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IETF RFC 6387
Last modified on Saturday, September 24th, 2011
 Permanent link to RFC 6387
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Internet Engineering Task Force (IETF) A. Takacs
Request for Comments: 6387 Ericsson
Obsoletes: 5467 L. Berger
Category: Standards Track LabN Consulting, L.L.C.
ISSN: 2070-1721 D. Caviglia
Ericsson
D. Fedyk
Alcatel-Lucent
J. Meuric
France Telecom Orange
September 2011
GMPLS Asymmetric Bandwidth Bidirectional Label Switched Paths (LSPs)
 Abstract
This document defines a method for the support of GMPLS asymmetric
bandwidth bidirectional Label Switched Paths (LSPs). The approach
presented is applicable to any switching technology and builds on the
original Resource Reservation Protocol (RSVP) model for the transport
of traffic-related parameters. This document moves the experiment
documented in RFC 5467 to the standards track and obsoletes RFC 5467.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/RFC 6387.
Takacs, et. al. Standards Track PAGE 1 
RFC 6387 Asymmetric Bandwidth Bidirectional LSP September 2011
Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Background . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2. Approach Overview . . . . . . . . . . . . . . . . . . . . 3
1.3. Conventions Used in This Document . . . . . . . . . . . . 4
2. Generalized Asymmetric Bandwidth Bidirectional LSPs . . . . . 4
2.1. UPSTREAM_FLOWSPEC Object . . . . . . . . . . . . . . . . . 5
2.1.1. Procedures . . . . . . . . . . . . . . . . . . . . . . 5
2.2. UPSTREAM_TSPEC Object . . . . . . . . . . . . . . . . . . 5
2.2.1. Procedures . . . . . . . . . . . . . . . . . . . . . . 5
2.3. UPSTREAM_ADSPEC Object . . . . . . . . . . . . . . . . . . 6
2.3.1. Procedures . . . . . . . . . . . . . . . . . . . . . . 6
3. Packet Formats . . . . . . . . . . . . . . . . . . . . . . . . 6
4. Compatibility . . . . . . . . . . . . . . . . . . . . . . . . 7
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
5.1. UPSTREAM_FLOWSPEC Object . . . . . . . . . . . . . . . . . 8
5.2. UPSTREAM_TSPEC Object . . . . . . . . . . . . . . . . . . 8
5.3. UPSTREAM_ADSPEC Object . . . . . . . . . . . . . . . . . . 8
6. Security Considerations . . . . . . . . . . . . . . . . . . . 8
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9
7.1. Normative References . . . . . . . . . . . . . . . . . . . 9
7.2. Informative References . . . . . . . . . . . . . . . . . . 9
1. Introduction
GMPLS [RFC 3473] introduced explicit support for bidirectional Label
Switched Paths (LSPs). The defined support matched the switching
technologies covered by GMPLS, notably Time Division Multiplexing
(TDM) and lambdas; specifically, it only supported bidirectional LSPs
with symmetric bandwidth allocation. Symmetric bandwidth
requirements are conveyed using the semantics objects defined in
[RFC 2205] and [RFC 2210].
Takacs, et. al. Standards Track PAGE 2
RFC 6387 Asymmetric Bandwidth Bidirectional LSP September 2011
GMPLS asymmetric bandwidth bidirectional LSPs are bidirectional LSPs
that have different bandwidth reservations in each direction.
Support for bidirectional LSPs with asymmetric bandwidth was
previously discussed in the context of Ethernet, notably [RFC 6060]
and [RFC 6003]. In that context, asymmetric bandwidth support was
considered to be a capability that was unlikely to be deployed, and
hence [RFC 5467] was published as Experimental. The MPLS Transport
Profile, MPLS-TP, requires that asymmetric bandwidth bidirectional
LSPs be supported (see [RFC 5654]); therefore, this document is being
published on the Standards Track. This document has no technical
changes from the approach defined in [RFC 5467]. This document moves
the experiment documented in [RFC 5467] to the standards track and
obsoletes [RFC 5467]. This document also removes the Ethernet-
technology-specific alternative approach discussed in the appendix of
[RFC 5467] and maintains only one approach that is suitable for use
with any technology.
