Network Working Group A. G. Malis
Request for Comments: 3496 T. Hsiao
Category: Informational Vivace Networks
March 2003
Protocol Extension for Support of Asynchronous Transfer Mode (ATM)
Service Class-aware Multiprotocol Label Switching (MPLS)
Traffic Engineering
Status of this Memo
This memo provides information for the Internet community. It does
not specify an Internet standard of any kind. Distribution of this
memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved.
Abstract
This document specifies a Resource ReSerVation Protocol-Traffic
Engineering (RSVP-TE) signaling extension for support of Asynchronous
Transfer Mode (ATM) Service Class-aware Multiprotocol Label Switching
(MPLS) Traffic Engineering.
Table of Contents
1. Overview......................................................2
2. Extended RSVP-TE Path Message Format..........................2
2.1 PATH Message Format.......................................3
3. ATM_SERVICECLASS Object.......................................3
4. Handling the ATM_SERVICECLASS Object..........................4
5. Non-support of the ATM_SERVICECLASS Object....................4
6. Security Considerations.......................................4
7. IANA Considerations...........................................5
8. References....................................................5
9. Authors' Addresses............................................5
10. Full Copyright Statement......................................6
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RFC 3496 ATM Service Class-aware MPLS Traffic Engineering March 2003
1. Overview
This document defines a Resource ReSerVation Protocol-Traffic
Engineering (RSVP-TE) protocol addition to support ATM (Asynchronous
Transfer Mode) Service Class-aware MPLS (MultiProtocol Label
Switching) Traffic Engineering.
This protocol addition is used with all MPLS Label Switched Routers
(LSRs) and link types (including, but not restricted to, Packet over
SONET, Ethernet, and ATM links) to signal traffic engineered paths
that can support the ATM service classes as defined by the ATM Forum
[TM]. This document does not specify HOW to actually implement the
functionality in the MPLS LSRs to emulate the ATM Forum service
classes (such as necessary queuing and scheduling mechanisms), only
how to signal that the TE path must support the ATM Forum service
classes. A useful application for such paths is the carriage of ATM
cells encapsulated in IP or MPLS packets in order to use MPLS
networks as functional replacements for ATM networks.
2. Extended RSVP-TE Path Message Format
One new RSVP-TE Object is defined in this document: the
ATM_SERVICECLASS Object. Detailed description of this Object is
provided below. This new Object is applicable to PATH messages.
This specification only defines the use of the ATM_SERVICECLASS
Object in PATH messages used to establish LSP (Label Switched Path)
Tunnels in accordance with [RSVP-TE]. Such PATH messages contain a
Session Object with a C-Type equal to LSP_TUNNEL_IPv4 and a
LABEL_REQUEST object.
Restrictions defined in [RSVP-TE] for support of establishment of LSP
Tunnels via RSVP-TE are also applicable to the establishment of LSP
Tunnels supporting ATM Service Class-aware traffic engineering. For
instance, only unicast LSPs are supported and Multicast LSPs are for
further study.
This new ATM_SERVICECLASS object is optional with respect to RSVP-TE
so that general RSVP-TE implementations not concerned with ATM
Service Class-aware traffic engineering MPLS LSP setup do not have to
support this object.
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RFC 3496 ATM Service Class-aware MPLS Traffic Engineering March 2003
2.1 PATH Message Format
The format of the extended PATH message is as follows:
<PATH Message> ::= <Common Header> [ <INTEGRITY> ]
<SESSION> <RSVP_HOP>
<TIME_VALUES>
[ <EXPLICIT_ROUTE> ]
<LABEL_REQUEST>
[ <SESSION_ATTRIBUTE> ]
[ <DIFFSERV> ]
[ <ATM_SERVICECLASS> ]
[ <POLICY_DATA> ... ]
[ <sender descriptor> ]
<sender descriptor> ::= <SENDER_TEMPLATE> [ <SENDER_TSPEC> ]
[ <ADSPEC> ]
[ <RECORD_ROUTE> ]
3. ATM_SERVICECLASS Object
The ATM_SERVICECLASS object format is as follows:
Class Number = 227, C_Type = 1
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | SC |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Reserved : 29 bits
This field is reserved. It must be set to zero on transmission
and must be ignored on receipt.
