ION WG M. Maher
Category: internet-draft March 1997
draft-ietf-ion-sig-uni4.0-02.txt Expires: August 25, 1997
ATM Signalling Support for IP over ATM - UNI 4.0 Update
Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as ``work in progress.''
To learn the current status of any Internet-Draft, please check the
``1id-abstracts.txt'' listing contained in the Internet-Drafts Shadow
Directories on ds.internic.net (US East Coast), nic.nordu.net
(Europe), ftp.isi.edu (US West Coast), or munnari.oz.au (Pacific
Rim).
Abstract
This memo describes how to efficiently use the ATM call control
signalling procedures defined in UNI 4.0 [UNI96] to support IP over
ATM environments as described in RFC 1577 [LAUB94] and in [KATZ96].
Among the new features found in UNI 4.0 signalling are Available Bit
Rate (ABR) signalling and traffic parameter negotiation. This
initial draft highlights the features of UNI 4.0 signalling that
provide IP entities capabilities for requesting ATM service in sites
with SVC support, whether it is private ATM or publicly provisioned
ATM, in which case the SVC support is probably configured inside
PVPs.
This document is only relevant to IP when used as the well known
"best effort" connectionless service. In particular, this means that
this document does not pertain to IP in the presence of implemented
IP Integrated Services (ISS). The topic of IP with ISS over ATM will
be handled by a different specification or set of specifications
being worked on in the ISSLL WG.
Maher [Page 1]
INTERNET DRAFT IP over ATM Signalling - UNI 4.0 Update November 1996
This specification is follow-on to RFC 1755, "ATM Signaling Support
for IP over ATM", which is based on UNI signalling 3.1. Readers are
assumed to be familiar with RFC 1755.
Table of Contents
1. Conventions ............................................... 2
2. Overview .................................................. 3
3. Use of Protocol Procedures ................................ 3
3.1 VC Teardown........................................... 3
4. Overview of Call Establishment Message Content ............ 3
5. Description of Information Elements ....................... 4
5.1 ATM Adaptation Layer Parameters ...................... 4
5.2 Broadband Low Layer Information ..................... 5
5.3 Traffic Management Issues and Related IEs............. 5
5.3.1 ATM Traffic Descriptor ........................ 7
5.3.1.1 Tagging vs. Dropping ................. 7
5.3.2 Traffic Parameter Negotiation .................. 8
5.3.3 Broadband Bearer Capability .................... 8
5.3.4 QoS Parameter .................................. 9
5.3.4.1 Signalling of Individual QoS Parameters 9
5.6 ATM Addressing Information ........................... 9
6. ABR Signalling In More Detail ............................ 9
7. Frame Discard Capability .................................. 10
8. Security Consideration .................................... 10
9. Open Issues ............................................... 10
10. Acknowledgements........................................... 11
11. References ................................................ 11
12. Authors ................................................... 12
Appendix A Sample Signaling Messages ......................... 13
Appendix B Combinations of Traffic Related Parameters ........ 15
1. Conventions
The following language conventions are used in the items of specifi-
cation in this document:
o MUST, SHALL, or MANDATORY -- the item is an absolute requirement
of the specification.
o SHOULD or RECOMMEND -- this item SHOULD generally be followed for
all but exceptional circumstances.
o MAY or OPTIONAL -- the item is truly optional and MAY be followed
or ignored according to the needs of the implementor.
Maher [Page 2]
INTERNET DRAFT IP over ATM Signalling - UNI 4.0 Update November 1996
2. Overview
UNI Signalling version 4.0 is the ATM Forum follow-on specification
to UNI Signalling 3.1. Among the new features in UNI 4.0, those of
particular interest to IP over ATM environments are:
o ABR Signalling for Point-to-Point Calls
o Traffic Parameter Negotiation
o Frame Discard Support
o Leaf Initiated Join (LIJ) Capability
o ATM Anycast Capability
o Switched Virtual Path (VP) Service
This draft highlights the first three capabilities listed above. The
last three capabilities are not discussed because models for their
use in IP over ATM environments have not yet been defined or IP
imposes no special requirements on them.
3. Use of Protocol Procedures
Section 3 in RFC 1755 introduces requirements of virtual circuit (VC)
management intended to prevent VC thrashing, excessive VC consump-
tion, and other related problems. This section updates RFC 1755's
requirements related to VC teardown.
3.1. VC Teardown
In environments running layer 3 (L3) signalling protocols, such as
RSVP [RSVP], over ATM, data VCs might correspond to L3 reserved flows
(even if the VC is a 'best effort' VC). In such environments it is
beneficial for VCs to be torn down only when the L3 reservation has
expired. In other words, it is more efficient for the sender of a L3
reserved flow to initiate VC tear-down when the receiver(s) has
ceased refreshing the reservation. To support such L3 behavior, sys-
tems implementing a Public ATM UNI interface and serving as the
_called_ party of a VC, MUST NOT use an inactivity timer to clear
connections that are idle for some period of time.