1.1. Background
Bandwidth parameters are transported within RSVP ([RFC 2210],
[RFC 3209], and [RFC 3473]) via several objects that are opaque to
RSVP. While opaque to RSVP, these objects support a particular model
for the communication of bandwidth information between an RSVP
session sender (ingress) and receiver (egress). The original model
of communication, defined in [RFC 2205] and maintained in [RFC 3209],
used the SENDER_TSPEC and ADSPEC objects in Path messages and the
FLOWSPEC object in Resv messages. The SENDER_TSPEC object was used
to indicate a sender's data generation capabilities. The FLOWSPEC
object was issued by the receiver and indicated the resources that
should be allocated to the associated data traffic. The ADSPEC
object was used to inform the receiver and intermediate hops of the
actual resources available for the associated data traffic.
With the introduction of bidirectional LSPs in [RFC 3473], the model
of communication of bandwidth parameters was implicitly changed. In
the context of [RFC 3473] bidirectional LSPs, the SENDER_TSPEC object
indicates the desired resources for both upstream and downstream
directions. The FLOWSPEC object is simply confirmation of the
allocated resources. The definition of the ADSPEC object is either
unmodified and only has meaning for downstream traffic, or is
implicitly or explicitly ([RFC 4606] and [RFC 6003]) irrelevant.
1.2. Approach Overview
The approach for supporting asymmetric bandwidth bidirectional LSPs
defined in this document builds on the original RSVP model for the
transport of traffic-related parameters and GMPLS's support for
bidirectional LSPs.
Takacs, et. al. Standards Track PAGE 3
RFC 6387 Asymmetric Bandwidth Bidirectional LSP September 2011
The defined approach is generic and can be applied to any switching
technology supported by GMPLS. With this approach, the existing
SENDER_TSPEC, ADSPEC, and FLOWSPEC objects are complemented with the
addition of new UPSTREAM_TSPEC, UPSTREAM_ADSPEC, and
UPSTREAM_FLOWSPEC objects. The existing objects are used in the
original fashion defined in [RFC 2205] and [RFC 2210], and refer only
to traffic associated with the LSP flowing in the downstream
direction. The new objects are used in exactly the same fashion as
the old objects, but refer to the upstream traffic flow Figure 1
shows the bandwidth-related objects used for asymmetric bandwidth
bidirectional LSPs.
|---| Path |---|
| I |------------------->| E |
| n | -SENDER_TSPEC | g |
| g | -ADSPEC | r |
| r | -UPSTREAM_FLOWSPEC | e |
| e | | s |
| s | Resv | s |
| s |<-------------------| |
| | -FLOWSPEC | |
| | -UPSTREAM_TSPEC | |
| | -UPSTREAM_ADSPEC | |
|---| |---|
Figure 1: Generic Asymmetric Bandwidth Bidirectional LSPs
The extensions defined in this document are limited to Point-to-Point
(P2P) LSPs. Support for Point-to-Multipoint (P2MP) bidirectional
LSPs is not currently defined and, as such, not covered in this
document.
1.3. Conventions Used in This Document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC 2119].
2. Generalized Asymmetric Bandwidth Bidirectional LSPs
The setup of an asymmetric bandwidth bidirectional LSP is signaled
using the bidirectional procedures defined in [RFC 3473] together with
the inclusion of the new UPSTREAM_FLOWSPEC, UPSTREAM_TSPEC, and
UPSTREAM_ADSPEC objects.
The new upstream objects carry the same information and are used in
the same fashion as the existing downstream objects; they differ in
that they relate to traffic flowing in the upstream direction while
Takacs, et. al. Standards Track PAGE 4
RFC 6387 Asymmetric Bandwidth Bidirectional LSP September 2011
the existing objects relate to traffic flowing in the downstream
direction. The new objects also differ in that they are carried in
messages traveling in the opposite direction.