SC : 3 bits
Indicates the ATM Service Class. Values currently allowed are:
0: UBR (Unspecified Bit Rate)
1: VBR-NRT (Variable Bit Rate, Non-Real Time)
2: VBR-RT (Variable Bit Rate, Real Time)
3: CBR (Constant Bit Rate)
4-7: reserved
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4. Handling the ATM_SERVICECLASS Object
To establish an LSP tunnel with RSVP-TE, the sender LSR creates a
PATH message with a session type of LSP_Tunnel_IPv4 and with a
LABEL_REQUEST object as per [RSVP-TE]. The sender LSR may also
include the DIFFSERV object as per [DIFF-MPLS].
If the LSP is associated with an ATM Service Class, the sender LSR
must include the ATM_SERVICECLASS object in the PATH message with the
Service-Class (SC) field set to signify the desired ATM Service
Class.
If a path message contains multiple ATM_SERVICECLASS objects, only
the first one is meaningful; subsequent ATM_SERVICECLASS object(s)
must be ignored and must not be forwarded.
Each LSR along the path that is ATM_SERVICECLASS-aware records the
ATM_SERVICECLASS object, when present, in its path state block.
The destination LSR responds to the PATH message by sending a RESV
message without an ATM_SERVICECLASS object (whether the PATH message
contained an ATM_SERVICECLASS object or not).
5. Non-support of the ATM_SERVICECLASS Object
An LSR that does not recognize the ATM_SERVICECLASS object Class
Number must behave in accordance with the procedures specified in
[RSVP] for an unknown Class Number with the binary format 11bbbbbb,
where b=0 or 1 (i.e., RSVP will ignore the object but forward it
unexamined and unmodified).
An LSR that recognizes the ATM_SERVICECLASS object Class Number but
does not recognize the ATM_SERVICECLASS object C-Type, must behave in
accordance with the procedures specified in [RSVP] for an unknown
C-type (i.e., it must send a PathErr with the error code 'Unknown
object C-Type' toward the sender).
In both situations, this causes the path setup to fail. The sender
should notify management that a LSP cannot be established and
possibly might take action to retry reservation establishment without
the ATM_SERVICECLASS object.
6. Security Considerations
The solution is not expected to add specific security requirements
beyond those of Diff-Serv and existing TE. The security mechanisms
currently used with Diff-Serv and existing TE can be used with this
solution.
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RFC 3496 ATM Service Class-aware MPLS Traffic Engineering March 2003
7. IANA Considerations
The IANA has registered a new RSVP Class Number for ATM_SERVICECLASS
(227). (See http://www.iana.org/assignments/rsvp-parameters).
8. References
[DIFF-MPLS] Le Faucheur, F., Wu, L., Davie, B., Davari, S., Vaananen,
P., Krishnan, R., Cheval, P. and J. Heinanen, "Multi-
Protocol Label Switching (MPLS) Support of Differentiated
Services", RFC 3270, May 2002.
[RSVP] Braden, R., Ed., Zhang, L., Berson, S., Herzog, S. and S.
Jazmin , "Resource ReSerVation Protocol (RSVP) -- Version
1 Functional Specification", RFC 2205, September 1997.
[RSVP-TE] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.
and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
Tunnels", RFC 3209, December 2001.
[TM] ATM Forum Traffic Management Specification Version 4.0,
af-tm-0056.000, April 1996.
9. Authors' Addresses
Andrew G. Malis
Vivace Networks, Inc.
2730 Orchard Parkway
San Jose, CA 95134
EMail: Andy.Malis@vivacenetworks.com
Tony Hsiao
Vivace Networks, Inc.
2730 Orchard Parkway
San Jose, CA 95134
EMail: Tony.Hsiao@VivaceNetworks.com
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RFC 3496 ATM Service Class-aware MPLS Traffic Engineering March 2003
10. Full Copyright Statement
Copyright (C) The Internet Society (2003). All Rights Reserved.
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The limited permissions granted above are perpetual and will not be
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Acknowledgement
Funding for the RFC Editor function is currently provided by the
Internet Society.
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