draft-ietf-issll-atm-mapping-01.txt   draft-ietf-issll-atm-mapping-02.txt 
INTERNET-DRAFT Mark W. Garrett, INTERNET-DRAFT Mark W. Garrett,
Bellcore Bellcore
Expires 26 September 1997
Marty Borden, Marty Borden,
New Oak, Inc. New Oak Communications
Interoperation of Controlled-Load and Guaranteed Services with ATM
November, 1996. <draft-ietf-issll-atm-mapping-02.txt>
Interoperation of Controlled-Load and Guaranteed-Service with ATM
<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. This document
and ATM technologies have well-defined service architectures. These provides guidelines for ATM virtual connection features and
include definitions of several services and associated parameters parameters to be used in support of the IP integrated services
which quantify source traffic and Quality of Service (QoS) protocols. The specifications include IP Guaranteed Service,
requirements. Controlled-Load Service and ATM Forum UNI specification, versions
3.0, 3.1 and 4.0.
This draft provides mappings between IP and ATM services which will These service mappings are intended to facilitate effective end-to-
facilitate effective end-to-end Quality of Service for IP networks end Quality of Service for IP networks containing ATM subnetworks.
containing ATM subnetworks. We discuss the various features of We discuss the various features of the IP and ATM protocols, and
Guaranteed Service and Controlled Load Service, and identify identify solutions and difficult issues of compatibility and
appropriate mechanisms in ATM Virtual Circuits (VCs), which interoperation.
facilitate these services.
0.0 What's New in This Version Table of Contents
Section 3.2 on use of AdSpec in Guaranteed Service. 0.0 What's New in This Version ......................................... 3
Expanded Section 2.5 on traffic descriptor mapping. 1.0 Introduction ....................................................... x
1.1 General System Architecture .................................... x
1.2 Related Documents .............................................. x
Placeholder Section 3.1 on handling of excess traffic 2.0 Discussion of ATM Protocol Features ................................ x
2.1 Service Category and Bearer Capability ......................... x
2.1.1 Service Categories for Guaranteed Service ................ x
2.1.2 Service Categories for Controlled Load ................... x
2.1.3 Service Categories for Best Effort ....................... x
2.2 Cell Loss Priority Bit, Tagging and Conformance Definitions .... x
2.3 ATM Adaptation Layer ........................................... x
2.4 Broadband Low Layer Information ................................ x
2.5 Traffic Descriptors ............................................ x
2.5.1 Translating Traffic Descriptors for Guaranteed Service ... x
2.5.2 Translating Traffic Descriptors for Controlled Load Service x
2.5.3 Translating Traffic Descriptors for Best Effort Service .... x
2.6 QoS Classes and Parameters ..................................... x
2.7 Additional Parameters -- Frame Discard Mode .................... x
Mention of new I.356 version, which changes ITU QoS class definitions. 3.0 Discussion of IP-IS Protocol Features .............................. x
3.1 Handling of Excess Traffic ..................................... x
3.2 Use of AdSpec in Guaranteed Service with ATM ................... x
General cleanup of text. 4.0 Discussion of Miscellaneous Items .................................. x
4.1 Units Conversion ............................................... x
5.0 Summary of ATM VC Setup Parameters for Guaranteed Service .......... x
5.1 Encoding GS Using Real-Time VBR ................................ x
5.2 Encoding GS Using CBR .......................................... x
5.3 Encoding GS Using Non-Real-Time VBR ............................ x
5.4 Encoding GS Using ABR .......................................... x
5.5 Encoding GS Using UBR .......................................... x
5.6 Encoding GS Using UNI 3.0 and UNI 3.1. ......................... x
6.0 Summary of ATM VC Setup Parameters for Controlled Load Service ..... x
6.1 Encoding CLS Using ABR ......................................... x
6.2 Encoding CLS Using Non-Real-Time VBR ........................... x
6.3 Encoding CLS Using Real-Time VBR ............................... x
6.4 Encoding CLS Using CBR ......................................... x
6.5 Encoding CLS Using UBR ......................................... x
6.6 Encoding CLS Using UNI 3.0 and UNI 3.1. ........................ x
7.0 Summary of ATM VC Setup Parameters for Best Effort Service ......... x
7.1 Encoding Best Effort Service Using UBR ......................... x
7.2 Encoding Best Effort Service Using Other ATM Service Categories x
8.0 Acknowledgements ................................................... x
Appendix 1 Abbreviations .............................................. x
REFERENCES ............................................................. x
AUTHORS' ADDRESSES ..................................................... x
0.0 What's New in This Version
Corrections to VC setup parameter tables.
Deleted specific QoS parameter values in tables.
Section 3.1 on handling of excess traffic.
1.0 Introduction 1.0 Introduction
We consider the problem of providing IP Integrated Services [1] with We consider the problem of providing IP Integrated Services [1] with
an ATM subnetwork. This document is intended to be consistent with an ATM subnetwork. This document is intended to be consistent with
the rsvp protocol [2] for IP-level resource reservation (although it the rsvp protocol [2] for IP-level resource reservation (although it
is independent of rsvp to the extent that GS and CLS services could is, strictly speaking, independent of rsvp, since GS and CLS services
be supported through another mechanism). In the ATM network, we can be supported through other mechanisms). In the ATM network, we
consider ATM Forum UNI Signaling, versions 3.0, 3.1 and 4.0 [3, 4, 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 5]. The latter uses the more complete service model of The ATM
Forum's TM 4.0 specification [6, 7]. 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 document, we
on the service types, parameters and signalling elements needed for focus on the service types, parameters and signalling elements needed
service interoperation. The resulting service mappings can be used for service interoperation. The resulting service mappings can be
to provide effective end-to-end Quality of Service (QoS) for IP used 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) [8] and The IP services considered are Guaranteed Service (GS) [8] and
Controlled Load Service (CLS) [9]. We also treat the default Best Controlled Load Service (CLS) [9]. We also treat the default Best
Effort Service (BE) in parallel with these. Our recommendations for Effort Service (BE) in parallel with these. Our recommendations for
BE are intended to be consistent with RFC 1755 [10], and its revision BE are intended to be consistent with RFC 1755 [10], and its revision
(still in progress) [11], which defines how ATM VCs can be used in (in progress) [11], which defines how ATM VCs can be used in support
support of normal BE IP service. The ATM services we consider are: 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
(Note, Appendix 1 provides definitions for all abbreviations.) In (Note, Appendix 1 provides definitions for all abbreviations.) In
the case of UNI 3.0 and 3.1 signaling, where these service are not 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 the appropriate available
possible. services.