4. Overview of Call Establishment Message Content
Signalling messages are structured to contain mandatory and optional
variable length information elements (IEs). A SETUP message which
establishes an ATM connection to be used for IP and multiprotocol
interconnection calls MUST contain the following IEs:
Maher [Page 3]
INTERNET DRAFT IP over ATM Signalling - UNI 4.0 Update November 1996
AAL Parameters
ATM Traffic Descriptor
Broadband Bearer Capability
Broadband Low Layer Information
QoS Parameter
Called Party Number
Calling Party Number
and MAY, under certain circumstance contain the following IEs :
Calling Party Subaddress
Called Party Subaddress
Transit Network Selection
(New in UNI 4.0:)
Minimum Acceptable ATM Traffic Descriptor
Alternative ATM Traffic Descriptor
ABR Setup Parameters
ABR Additional Parameters
Connection Scope Selection
Extended QoS Parameters
End-to-End Transit Delay
In UNI 4.0, like UNI 3.1, the AAL Parameters and the Broadband Low
Layer Information IEs are optional in a SETUP message. However, in
support of IP over ATM these two IEs MUST be included. Appendix A
shows a sample setup message.
5. Description of Information Elements
This section describes the coding of, and procedures surrounding,
information elements in SETUP and CONNECT messages. The first two IEs
described, ATM Adaptation Layer Parameters and Broadband Low Layer
Information, are categorized as having significance only to the end-
points of an ATM call supporting IP. That is, the network does not
process these IEs.
5.1. ATM Adaptation Layer (AAL) Parameters
The AAL Parameters IE carries information about the ATM adaptation
layer to be used on the connection. The parameters specified in this
IE are the same as specified in [PER95].
Maher [Page 4]
INTERNET DRAFT IP over ATM Signalling - UNI 4.0 Update November 1996
Format and field values of AAL Parameters IE
----------------------------------------------------------
| aal_parameters |
----------------------------------------------------------
| aal_type 5 (AAL 5) |
| fwd_max_sdu_size_identifier 140 |
| fwd_max_sdu_size 65,535 (desired IP MTU) |
| bkw_max_sdu_size_identifier 129 |
| bkw_max_sdu_size 65,535 (desired IP MTU) |
| sscs_type identifier 132 |
| sscs_type 0 (null SSCS) |
----------------------------------------------------------
This shows maximum size MTUs. In practice, most sites have used 9180
IP MTUs for ATM [RFC1626].
5.2. Broadband Low Layer Information
Selection of an encapsulation to support IP over an ATM VCC is done
using the Broadband Low Layer Information (B-LLI) IE, along with the
AAL Parameters IE, and the B-LLI negotiation procedure. B-LLI nego-
tiation is described in [PER95] in Appendix D. The procedures remain
the same for this UNI 4.0 based specification.
Format of B-LLI IE indicating LLC/SNAP encapsulation
----------------------------------------------------------
| bb_low_layer_information |
----------------------------------------------------------
| layer_2_id 2 |
| user_information_layer 12 (lan_llc - ISO 8802/2) |
----------------------------------------------------------
5.3. Traffic Management Issues and Related IEs
The ATM Forum Traffic Management Sub-working group has completed ver-
sion 4.0 of their specification [TMGT96]. This latest version focuses
primarily on the definition of the ABR service category. As opposed
to the Unspecified Bit Rate (UBR) traffic class, ABR uses a rate-
based flow control mechanism to assure certain traffic guarantees
(bandwidth and delay). There has been much debate on whether IP
benefits from ABR, and if so, how IP should use ABR. The Integrated
Internet Services (IIS) and RSVP models in IP add complexity to this
issue because mapping IIS traffic classes to ATM traffic classes is
Maher [Page 5]
INTERNET DRAFT IP over ATM Signalling - UNI 4.0 Update November 1996
not straightforward.
This document attempts only to present the required IP to ATM signal-
ling interface for IP over ATM systems that do not support IIS as
yet. It is an attempt to cause IP over ATM vendors to support enough
options for signalling the traffic characteristics of VCs serving
non-IIS IP datagrams. This specification also aims to give guidance
to ATM system administrators so that they can configure their IP over
ATM entities to conform to the varied services that their ATM pro-
vider may have sold to them. By definition, IP without IIS cannot be
expected to provide a signalling interface that is flexible and
allows application specific traffic descriptors. The topic of IP over
ATM signalling for IP _with_ IIS is to presented other specifications
produced by the ISSLL WG of the IETF.
