low' loss rates which,
via flow control, can result in delays. The introduction of delays via flow control, can result in delays. The introduction of delays
is contrary to the point of GS. is contrary to the point of GS.
4.5 Encoding GS as an UBR service 5.5 Encoding GS Using UBR
The UBR service is the default lowest common denominator of the The UBR service is the default lowest common denominator of the
services. It cannot provide delay or loss guarantees. However if it services. It cannot provide delay or loss guarantees. However if it
is used for GS, it will be encoded in the same way as Best Effort is used for GS, it will be encoded in the same way as Best Effort
over UBR, with the exception that the PCR would be determined from over UBR, with the exception that the PCR would be determined from
the peak rate of the Tspec. See section 5.1. the peak rate of the Tspec. See Section 5.1.
5.0 Controlled Load Service over ATM 5.6 Encoding GS Using UNI 3.0 and UNI 3.1.
(Placeholder for text.)
6.0 Summary of ATM VC Setup Parameters for Controlled Load Service
This section describes how to create ATM VCs appropriately matched This section describes how to create ATM VCs appropriately matched
for Controlled Load. CL traffic is partly delay tolerant and of for Controlled Load. CLS traffic is partly delay tolerant and of
variable rate. We see nrtVBR and ABR (for TM/UNI 4.0 only) as variable rate. NrtVBR and ABR (for TM/UNI 4.0 only) are the possible
possible choices in supporting CL. choices in supporting CLS.
Generally we prefer to use point-to-multipoint connections. However Generally we prefer to use point-to-multipoint connections. However
this is not yet available in ABR. Other than in ABR, the encodings this is not yet available in ABR. Other than in ABR, the encodings
assume a point-to-multipoint connection. For a unicast connection, assume a point-to-multipoint connection. For a unicast connection,
the backward parameters would be equal to the forward parameters. the backward parameters would be equal to the forward parameters.
5.1 Encoding CL using an ABR service 6.1 Encoding CLS Using ABR
AAL AAL
Type 5 Type 5
Forward CPCS-SDU Size parameter M of TSpec Forward CPCS-SDU Size parameter M of TSpec
Backward CPCS-SDU Size parameter M of TSpec Backward CPCS-SDU Size parameter M of TSpec
SSCS Type 0 (Null SSCS) SSCS Type 0 (Null SSCS)
Traffic Descriptor Traffic Descriptor
Forward PCR CLP=0+1 From line rate Forward PCR CLP=0+1 From line rate
Backward PCR CLP=0+1 From line rate Backward PCR CLP=0+1 From line rate
skipping to change at page 21, line 6 skipping to change at page 24, line 19
User Plane Configuration 00 (For pt-to-pt) User Plane Configuration 00 (For pt-to-pt)
Broadband Low Layer Information Broadband Low Layer Information
Layer 2 protocol 12 (ISO 8802/2) Layer 2 protocol 12 (ISO 8802/2)
Layer 3 protocol 204 (ISO/IEC TR 9577) Layer 3 protocol 204 (ISO/IEC TR 9577)
QoS Class QoS Class
QoS Class Forward 3 Note 4 QoS Class Forward 3 Note 4
QoS Class Backward 3 Note 4 QoS Class Backward 3 Note 4
ABR Setup Parameters For Further Study ABR Setup Parameters for further study (FFS)
ABR Additional Parameters For Further Study ABR Additional Parameters for further study (FFS)
Note 3: Value 3 (BCOB-C) can also be used. Note 3: Value 3 (BCOB-C) can also be used.
Note 4: Optional in TM/UNI 4.0. Note 4: Optional in TM/UNI 4.0. Cf ITU I.365 (Oct 1996) for new definition.
5.2 Encoding CL using a non-real-time variable bit rate service 6.2 Encoding CLS Using Non-Real-Time VBR
AAL AAL
Type 5 Type 5
Forward CPCS-SDU Size parameter M of TSpec Forward CPCS-SDU Size parameter M of TSpec
Backward CPCS-SDU Size 0 Backward CPCS-SDU Size 0
Mode 1 (Message mode) Note 1 Mode 1 (Message mode) Note 1
SSCS Type 0 (Null SSCS) SSCS Type 0 (Null SSCS)
Traffic Descriptor Traffic Descriptor
Forward PCR CLP=0+1 From line rate Forward PCR CLP=0+1 From line rate
skipping to change at page 22, line 8 skipping to change at page 25, line 21
Broadband Low Layer Information Broadband Low Layer Information
Layer 2 protocol 12 (ISO 8802/2) Layer 2 protocol 12 (ISO 8802/2)
Layer 3 protocol 204 (ISO/IEC TR 9577) Layer 3 protocol 204 (ISO/IEC TR 9577)
QoS Class QoS Class
QoS Class Forward 3 Note 4 QoS Class Forward 3 Note 4
QoS Class Backward 3 Note 4 QoS Class Backward 3 Note 4
QoS Parameters QoS Parameters
Forward CLR (CLP=0) 1.0e-6 Notes 2,5 Forward CLR (CLP=0) 1.0e-9 Notes 2,5,6
Backward CLR (CLP=0) 1.0e-6 Notes 2,5 Backward CLR (CLP=0) 1.0e-9 Notes 2,5,6
Note 1: Only included for UNI 3.0. Note 1: Only included for UNI 3.0.