The service mappings which follow most naturally from the service 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
For completeness we provide detailed mappings for all service For completeness we provide detailed mappings for all service
combinations and identify how each meets or fails to meet the combinations and identify how each meets or fails to meet the
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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
soft state (in the control path), and to classify and schedule soft state (in the control path), and to classify and schedule
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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, the topic of VC management (LIJ) feature in ATM may be used. Note, the topic of VC management
and mapping of flows onto VCs is considered at length in another and mapping of flows onto VCs is considered at length in another
issll working group draft [12]. 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 |
| | | |
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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. (iii) There must exist a based on an empiric of changing TSpecs. (iii) There must exist a
path for best effort flows and for sending the rsvp control messages. path for best effort flows and for sending the rsvp control messages.
How this interacts with the establishment of VCs for QoS traffic may How this interacts with the establishment of VCs for QoS traffic may
alter the characteristics required of those VCs. See [12] for alter the characteristics required of those VCs. See [12] for
further details on VC management. further details on VC management.
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 document, 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
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Within the IETF area, related material includes the work of the rsvp 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 [2], int-serv [1, 8, 9, 13, 14] and ion working groups [10, 11] of
the IETF. Rsvp defines the resource reservation protocol (which is the IETF. Rsvp defines the resource reservation protocol (which is
analogous to signaling in ATM). Int-serv defines the behavior and analogous to signaling in ATM). Int-serv defines the behavior and
semantics of particular services (analogous e.g., to the Traffic semantics of particular services (analogous e.g., to the Traffic
Management working group in the ATM Forum). Ion defines interworking Management working group in the ATM Forum). Ion defines interworking
of IP and ATM for traditional Best Effort service, and covers all of IP and ATM for traditional Best Effort service, and covers all
issues related to routing and addressing. issues related to routing and addressing.
RFC 1821 [15], represent an early discussions of issues involved with A large number of ATM signaling details are covered in RFC 1755 [10],
interoperating IP and ATM protocols for integrated services and QoS. e.g., differences between UNI 3.0 and UNI 3.1, encapsulation, frame-
relay interworking, etc. These considerations generally extend to IP
over ATM with QoS as well. Any description given in this document of
IP Best Effort service (i.e. the default behavior) over ATM is
intended to be consistent with RFC 1755 and it's extension for UNI
4.0 [11], and those documents are to be considered definitive. In
some instances with non-best-effort services, certain IP/ATM features
will diverge from the following RFC 1755. The authors have attempted
to note such differences explicitly. (For example, best effort VCs
are taken down on timeout by either edge device, while QoS VCs are
only removed by the upstream edge device when the corresponding rsvp
reservation is deleted.)
RFC 1821 [15], represents an early discussions of issues involved
with interoperating IP and ATM protocols for integrated services and
QoS.
2.0 Discussion of 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
three 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
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be used, although the edge device must choose a value for CTD and CDV be used, although the edge device must choose a value for CTD and CDV
as a matter of local policy. as a matter of local policy.
The UBR category does not provide enough capability for Controlled The UBR category does not provide enough capability for Controlled
Load. The point of CLS is to allow an allocation of resources, which Load. The point of CLS is to allow an allocation of resources, which
is facilitated by the token bucket traffic descriptor, and is is facilitated by the token bucket traffic descriptor, and is
unavailable in UBR. 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 All of the service categories have the capability to carry Best
service, but the natural service category is UBR (or, in UNI 3.x, Effort service, but the natural service category is UBR (or, in UNI
BCOB-C or BCOB-X, with the best effort indicator flag). A CBR or 3.x, BCOB-C or BCOB-X, with the best effort indication set). A CBR
rtVBR clearly could be used, and since the service is not real-time, or rtVBR clearly could be used, and since the service is not real-
a nrtVBR connection could also be used. In these cases the rate time, a nrtVBR connection could also be used. In these cases the
parameter used reflects a bandwidth allocation in support of the edge rate parameter used reflects a bandwidth allocation in support of the
device's best effort connectivity to the far edge router. It would edge device's best effort connectivity to the far edge router. It
be normal for many flows to be aggregated on this connection; indeed, would be normal for traffic from many source/destination pairs to be
since Best Effort is the default IP behavior, the individual flows aggregated on this connection; indeed, since Best Effort is the
are not necessarily identified or accounted for. CBR may be a default IP behavior, the individual flows are not necessarily
preferred solution in the case where best effort traffic is identified or accounted for. CBR may be a preferred solution in the
sufficiently highly aggregated that a simple fixed-rate pipe is case where best effort traffic is sufficiently highly aggregated that
efficient. An ABR connection could similarly be used to support Best a simple fixed-rate pipe is efficient. Both CBR and nrt-VBR provide
Effort traffic. This is the purpose for which ABR was specifically bandwidth allocation which may be useful for billing purposes. An
designed. It is conceivable that a separate ABR connection would be ABR connection could similarly be used to support Best Effort
made for different IP flows, although the normal case would probably traffic. The support of data communications protocols such as TCP/IP
have all IP Best Effort traffic with a common exit router sharing a is the explicit purpose for which ABR was specifically designed. It
single ABR connection. is conceivable that a separate ABR connection would be made for
different IP flows, although the normal case would probably have all
IP Best Effort traffic with a common egress router sharing a single
ABR connection.
The rt-VBR service category may be considered less suitable, simply
because both the real-time delay constraint and the use of SCR/BT add
unnecessary complexity.
See specifications from the IETF ion working group [10, 11] for See specifications from the IETF ion working group [10, 11] for
related work on support of Best Effort service with ATM. 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 CLP=1 are said to be ``tagged'' and have lower priority. This
tagging may have been done by the source or an upstream switch. tagging may be done by the source, to indicate relative priority
Options involving the use of tagging are decided at call setup time. within the VC, or by a switch, to indicate traffic in violation of
policing parameters. 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),
also known as a "leaky bucket" algorithm, for CBR and VBR services. also known as a "leaky bucket" algorithm, for CBR and VBR services.