An IP over ATM interface may be configured to support all the defined
ATM Service Categories (ASC). They are:
- CBR
- CBR with CLR specified (loss-permitting CBR)
- ABR
- UBR
- real time VBR
- non-real time VBR
The ATM Traffic Descriptor IE, Broadband Bearer Capability IE, and
the QoS Parameter IE together define the signalling view of ATM
traffic management. Additionally, the Extended QoS parameters IE and
the End-to-end Transit Delay IE may be used to provide more specifics
about traffic requirements, however this note does not provide expli-
cit recommendations on their use. Annex 9 of [TMGT96] describes a
set of allowable combinations of traffic and QoS related paramenters
defined for UNI 4.0 signalling. This set includes all forms of non-
IIS IP signalling configurations that MUST be implemented in ATM
endsystems to accommodate varied sites' needs. The principle is that
IP over ATM service may be available in different sites by different
types of procured ATM service; for one site, a CBR PVP might be
cost-effective and then the SVCs that IP over ATM without IIS must
establish must be CBR. Similarly, VBR or ABR PVPs could be pro-
visioned. The intent of this document is to specify the use of the
most sensible parameters within this non-IIS configuration. For
instance, for non-IIS VBR, the SCR value may need to be hand-
configured for IP users, or for ABR, the PCR value may be link-rate
with a 0 MCR.
For the reader's convenience, we have replicated the tables found in
Annex 9 of [TMGT96] in Appendix B of this document. Ideally this
Maher [Page 6]
INTERNET DRAFT IP over ATM Signalling - UNI 4.0 Update November 1996
document could recommend specific values for the various table param-
eters that would offer the most sensible IP over ATM service.
Nevertheless, it is not possible to mandate specific values given the
varied scenarios of procured ATM service.
5.3.1. ATM Traffic Descriptor
Even with the newly defined ABR ASC, the most convenient model of IP
behavior still corresponds to the best effort capability. If a a
site's configuration allows this capability, a user MAY signal for it
using the IE's and parameters pertaining to the UBR ATM service
category. See Appendix B for the list of IE's and parameters.
Although we make no recommendations for signalling ABR service, we
note here that in support of ABR service two new subfields have been
added in UNI 4.0 to the Traffic Descriptor IE. These fields are the
forward and backward 'Minimum Cell Rate' fields.
5.3.1.1. Tagging vs. Dropping
The Traffic Descriptor IE contains a 'tagging' subfield used for
indicating whether the network is allowed to tag the source's data
cells. Tagging in the network may occur during periods of congestion
or when the source's traffic has violated the traffic contract for
the connection. See Section 4 of [TMGT96] for an explanation of ATM
connection conformance and the Usage Parameter Control (UPC) func-
tion.
UNI 4.0 and TMGT 4.0 define two modes of UBR, UBR.1 which disables
tagging and UBR.2 which enables tagging (see Appendix B). In some
network environments there is no potential for UBR traffic sources to
violate the connection traffic contract because, either the user's
terminal equipment supports traffic shaping, or the network does not
enforce PCR. In such environments, the user SHOULD specify 'no tag-
ging' in the SETUP message (UBR.1). Specifying 'no tagging' indi-
cates to the network that cells should be dropped during periods of
congestion instead of being randomly marked/tagged as low priority.
Cells of packets that the source itself has marked as low priority
are dropped first, thereby preserving the source's characterization
of the traffic.
On the other hand, when the network applies PCR to the UPC function,
meaning it enforces PCR, and traffic shaping is not enabled at the
source, the source has the potential to violate the traffic contract
and SHOULD therefore signal for tagging (UBR.2). Tagging allows the
source's non-conforming cells to be tagged and forwarded instead of
Maher [Page 7]
INTERNET DRAFT IP over ATM Signalling - UNI 4.0 Update November 1996
dropped.
5.3.2. Traffic Parameter Negotiation
UNI 4.0 allows certain traffic parameters to be negotiated during the
call establishment phase Traffic parameters cannot be 'renegotiated'
after the call is active. Two new IEs make negotiation possible:
- the Minimum Acceptable ATM Traffic Descriptor IE allows
negotiation of PCR parameters
- the Alternative ATM Traffic Descriptor IE allows negotiation of
other traffic parameters
A SETUP or CONNECT message may include ONLY one of the above IEs.
That is, the calling party may only offer an 'alternative' or
'minimum' to the requested traffic parameters. (See Section 8 of
[UNI96].) IP over ATM entities SHOULD take advantage of this capabil-
ity whenever possible. In order to do so, IP over ATM entities SHOULD
specify PCR _equal_ to the link rate in the ATM Traffic Descriptor IE
of the SETUP message and a minimum of zero PCR in the Minimum Accept-
able ATM Traffic Descriptor IE.
5.3.3. Broadband Bearer Capability
A new field in UNI signalling 4.0 called, 'ATM Transfer Capability'
(ATC), has been defined in the Broadband Bearer Capability IE for the
purpose of explicitly specifying the desired ATM traffic category.
The figure below shows the allowable ATC values.
