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Versions: (draft-berger-ccamp-attribute-bnf)
00 01 02 RFC 6510
Internet Draft Lou Berger (LabN)
Updates: 4875, 5420
Category: Standards Track George Swallow (Cisco)
Expiration Date: February 19, 2012
August 19, 2011
LSP Attributes Related Routing Backus-Naur Form
draft-ietf-ccamp-attribute-bnf-02.txt
Abstract
Multiprotocol Label Switching (MPLS) Label Switched Paths (LSPs)
established using the Resource Reservation Protocol Traffic
Engineering (RSVP-TE) extensions may be signaled with a set of LSP
specific attributes. These attributes may be carried in both Path
and Resv messages. This document specifies how LSP attribute are
to be carried in RSVP Path and Resv messages using the Routing
Backus-Naur Form, and clarifies related Resv message formats.
This document updates RFC 4875 and RFC 5420.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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This Internet-Draft will expire on February 19, 2012
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Copyright and License 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
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1 Introduction ........................................... 2
1.1 Conventions Used In This Document ...................... 3
2 Path Messages .......................................... 3
2.1 Path Message Format .................................... 4
3 Resv Messages .......................................... 4
3.1 Resv Message Format -- Per LSP Operational Status ...... 5
3.2 Resv Message Format -- Per S2L Operational Status ...... 6
3.2.1 Compatibility .......................................... 6
4 Security Considerations ................................ 7
5 IANA Considerations .................................... 7
6 Acknowledgments ........................................ 7
7 References ............................................. 7
7.1 Normative References ................................... 7
7.2 Informative References ................................. 8
8 Authors' Addresses ..................................... 8
1. Introduction
Signaling in support of Multiprotocol Label Switching (MPLS) and
Generalized MPLS (GMPLS) point-to-point Label Switched Paths (LSPs)
is defined in [RFC3209] and [RFC3473]. [RFC4875] defines signaling
support for point-to-multipoint (P2MP) TE LSPs.
Two LSP Attributes related objects are defined in [RFC5420]. These
objects may be used to provide additional information related to how
an LSP should be setup when carried in a Path message and, when
carried in a Resv message, how an LSP has been established. The
definition of the objects includes a narrative description of related
message formats, see Section 9 of [RFC5420]. This definition does
not provide the related Routing Backus-Naur Form (BNF), [RFC5511],
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that is typically used to define how messages are to be constructed
using RSVP objects. The current message format description has led
to an issue in how the LSP Attributes related objects are to be
processed in Resv messages of P2MP LSPs.
This document provides the BNF for Path and Resv messages carrying
the LSP Attributes related object. The definition clarifies how the
objects are to be carried for all LSP types. Both Path and Resv
message BNF is provided for completeness.
This document presents the RSVP message related formats as modified
by [RFC5420]. This document modifies formats defined in [RFC3209],
[RFC3473] and [RFC4875]. See [RFC5511] for the syntax used by RSVP.
Unmodified formats are not listed. An example of a case where the
modified formats are applicable is described in [NO-PHP-OOB].
1.1. 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. Path Messages
This section updates [RFC4875]. Path message formatting is
unmodified from the narrative description provided in Section 9 of
[RFC5420]. As stated in [RFC5420]:
The LSP_ATTRIBUTES object and the LSP_REQUIRED_ATTRIBUTES object
MAY be carried in a Path message.
The order of objects in RSVP-TE messages is recommended, but
implementations must be capable of receiving the objects in any
meaningful order.
On a Path message, the LSP_ATTRIBUTES object and
LSP_REQUIRED_ATTRIBUTES objects are RECOMMENDED to be placed
immediately after the SESSION_ATTRIBUTE object if it is present,
or otherwise immediately after the LABEL_REQUEST object.
If both the LSP_ATTRIBUTES object and the LSP_REQUIRED_ATTRIBUTES
object are present, the LSP_REQUIRED_ATTRIBUTES object is
RECOMMENDED to be placed first.
LSRs MUST be prepared to receive these objects in any order in any
position within a Path message. Subsequent instances of these
objects within a Path message SHOULD be ignored and MUST be
forwarded unchanged.
