Internet Engineering Task Force (IETF) L. Berger
Request for Comments: 6780 LabN
Updates: 2205, 3209, 3473, 4872 F. Le Faucheur
Category: Standards Track A. Narayanan
ISSN: 2070-1721 Cisco
October 2012
RSVP ASSOCIATION Object Extensions
Abstract
The RSVP ASSOCIATION object was defined in the context of GMPLS-
controlled Label Switched Paths (LSPs). In this context, the object
is used to associate recovery LSPs with the LSP they are protecting.
This object also has broader applicability as a mechanism to
associate RSVP state. This document defines how the ASSOCIATION
object can be more generally applied. This document also defines
Extended ASSOCIATION objects that, in particular, can be used in the
context of the MPLS Transport Profile (MPLS-TP). This document
updates RFC 2205, RFC 3209, and RFC 3473. It also generalizes the
definition of the Association ID field defined in RFC 4872.
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/rfc6780.
Berger, et al. Standards Track [Page 1]
RFC 6780 RSVP Extensions October 2012
Copyright Notice
Copyright (c) 2012 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. Conventions Used in This Document ..........................4
2. Generalized Association ID Field Definition .....................4
3. Non-GMPLS and Non-Recovery Usage ................................4
3.1. Upstream Initiated Association .............................5
3.1.1. Path Message Format .................................5
3.1.2. Path Message Processing .............................6
3.2. Downstream Initiated Association ...........................7
3.2.1. Resv Message Format .................................8
3.2.2. Resv Message Processing .............................8
3.3. Association Types ..........................................9
3.3.1. Resource Sharing Association Type ...................9
3.3.2. Unknown Association Types ..........................10
4. IPv4 and IPv6 Extended ASSOCIATION Objects .....................10
4.1. IPv4 and IPv6 Extended ASSOCIATION Object Format ..........11
4.2. Processing ................................................13
5. Compatibility ..................................................14
6. Security Considerations ........................................14
7. IANA Considerations ............................................15
7.1. IPv4 and IPv6 Extended ASSOCIATION Objects ................15
7.2. Resource Sharing Association Type .........................15
8. Acknowledgments ................................................16
9. References .....................................................16
9.1. Normative References ......................................16
9.2. Informative References ....................................16
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1. Introduction
End-to-end and segment recovery are defined for GMPLS-controlled
Label Switched Paths (LSPs) in [RFC4872] and [RFC4873], respectively.
Both definitions use the ASSOCIATION object to associate recovery
LSPs with the LSP they are protecting. Additional narrative on how
such associations are to be identified is provided in [RFC6689].
This document expands the possible usage of the ASSOCIATION object to
non-GMPLS and non-recovery contexts. The expanded usage applies
equally to GMPLS LSPs [RFC3473], MPLS LSPs [RFC3209], and non-LSP
RSVP sessions [RFC2205] [RFC2207] [RFC3175] [RFC4860]. This document
also reviews how associations should be made in the case in which the
object is carried in a Path message; additionally, it defines usage
with Resv messages. This section also discusses usage of the
ASSOCIATION object outside the context of GMPLS LSPs.
Some examples of non-LSP association being used to enable resource
sharing are:
o Voice Call-Waiting:
A bidirectional voice call between two endpoints, A and B, is
signaled using two separate unidirectional RSVP reservations for
the flows A->B and B->A. If endpoint A wishes to put the A-B call
on hold and join a separate A-C call, it is desirable that network
resources on common links be shared between the A-B and A-C calls.
The B->A and C->A subflows of the call can share resources using
existing RSVP sharing mechanisms, but only if they use the same
destination IP addresses and ports. Since by definition, the RSVP
reservations for the subflows A->B and A->C of the call must have
different IP addresses in the SESSION objects, this document
defines a new mechanism to associate the subflows and allow them
to share resources.
o Voice Shared Line:
A voice shared line is a single number that rings multiple
endpoints (which may be geographically diverse), such as phone
lines to a manager's desk and to their assistant. A Voice over IP
(VoIP) system that models these calls as multiple point-to-point
unicast pre-ring reservations would result in significantly over-
counting bandwidth on shared links, since RSVP unicast
reservations to different endpoints cannot share bandwidth. So, a
new mechanism is defined in this document to allow separate
unicast reservations to be associated and to share resources.