Format and field values of Broadband Bearer Capability IE
-------------------------------------------------------------
| bb_bearer_capability |
------------------------------------------------------------|
| spare 0 |
| bearer_class 16 (bcob-x,c,a or VP) |
| transfer_capability cbr, rt-vbr, nrt-vbr, abr |
| susceptibility_to_clipping 0 (not suscept) |
| spare 0 |
| user_plane_configuration pt-to-pt, pt-to-mpt |
-------------------------------------------------------------
Maher [Page 8]
INTERNET DRAFT IP over ATM Signalling - UNI 4.0 Update November 1996
5.3.4. QoS Parameter
Inclusion of the QoS Parameter IE is optional in UNI 4.0 signalling.
It may be omitted from a SETUP message when the Extended QoS Parame-
ters IE, discussed in the next section, is included. This specifica-
tion makes no explicit recommendation on the use of the QoS related
IEs.
5.3.4.1. Two IEs for Signalling of Individual QoS Parameters
UNI 4.0 allows for signalling of individual QoS parameters for the
purpose of giving the the network and called party a more exact
description of the desired delay and cell loss characteristics. The
two individual QoS related IEs, Extended QoS Parameters IE and End-
to-End Transit Delay IE, can be used in the SETUP and CONNECT signal-
ling messages in place of the 'generic' QoS Parameter IE. Note that
inclusion of these two IEs depends on the type of ATM service
category requested (see Annex 9 in [TMGT96]).
5.4. ATM Addressing Information
ATM addressing information is carried in the Called Party Number,
Calling Party Number, and, under certain circumstance, Called Party
Subaddress, and Calling Party Subaddress IE. The ATM Forum ILMI
Specification 4.0 provides the procedure for an ATM endsystem to
learn its own ATM address from the ATM network, for use in populating
the Calling Party Number IE.
Format and field values of Called Party Number IE
----------------------------------------------------------
| called_party_number |
----------------------------------------------------------
| type_of_number (international number / unknown) |
| addr_plan_ident (ISDN / ATM Endsystem Address) |
| addr_number (E.164 / ATM Endsystem Address) |
----------------------------------------------------------
6. ABR Signalling In More Detail
The IEs and procedures pertaining to ABR signalling are briefly
described in this section. Nevertheless, this document makes no
specific recommendation on when to use the ABR service category for
IP VCCs or give suggestions on appropriate values for the various
parameters in the ABR related IEs.
Maher [Page 9]
INTERNET DRAFT IP over ATM Signalling - UNI 4.0 Update November 1996
Two new IEs have been defined for ABR signalling:
o ABR Setup Parameters
o ABR Additional Parameters
These IEs may be optionally included in a SETUP or CONNECT message.
The ABR Setup Parameters IE contains the following subfields:
- Forward/Backward ABR Initial Cell Rate
- Forward/Backward ABR Transient Buffer Exposure
- Cumulative RM Fixed Round Trip Time
- Forward/Backward Rate Increment Factor
- Forward/Backward Rate Decrease Factor
The ABR Additional Parameters IE contains one subfield:
- Forward/Backward Additional Parameters Record
The Additional Parameters Record value is a compressed encoding of a
set of ABR parameters (see TMGT96).
7. Frame Discard Capability
The frame discard capability in UNI 4.0 is primarily based on the
'Partial Packet Discard' strategy [ROM94]. Its use is defined for any
of the ATM services, except for loss-less CBR. Frame discard signal-
ling MUST be supported by all IP over ATM entities and it is RECOM-
MENDED that frame discard be signalled for all IP SVCs because it has
been proven to increase throughput under network congestion. Signal-
ling for frame discard is done by setting the frame discard bit in
the 'Traffic Management Options' subfield in the Traffic Descriptor
IE. It is possible that not all network entities in the SVC path
support frame discard, but it is required that they all forward the
signalling.
8. Security Considerations
The ATM Forum has established an ATM Security sub-working group for
the purpose of defining security mechanisms in ATM. It is therefore
premature to begin defining IP over ATM signalling's use of ATM secu-
rity. IP Security (RFC1825) can be applied to IP datagrams over any
medium.
Maher [Page 10]
INTERNET DRAFT IP over ATM Signalling - UNI 4.0 Update November 1996
9. Open Issues
Description of Leaf Initiated Join (LIJ) signalling is not discussed
because the use of LIJ in IP over ATM has not been defined.
10. Acknowledgements
The authors would like to thank the members of the ION working group
for their input.
REFERENCES
[PER95] Perez Maher, M. et al, ""ATM Signaling Support for IP over
ATM", RFC1755, February 1995
[LAUB93] Laubach, M., "Classical IP and ARP over ATM", RFC1577,
Hewlett-Packard Laboratories, December 1993
[UNI96] ATM Forum, "ATM User-Network Interface Specification Version
4.0", Prentice Hall, Upper Saddle River, NJ, specification final-
ized July 1996; expected publication, late 1996; available at
ftp://ftp.atmforum.com/pub.
[UNI94] ATM Forum, "ATM User-Network Interface Specification Version
3.1", Prentice Hall, Upper Saddle River, NJ, 1995
[TMGT96] ATM Forum, "ATM Forum Traffic Management Specification Ver-
sion 4.0", Prentice Hall, Upper Saddle River NJ; specification
finalized April 1996; expected publication, late 1996; available
at ftp://ftp.atmforum.com/pub.