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2.1. Path Message Format
This section presents the Path message format as modified by
[RFC5420]. Unmodified formats are not listed.
<Path Message> ::= <Common Header> [ <INTEGRITY> ]
[ [<MESSAGE_ID_ACK> | <MESSAGE_ID_NACK>] ...]
[ <MESSAGE_ID> ]
<SESSION> <RSVP_HOP>
<TIME_VALUES>
[ <EXPLICIT_ROUTE> ]
<LABEL_REQUEST>
[ <PROTECTION> ]
[ <LABEL_SET> ... ]
[ <SESSION_ATTRIBUTE> ]
[ <LSP_REQUIRED_ATTRIBUTES> ... ]
[ <LSP_ATTRIBUTES> ... ]
[ <NOTIFY_REQUEST> ]
[ <ADMIN_STATUS> ]
[ <POLICY_DATA> ... ]
<sender descriptor>
[<S2L sub-LSP descriptor list>]
Note that PathErr and PathTear messages are not impacted by the
introduction of the LSP attributed related objects.
3. Resv Messages
This section updates [RFC4875] and [RFC5420]. Section 9 of [RFC5420]
contains the following Resv message related text:
The LSP_ATTRIBUTES object MAY be carried in a Resv message.
The order of objects in RSVP-TE messages is recommended, but
implementations must be capable of receiving the objects in any
meaningful order.
On a Resv message, the LSP_ATTRIBUTES object is placed in the flow
descriptor and is associated with the FILTER_SPEC object that
precedes it. It is RECOMMENDED that the LSP_ATTRIBUTES object be
placed immediately after the LABEL object.
LSRs MUST be prepared to receive this object in any order in any
position within a Resv message, subject to the previous note.
Only one instance of the LSP_ATTRIBUTES object is meaningful
within the context of a FILTER_SPEC object. Subsequent instances
of the object SHOULD be ignored and MUST be forwarded unchanged.
This means that LSP attributes may be present per sender (LSP) and
allows for LSP attributes object to be modified using make-before-
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break, see RFC3209. This definition is sufficient for point-to-point
([RFC3209] and [RFC3473]) LSPs, and the special case where all point-
to-multipoint source-to-leaf (S2L) sub-LSPs ([RFC4875]) report the
same operational status (as used in [RFC5420]). But, this definition
does not allow for different egress LSRs to report different
operational status. In order to allow such reporting, this document
adds the following definition:
An LSR that wishes to report operational status of a (point-to-
multipoint) S2L sub-LSP, it may include the LSP_ATTRIBUTES object
in a Resv message, or update the object that is already carried in
a Resv message. LSP_ATTRIBUTES objects representing S2L sub-LSP
status MUST follow a S2L_SUB_LSP object. Only the first instance
of the LSP_ATTRIBUTES object is meaningful within the context of a
S2L_SUB_LSP object. Subsequent instances of the object SHOULD be
ignored and MUST be forwarded unchanged.
When an LSP_ATTRIBUTES object is present before the first
S2L_SUB_LSP object, the LSP_ATTRIBUTES object represents the
operational status of all S2L sub-LSPs identified in the message.
Subsequent instances of the object (e.g, in the filter spec or the
S2L sub-LSP flow descriptor) SHOULD be ignored and MUST be
forwarded unchanged. When a branch node is combining Resv state
from multiple receivers into a single Resv message and an
LSP_ATTRIBUTES object is present before the first S2L_SUB_LSP
object in a received Resv message, the received LSP_ATTRIBUTES
object SHOULD be moved to follow the first received S2L_SUB_LSP
object, and then SHOULD be duplicated for, and placed after, each
subsequent S2L_SUB_LSP object.
3.1. Resv Message Format -- Per LSP Operational Status
This section presents the Resv message format for LSPs as modified by
[RFC5420], and can be used to report operational status per LSP.
Unmodified formats are not listed. This following is based on
[RFC4875].
