Network Working Group L. Berger

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.

Copyright Notice

Copyright (c) 2009 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 in effect on the date of
publication of this document (http://trustee.ietf.org/license-info).
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document.

This document may contain material from IETF Documents or IETF
Contributions published or made publicly available before November
10, 2008. The person(s) controlling the copyright in some of this
material may not have granted the IETF Trust the right to allow
modifications of such material outside the IETF Standards Process.
Without obtaining an adequate license from the person(s) controlling
the copyright in such materials, this document may not be modified
outside the IETF Standards Process, and derivative works of it may
not be created outside the IETF Standards Process, except to format
it for publication as an RFC or to translate it into languages other
than English.

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:

<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
[RFC2205], [RFC3209], and [RFC3473] to support bidirectional LSPs
with asymmetric bandwidth. To indicate the use of asymmetric
bandwidth, three new objects are defined. Each of these objects is
defined with class numbers in the form 0bbbbbbb. Per [RFC2205],
nodes not supporting this extension will not recognize the new class
numbers and should 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 may simply
terminate the session.

Berger, et al. Experimental [Page 7]

RFC 5467 Asymmetric Bandwidth Bidirectional LSP March 2009

5. IANA Considerations

IANA has assigned new values for namespaces defined in this section
and reviewed in this subsection.

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

A new class named UPSTREAM_FLOWSPEC has been created 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

A new class named UPSTREAM_TSPEC has been created 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

A new class named UPSTREAM_ADSPEC has been created 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 [RFC3473] -- specifically the UPSTREAM_TSPEC,
UPSTREAM_ADSPEC, and UPSTREAM_FLOWSPEC objects. These objects
parallel the exiting 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.

Berger, et al. Experimental [Page 8]

RFC 5467 Asymmetric Bandwidth Bidirectional LSP March 2009

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.

See [RFC3473] for relevant security considerations, and [SEC-
FRAMEWORK] for a more general discussion on RSVP-TE security
discussions.

7. References

7.1. Normative References

[RFC2205] Braden, R., Ed., Zhang, L., Berson, S., Herzog, S.,
and S. Jamin, "Resource ReSerVation Protocol (RSVP)
-- Version 1 Functional Specification", RFC 2205,
September 1997.

[RFC2210] Wroclawski, J., "The Use of RSVP with IETF Integrated
Services", RFC 2210, September 1997.

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.

[RFC3209] 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.

[RFC3473] 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

[GMPLS-PBBTE] Fedyk, D., et al "GMPLS Control of Ethernet", Work in
Progress, July 2008.

[MEF-TRAFFIC] Papadimitriou, D., "MEF Ethernet Traffic Parameters,"
Work in Progress, October 2008.

[RFC4606] 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.

Berger, et al. Experimental [Page 9]

RFC 5467 Asymmetric Bandwidth Bidirectional LSP March 2009

[RFC4328] Papadimitriou, D., Ed., "Generalized Multi-Protocol
Label Switching (GMPLS) Signaling Extensions for
G.709 Optical Transport Networks Control", RFC 4328,
January 2006.

[RSVP-BNF] Farrel, A. "Reduced Backus-Naur Form (RBNF) A Syntax
Used in Various Protocol Specifications", Work in
Progress, November 2008.

[SEC-FRAMEWORK] Fang, L., Ed., "Security Framework for MPLS and GMPLS
Networks", Work in Progress, November 2008.

Berger, et al. Experimental [Page 10]

RFC 5467 Asymmetric Bandwidth Bidirectional LSP March 2009

A. Appendix A: Alternate Approach Using ADSPEC Object

This section is included for historic purposes and its implementation
is NOT RECOMMENDED.

A.1. Applicability

This section presents an alternate method for the support of
asymmetric bandwidth bidirectional LSP establishment with a single
RSVP-TE signaling session. This approach differs in applicability
and generality from the approach presented in the main body of this
document. In particular, this approach is technology-specific; it
uses the ADSPEC object to carry traffic parameters for upstream data
and requires the Metro Ethernet Forum (MEF) Ethernet Traffic
Parameter, while the approach presented above is suitable for use
with any technology.

The generalized asymmetric bandwidth bidirectional LSP presented in
the main body of this document has the benefit of being applicable to
any switching technology, but requires support for three new types of
object classes, i.e., the UPSTREAM_TSPEC, UPSTREAM_ADSPEC, and
UPSTREAM_FLOWSPEC objects.

The solution presented in this section is based on the
Ethernet-specific ADSPEC object, and is referred to as the "ADSPEC
Object" approach. This approach limits applicability to cases where
the [MEF-TRAFFIC] traffic parameters are appropriate, and to
switching technologies that define no use for the ADSPEC object.
While ultimately it is this limited scope that has resulted in this
approach being relegated to an Appendix, the semantics of this
approach are quite simple in that they only require the definition of
a new ADSPEC object C-Type.