2.1. UPSTREAM_FLOWSPEC Object
The format of an UPSTREAM_FLOWSPEC object is the same as a FLOWSPEC
object [RFC 2210]. This includes the definition of class types and
their formats. The class number of the UPSTREAM_FLOWSPEC object is
120 (of the form 0bbbbbbb).
2.1.1. Procedures
The Path message of an asymmetric bandwidth bidirectional LSP MUST
contain an UPSTREAM_FLOWSPEC object and MUST use the bidirectional
LSP formats and procedures defined in [RFC 3473]. The C-Type of the
UPSTREAM_FLOWSPEC object MUST match the C-Type of the SENDER_TSPEC
object used in the Path message. The contents of the
UPSTREAM_FLOWSPEC object MUST be constructed using a format and
procedures consistent with those used to construct the FLOWSPEC
object that will be used for the LSP, e.g., [RFC 2210] or [RFC 4328].
Nodes processing a Path message containing an UPSTREAM_FLOWSPEC
object MUST use the contents of the UPSTREAM_FLOWSPEC object in the
upstream label and the resource allocation procedure defined in
Section 3.1 of [RFC 3473]. Consistent with [RFC 3473], a node that is
unable to allocate a label or internal resources based on the
contents of the UPSTREAM_FLOWSPEC object MUST issue a PathErr message
with a "Routing problem/MPLS label allocation failure" indication.
2.2. UPSTREAM_TSPEC Object
The format of an UPSTREAM_TSPEC object is the same as a SENDER_TSPEC
object, which includes the definition of class types and their
formats. The class number of the UPSTREAM_TSPEC object is 121 (of
the form 0bbbbbbb).
2.2.1. Procedures
The UPSTREAM_TSPEC object describes the traffic flow that originates
at the egress. The UPSTREAM_TSPEC object MUST be included in any
Resv message that corresponds to a Path message containing an
UPSTREAM_FLOWSPEC object. The C-Type of the UPSTREAM_TSPEC object
MUST match the C-Type of the corresponding UPSTREAM_FLOWSPEC object.
The contents of the UPSTREAM_TSPEC object MUST be constructed using a
format and procedures consistent with those used to construct the
FLOWSPEC object that will be used for the LSP, e.g., [RFC 2210] or
[RFC 4328]. The contents of the UPSTREAM_TSPEC object MAY differ from
Takacs, et. al. Standards Track PAGE 5
RFC 6387 Asymmetric Bandwidth Bidirectional LSP September 2011
contents of the UPSTREAM_FLOWSPEC object based on application data
transmission requirements.
When an UPSTREAM_TSPEC object is received by an ingress, the ingress
MAY determine that the original reservation is insufficient to
satisfy the traffic flow. In this case, the ingress MAY tear down
the LSP and send a PathTear message. Alternatively, the ingress MAY
issue a Path message with an updated UPSTREAM_FLOWSPEC object to
modify the resources requested for the upstream traffic flow. This
modification might require the LSP to be re-routed, and in extreme
cases might result in the LSP being torn down when sufficient
resources are not available along the path of the LSP.
2.3. UPSTREAM_ADSPEC Object
The format of an UPSTREAM_ADSPEC object is the same as an ADSPEC
object. This includes the definition of class types and their
formats. The class number of the UPSTREAM_ADSPEC object is 122 (of
the form 0bbbbbbb).
2.3.1. Procedures
The UPSTREAM_ADSPEC object MAY be included in any Resv message that
corresponds to a Path message containing an UPSTREAM_FLOWSPEC object.
The C-Type of the UPSTREAM_TSPEC object MUST be consistent with the
C-Type of the corresponding UPSTREAM_FLOWSPEC object. The contents
of the UPSTREAM_ADSPEC object MUST be constructed using a format and
procedures consistent with those used to construct the ADSPEC object
that will be used for the LSP, e.g., [RFC 2210] or [RFC 6003]. The
UPSTREAM_ADSPEC object is processed using the same procedures as the
ADSPEC object and, as such, MAY be updated or added at transit nodes.
3. Packet Formats
This section presents the RSVP message-related formats as modified by
this section. This document modifies formats defined in [RFC 2205],
[RFC 3209], and [RFC 3473]. See [RFC 5511] for the syntax used by RSVP.