Note 2: Only included in TM/UNI 4.0. Note 2: Only included in TM/UNI 4.0.
Note 3: Value 3 (BCOB-C) can also be used. Note 3: Value 3 (BCOB-C) can also be used.
Note 4: Optional in TM/UNI 4.0. Note 4: Optional in TM/UNI 4.0. Cf ITU I.365 (Oct 1996) for new definition.
Note 5: Values chosen to initiate discussion. Note 5: Values chosen to initiate discussion. May be network specific.
Note 6: CLR should include physical link errors with no queueing loss.
5.3 Encoding CL using a real-time variable bit rate service 6.3 Encoding CLS Using Real-Time VBR
The encoding of CL using rtVBR imposes a hard limit on the delay, The encoding of CLS using rtVBR imposes a hard limit on the delay,
which is specified as an end-to-end delay in the ATM network. This which is specified as an end-to-end delay in the ATM network. This
is more stringent than the CL service specifies and may result in is more stringent than the CLS service specifies and may result in
less utilization of the network. less utilization of the network.
If rtVBR is used to encode CL, then the encoding is essentially the If rtVBR is used to encode CLS, then the encoding is essentially the
same as that for GS. The exceptions are that the Forward PCR is same as that for GS. The exceptions are that the Forward PCR is
derived from the line rate and probably a different value of the derived from the line rate and probably a different value of the
transit delay and CDV will be specified. See section 3.1. transit delay and CDV will be specified. See Section 3.1.
5.4 Encoding CL using a constant bit rate service 6.4 Encoding CLS Using CBR
The encoding of CL using CBR is more stringent than using rtVBR since The encoding of CLS using CBR is more stringent than using rtVBR
it does not take into account the variable rate of the data. since it does not take into account the variable rate of the data.
Consequently there may be even lower utilization of the network. Consequently there may be even lower utilization of the network.
To use CBR for CL, the same encoding as in section 3.2 would be used. To use CBR for CLS, the same encoding as in Section 3.2 would be
However a different set of values of the QoS parameters will likely used. However a different set of values of the QoS parameters will
be used. likely be used.
5.5 Encoding CL using a UBR service 6.5 Encoding CLS Using UBR
This encoding gives no QoS guarantees and would be done in the same This encoding gives no QoS guarantees and would be done in the same
way as for BE traffic. See section 5.1. way as for BE traffic. See Section 5.1.
6.0 Best Effort Service over ATM 6.6 Encoding CLS Using UNI 3.0 and UNI 3.1.
(Placeholder for text.)
7.0 Summary of ATM VC Setup Parameters for Best Effort Service
This section describes how to create ATM VCs appropriately matched This section describes how to create ATM VCs appropriately matched
for Best Effort. The BE service does not need a reservation of for Best Effort. The BE service does not need a reservation of
resources. resources.
5.1 Best Effort Service using UBR 7.1 Encoding Best Effort Service Using UBR
AAL AAL
Type 5 Type 5
Forward CPCS-SDU Size MTU of link Forward CPCS-SDU Size MTU of link
Backward CPCS-SDU Size MTU of link Backward CPCS-SDU Size MTU of link
Mode 1 (Message mode) Note 1 Mode 1 (Message mode) Note 1
SSCS Type 0 (Null SSCS) SSCS Type 0 (Null SSCS)
Traffic Descriptor Traffic Descriptor
Forward PCR CLP=0+1 From line rate Forward PCR CLP=0+1 From line rate
skipping to change at page 24, line 5 skipping to change at page 27, line 22
Layer 2 protocol 12 (ISO 8802/2) Layer 2 protocol 12 (ISO 8802/2)
Layer 3 protocol 204 (ISO/IEC TR 9577) Layer 3 protocol 204 (ISO/IEC TR 9577)
QoS Class QoS Class
QoS Class Forward 0 QoS Class Forward 0
QoS Class Backward 0 QoS Class Backward 0
Note 1: Only included for UNI 3.0. Note 1: Only included for UNI 3.0.