(UBR and ABR have network-specific conformance definitions. Note, (UBR and ABR have network-specific conformance definitions. Note,
the term "compliance" in ATM is used to describe the behavior of a the term "compliance" in ATM is used to describe the behavior of a
connection.) connection.)
The network may tag cells which are non-conforming, rather than The network may tag cells which are non-conforming, rather than
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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'' non- supported) in the VC setup as a means of ``downgrading'' non-
conformant cells. However, we wish to point out that the term ``best conformant cells. However, the term ``best effort'' seems to be used
effort'' seems to be used with two distinguishable meanings in the with two distinguishable meanings in the int-serv specs. The first
int-serv specs. The first interpretation is that of a service class is that of a service class that, in some typical scheduler
that, in some typical scheduler implementations, would correspond to implementations, would correspond to a separate queue. Placing
a separate queue. Placing excess traffic in best effort in this excess traffic in best effort in this sense would be giving it lower
sense would be giving it lower delay priority. The other sense is delay priority. The other sense is more generic, meaning that the
more generic, meaning that the network would make a best effort to network would make a best effort to transport the traffic. A
transport the traffic. A reasonable expectation is that a network reasonable expectation is that a network with no contending traffic
with no contending traffic would transport the packet, while a very would transport the packet, while a very congested network would drop
congested network would drop the packet. A packet that could be the packet. A packet that could be tagged with lower loss priority
tagged with lower loss priority (such as the ATM CLP bit) would be (such as the ATM CLP bit) would be more likely to be dropped, but
more likely to be dropped, but would not normally be transported out would not normally be transported out of order with respect to the
of order with respect to the conforming portion of the flow. Such a conforming portion of the flow. Such a mechanism would agree with
mechanism would agree with the latter definition of best effort, but the latter definition of 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.
Once an ATM connection is established, the use of the conformance Once an ATM connection is established, and the particular conformance
definition and resulting policing action is mandatory. Since the definition is determined, the resulting policing action is mandatory.
conformance algorithm operates on cells, when mapping rates and Since the conformance algorithm operates on cells, when mapping rates
bucket sizes from IP services to corresponding ATM parameters, a and bucket sizes from IP services to corresponding ATM parameters, a
correction needs to be made (at call setup time) for the ATM correction needs to be made (at call setup time) for the ATM
segmentation overhead. Unfortunately this overhead, as a ratio, segmentation overhead. Unfortunately this overhead, as a ratio,
depends on packet length, with the overhead largest for small depends on packet length, with the overhead largest for small
packets. Thus the appropriate correction could be based on minimum packets. Thus the appropriate correction could be based on minimum
packet size, expected packet size, or otherwise in a network specific packet size, expected packet size, or otherwise in a network specific
manner, determined at the edge device IWF. manner, determined at the edge device IWF. See Section 4.1.
It is always better fo the IWF to tag cells when it can anticipate
that the ATM network would do so. This is because the IWF knows the
IP packet boundaries and can tag all of the cells corresponding to a
packet. If left to the ATM layer UPC, the network would inevitably
carry some cells of packets which are worthless, because some other
cells from those packet are dropped due to non-conformance.
Therefore, the IWF, knowing the VC GCRA parameters, should always
anticipate the cells which will be tagged by the ATM UPC and tag all
of the cells uniformly across each affected packet.
2.3 ATM Adaptation Layer 2.3 ATM Adaptation Layer
The AAL type 5 encoding must be used, as specified in RFC 1483 and The AAL type 5 encoding must be used, as specified in RFC 1483 and
RFC 1755. AAL5 requires specification of the maximum SDU size in both RFC 1755. AAL5 requires specification of the maximum SDU size in both
the forward and reverse directions. Both GS and CLS specify a maximum the forward and reverse directions. Both GS and CLS specify a maximum
packet size as part of the TSpec and this value shall be used as the packet size as part of the TSpec and this value shall be used as the
maximum SDU in each direction for unicast connections, but only in maximum SDU in each direction for unicast connections, but only in
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,
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is used for policing, while the Rspec rate (which cannot be smaller) is used for policing, while the Rspec rate (which cannot be smaller)
is the allocated service rate. A receiver increases R over r to is the allocated service rate. A receiver increases R over r to
reduce the delay. reduce the delay.
When mapping Guaranteed Service onto a rtVBR VC, the ATM traffic When mapping Guaranteed Service onto a rtVBR VC, the ATM traffic
descriptor parameters (PCR, SCR, MBS) can be set within the following descriptor parameters (PCR, SCR, MBS) can be set within the following
bounds: bounds:
R <= PCR <= min(p, line rate) R <= PCR <= min(p, line rate)
r <= SCR <= PCR r <= SCR <= PCR
b <= MBS. 0 <= MBS <- b.
Note that a receiver can choose R > p to lower the delay. This Note that a receiver can choose R > p to lower the delay. This
leaves the first equation somewhat subject to interpretation. If a leaves the first equation somewhat subject to interpretation. If a
receiver chooses R > line rate, it seems clear that the admission receiver chooses R > line rate, it seems clear that the admission
control would simply reject the reservation. control would simply reject the reservation.
The edge device has a buffer preceding the ATM network which must be The edge device has a buffer preceding the ATM network which must be
sufficient to absorb bursts arriving faster than they can be admitted sufficient to absorb bursts arriving faster than they can be admitted
into the ATM network. For example, parameters may be set as PCR = R, into the ATM network. For example, parameters may be set as PCR = R,
SCR = r, MBS = b. The edge device buffer of size b would absorb a SCR = r, MBS = b. The edge device buffer of size b would absorb a
skipping to change at page 14, line 26 skipping to change at page 16, line 19
PCR is greater than R, the buffer requirement may be relaxed PCR is greater than R, the buffer requirement may be relaxed
accordingly. accordingly.
2.5.2 Translating Traffic Descriptors for Controlled Load Service 2.5.2 Translating Traffic Descriptors for Controlled Load Service
Controlled Load service has a peak rate, p, a Tspec rate, r, and a Controlled Load service has a peak rate, p, a Tspec rate, r, and a
corresponding bucket depth parameter, b. The ATM traffic parameters corresponding bucket depth parameter, b. The ATM traffic parameters
for nrtVBR service category are constrained by for nrtVBR service category are constrained by
r <= SCR <= PCR <= min(p, line rate) r <= SCR <= PCR <= min(p, line rate)
b <= MBS. 0 <= MBS <- b.