[RSVP] R. Braden, L. Zhang, S. Berson, S. Herzog and S. Jamin,
"Resource ReSerVation Protocol (RSVP) - Version 1 Functional
Specification", Internet Draft, May 1996, <draft-ietf-rsvp-spec-
14.txt>
[KATZ96] "NBMA Next Hop Resolution Protocol (NHRP)", Katz, Pisci-
tello, Cole, Luciani, draft-ietf-rolc-nhrp-08.txt. Work in Pro-
gress.
[BRAD89] Braden, R., Editor, "Requirements for Internet Hosts -- Com-
munication Layers", RFC 1122, USC/Information Science Institute,
October 1989.
Maher [Page 11]
INTERNET DRAFT IP over ATM Signalling - UNI 4.0 Update November 1996
[BRAD94] Braden, R., Clark, D, Shenker, S., "Integrated Service in
the Internet Architecture: An Overview", RFC 1633,
USC/Information Science Institute, June 1994.
[HEIN93] Heinanen, J., "Multiprotocol Encapsulation over ATM Adapta-
tion Layer 5", RFC 1483, Telecom Finland, July 1993.
[ISO8473] ISO/IEC 8473, Information processing systems - Data commun-
ications - Protocol for providing the connectionless-mode network
service, 1988.
[ISO9577] Information Technology - Telecommunication and information
exchange between systems - Protocol identification in the network
layer ISO/IEC TR9577 (International Standards Organization:
Geneva, 1990)
[ROM94] Romanow, A., and Floyd, S., Dynamics of TCP Traffic over ATM
Networks. IEEE JSAC, V. 13 N. 4, May 1995, p. 633-641. Abstract.
An earlier version appeared in SIGCOMM '94, August 1994, pp. 79-
88.
Author's Address
Maryann Perez Maher
USC/ISI
4350 N. Fairfax Drive, Suite 620
Arlington VA 22203
Maher [Page 12]
INTERNET DRAFT IP over ATM Signalling - UNI 4.0 Update November 1996
Appendix A. A Sample UNI 4.0 SETUP Message
+--------------------------------------------------------------------+
SETUP
Information Elements/
Fields Value/(Meaning)
-------------------- ---------------
aal_parameters
aal_type 5 (AAL 5)
fwd_max_sdu_size_ident 140
fwd_max_sdu_size (xmit IP MTU value)
bkw_max_sdu_size_ident 129
bkw_max_sdu_size (recv IP MTU, 0 for disallowing return traffic)
sscs_type identifier 132
sscs_type 0 (null SSCS)
traffic_descriptor
fwd_peak_cell_rate_0_1_ident 132
fwd_peak_cell_rate_0_1 (link rate)
bkw_peak_cell_rate_0_1_ident 133
bkw_peak_cell_rate_0_1 (link rate)
traff_mngt_options_ident 191
fwd_frame_discard 1 (on)
bkw_frame_discard 1 (on if return traffic indicated)
spare 0
tagging_bkw 1 (on)
tagging_fwd 1 (on if return traffic indicated)
best_effort_indication 190 (on)
minimum_acceptable_traffic_descriptor
fwd_peak_cell_rate_0_1_ident 132
fwd_peak_cell_rate_0_1 0
bkw_peak_cell_rate_0_1_ident 133
bkw_peak_cell_rate_0_1 0
bb_bearer_capability /* a coding for specifying UBR like service */
spare 0
bearer_class 16 (BCOC-X)
spare 0
atm_transfer_capability 10 (nrt-vbr)
timing_requirements 10 (timing not required)
susceptibility_to_clipping 0 (not susceptible to clipping)
spare 0
user_plane_configuration 0 (point_to_point)
Maher [Page 13]
INTERNET DRAFT IP over ATM Signalling - UNI 4.0 Update November 1996
bb_low_layer_information
layer_2_id 2
user_information_layer 12 (lan_llc - ISO 8802/2)
qos_parameter
qos_class_fwd 0 (class 0)
qos_class_bkw 0 (class 0)
called_party_number
type_of_number (international number / unknown)
addr_plan_ident (ISDN / ATM Endsystem Address)
number (E.164 / ATM Endsystem Address)
calling_party_number
type_of_number (international number / unknown)
addr_plan_ident (ISDN / ATM Endsystem Address)
presentation_indic (presentation allowed)
spare 0
screening_indic (user_provided verified and passed)
number (E.164 / ATM Endsystem Address)
+--------------------------------------------------------------------+
Figure 1.
Sample contents of SETUP message
Maher [Page 14]
INTERNET DRAFT IP over ATM Signalling - UNI 4.0 Update November 1996
Appendix B. Combinations of Traffic Related Parameters
This appendix contains a copy of the five tables found in Annex 9 of
[UNI96] which show the allowable combinations of traffic and QoS related
parameters in a UNI 4.0 SETUP message.