Berger, et al. Standards Track [Page 3]
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o Symmetric NAT:
RSVP permits sharing of resources between multiple flows addressed
to the same destination D, even from different senders S1 and S2.
However, if D is behind a NAT operating in symmetric mode
[RFC5389], it is possible that the destination port of the flows
S1->D and S2->D may be different outside the NAT. In this case,
these flows cannot share resources using RSVP, since the SESSION
objects for these two flows outside the NAT have different
destination ports. This document defines a new mechanism to
associate these flows and allow them to share resources.
In order to support the wider usage of the ASSOCIATION object, this
document generalizes the definition of the Association ID field
defined in RFC 4872. This generalization has no impact on existing
implementations. When using the procedures defined below,
association is identified based on exact ASSOCIATION object matching.
Some of the other matching mechanisms defined in RFC 4872, e.g.,
matching based on Session IDs, are not generalized. This document
allows for, but does not specify, association type-specific
processing.
This document also defines the Extended ASSOCIATION objects that can
be used in the context of MPLS-TP. The scope of the Extended
ASSOCIATION objects is not limited to MPLS-TP.
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. Generalized Association ID Field Definition
The Association ID field is carried in the IPv4 and IPv6 ASSOCIATION
objects defined in [RFC4872]. The [RFC4872] definition of the field
reads:
A value assigned by the LSP head-end. When combined with the
Association Type and Association Source, this value uniquely
identifies an association.
This document allows for the origination of ASSOCIATION objects by
nodes other than "the LSP head-end". As such, the definition of the
Association ID field needs to be generalized to accommodate such
usage. This document defines the Association ID field of the IPv4
and IPv6 ASSOCIATION objects as:
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A value assigned by the node that originated the association.
When combined with the other fields carried in the object, this
value uniquely identifies an association.
This change in definition does not impact the procedures or
mechanisms defined in [RFC4872] or [RFC4873], nor does it impact the
existing implementations of [RFC4872] or [RFC4873].
3. Non-GMPLS and Non-Recovery Usage
While the ASSOCIATION object [RFC4872] is defined in the context of
GMPLS recovery, the object can have wider application. [RFC4872]
defines the object to be used to "associate LSPs with each other",
and then defines an Association Type field to identify the type of
association being identified. It also specifies that the Association
Type field is to be considered when determining association, i.e.,
there may be type-specific association rules. As defined by
[RFC4872] and reviewed in [RFC6689], this is the case for recovery
type ASSOCIATION objects. [RFC6689], notably the text related to
resource sharing types, can also be used as the foundation for a
generic method for associating LSPs when there is no type-specific
association defined.
The remainder of this section defines the general rules to be
followed when processing ASSOCIATION objects. Object usage in both
Path and Resv messages is discussed. The usage applies equally to
GMPLS LSPs [RFC3473], MPLS LSPs [RFC3209], and non-LSP RSVP sessions
[RFC2205] [RFC2207] [RFC3175] [RFC4860]. As described below,
association is always done based on matching either Path state to
Path state, or Resv state to Resv state, but not Path state to Resv
State. This section applies to the ASSOCIATION objects defined in
[RFC4872].
3.1. Upstream-Initiated Association
Upstream-initiated association is represented in ASSOCIATION objects
carried in Path messages and can be used to associate RSVP Path state
across MPLS Tunnels / RSVP sessions. (Note, per [RFC3209], an MPLS
tunnel is represented by an RSVP SESSION object, and multiple LSPs
may be represented within a single tunnel.) Cross-LSP association
based on Path state is defined in [RFC4872]. This section extends
that definition by specifying generic association rules and usage for
non-LSP uses. This section does not modify processing required to
support [RFC4872] and [RFC4873], which is reviewed in Section 3 of
[RFC6689]. The use of an ASSOCIATION object in a single session is
not precluded.