For ABR VCs, the Tspec rate would be used to set the minimum cell For ABR VCs, the Tspec rate would be used to set the minimum cell
rate (MCR) parameter. The bucket depth parameter does not map rate (MCR) parameter. The bucket depth parameter does not map
directly to a signalled ATM parameter, so the edge device must have a directly to a signalled ATM parameter, so the edge device must have a
buffer of at least b bytes. buffer of at least b bytes.
For CBR, the Tspec rate sets a lower bound on PCR, and again, the For CBR, the Tspec rate sets a lower bound on PCR, and again, the
available buffering in the edge device must be adequate to available buffering in the edge device must be adequate to
accommodate possible bursts. accommodate possible bursts.
2.5.2 Translating Traffic Descriptors for Best Effort Service 2.5.3 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 allow the service category allows negotiation of PCR, simply to allow the
source to discover 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
skipping to change at page 16, line 20 skipping to change at page 18, line 11
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 IP-IS Protocol Features 3.0 Discussion of IP-IS Protocol Features
3.1 Handling of Excess Traffic 3.1 Handling of Excess Traffic
(Placeholder for text.) (Placeholder for text.)
Reiterate that whole packets should be tagged, See Section
2.2.
3.2 Use of AdSpec in Guaranteed Service with ATM 3.2 Use of AdSpec in Guaranteed Service with ATM
The AdSpec is a feature of Guaranteed Service which allows a receiver The AdSpec is a feature of Guaranteed Service which allows a receiver
to calculate the worst-case delay associated with a GS flow. Three to calculate the worst-case delay associated with a GS flow. Three
quantities, C, D, and MPL, are accumulated (by simple addition of quantities, C, D, and MPL, are accumulated (by simple addition of
components, one for each network element) in the PATH message from components, one for each network element) in the PATH message from
source to receiver. The resulting values can be different for each source to receiver. The resulting values can be different for each
unique receiver. The maximum delay is then found by unique receiver. The maximum delay is then found by
delay <= b/R + C/R + D + MPL delay <= b/R + C/R + D + MPL
skipping to change at page 19, line 49 skipping to change at page 21, line 41
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 required to be in agreement with the definition of GS. best effort is required to be in agreement with the definition of GS.
For this reason, we prefer an rtVBR service in which tagging is For this reason, we prefer an rtVBR service in which tagging is
supported. Another good match is to use CBR with special handling of supported. Another good match is to use CBR with special handling of
any non-conforming traffic. any non-conforming traffic.
The encodings assume a point-to-multipoint connection. For a unicast Note, in all cases the encodings assume point to multipoint
connection, the backward parameters would be equal to the forward connections, where the backward channel is not used. This is done to
parameters. be consistent with rsvp, which generally assumes a multicast
scenerio. If a specific situation does not involve multicast, then
the IWF may make use of the backward channel in a point-to-point VC,
provided that the QoS parameters are mapped consistently for the
service provided.
5.1 Encoding GS Using Real-Time VBR 5.1 Encoding GS Using Real-Time VBR (ATM Forum TM/UNI 4.0)
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
SSCS Type 0 (Null SSCS) SSCS Type 0 (Null SSCS)
Traffic Descriptor Traffic Descriptor
Forward PCR CLP=0+1 Note 6 Forward PCR CLP=0+1 Note 1
Backward PCR CLP=0+1 0 Backward PCR CLP=0+1 0
Forward SCR CLP=0 Note 6 Forward SCR CLP=0 Note 1
Backward SCR CLP=0 0 Backward SCR CLP=0 0
Forward MBS (CLP=0) Note 6 Forward MBS (CLP=0) Note 1
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
Backward Frame Discard bit 1 Note 2 Backward Frame Discard bit 1
Tagging Forward bit 1 (Tagging requested) Note 2 Tagging Forward bit 1 (Tagging requested)
Tagging Backward bit 0 (No Tagging) Note 2 Tagging Backward bit 1 (Tagging requested)
Broadband Bearer Capability Broadband Bearer Capability
Bearer Class 16 (BCOB-X) Note 3 Bearer Class 16 (BCOB-X) Note 2
ATM Transfer Capability 9 Note 2 ATM Transfer Capability 9 (Real time VBR) Note 3
Traffic Type 010 (Variable Bit Rate) Susceptible to Clipping 00 (bit encoding for Not
Timing Requirements 01 (Timing Required) susceptible)
Susceptible to Clipping 00 (Not susceptible) User Plane Configuration 01 (bit encoding for pt-to-mpt)
User Plane Configuration 01 (For pt-to-mpt)
Broadband Low Layer Information Broadband Low Layer Information
Layer 2 protocol 12 (ISO 8802/2) User Information Layer 2
Layer 3 protocol 204 (ISO/IEC TR 9577) Protocol 12 (ISO 8802/2)
User Information Layer 3
Protocol 11 (ISO/IEC TR 9577) Note 4
ISO/IEC TR 9577 IPI 204
QoS Class QoS Class
QoS Class Forward 1 Note 4 QoS Class Forward 1 Note 5
QoS Class Backward 1 Note 4 QoS Class Backward 1 Note 5
QoS Parameters QoS Parameters Note 6
Transit Delay 100ms Notes 2,5 Acceptable Forward CDV
Forward CLR (CLP=0) 1.0e-9 Notes 2,5,7 Acceptable Forward CLR
Backward CLR (CLP=0) 1.0e-9 Notes 2,5,7 Forward Max CTD
Forward CDV 30ms Notes 2,5
Backward CDV 30ms Notes 2,5
Note 1: Only included for UNI 3.0.
Note 2: Only included in TM/UNI 4.0.
Note 3: Value 1 (BCOB-A) can also be used.
Note 4: Optional in TM/UNI 4.0. Cf ITU I.365 (Oct 1996) for new definition.
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.
5.2 Encoding GS Using CBR Note 1: See discussion Section 2.5.1.
Note 2: Value 3 (BCOB-C) can also be used.