+--------------------------------------------------------------------+
|ATM Service Category| CBR |
|--------------------|---------------|---------------|---------------|
| Conformance |CBR.1 (note 10)| (note 4) | (note 4) |
|--------------------|---------------|---------------|---------------|
| Bearer Capability | | | |
|--------------------|---------------|---------------|---------------|
| BB Bearer Class | A | X | VP | A | X | VP^| A | X | VP^|
|--------------------|---------------|----|-----|----|----|-----|----|
| ATM Transfer | | | 4,5,| | | 4,5,| |
| Capability (note 1)| 7 | abs| or 6| 5 | abs| or 6| 5 |
|--------------------|---------------|---------------|---------------|
| Traffic Descriptor | | | |
| for a given dir. | | | |
|--------------------|---------------|---------------|---------------|
| PCR (CLP=0) | | | S |
|--------------------|---------------|---------------|---------------|
| PCR (CLP=0+1) | S | S | S |
|--------------------|---------------|---------------|---------------|
| SCR, MBS (CLP=0) | | | |
|--------------------|---------------|---------------|---------------|
| SCR, MBS (CLP=0+1) | | | |
|--------------------|---------------|---------------|---------------|
| Best Effort | | | |
|--------------------|---------------|---------------|---------------|
| Tagging | N | N | Y/N |
|--------------------|---------------|---------------|---------------|
| Frame Discard | Y/N | Y/N | Y/N |
|--------------------|---------------|---------------|---------------|
| QoS Classes | * | * | * |
|--------------------|---------------|---------------|---------------|
| Transit Delay | O | O | O |
|--------------------|---------------|---------------|---------------|
| Peak-to-Peak CDV | O | O | O |
|--------------------|---------------|---------------|---------------|
| CLR (CLP=0)~ | | O | O |
|--------------------|---------------|---------------|---------------|
| CLR (CLP=0+1)~ | O | | |
+--------------------------------------------------------------------+
Maher [Page 15]
INTERNET DRAFT IP over ATM Signalling - UNI 4.0 Update November 1996
+--------------------------------------------------------------------+
|ATM Service Category| Real Time VBR |
|--------------------|---------------|---------------|---------------|
| Conformance |VBR.1 (note 10)| VBR.2 | VBR.3 |
|--------------------|---------------|---------------|---------------|
| Bearer Capability | | | |
|--------------------|---------------|---------------|---------------|
| BB Bearer Class | C | X | VP | C | X | VP | C | X | VP |
|--------------------|---------------|----|-----|----|----|-----|----|
| ATM Transfer | | | 1 | | | 1 | |
| Capability | 19 | 9 | or 9| 9 | 9 | or 9| 9 |
|--------------------|---------------|---------------|---------------|
| Traffic Descriptor | | | |
| for a given dir. | | | |
|--------------------|---------------|---------------|---------------|
| PCR (CLP=0) | | | |
|--------------------|---------------|---------------|---------------|
| PCR (CLP=0+1) | S | S | S |
|--------------------|---------------|---------------|---------------|
| SCR, MBS (CLP=0) | | S | S |
|--------------------|---------------|---------------|---------------|
| SCR, MBS (CLP=0+1) | S | | |
|--------------------|---------------|---------------|---------------|
| Best Effort | | | |
|--------------------|---------------|---------------|---------------|
| Tagging | N | N | Y/N |
|--------------------|---------------|---------------|---------------|
| Frame Discard | Y/N | Y/N | Y/N |
|--------------------|---------------|---------------|---------------|
| QoS Classes | * | * | * |
|--------------------|---------------|---------------|---------------|
| Transit Delay(nt.2)| O | O | O |
|--------------------|---------------|---------------|---------------|
| Peak-to-Peak CDV | O | O | O |
|--------------------|---------------|---------------|---------------|
| CLR (CLP=0)~ | | O | O |
|--------------------|---------------|---------------|---------------|
| CLR (CLP=0+1)~ | O | | |
+--------------------------------------------------------------------+
Maher [Page 16]
INTERNET DRAFT IP over ATM Signalling - UNI 4.0 Update November 1996
+--------------------------------------------------------------------+
|ATM Service Category| Real Time VBR |
|--------------------|---------------|---------------|---------------|
| Conformance | (note 4,7) | (note 4,8) | (note 4) |
|--------------------|---------------|---------------|---------------|
| Bearer Capability | | | |
|--------------------|---------------|---------------|---------------|
| BB Bearer Class | X | X | X | C or VP^|
|--------------------|---------------|---------------|-----|---------|
| ATM Transfer | | | | |
| Capability | 1 or 9 | 1 or 9 | 1or9| 9 |
|--------------------|---------------|---------------|---------------|
| Traffic Descriptor | | | |
| for a given dir. | | | |
|--------------------|---------------|---------------|---------------|
| PCR (CLP=0) | S | | |