Note 2: Only included in TM/UNI 4.0. Note 2: Only included in TM/UNI 4.0.
1. REFERENCES 7.2 Encoding Best Effort Service Using Other ATM Service Categories
[RFC1633]
R. Braden, D. Clark and S. Shenker, "Integrated Services in the
Internet Architecture: an Overview", RFC 1633, June 1994.
[RFC1755] See the IETF ION working group draft on ATM signalling support for IP
M. Perez, F. Liaw, A. Mankin, E. Hoffman, D. Grossman and A. over ATM using UNI 4.0 [11].
Malis, "ATM Signlaing Support for IP over ATM", RFC 1755, Febru-
ary 1995.
[IPATM] 8.0 Acknowledgements
M. Perez and A. Mankin, "ATM Signalling Support for IP over ATM
- UNI 4.0 Update", Internet Draft, June 1996, <draft-ietf-ion-
sig-uni4.0-oo.txt>
[RFC1821] The authors would like to thank the members of the ISSLL working
M. Borden, E. Crawley, B. Davie and S. Batsell, "Integration of group for their input. In particular, thanks to Jon Bennett of Fore
Real-time Sevices in an IP-ATM Network Architecture", "IP Systems, Roch Guerin of IBM and Susan Thomson of Bellcore.
Authentication Header", RFC 1821, August 1995.
[RSVP]R. Braden, L. Zhang, S. Berson, S. Herzog and S. Jamin, Appendix 1 Abbreviations
"Resource ReSevVation Protocol (RSVP) - Version 1 Functional
Specification", Internet Draft, May 1996, <draft-ietf-rsvp-
spec-12.txt>
[GS] S. Shenker, C. Partridge and R. Guerin, "Specification of AAL ATM Adaptation Layer
Guaranteed Quality of Service", Internet Draft, August 1996, ABR Available Bit Rate
<draft-ietf-intserv-guaranteed-svc-06.txt> ATM Asynchronous Transfer Mode
B-LLI Broadband Low Layer Information
BCOB Broadband Connection-Oriented Bearer Capability
BCOB-{A,C,X} Bearer Class A, C, or X
BE Best Effort
BT Burst Tolerance
CBR Constant Bit Rate
CDV Cell Delay Variation
CDVT Cell Delay Variation Tolerance
CLP Cell Loss Priority (bit)
CLR Cell Loss Ratio
CLS Controlled Load Service
CPCS
CTD Cell Transfer Delay
EOM End of Message
FFS For Further Study
GCRA Generic Cell Rate Algorithm
GS Guaranteed Service
IE Information Element
IETF Internet Engineering Task Force
IP Internet Protocol
IS Integrated Services
ISSLL Integrated Services over Specific Link Layers
ITU International Telecommunication Union
IWF Interworking Function
LIJ Leaf Initiated Join
LLC Logical Link Control
MBS Maximum Burst Size
MCR Minimum Cell Rate
MPL Minimum Path Latency
MTU Maximum Transfer Unit
nrtVBR Non-real-time VBR
PCR Peak Cell Rate
PDU Protocol Data Unit
QoS Quality of Service
RESV Reservation Message (of rsvp protocol)
RFC Request for Comment
RSVP Resource Reservation Protocol
Rspec Reservation Specification
rtVBR Real-time VBR
SCR Sustained Cell Rate
SDU Service Data Unit
SIG ATM Signaling (ATM Forum document)
SNAP Subnetwork Attachment Point
SSCS
Sw Switch
TCP Transport Control Protocol
TM Traffic Management
TSpec Traffic Specification
UBR Unspecified Bit Rate
UNI User-Network Interface
VBR Variable Bit Rate
VC (ATM) Virtual Connection
[CLS]J. Wroclawski, "Specification of the Controlled-Load Network REFERENCES
Element Service", Internet Draft, August 1996, draft-ietf-
intserv-ctrl-load-svc-03.txt
[USE-RSVP-IS] [1] R. Braden, D. Clark and S. Shenker, "Integrated Services in the
J. Wroclawski, "The Use of RSVP with IETF Integrated Services", Internet Architecture: an Overview", RFC 1633, June 1994.
