RSVP-TE Extensions in Support of End-to-End Generalized Multi-Protocol Label Switching (GMPLS) Recovery :: RFC4872
Network Working Group J.P. Lang, Ed.
Request for Comments: 4872 Sonos
Updates: 3471 Y. Rekhter, Ed.
Category: Standards Track Juniper
D. Papadimitriou, Ed.
Alcatel
May 2007
RSVP-TE Extensions in Support of End-to-End
Generalized Multi-Protocol Label Switching (GMPLS) Recovery
Status of This Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Copyright Notice
Copyright (C) The IETF Trust (2007).
Abstract
This document describes protocol-specific procedures and extensions
for Generalized Multi-Protocol Label Switching (GMPLS) Resource
ReSerVation Protocol - Traffic Engineering (RSVP-TE) signaling to
support end-to-end Label Switched Path (LSP) recovery that denotes
protection and restoration. A generic functional description of
GMPLS recovery can be found in a companion document, RFC 4426.
Table of Contents
1. Introduction .....................................................3
2. Conventions Used in This Document ...............................5
3. Relationship to Fast Reroute (FRR) ..............................5
4. Definitions .....................................................6
4.1. LSP Identification .........................................6
4.2. Recovery Attributes ........................................7
4.2.1. LSP Status ..........................................7
4.2.2. LSP Recovery ........................................8
4.3. LSP Association ............................................9
5. 1+1 Unidirectional Protection ...................................9
5.1. Identifiers ...............................................10
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6. 1+1 Bidirectional Protection ...................................10
6.1. Identifiers ...............................................11
6.2. End-to-End Switchover Request/Response ....................11
7. 1:1 Protection with Extra-Traffic ..............................13
7.1. Identifiers ...............................................14
7.2. End-to-End Switchover Request/Response ....................15
7.3. 1:N (N > 1) Protection with Extra-Traffic .................16
8. Rerouting without Extra-Traffic ................................17
8.1. Identifiers ...............................................19
8.2. Signaling Primary LSPs ....................................19
8.3. Signaling Secondary LSPs ..................................19
9. Shared-Mesh Restoration ........................................20
9.1. Identifiers ...............................................22
9.2. Signaling Primary LSPs ....................................22
9.3. Signaling Secondary LSPs ..................................23
10. LSP Preemption ................................................23
11. (Full) LSP Rerouting ..........................................25
11.1. Identifiers ..............................................25
11.2. Signaling Reroutable LSPs ................................26
12. Reversion .....................................................26
13. Recovery Commands .............................................29
14. PROTECTION Object .............................................31
14.1. Format ...................................................31
14.2. Processing ...............................................33
15. PRIMARY_PATH_ROUTE Object .....................................33
15.1. Format ...................................................34
15.2. Subobjects ...............................................34
15.3. Applicability ............................................35
15.4. Processing ...............................................36
16. ASSOCIATION Object ............................................37
16.1. Format ...................................................37
16.2. Processing ...............................................38
17. Updated RSVP Message Formats ..................................39
18. Security Considerations .......................................40
19. IANA Considerations ...........................................41
20. Acknowledgments ...............................................43
21. References ....................................................43
21.1. Normative References .....................................43
21.2. Informative References ...................................44
22. Contributors ..................................................45
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1. Introduction
Generalized Multi-Protocol Label Switching (GMPLS) extends MPLS to
include support for Layer-2 Switch Capable (L2SC), Time-Division
Multiplex (TDM), Lambda Switch Capable (LSC), and Fiber Switch
Capable (FSC) interfaces. GMPLS recovery uses control plane
mechanisms (i.e., signaling, routing, and link management mechanisms)
to support data plane fault recovery. Note that the analogous (data
plane) fault detection mechanisms are required to be present in
support of the control plane mechanisms. In this document, the term
"recovery" is generically used to denote both protection and
restoration; the specific terms "protection" and "restoration" are
only used when differentiation is required. The subtle distinction
between protection and restoration is made based on the resource
allocation done during the recovery phase (see [RFC4427]).
A functional description of GMPLS recovery is provided in [RFC4426]
and should be considered as a companion document. The present
document describes the protocol-specific procedures for GMPLS RSVP-
TE (Resource ReSerVation Protocol - Traffic Engineering) signaling
(see [RFC3473]) to support end-to-end recovery. End-to-end recovery
refers to the recovery of an entire LSP from its head-end (ingress
node endpoint) to its tail-end (egress node endpoint). With end-to-
end recovery, working LSPs are assumed to be resource-disjoint (where
a resource is a link, node, or Shared Risk Link Group (SRLG)) in the
network so that they do not share any failure probability, but this
is not mandatory. With respect to a given set of network resources,
a pair of working/protecting LSPs SHOULD be resource disjoint in case
of dedicated recovery type (see below). On the other hand, in case
of shared recovery (see below), a group of working LSPs SHOULD be
mutually resource-disjoint in order to allow for a (single and
commonly) shared protecting LSP, itself resource-disjoint from each
of the working LSPs. Note that resource disjointness is a necessary
(but not sufficient) condition to ensure LSP recoverability.
The present document addresses four types of end-to-end LSP recovery:
1) 1+1 (unidirectional/bidirectional) protection, 2) 1:N (N >= 1) LSP
protection with extra-traffic, 3) pre-planned LSP rerouting without
extra-traffic (including shared mesh), and 4) full LSP rerouting.