Note 3: The ATC value 19 is not used. The value 19 implies CLR
objective applies to the aggregate CLP=0+1 stream and
that does not give desirable treatment of excess
traffic in the case of IP.
Note 4: For QoS VCs supporting GS or CLS, the layer 3 protocol should
be specified. For BE VCs, it can be left unspecified, allowing
the VC to be shared by multiple protocols, following RFC 1755.
Note 5: Cf ITU I.365 (Oct 1996) for new definition.
Note 6: See section 2.6 for the values to be used The cumulative CDV
is also provided, but it depends on local implementation, and
not on values mapped from IP level service parameters.
5.2 Encoding GS Using CBR (ATM Forum TM/UNI 4.0)
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
SSCS Type 0 (Null SSCS) SSCS Type 0 (Null SSCS)
Traffic Descriptor Traffic Descriptor
Forward PCR 0+1 Note 6 Forward PCR 0 Note 1
Backward PCR 0
Forward PCR 0+1 Note 1
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
Backward Frame Discard bit 1 Note 2 Backward Frame Discard bit 1
Tagging Forward bit 0 (No Tagging) Note 2 Tagging Forward bit 1 (Tagging requested)
Tagging Backward bit 0 (No Tagging) Note 2 Tagging Backward bit 1 (Tagging requested)
Broadband Bearer Capability Broadband Bearer Capability
Bearer Class 16 (BCOB-X) Note 3 Bearer Class 16 (BCOB-X) Note 2
ATM Transfer Capability 7 Note 2 ATM Transfer Capability 5 (CBR) Note 3, 4
Traffic Type 001 (Constant Bit Rate) Susceptible to Clipping 00 (bit encoding for Not
Timing Requirements 01 (Timing Required) susceptible)
Susceptible to Clipping 00 (Not susceptible) User Plane Configuration 01 (bit encoding for pt-to-mpt)
User Plane Configuration 01 (For pt-to-mpt)
Broadband Low Layer Information Broadband Low Layer Information
Layer 2 protocol 12 (ISO 8802/2) User Information Layer 2
Layer 3 protocol 204 (ISO/IEC TR 9577) Protocol 12 (ISO 8802/2)
User Information Layer 3
Protocol 11 (ISO/IEC TR 9577) Note 5
ISO/IEC TR 9577 IPI 204
QoS Class QoS Class
QoS Class Forward 1 Note 4 QoS Class Forward 1 Note 6
QoS Class Backward 1 Note 4 QoS Class Backward 1 Note 6
QoS Parameters QoS Parameters Note 7
Transit Delay 100ms Notes 2,5 Acceptable Forward CDV
Forward CLR (CLP=0) 1.0e-9 Notes 2,5,7 Acceptable Forward CLR
Backward CLR (CLP=0) 1.0e-9 Notes 2,5,7 Forward Max CTD
Forward CDV 30ms Notes 2,5
Backward CDV 30ms Notes 2,5
Note 1: Only included for UNI 3.0. Note 1: See discussion Section 2.5.1.
Note 2: Only included in TM/UNI 4.0. Note 2: Value 1 (BCOB-A) can also be used.
Note 3: Value 1 (BCOB-A) can also be used. Note 3: If bearer class A is chosen the ATC field must be absent.
Note 4: Optional in TM/UNI 4.0. Cf ITU I.365 (Oct 1996) for new definition. Note 4: The ATC value 7 is not used. The value 7 implies CLR
Note 5: Values chosen to initiate discussion. May be network specific. objective applies to the aggregate CLP=0+1 stream and
Note 6: See discussion on AdSpec, Section 3.2. that does not give desirable treatment of excess
Note 7: CLR should include physical link errors with no queueing loss. traffic in the case of IP.
Note 5: For QoS VCs supporting GS or CLS, the layer 3 protocol should
be specified. For BE VCs, it can be left unspecified, allowing
the VC to be shared by multiple protocols, following RFC 1755.
Note 6: Cf ITU I.365 (Oct 1996) for new definition.
Note 7: See section 2.6 for the values to be used The cumulative CDV
is also provided, but it depends on local implementation, and
not on values mapped from IP level service parameters.
5.3 Encoding GS Using Non-Real-Time VBR 5.3 Encoding GS Using Non-Real-Time VBR (ATM Forum TM/UNI 4.0)
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 CLS 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 6.2 below. would be derived from the Tspec peak rate. See Section 6.2 below.
5.4 Encoding GS Using ABR 5.4 Encoding GS Using ABR (ATM Forum TM/UNI 4.0)
The authors feel that this is a very unlikely combination. The This is a very unlikely combination. The objective of the ABR
objective of the ABR service is to provide `low' loss rates which, service is to provide `low' loss rates which, via flow control, can
via flow control, can result in delays. The introduction of delays result in delays. The introduction of delays is contrary to the
is contrary to the point of GS. design objectives of GS. If ABR were used for GS, the VC parameters
would follow as for CLS over ABR. See Section 6.1.
5.5 Encoding GS Using UBR 5.5 Encoding GS Using UBR (ATM Forum TM/UNI 4.0)
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.
5.6 Encoding GS Using UNI 3.0 and UNI 3.1. 5.6 Encoding GS Using ATM Forum UNI 3.0/3.1 Specifications
(Placeholder for text.) It is not recommended to support GS using VBR for the following
reasons. The Class C bearer class does not represent real-time
behavior. Appendix F of UNI 3.1 specification precludes the
specification of traffic type "VBR" with the timing requirement "End
to End timing Required" in conjunction with bearer class X.
It is possible to support GS using a CBR ``pipe.'' The following
table specifies the support of GS using CBR.
AAL
Type 5
Forward CPCS-SDU Size parameter M of TSpec
Backward CPCS-SDU Size parameter M of TSpec
Mode 1 (Message mode) Note 1
SSCS Type 0 (Null SSCS)
Traffic Descriptor
Forward PCR 0 Note 2
Backward PCR 0
Forward PCR 0+1 Note 2
Backward PCR 0+1 0
BE indicator NOT included
Tagging Forward bit 1 (Tagging requested)
Tagging Backward bit 1 (Tagging requested)
Broadband Bearer Capability
Bearer Class 16 (BCOB-X) Note 3
Traffic Type 001 (bit encoding for Constant Bit
Rate)
Timing Requirements 01 (bit encoding for Timing
Required)
Susceptible to Clipping 00 (bit encoding for Not
susceptible)
User Plane Configuration 01 (bit encoding for pt-to-mpt)
Broadband Low Layer Information
User Information Layer 2
Protocol 12 (ISO 8802/2)
User Information Layer 3
Protocol 11 (ISO/IEC TR 9577) Note 4
ISO/IEC TR 9577 IPI 204
QoS Class
QoS Class Forward 1
QoS Class Backward 1
QoS Parameters
Parameters are implied by the QOS Class
Note 1: Only included for UNI 3.0.
