Network Working Group L. Berger
Request for Comments: 5467 LabN
Category: Experimental A. Takacs
Ericsson
D. Caviglia
Ericsson
D. Fedyk
Nortel
J. Meuric
France Telecom
March 2009
GMPLS Asymmetric Bandwidth Bidirectional Label Switched Paths (LSPs)
Status of This Memo
This memo defines an Experimental Protocol for the Internet
community. It does not specify an Internet standard of any kind.
Discussion and suggestions for improvement are requested.
Distribution of this memo is unlimited.
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Berger, et al. Experimental [Page 1]
RFC 5467 Asymmetric Bandwidth Bidirectional LSP March 2009
Abstract
This document defines a method for the support of GMPLS asymmetric
bandwidth bidirectional Label Switched Paths (LSPs). The presented
approach is applicable to any switching technology and builds on the
original Resource Reservation Protocol (RSVP) model for the transport
of traffic-related parameters. The procedures described in this
document are experimental.
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
Appendix A. Alternate Approach Using ADSPEC Object.................11
A.1. Applicability .............................................11
A.2. Overview ..................................................11
A.3. Procedures ................................................12
A.4. Compatibility .............................................13
1. Introduction
GMPLS [RFC3473] 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
[RFC2205] and [RFC2210].
Berger, et al. Experimental [Page 2]
RFC 5467 Asymmetric Bandwidth Bidirectional LSP March 2009
Recent work ([GMPLS-PBBTE] and [MEF-TRAFFIC]) has looked at extending
GMPLS to control Ethernet switching. In this context, there has been
discussion of the support of bidirectional LSPs with asymmetric
bandwidth. (That is, bidirectional LSPs that have different
bandwidth reservations in each direction.) This discussion motivated
the extensions defined in this document, which may be used with any
switching technology to signal asymmetric bandwidth bidirectional
LSPs. The procedures described in this document are experimental.
1.1. Background
Bandwidth parameters are transported within RSVP ([RFC2210],
[RFC3209], and [RFC3473]) 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 [RFC2205] and maintained in [RFC3209],
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 allocated for the associated data traffic.
With the introduction of bidirectional LSPs in [RFC3473], the model
of communication of bandwidth parameters was implicitly changed. In
the context of [RFC3473] 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 ([RFC4606] and [MEF-TRAFFIC]) 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. An alternative approach was considered and
rejected in favor of the more generic approach presented below. For
reference purposes only, the rejected approach is summarized in
Appendix A.
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
Berger, et al. Experimental [Page 3]
RFC 5467 Asymmetric Bandwidth Bidirectional LSP March 2009
UPSTREAM_FLOWSPEC objects. The existing objects are used in the
original fashion defined in [RFC2205] and [RFC2210], 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 [RFC2119].
2. Generalized Asymmetric Bandwidth Bidirectional LSPs
The setup of an asymmetric bandwidth bidirectional LSP is signaled
using the bidirectional procedures defined in [RFC3473] 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
the existing objects relate to traffic flowing in the downstream
direction. The new objects also differ in that they are used on
messages in the opposite directions.
Berger, et al. Experimental [Page 4]
RFC 5467 Asymmetric Bandwidth Bidirectional LSP March 2009
2.1. UPSTREAM_FLOWSPEC Object
The format of an UPSTREAM_FLOWSPEC object is the same as a FLOWSPEC
object. 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 [RFC3473]. 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., [RFC2210] or [RFC4328].
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 [RFC3473]. Consistent with [RFC3473], 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. This 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., [RFC2210] or
[RFC4328]. The contents of the UPSTREAM_TSPEC object MAY differ from
contents of the UPSTREAM_FLOWSPEC object based on application data
transmission requirements.
Berger, et al. Experimental [Page 5]
RFC 5467 Asymmetric Bandwidth Bidirectional LSP March 2009
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 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.
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., [RFC2210] or [MEF-TRAFFIC]. 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 [RFC2205],
[RFC3209], and [RFC3473]. See [RSVP-BNF] 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)
Berger, et al. Experimental [Page 6]
RFC 5467 Asymmetric Bandwidth Bidirectional LSP March 2009
The format of the sender description for bidirectional asymmetric
LSPs is:
::=
[ ]
[ ]
[ ]
[ ]
The format of the flow descriptor list for bidirectional asymmetric
LSPs is:
::=
|
::=
[ ]
RFC, FYI, BCP