|--------------------|---------------|---------------|---------------|
| PCR (CLP=0+1) | S | S | S |
|--------------------|---------------|---------------|---------------|
| SCR, MBS (CLP=0) | | | |
|--------------------|---------------|---------------|---------------|
| SCR, MBS (CLP=0+1) | | | S |
|--------------------|---------------|---------------|---------------|
| Best Effort | | | |
|--------------------|---------------|---------------|---------------|
| Tagging | Y/N | N | N |
|--------------------|---------------|---------------|---------------|
| Frame Discard | Y/N | Y/N | Y/N |
|--------------------|---------------|---------------|---------------|
| QoS Classes | * | * | * |
|--------------------|---------------|---------------|---------------|
| Transit Delay(nt.2)| O | O | O |
|--------------------|---------------|---------------|---------------|
| Peak-to-Peak CDV | O | O | O |
|--------------------|---------------|---------------|---------------|
| CLR (CLP=0)~ | O | O | O |
|--------------------|---------------|---------------|---------------|
| CLR (CLP=0+1)~ | | | |
+--------------------------------------------------------------------+
Maher [Page 17]
INTERNET DRAFT IP over ATM Signalling - UNI 4.0 Update November 1996
+--------------------------------------------------------------------+
|ATM Service Category| Non-Real Time VBR |
|--------------------|---------------|---------------|---------------|
| Conformance |VBR.1 (note 10)| VBR.2 | VBR.3 |
|--------------------|---------------|---------------|---------------|
| Bearer Capability | | | |
|--------------------|---------------|---------------|---------------|
| BB Bearer Class | C | X | VP |C | X | VP|C | X | VP|
|--------------------|---------------|--|--------|---|--|--------|---|
| ATM Transfer | | |abs,0,2,|abs| |abs,0,2,|abs|
| Capability | 11 |ab| 8,10 |10 |ab| 8,10 |10 |
|--------------------|---------------|---------------|---------------|
| Traffic Descriptor | | | |
| for a given dir. | | | |
|--------------------|---------------|---------------|---------------|
| PCR (CLP=0) | | | |
|--------------------|---------------|---------------|---------------|
| PCR (CLP=0+1) | S | S | S |
|--------------------|---------------|---------------|---------------|
| SCR, MBS (CLP=0) | | S | S |
|--------------------|---------------|---------------|---------------|
| SCR, MBS (CLP=0+1) | S | | |
|--------------------|---------------|---------------|---------------|
| Best Effort | | | |
|--------------------|---------------|---------------|---------------|
| Tagging | N | N | Y |
|--------------------|---------------|---------------|---------------|
| Frame Discard | Y/N | Y/N | Y/N |
|--------------------|---------------|---------------|---------------|
| QoS Classes | * | * | * |
|--------------------|---------------|---------------|---------------|
| Transit Delay(nt.2)| (note 3) | (note 3) | (note 3) |
|--------------------|---------------|---------------|---------------|
| Peak-to-Peak CDV | | | |
|--------------------|---------------|---------------|---------------|
| CLR (CLP=0)~ | | O | O |
|--------------------|---------------|---------------|---------------|
| CLR (CLP=0+1)~ | O | | |
+--------------------------------------------------------------------+
Maher [Page 18]
INTERNET DRAFT IP over ATM Signalling - UNI 4.0 Update November 1996
+--------------------------------------------------------------------+
|ATM Service Category| Non-Real Time VBR |
|--------------------|---------------|---------------|---------------|
| Conformance | (note 4,7) | (note 4,8) | (note 4) |
|--------------------|---------------|---------------|---------------|
| Bearer Capability | | | |
|--------------------|---------------|---------------|---------------|
| BB Bearer Class | C | X | C | X |C | X |VP^|
|--------------------|-------|-------|-------|-------|--|--------|---|
| ATM Transfer | |abs,0,2| |abs,0,2| |abs,0,2,|abs|
| Capability | abs |8 or 10| |8 or 10|ab| 8 or10 |10 |
|--------------------|---------------|---------------|---------------|
| Traffic Descriptor | | | |
| for a given dir. | | | |
|--------------------|---------------|---------------|---------------|
| PCR (CLP=0) | S | | |
|--------------------|---------------|---------------|---------------|
| PCR (CLP=0+1) | S | S | S |
|--------------------|---------------|---------------|---------------|
| SCR, MBS (CLP=0) | | | |
|--------------------|---------------|---------------|---------------|
| SCR, MBS (CLP=0+1) | | | S |
|--------------------|---------------|---------------|---------------|
| Best Effort | | | |
|--------------------|---------------|---------------|---------------|
| Tagging | Y/N | N | N |
|--------------------|---------------|---------------|---------------|
| Frame Discard | Y/N | Y/N | Y/N |
|--------------------|---------------|---------------|---------------|
| QoS Classes | * | * | * |
|--------------------|---------------|---------------|---------------|
| Transit Delay(nt.2)| (note 3) | (note 3) | (note 3) |