<FF flow descriptor list> ::= <FF flow descriptor>
[ <FF flow descriptor list> ]
<FF flow descriptor> ::= [ <FLOWSPEC> ] <FILTER_SPEC> <LABEL>
[ <LSP_ATTRIBUTES> ... ]
[ <RECORD_ROUTE> ]
[ <S2L sub-LSP flow descriptor list> ]
<SE flow descriptor> ::= <FLOWSPEC> <SE filter spec list>
<SE filter spec list> ::= <SE filter spec>
[ <SE filter spec list> ]
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<SE filter spec> ::= <FILTER_SPEC> <LABEL>
[ <LSP_ATTRIBUTES> ... ]
[ <RECORD_ROUTE> ]
[ <S2L sub-LSP flow descriptor list> ]
3.2. Resv Message Format -- Per S2L Operational Status
This section presents the Resv message format for LSPs as modified by
this document and [RFC5420], and can be used to report operational
status per S2L sub-LSP. Unmodified formats are not listed. This
following is based on [RFC4875].
<FF flow descriptor> ::= [ <FLOWSPEC> ] <FILTER_SPEC> <LABEL>
[ <RECORD_ROUTE> ]
[ <S2L sub-LSP flow descriptor list> ]
<SE filter spec> ::= <FILTER_SPEC> <LABEL> [ <RECORD_ROUTE> ]
[ <S2L sub-LSP flow descriptor list> ]
<S2L sub-LSP flow descriptor list> ::=
<S2L sub-LSP flow descriptor>
[ <S2L sub-LSP flow descriptor list> ]
<S2L sub-LSP flow descriptor> ::= <S2L_SUB_LSP>
[ <LSP_ATTRIBUTES> ... ]
[ <P2MP_SECONDARY_RECORD_ROUTE> ]
3.2.1. Compatibility
A node that does not support the LSP Attribute object formatting as
defined in this section will interpret the first present LSP
Attribute object as representing LSP operational status even when it
is intended to represent S2L sub-LSP status. It is unclear if this
is a significant issue as the LSP Attribute object is currently
considered to be an unsuitable mechanism for reporting operational
status of P2MP LSPs, for example see Section 2.1 of [NO-PHP-OOB].
The intent of this document is to correct this limitation and it is
expected that networks that wish to make use of such operational
reporting will deploy this extension.
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4. Security Considerations
This document clarifies usage of objects defined in [RFC5420]. No
new information is conveyed and therefore neither are there any
additional security considerations. For a general discussion on MPLS
and GMPLS related security issues, see the MPLS/GMPLS security
framework [RFC5920].
5. IANA Considerations
There are no new IANA considerations introduced by this document.
6. Acknowledgments
The authors would like to acknowledge the contributions of Adrian
Farrel.
7. References
7.1. Normative References
[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",
January 2003.
[RFC4875] R. Aggarwal, D. Papadimitriou, and S. Yasukawa,
"Extensions to Resource Reservation Protocol - Traffic
Engineering (RSVP-TE) for Point-to-Multipoint TE Label
Switched Paths (LSPs)", RFC4875, May 2007.
[RFC5420] Farrel, A., Ed. "Encoding of Attributes for MPLS LSP
Establishment Using Resource Reservation Protocol
Traffic Engineering (RSVP-TE)", RFC 5420, February 2009.
[RFC5511] Farrel, A., "Routing Backus-Naur Form (RBNF): A Syntax
Used to Form Encoding Rules in Various Routing Protocol
Specifications", RFC 5511, April 2009
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7.2. Informative References
[NO-PHP-OOB] Ali, Z., Swallow, G., "Non PHP Behavior and
out-of-band mapping for RSVP-TE LSPs", work in
progress, draft-ietf-mpls-rsvp-te-no-php-oob-mapping.
[RFC5920] Fang, L.,
"Security Framework for MPLS and GMPLS Networks",
RFC 5920, July 2010.
8. Authors' Addresses
Lou Berger
LabN Consulting, L.L.C.
Phone: +1-301-468-9228
Email: lberger@labn.net
George Swallow
Cisco Systems, Inc.
Email: swallow@cisco.com
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