In summary, the "ADSPEC Object" approach presented in this section
SHOULD NOT be implemented.

A.2. Overview

The "ADSPEC Object" approach is specific to Ethernet and uses [MEF-
TRAFFIC] traffic parameters. This approach is not generic and is
aimed at providing asymmetric bandwidth bidirectional LSPs for just
Ethernet transport. With this approach, the ADSPEC object carries
the traffic parameters for the upstream data flow. SENDER_TSPEC
object is used to indicate the traffic parameters for the downstream
data flow. The FLOWSPEC object provides confirmation of the
allocated downstream resources. Confirmation of the upstream
resource allocation is a Resv message, as any resource allocation

Berger, et al. Experimental [Page 11]

RFC 5467 Asymmetric Bandwidth Bidirectional LSP March 2009

failure for the upstream direction will always result in a PathErr
message. Figure 2 shows the bandwidth-related objects used in the
first approach.

|---| Path |---|
| I |----------------->| E |
| n | -SENDER_TSPEC | g |
| g | -ADSPEC | r |
| r | | e |
| e | Resv | s |
| s |<-----------------| s |
| s | -FLOWSPEC | |
|---| |---|

Figure 2: Asymmetric Bandwidth Bidirectional LSPs Using ADSPEC Object

In the "ADSPEC Object" approach, the setup of an asymmetric bandwidth
bidirectional LSP would be signaled using the bidirectional
procedures defined in [RFC3473] together with the inclusion of a new
ADSPEC object. The new ADSPEC object would be specific to Ethernet
and could be called the Ethernet Upstream Traffic Parameter ADSPEC
object. The Ethernet Upstream Traffic Parameter ADSPEC object would
use the Class-Number 13 and C-Type UNASSIGNED (this approach should
not be implemented). The format of the object would be the same as
the Ethernet SENDER_TSPEC object defined in [MEF-TRAFFIC].

This approach would not modify behavior of symmetric bandwidth LSPs.
Per [MEF-TRAFFIC], such LSPs are signaled either without an ADSPEC or
with an INTSERV ADSPEC.

The defined approach could be reused to support asymmetric bandwidth
bidirectional LSPs for other types of switching technologies. All
that would be needed would be to define the proper ADSPEC object.

A.3. Procedures

Using the approach presented in this section, the process of
establishing an asymmetric bandwidth bidirectional LSP would follow
the process of establishing a symmetric bandwidth bidirectional LSP,
as defined in Section 3 of [RFC3473], with two modifications. These
modifications would be followed when an incoming Path message is
received containing an Upstream_Label object and the Ethernet
Upstream Traffic Parameter ADSPEC object.

The first modification to the symmetric bandwidth process would be
that when allocating the upstream label, the bandwidth associated
with the upstream label would be taken from the Ethernet Upstream
Traffic Parameter ADSPEC object, see Section 3.1 of [RFC3473].

Berger, et al. Experimental [Page 12]

RFC 5467 Asymmetric Bandwidth Bidirectional LSP March 2009

Consistent with [RFC3473], a node that is unable to allocate a label
or internal resources based on the contents of the ADSPEC object,
would issue a PathErr message with a "Routing problem/MPLS label
allocation failure" indication.

The second modification would be that the ADSPEC object would not be
modified by transit nodes.

A.4. Compatibility

The approach presented in this section reuses semantics and
procedures defined in [RFC3473]. To indicate the use of asymmetric
bandwidth, a new ADSPEC object C-type would be defined. Per
[RFC2205], nodes not supporting the approach should not recognize
this new C-type and respond with an "Unknown object C-Type" error.

Berger, et al. Experimental [Page 13]

RFC 5467 Asymmetric Bandwidth Bidirectional LSP March 2009

Authors' Addresses

Lou Berger
LabN Consulting, L.L.C.

EMail: [email protected]

Attila Takacs
Ericsson
1. Laborc u.
1037 Budapest, Hungary

Phone: +36-1-4377044
EMail: [email protected]

Diego Caviglia
Ericsson
Via A. Negrone 1/A
Genova-Sestri Ponente, Italy

Phone: +390106003738
EMail: [email protected]

Don Fedyk
Nortel Networks
600 Technology Park Drive
Billerica, MA, USA 01821

Phone: +1-978-288-3041
EMail: [email protected]

Julien Meuric
France Telecom
Research & Development
2, avenue Pierre Marzin
22307 Lannion Cedex - France

Phone: +33 2 96 05 28 28
EMail: [email protected]

Berger, et al. Experimental [Page 14]