Note 2: See discussion, Section 2.5.1.
Note 3: Value 1 (BCOB-A) can also be used. If BCOB-A is used Traffic
Type and Timing Requirements fields are not included.
Note 4: For QoS VCs supporting GS or CLS, the layer 3 protocol should
be specified. For BE VCs, it can be left unspecified, allowing
the VC to be shared by multiple protocols, following RFC 1755.
6.0 Summary of ATM VC Setup Parameters for Controlled Load Service 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. CLS traffic is partly delay tolerant and of for Controlled Load. CLS traffic is partly delay tolerant and of
variable rate. NrtVBR and ABR (for TM/UNI 4.0 only) are the possible variable rate. NrtVBR and ABR (for TM/UNI 4.0 only) are the possible
choices in supporting CLS. 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.
6.1 Encoding CLS Using ABR 6.1 Encoding CLS Using ABR (ATM Forum TM/UNI 4.0)
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
Forward MCR CLP 0+1 From TSpec token bucket rate Forward MCR CLP 0+1 From TSpec token bucket rate
Backward MCR CLP 0+1 From TSpec token bucket rate Backward MCR CLP 0+1 From TSpec token bucket rate
BE indicator NOT included BE indicator NOT included
Forward Frame Discard bit 1 Forward Frame Discard bit 1
Backward Frame Discard bit 1 Backward Frame Discard bit 1
Tagging Forward bit 0 (Tagging not requested) Tagging Forward bit 0 (Tagging not requested)
Tagging Backward bit 0 (Tagging not requested) Tagging Backward bit 0 (Tagging not requested)
Broadband Bearer Capability Broadband Bearer Capability
Bearer Class 16 (BCOB-X) Note 3 Bearer Class 16 (BCOB-X) Note 1
ATM Transfer Capability 12 ATM Transfer Capability 12 (ABR)
Traffic Type 010 (Variable Bit Rate) Traffic Type 010 (Variable Bit Rate)
Timing Requirements 10 (Timing Not Required) Timing Requirements 10 (Timing Not Required)
Susceptible to Clipping 00 (Not susceptible) Susceptible to Clipping 00 (Not susceptible)
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) User Information Layer 2
Layer 3 protocol 204 (ISO/IEC TR 9577) Protocol 12 (ISO 8802/2)
User Information Layer 3
Protocol 11 (ISO/IEC TR 9577) Note 2
ISO/IEC TR 9577 IPI 204
QoS Class QoS Class
QoS Class Forward 3 Note 4 QoS Class Forward 3 Note 3
QoS Class Backward 3 Note 4 QoS Class Backward 3 Note 3
QoS Parameters Note 4
Acceptable Forward CDV
Acceptable Forward CLR
Forward Max CTD
ABR Setup Parameters for further study (FFS) ABR Setup Parameters Note 5 ABR
ABR Additional Parameters for further study (FFS) Additional Parameters Note 5
Note 3: Value 3 (BCOB-C) can also be used. Note 1: Value 3 (BCOB-C) can also be used.
Note 4: Optional in TM/UNI 4.0. Cf ITU I.365 (Oct 1996) for new definition. Note 2: For QoS VCs supporting GS or CLS, the layer 3 protocol should
be specified. For BE VCs, it can be left unspecified, allowing
the VC to be shared by multiple protocols, following RFC 1755.
Note 3: Cf ITU I.365 (Oct 1996) for new definition.
Note 4: See section 2.6 for the values to be used. The cumulative CDV
is also provided, but it depends on local implementation, and
not on values mapped from IP level service parameters.
Note 5: Discussion of these parameters is beyond the scope of this draft.
6.2 Encoding CLS Using Non-Real-Time VBR 6.2 Encoding CLS Using Non-Real-Time VBR (ATM Forum TM/UNI 4.0)
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
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 0 Backward PCR CLP=0+1 0
Forward SCR CLP=0 From TSpec token bucket rate Forward SCR CLP=0 From TSpec token bucket rate
Backward SCR CLP=0 0 Backward SCR CLP=0 0
Forward MBS (CLP=0) From TSpec bucket size param Forward MBS (CLP=0) From TSpec bucket size param
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
Backward Frame Discard bit 1 Note 2 Backward Frame Discard bit 1
Tagging Forward bit 1 (Tagging requested) Note 2 Tagging Forward bit 1 (Tagging requested)
Tagging Backward bit 0 (No Tagging) Note 2 Tagging Backward bit 1 (Tagging requested)
Broadband Bearer Capability Broadband Bearer Capability
Bearer Class 16 (BCOB-X) Note 3 Bearer Class 16 (BCOB-X) Note 1
ATM Transfer Capability Absent Note 2 ATM Transfer Capability 10 (Non-real time VBR) Note 2, 3
Traffic Type 010 (Variable Bit Rate) Susceptible to Clipping 00 (bit encoding Not susceptible)
Timing Requirements 10 (Timing Not Required) User Plane Configuration 01 (bit encoding pt-to-mpt)
Susceptible to Clipping 00 (Not susceptible)
User Plane Configuration 01 (For pt-to-mpt)
Broadband Low Layer Information Broadband Low Layer Information
Layer 2 protocol 12 (ISO 8802/2) User Information Layer 2
Layer 3 protocol 204 (ISO/IEC TR 9577) Protocol 12 (ISO 8802/2)
User Information Layer 3
Protocol 11 (ISO/IEC TR 9577) Note 4
ISO/IEC TR 9577 IPI 204
QoS Class QoS Class
QoS Class Forward 3 Note 4 QoS Class Forward 3 Note 5
QoS Class Backward 3 Note 4 QoS Class Backward 3 Note 5
QoS Parameters QoS Parameters Note 6
Forward CLR (CLP=0) 1.0e-9 Notes 2,5,6 Acceptable Forward CDV
Backward CLR (CLP=0) 1.0e-9 Notes 2,5,6 Acceptable Forward CLR
Forward Max CTD
Note 1: Only included for UNI 3.0. Note 1: Value 3 (BCOB-C) can also be used.