Unmodified formats are not listed. Three new objects are defined in
this section:
Object name Applicable RSVP messages
--------------- ------------------------
UPSTREAM_FLOWSPEC Path, PathTear, PathErr, and Notify
(via sender descriptor)
UPSTREAM_TSPEC Resv, ResvConf, ResvTear, ResvErr, and
Notify (via flow descriptor list)
UPSTREAM_ADSPEC Resv, ResvConf, ResvTear, ResvErr, and
Notify (via flow descriptor list)
Takacs, et. al. Standards Track PAGE 6
RFC 6387 Asymmetric Bandwidth Bidirectional LSP September 2011
The format of the sender description for bidirectional asymmetric
LSPs is:
<sender descriptor> ::= <SENDER_TEMPLATE> <SENDER_TSPEC>
[ <ADSPEC> ]
[ <RECORD_ROUTE> ]
[ <SUGGESTED_LABEL> ]
[ <RECOVERY_LABEL> ]
<UPSTREAM_LABEL>
<UPSTREAM_FLOWSPEC>
The format of the flow descriptor list for bidirectional asymmetric
LSPs is:
<flow descriptor list> ::= <FF flow descriptor list>
| <SE flow descriptor>
<FF flow descriptor list> ::= <FLOWSPEC>
<UPSTREAM_TSPEC> [ <UPSTREAM_ADSPEC> ]
<FILTER_SPEC>
<LABEL> [ <RECORD_ROUTE> ]
| <FF flow descriptor list>
<FF flow descriptor>
<FF flow descriptor> ::= [ <FLOWSPEC> ]
[ <UPSTREAM_TSPEC>] [ <UPSTREAM_ADSPEC> ]
<FILTER_SPEC> <LABEL>
[ <RECORD_ROUTE> ]
<SE flow descriptor> ::= <FLOWSPEC>
<UPSTREAM_TSPEC> [ <UPSTREAM_ADSPEC> ]
<SE filter spec list>
<SE filter spec list> is unmodified by this document.
4. Compatibility
This extension reuses and extends semantics and procedures defined in
[RFC 2205], [RFC 3209], and [RFC 3473] to support bidirectional LSPs
with asymmetric bandwidth. Three new objects are defined to indicate
the use of asymmetric bandwidth. Each of these objects is defined
with class numbers in the form 0bbbbbbb. Per [RFC 2205], nodes not
supporting this extension will not recognize the new class numbers
and will respond with an "Unknown Object Class" error. The error
message will propagate to the ingress, which can then take action to
avoid the path with the incompatible node or can simply terminate the
session.
Takacs, et. al. Standards Track PAGE 7
RFC 6387 Asymmetric Bandwidth Bidirectional LSP September 2011
5. IANA Considerations
The IANA has made the assignments described below in the "Class
Names, Class Numbers, and Class Types" section of the "RSVP
PARAMETERS" registry.
5.1. UPSTREAM_FLOWSPEC Object
The class named UPSTREAM_FLOWSPEC has been assigned in the 0bbbbbbb
range (120) with the following definition:
Class Types or C-types:
Same values as FLOWSPEC object (C-Num 9)
5.2. UPSTREAM_TSPEC Object
The class named UPSTREAM_TSPEC has been assigned in the 0bbbbbbb
range (121) with the following definition:
Class Types or C-types:
Same values as SENDER_TSPEC object (C-Num 12)
5.3. UPSTREAM_ADSPEC Object
The class named UPSTREAM_ADSPEC has been assigned in the 0bbbbbbb
range (122) with the following definition:
Class Types or C-types:
Same values as ADSPEC object (C-Num 13)
6. Security Considerations
This document introduces new message objects for use in GMPLS
signaling [RFC 3473] -- specifically the UPSTREAM_TSPEC,
UPSTREAM_ADSPEC, and UPSTREAM_FLOWSPEC objects. These objects
parallel the existing SENDER_TSPEC, ADSPEC, and FLOWSPEC objects but
are used in the opposite direction. As such, any vulnerabilities
that are due to the use of the old objects now apply to messages
flowing in the reverse direction.