Internet Draft, August 1996, <draft-ietf-intserv-use-00.txt>
[TEMPLATE] [2] R. Braden, L. Zhang, S. Berson, S. Herzog and S. Jamin,
S. Shenker and J. Wroclawski, "Network Element Service Specifi- "Resource ReSerVation Protocol (RSVP) - Version 1 Functional
cation Template", Internet Draft, November 1995, <draft-ietf- Specification", Internet Draft, May 1996, <draft-ietf-rsvp-
intserv-svc-template-02.txt> spec-12.txt>
[UNI3.0] [3] The ATM Forum, "ATM User-Network Interface Specification, Ver-
The ATM Forum, "ATM User-Network Interface Specification, Ver-
sion 3.0", Prentice Hall, Englewood Cliffs NJ, 1993. sion 3.0", Prentice Hall, Englewood Cliffs NJ, 1993.
[UNI3.1] [4] The ATM Forum, "ATM User-Network Interface Specification, Ver-
The ATM Forum, "ATM User-Network Interface Specification, Ver-
sion 3.1", Prentice Hall, Upper Saddle River NJ, 1995. sion 3.1", Prentice Hall, Upper Saddle River NJ, 1995.
[UNI4.0] [5] The ATM Forum, "ATM User-Network Interface (UNI) Signalling
The ATM Forum, "ATM User-Network Interface (UNI) Signalling
Specification, Version 4.0", Prentice Hall, Upper Saddle River Specification, Version 4.0", Prentice Hall, Upper Saddle River
NJ, specification finalized July 1996; expected publication, NJ, specification finalized July 1996; expected publication,
late 1996; available at ftp://ftp.atmforum.com/pub. The ATM late 1996; available at ftp://ftp.atmforum.com/pub.
Forum, "ATM Traffic Management Specification, Version 4.0",
Prentice Hall, Upper Saddle River NJ; specification finalized [6] The ATM Forum, "ATM Traffic Management Specification, Version
April 1996; expected publication, late 1996; available at 4.0", Prentice Hall, Upper Saddle River NJ; specification final-
ized April 1996; expected publication, late 1996; available at
ftp://ftp.atmforum.com/pub. ftp://ftp.atmforum.com/pub.
[ATMsvc] [7] M. W. Garrett, "A Service Architecture for ATM: From Applica-
M. W. Garrett, "A Service Architecture for ATM: From Applica-
tions to Scheduling", IEEE Network Mag., Vol. 10, No. 3, pp. 6- tions to Scheduling", IEEE Network Mag., Vol. 10, No. 3, pp. 6-
14, May 1996. 14, May 1996.
Acknowledgements [8] S. Shenker, C. Partridge and R. Guerin, "Specification of
Guaranteed Quality of Service", Internet Draft, August 1996,
<draft-ietf-intserv-guaranteed-svc-06.txt>
The authors would like to thank the members of the ISSLL working group [9] J. Wroclawski, "Specification of the Controlled-Load Network
for their input. In particular, thanks to Jon Bennett of Fore Systems. Element Service", Internet Draft, August 1996, draft-ietf-
intserv-ctrl-load-svc-03.txt
[10] M. Perez, F. Liaw, A. Mankin, E. Hoffman, D. Grossman and A.
Malis, "ATM Signaling Support for IP over ATM", RFC 1755, Febru-
ary 1995.
[11] M. Perez and A. Mankin, "ATM Signalling Support for IP over ATM
- UNI 4.0 Update", Internet Draft, November 1996, <draft-ietf-
ion-sig-uni4.0-01.txt>
[12] S. Berson, L. Berger, "IP Integrated Services with RSVP over
ATM", Internet Draft, September 1996, <draft-ietf-issll-atm-
support-01.txt>
[13] S. Shenker and J. Wroclawski, "Network Element Service Specifi-
cation Template", Internet Draft, November 1995, <draft-ietf-
intserv-svc-template-02.txt>
[14] J. Wroclawski, "The Use of RSVP with IETF Integrated Services",
Internet Draft, August 1996, <draft-ietf-intserv-use-00.txt>
[15] M. Borden, E. Crawley, B. Davie and S. Batsell, "Integration of
Real-time Services in an IP-ATM Network Architecture", "IP
Authentication Header", RFC 1821, August 1995.
[16] J. Heinanen, "Multiprotocol Encapsulation over ATM Adaptation
Layer 5", RFC 1483, July 1993.
AUTHORS' ADDRESSES AUTHORS' ADDRESSES
Marty Borden Mark W. Garrett Mark W. Garrett Marty Borden
Bay Networks Bellcore Bellcore New Oak, Inc.
3 Federal Street 445 South Street 445 South Street
Billerica, MA 01821 Morristown, NJ 07960 Morristown, NJ 07960
USA USA USA USA
phone: +1 508 436-3903 phone: +1 201 829-4439 phone: +1 201 829-4439 phone: +1 508
email: mborden@baynetworks.com email: mwg@bellcore.com email: mwg@bellcore.com email: mborden@newoak.com
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