Note 2: Only included in TM/UNI 4.0. Note 2: If bearer class C is used, the ATC field must be absent
Note 3: Value 3 (BCOB-C) can also be used. Note 3: The ATC value 11 is not used. The value 11 implies CLR
Note 4: Optional in TM/UNI 4.0. Cf ITU I.365 (Oct 1996) for new definition. objective applies to the aggregate CLP=0+1 stream and
Note 5: Values chosen to initiate discussion. May be network specific. that does not give desirable treatment of excess
Note 6: CLR should include physical link errors with no queueing loss. traffic in the case of IP.
Note 4: For QoS VCs supporting GS or CLS, the layer 3 protocol should
be specified. For BE VCs, it can be left unspecified, allowing
the VC to be shared by multiple protocols, following RFC 1755.
Note 5: Cf ITU I.365 (Oct 1996) for new definition.
Note 6: See section 2.6 for the values to be used. The cumulative CDV
is also provided, but it depends on local implementation, and
not on values mapped from IP level service parameters.
6.3 Encoding CLS Using Real-Time VBR 6.3 Encoding CLS Using Real-Time VBR (ATM Forum TM/UNI 4.0)
The encoding of CLS 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 CLS 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 CLS, 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.
6.4 Encoding CLS Using CBR 6.4 Encoding CLS Using CBR (ATM Forum TM/UNI 4.0)
The encoding of CLS using CBR is more stringent than using rtVBR The encoding of CLS using CBR is more stringent than using rtVBR
since 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 CLS, the same encoding as in Section 3.2 would be To use CBR for CLS, the same encoding as in Section 3.2 would be
used. However a different set of values of the QoS parameters will used. However a different set of values of the QoS parameters will
likely be used. likely be used.
6.5 Encoding CLS Using UBR 6.5 Encoding CLS Using UBR (ATM Forum TM/UNI 4.0)
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.
6.6 Encoding CLS Using UNI 3.0 and UNI 3.1. 6.6 Encoding CLS Using Non-Real-Time VBR as in UNI 3.0/3.1
Specifications
(Placeholder for text.) AAL
Type 5
Forward CPCS-SDU Size parameter M of TSpec
Backward CPCS-SDU Size 0
Mode 1 (Message mode) Note 1
SSCS Type 0 (Null SSCS)
Traffic Descriptor
Forward PCR CLP=0+1 From line rate
Backward PCR CLP=0+1 0
Forward SCR CLP=0 From TSpec token bucket rate
Backward SCR CLP=0 0
Forward MBS (CLP=0) From TSpec bucket size param
Backward MBS (CLP=0) 0
BE indicator NOT included
Tagging Forward bit 1 (Tagging requested)
Tagging Backward bit 1 (Tagging requested)
Broadband Bearer Capability
Bearer Class 16 (BCOB-X) Note 2
Traffic Type 010 (bit encoding for Variable Bit
Rate)
Timing Requirements 00 (bit encoding for No Indication)
Susceptible to Clipping 00 (bit encoding for Not
susceptible)
User Plane Configuration 01 (bit encoding for For pt-to-mpt)
Broadband Low Layer Information
User Information Layer 2
Protocol 12 (ISO 8802/2)
User Information Layer 3
Protocol 11 (ISO/IEC TR 9577) Note 3
ISO/IEC TR 9577 IPI 204
QoS Class
QoS Class Forward 3
QoS Class Backward 3
QoS Parameters
Parameters are implied by the QOS Class
Note 1: Only included for UNI 3.0.
Note 2: Value 3 (BCOB-C) can also be used. If BCOB-C is used Traffic
Type and Timing Requirements fields are not included.
Note 3: For QoS VCs supporting GS or CLS, the layer 3 protocol should
be specified. For BE VCs, it can be left unspecified, allowing
the VC to be shared by multiple protocols, following RFC 1755.
7.0 Summary of ATM VC Setup Parameters for Best Effort Service 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
for Best Effort. The BE service does not need a reservation of Best Effort. The BE service does not need a reservation of resources.
resources.
7.1 Encoding Best Effort Service Using UBR The following subsections are for information only. See the IETF ION
working group draft on ATM signalling support for IP over ATM using UNI
4.0 [11] for recommendations.
7.1 Encoding Best Effort Service Using UBR (ATM Forum TM/UNI 4.0)
This section is for information only. For recommendation, see the
IETF ION working group draft on ATM signalling support for IP over
ATM using UNI 4.0 [11].
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
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 0 Backward PCR CLP=0+1 0
BE indicator included BE indicator included
Forward Frame Discard bit 1 Note 2 Forward Frame Discard bit 1
Backward Frame Discard bit 1 Note 2 Backward Frame Discard bit 1
Tagging Forward bit 1 (Tagging requested) Note 2 Tagging Forward bit 1 (Tagging requested)
Tagging Backward bit 0 (no tagging) Note 2 Tagging Backward bit 1 (Tagging requested)
Broadband Bearer Capability Broadband Bearer Capability
Bearer Class 16 (BCOB-X) Bearer Class 16 (BCOB-X) Note 1
Traffic Type 010 (Variable Bit Rate) ATM Transfer Capability 10 (Non-real time VBR) Note 2
Timing Requirements 10 (Timing not required) Susceptible to Clipping 00 (bit encoding for Not susceptible)
Susceptible to Clipping 00 (Not susceptible) User Plane Configuration 01 (bit encoding for pt-to-mpt)
User Plane Configuration 01 (For pt-to-mpt)
Broadband Low Layer Information Broadband Low Layer Information
Layer 2 protocol 12 (ISO 8802/2) User Information Layer 2
Layer 3 protocol 204 (ISO/IEC TR 9577) Protocol 12 (ISO 8802/2)
User Information Layer 3
Protocol 11 (ISO/IEC TR 9577) Note 3
ISO/IEC TR 9577 IPI 204
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: Value 3 (BCOB-C) can also be used.