|--------------------|---------------|---------------|---------------|
| Peak-to-Peak CDV | | | |
|--------------------|---------------|---------------|---------------|
| CLR (CLP=0)~ | O | O | O |
|--------------------|---------------|---------------|---------------|
| CLR (CLP=0+1)~ | | | |
+--------------------------------------------------------------------+
Maher [Page 19]
INTERNET DRAFT IP over ATM Signalling - UNI 4.0 Update November 1996
+--------------------------------------------------------------------+
|ATM Service Category| ABR | UBR |
|--------------------|---------------|---------------|---------------|
| Conformance | ABR | UBR.1 | UBR.2 |
|--------------------|---------------|---------------|---------------|
| Bearer Capability | | | |
|--------------------|---------------|---------------|---------------|
| BB Bearer Class | C | X | VP |C | X | VP|C | X | VP|
|--------------------|---------------|--|--------|---|--|--------|---|
| ATM Transfer | | |abs,0,2,|abs| |abs,0,2,|abs|
| Capability | 12 |ab| 8,10 |10 |ab| 8,10 |10 |
|--------------------|---------------|---------------|---------------|
| Traffic Descriptor | | | |
| for a given dir. | | | |
|--------------------|---------------|---------------|---------------|
| PCR (CLP=0) | | | |
|--------------------|---------------|---------------|---------------|
| PCR (CLP=0+1) | S | S | S |
|--------------------|---------------|---------------|---------------|
| SCR, MBS (CLP=0) | | S | S |
|--------------------|---------------|---------------|---------------|
| SCR, MBS (CLP=0+1) | S | | |
|--------------------|---------------|---------------|---------------|
| ABR MCR | (note 6) | | |
|--------------------|---------------|---------------|---------------|
| Best Effort | | S (note 9) | S (note 9) |
|--------------------|---------------|---------------|---------------|
| Tagging | N | N | N |
|--------------------|---------------|---------------|---------------|
| Frame Discard | Y/N | Y/N | Y/N |
|--------------------|---------------|---------------|---------------|
| QoS Classes | 0 | 0 | 0 |
|--------------------|---------------|---------------|---------------|
| Transit Delay(nt.2)| | | |
|--------------------|---------------|---------------|---------------|
| Peak-to-Peak CDV | | | |
|--------------------|---------------|---------------|---------------|
| CLR (CLP=0)~ | | | |
|--------------------|---------------|---------------|---------------|
| CLR (CLP=0+1)~ | | | |
+--------------------------------------------------------------------+
ab, abs = absent.
Y/N = either "Yes" or "No" is allowed.
Maher [Page 20]
INTERNET DRAFT IP over ATM Signalling - UNI 4.0 Update November 1996
O = Optional. May be specified using:
- an additional QoS parameter encoded i the Extended QoS parameters
information element or the end-to-end transit information
element; or,
- objectives implied from the QoS class
If an Extended QoS Parameters IE is not present in the message,
then any value of this parameter is acceptable. If neither the
parameter nor the Extended QoS Parameters IE is present, then the
objective for this parameter is determined from the QoS class
in the QoS Parameter IE.
S = Specified.
(blank) = Unspecified.
* = allowed QoS class values are a network option. Class 0 is always
for alignment with ITU-T.
^ = (note 5).
~ = (note 11).
Note 1 - Values 0,1,2,4,6, and 8 are not used on transmission but shall
be understood on reception.
Note 2 - Maximum end-2-end transit delay objectives may only be specified
for the forward direction.
Note 3 - Maximum end-2-end transit delay objectives may be specified for
the ATM Service Category of Non-real Time VBR for reasons of
backward compatibility with ITU-T Recommendations.
Note 4 - Included for reasons of backward compatibility with UNI 3.1 and
ITU-T Recommendations. With these conformance definitions, the
CLR commitment is only for the CLP=0 traffic stream.
Note 5 - Included to allow switched virtual paths to use the UNI 3.1
conformance definitions.
Note 6 - Optional in the user-to-network direction. Specified in the
network-to-user direction.
Note 7 - This combination should be treated as if the received PCR (CLP=0)
parameter were a SCR (CLP=0) parameter and a MBS (CLP=0) parameter
with a value of 1.
Note 8 - This combination should be treated as if an additional SCR (CLP=0)
parameter were received with the same value as a PCR (CLP=0+1)
parameter and a MBS (CLP=0) parameter
with a value of 1.
Note 9 - The best effort parameter applies to both the forward and backward
directions.
Note 10 - This combination should only be used when the CLR commitment on
CLP=0+1 is required versus CLR commitment on CLP=0 traffic, since
these combinations are not supported by UNI 3.0/3.1 nor ITU-T
Maher [Page 21]
INTERNET DRAFT IP over ATM Signalling - UNI 4.0 Update November 1996
Q.2931.
Note 11 - In this table the CLR commitment is shown as two entries to
indicated explicitly whether the CLR commitment is for the CLP=0
or the CLP=0+1 cells.
Maher [Page 22]