From a message standpoint, this document does not introduce any new
signaling messages or change the relationship between LSRs that are
adjacent in the control plane. As such, this document introduces no
additional message- or neighbor-related security considerations.
Takacs, et. al. Standards Track PAGE 8
RFC 6387 Asymmetric Bandwidth Bidirectional LSP September 2011
See [RFC 3473] for relevant security considerations and [RFC 5920] for
a more general discussion on RSVP-TE security discussions.
7. References
7.1. Normative References
[RFC 2205] Braden, R., Ed., Zhang, L., Berson, S., Herzog, S., and
S. Jamin, "Resource ReSerVation Protocol (RSVP) --
Version 1 Functional Specification", RFC 2205, September
1997.
[RFC 2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC 2210] Wroclawski, J., "The Use of RSVP with IETF Integrated
Services", RFC 2210, September 1997.
[RFC 3209] 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.
[RFC 3473] Berger, L., Ed., "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Resource ReserVation
Protocol-Traffic Engineering (RSVP-TE) Extensions", RFC
3473, January 2003.
7.2. Informative References
[RFC 4606] Mannie, E. and D. Papadimitriou, "Generalized Multi-
Protocol Label Switching (GMPLS) Extensions for
Synchronous Optical Network (SONET) and Synchronous
Digital Hierarchy (SDH) Control", RFC 4606, August 2006.
[RFC 4328] Papadimitriou, D., Ed., "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Extensions for G.709 Optical
Transport Networks Control", RFC 4328, January 2006.
[RFC 5511] Farrel, A., "Routing Backus-Naur Form (RBNF): A Syntax
Used to Form Encoding Rules in Various Routing Protocol
Specifications", RFC 5511, April 2009.
[RFC 5654] Niven-Jenkins, B., Ed., Brungard, D., Ed., Betts, M.,
Ed., Sprecher, N., and S. Ueno, "Requirements of an MPLS
Transport Profile", RFC 5654, September 2009.
[RFC 5920] Fang, L., Ed., "Security Framework for MPLS and GMPLS
Networks", RFC 5920, July 2010.
Takacs, et. al. Standards Track PAGE 9
RFC 6387 Asymmetric Bandwidth Bidirectional LSP September 2011
[RFC 5467] Berger, L., Takacs, A., Caviglia, D., Fedyk, D., and J.
Meuric, "GMPLS Asymmetric Bandwidth Bidirectional Label
Switched Paths (LSPs)", RFC 5467, March 2009.
[RFC 6003] Papadimitriou, D., "Ethernet Traffic Parameters", RFC
6003, October 2010.
[RFC 6060] Fedyk, D., Shah, H., Bitar, N., and A. Takacs,
"Generalized Multiprotocol Label Switching (GMPLS)
Control of Ethernet Provider Backbone Traffic Engineering
(PBB-TE)", RFC 6060, March 2011.
Takacs, et. al. Standards Track PAGE 10
RFC 6387 Asymmetric Bandwidth Bidirectional LSP September 2011
Authors' Addresses
Attila Takacs
Ericsson
Konyves Kalman krt. 11.
Budapest, 1097
Hungary
EMail: attila.takacs@ericsson.com
Lou Berger
LabN Consulting, L.L.C.
EMail: lberger@labn.net
Diego Caviglia
Ericsson
Via A. Negrone 1/A
Genova-Sestri Ponente,
Italy
Phone: +390106003738
Fax:
EMail: diego.caviglia@ericsson.com
Don Fedyk
Alcatel-Lucent
Groton, MA
USA
EMail: donald.fedyk@alcatel-lucent.com
Julien Meuric
France Telecom Orange
2, avenue Pierre Marzin
Lannion Cedex, 22307
France
EMail: julien.meuric@orange.com
Takacs, et. al. Standards Track PAGE 11
RFC TOTAL SIZE: 23329 bytes
PUBLICATION DATE: Saturday, September 24th, 2011
LEGAL RIGHTS: The IETF Trust (see BCP 78)
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