Note 2: Only included in TM/UNI 4.0. Note 2: If bearer class C is used, the ATC field must be absent
Note 3: For QoS VCs supporting GS or CLS, the layer 3 protocol should
be specified. For BE VCs, it can be left unspecified, allowing
the VC to be shared by multiple protocols, following RFC 1755.
.fi
7.2 Encoding Best Effort Service Using Other ATM Service Categories 7.2 Encoding Best Effort Service Using Other ATM Service Categories
See the IETF ION working group draft on ATM signalling support for IP See the IETF ION working group draft on ATM signalling support for IP
over ATM using UNI 4.0 [11]. over ATM using UNI 4.0 [11].
8.0 Acknowledgements 8.0 Security
Some security issues are raised in the rsvp specification [2], which
would apply here as well. There are no additional security
considerations raised in this document.
9.0 Acknowledgements
The authors would like to thank the members of the ISSLL working The authors would like to thank the members of the ISSLL working
group for their input. In particular, thanks to Jon Bennett of Fore group for their input. In particular, thanks to Jon Bennett of Fore
Systems, Roch Guerin of IBM and Susan Thomson of Bellcore. Systems, Roch Guerin of IBM and Susan Thomson of Bellcore.
Appendix 1 Abbreviations Appendix 1 Abbreviations
AAL ATM Adaptation Layer AAL ATM Adaptation Layer
ABR Available Bit Rate ABR Available Bit Rate
ATM Asynchronous Transfer Mode ATM Asynchronous Transfer Mode
skipping to change at page 28, line 7 skipping to change at page 33, line 38
BCOB Broadband Connection-Oriented Bearer Capability BCOB Broadband Connection-Oriented Bearer Capability
BCOB-{A,C,X} Bearer Class A, C, or X BCOB-{A,C,X} Bearer Class A, C, or X
BE Best Effort BE Best Effort
BT Burst Tolerance BT Burst Tolerance
CBR Constant Bit Rate CBR Constant Bit Rate
CDV Cell Delay Variation CDV Cell Delay Variation
CDVT Cell Delay Variation Tolerance CDVT Cell Delay Variation Tolerance
CLP Cell Loss Priority (bit) CLP Cell Loss Priority (bit)
CLR Cell Loss Ratio CLR Cell Loss Ratio
CLS Controlled Load Service CLS Controlled Load Service
CPCS CPCS Common Part Convergence Sublayer
CTD Cell Transfer Delay CTD Cell Transfer Delay
EOM End of Message EOM End of Message
FFS For Further Study FFS For Further Study
GCRA Generic Cell Rate Algorithm GCRA Generic Cell Rate Algorithm
GS Guaranteed Service GS Guaranteed Service
IE Information Element IE Information Element
IETF Internet Engineering Task Force IETF Internet Engineering Task Force
IP Internet Protocol IP Internet Protocol
IS Integrated Services IS Integrated Services
ISSLL Integrated Services over Specific Link Layers ISSLL Integrated Services over Specific Link Layers
skipping to change at page 28, line 39 skipping to change at page 34, line 27
QoS Quality of Service QoS Quality of Service
RESV Reservation Message (of rsvp protocol) RESV Reservation Message (of rsvp protocol)
RFC Request for Comment RFC Request for Comment
RSVP Resource Reservation Protocol RSVP Resource Reservation Protocol
Rspec Reservation Specification Rspec Reservation Specification
rtVBR Real-time VBR rtVBR Real-time VBR
SCR Sustained Cell Rate SCR Sustained Cell Rate
SDU Service Data Unit SDU Service Data Unit
SIG ATM Signaling (ATM Forum document) SIG ATM Signaling (ATM Forum document)
SNAP Subnetwork Attachment Point SNAP Subnetwork Attachment Point
SSCS SSCS Service-Specific Convergence Sub-layer
Sw Switch Sw Switch
TCP Transport Control Protocol TCP Transport Control Protocol
TM Traffic Management TM Traffic Management
TSpec Traffic Specification TSpec Traffic Specification
UBR Unspecified Bit Rate UBR Unspecified Bit Rate
UNI User-Network Interface UNI User-Network Interface
UPC Usage Parameter Control (ATM traffic policing function)
VBR Variable Bit Rate VBR Variable Bit Rate
VC (ATM) Virtual Connection VC (ATM) Virtual Connection
REFERENCES REFERENCES
[1] R. Braden, D. Clark and S. Shenker, "Integrated Services in the [1] R. Braden, D. Clark and S. Shenker, "Integrated Services in the
Internet Architecture: an Overview", RFC 1633, June 1994. Internet Architecture: an Overview", RFC 1633, June 1994.
[2] R. Braden, L. Zhang, S. Berson, S. Herzog and S. Jamin, [2] R. Braden, L. Zhang, S. Berson, S. Herzog and S. Jamin,
"Resource ReSerVation Protocol (RSVP) - Version 1 Functional "Resource ReSerVation Protocol (RSVP) - Version 1 Functional
skipping to change at page 30, line 24 skipping to change at page 36, line 11
[15] M. Borden, E. Crawley, B. Davie and S. Batsell, "Integration of [15] M. Borden, E. Crawley, B. Davie and S. Batsell, "Integration of
Real-time Services in an IP-ATM Network Architecture", "IP Real-time Services in an IP-ATM Network Architecture", "IP
Authentication Header", RFC 1821, August 1995. Authentication Header", RFC 1821, August 1995.
[16] J. Heinanen, "Multiprotocol Encapsulation over ATM Adaptation [16] J. Heinanen, "Multiprotocol Encapsulation over ATM Adaptation
Layer 5", RFC 1483, July 1993. Layer 5", RFC 1483, July 1993.
AUTHORS' ADDRESSES AUTHORS' ADDRESSES
Mark W. Garrett Marty Borden Mark W. Garrett Marty Borden
Bellcore New Oak, Inc. Bellcore New Oak Communications, Inc.
445 South Street 445 South Street 42 Nanog Park
Morristown, NJ 07960 Morristown, NJ 07960 Acton MA, 01720
USA USA USA USA
phone: +1 201 829-4439 phone: +1 508 phone: +1 201 829-4439 phone: +1 508 266-1011
email: mwg@bellcore.com email: mborden@newoak.com email: mwg@bellcore.com email: mborden@newoak.com
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