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3.1.1. Path Message Format
This section provides the Backus-Naur Form (BNF), see [RFC5511], for
Path messages containing ASSOCIATION objects. BNF is provided for
both MPLS and for non-LSP session usage. Unmodified RSVP message
formats and some optional objects are not listed.
The formats for MPLS and GMPLS sessions are unmodified from [RFC4872]
and can be represented based on the BNF in [RFC3209] as:
::= [ ]
[ ]
[ ]
[ ... ]
[ ... ]
The format for non-LSP sessions as based on the BNF in [RFC2205] is:
::= [ ]
[ ... ]
[ ... ]
[ ]
In general, relative ordering of ASSOCIATION objects with respect to
each other, as well as with respect to other objects, is not
significant. Relative ordering of ASSOCIATION objects of the same
type SHOULD be preserved by transit nodes.
3.1.2. Path Message Processing
This section is based on, and extends, the processing rules described
in [RFC4872] and [RFC4873], which is reviewed in [RFC6689]. This
section applies equally to GMPLS LSPs, MPLS LSPs, and non-LSP session
state. Note, as previously stated, this section does not modify
processing required to support [RFC4872] and [RFC4873].
A node sending a Path message chooses when an ASSOCIATION object is
to be included in the outgoing Path message. To indicate association
between multiple sessions, an appropriate ASSOCIATION object MUST be
included in the outgoing Path messages corresponding to each of the
associated sessions. In the absence of Association-Type-specific
rules for identifying association, the included ASSOCIATION object
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MUST be identical. When there is an Association-Type-specific
definition of association rules, the definition SHOULD allow for
association based on identical ASSOCIATION objects. This document
does not define any Association-Type-specific rules. (See Section 3
of [RFC6689] for a review of Association-Type-specific rules derived
from [RFC4872].)
When creating an ASSOCIATION object, the originator MUST format the
object as defined in Section 16.1 of [RFC4872]. The originator MUST
set the Association Type field based on the type of association being
identified. The Association ID field MUST be set to a value that
uniquely identifies the specific association within the context of
the Association Source field. The Association Source field MUST be
set to a unique address assigned to the node originating the
association.
A downstream node can identify an upstream-initiated association by
performing the following checks. When a node receives a Path
message, it MUST check each ASSOCIATION object received in the Path
message to determine if the object contains an Association Type field
value supported by the node. For each ASSOCIATION object containing
a supported association type, the node MUST then check to see if the
object matches an ASSOCIATION object received in any other Path
message. To perform this matching, a node MUST examine the Path
state of all other sessions and compare the fields contained in the
newly received ASSOCIATION object with the fields contained in the
Path state's ASSOCIATION objects. An association is deemed to exist
when the same values are carried in all fields of the ASSOCIATION
objects being compared. Type-specific processing of ASSOCIATION
objects is outside the scope of this document.
Note that as more than one association may exist, the described
matching MUST continue after a match is identified and MUST be
performed against all local Path state. It is also possible for
there to be no match identified.
Unless there are type-specific processing rules, downstream nodes
MUST forward all ASSOCIATION objects received in a Path message in
any corresponding outgoing Path messages without modification. This
processing MUST be followed for unknown Association Type field
values.
3.2. Downstream-Initiated Association
Downstream-initiated association is represented in ASSOCIATION
objects carried in Resv messages and can be used to associate RSVP
Resv state across MPLS Tunnels/RSVP sessions. Cross-LSP association,
based on Path state, is defined in [RFC4872]. This section defines
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cross-session association based on Resv state. This section places
no additional requirements on implementations supporting [RFC4872]
and [RFC4873]. Note, the use of an ASSOCIATION object in a single
session is not precluded.
3.2.1. Resv Message Format
This section provides the Backus-Naur Form (BNF), see [RFC5511], for
Resv messages containing ASSOCIATION objects. BNF is provided for
both MPLS and for non-LSP session usage. Unmodified RSVP message
formats and some optional objects are not listed.
The formats for MPLS, GMPLS, and non-LSP sessions are identical and
are represented based on the BNF in [RFC2205] and [RFC3209]:
::= [ ]
[ ] [ ]
[ ... ]
[ ... ]