1) The simplest notion of end-to-end LSP protection is 1+1
unidirectional protection. Using this type of protection, a
protecting LSP is signaled over a dedicated resource-disjoint
alternate path to protect an associated working LSP. Normal
traffic is simultaneously sent on both LSPs and a selector is used
at the egress node to receive traffic from one of the LSPs. If a
failure occurs along one of the LSPs, the egress node selects the
Lang, et al. Standards Track [Page 3]
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traffic from the valid LSP. No coordination is required between
the end nodes when a failure/switchover occurs.
In 1+1 bidirectional protection, a protecting LSP is signaled over
a dedicated resource-disjoint alternate path to protect the
working LSP. Normal traffic is simultaneously sent on both LSPs
(in both directions), and a selector is used at both
ingress/egress nodes to receive traffic from the same LSP. This
requires coordination between the end-nodes when switching to the
protecting LSP.
2) In 1:N (N >= 1) protection with extra-traffic, the protecting LSP
is a fully provisioned and resource-disjoint LSP from the N
working LSPs, that allows for carrying extra-traffic. The N
working LSPs MAY be mutually resource-disjoint. Coordination
between end-nodes is required when switching from one of the
working LSPs to the protecting LSP. As the protecting LSP is
fully provisioned, default operations during protection switching
are specified for a protecting LSP carrying extra-traffic, but
this is not mandatory. Note that M:N protection is out of scope
of this document (though mechanisms it defines may be extended to
cover it).
3) Pre-planned LSP rerouting (or restoration) relies on the
establishment between the same pair of end-nodes of a working LSP
and a protecting LSP that is link/node/SRLG disjoint from the
working one. Here, the recovery resources for the protecting LSP
are pre-reserved but explicit action is required to activate
(i.e., commit resource allocation at the data plane) a specific
protecting LSP instantiated during the (pre-)provisioning phase.
Since the protecting LSP is not "active" (i.e., fully
instantiated), it cannot carry any extra-traffic. This does not
mean that the corresponding resources cannot be used by other
LSPs. Therefore, this mechanism protects against working LSP(s)
failure(s) but requires activation of the protecting LSP after
working LSP failure occurrence. This requires restoration
signaling along the protecting path. "Shared-mesh" restoration
can be seen as a particular case of pre-planned LSP rerouting that
reduces the recovery resource requirements by allowing multiple
protecting LSPs to share common link and node resources. The
recovery resources are pre-reserved but explicit action is
required to activate (i.e., commit resource allocation at the data
plane) a specific protecting LSP instantiated during the (pre-)
provisioning phase. This procedure requires restoration signaling
along the protecting path.
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Note that in both cases, bandwidth pre-reserved for a protecting
(but not activated) LSP can be made available for carrying extra
traffic. LSPs for extra-traffic (with lower holding priority than
the protecting LSP) can then be established using the bandwidth
pre-reserved for the protecting LSP. Also, any lower priority LSP
that use the pre-reserved resources for the protecting LSP(s) must
be preempted during the activation of the protecting LSP.
4) Full LSP rerouting (or restoration) switches normal traffic to an
alternate LSP that is not even partially established until after
the working LSP failure occurs. The new alternate route is
selected at the LSP head-end node, it may reuse resources of the
failed LSP at intermediate nodes and may include additional
intermediate nodes and/or links.
Crankback signaling (see [CRANK]) and LSP segment recovery (see
[RFC4873]) are further detailed in dedicated companion documents.
2. 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].
In addition, the reader is assumed to be familiar with the
terminology used in [RFC3945], [RFC3471], [RFC3473] and referenced as
well as in [RFC4427] and [RFC4426].
3. Relationship to Fast Reroute (FRR)
There is no impact to RSVP-TE Fast Reroute (FRR) [RFC4090] introduced
by end-to-end GMPLS recovery i.e., it is possible to use either
method defined in FRR with end-to-end GMPLS recovery.
The objects used and/or newly introduced by end-to-end recovery will
be ignored by [RFC4090] conformant implementations, and FRR can
operate on a per LSP basis as defined in [RFC4090].
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4. Definitions
4.1. LSP Identification
This section reviews terms previously defined in [RFC2205],
[RFC3209], and [RFC3473]. LSP tunnels are identified by a
combination of the SESSION and SENDER_TEMPLATE objects (see also
[RFC3209]). The relevant fields are as follows:
IPv4 (or IPv6) tunnel endpoint address
IPv4 (or IPv6) address of the egress node for the tunnel.
Tunnel ID
A 16-bit identifier used in the SESSION that remains constant
over the life of the tunnel.
Extended Tunnel ID
A 32-bit (or 16-byte) identifier used in the SESSION that
remains constant over the life of the tunnel. Normally set to
all zeros. Ingress nodes that wish to narrow the scope of a
SESSION to the ingress-egress pair MAY place their IPv4 (or
IPv6) address here as a globally unique identifier.
IPv4 (or IPv6) tunnel sender address
IPv4 (or IPv6) address for a sender node.
LSP ID
A 16-bit identifier used in the SENDER_TEMPLATE and FILTER_SPEC
that can be changed to allow a sender to share resources with
itself.
The first three fields are carried in the SESSION object (Path and
Resv message) and constitute the basic identification of the LSP
tunnel.
The last two fields are carried in the SENDER_TEMPLATE (Path message)
and FILTER_SPEC objects (Resv message). The LSP ID is used to
differentiate LSPs that belong to the same LSP Tunnel (as identified
by its Tunnel ID).
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4.2. Recovery Attributes
The recovery attributes include all the parameters that determine the
status of an LSP within the recovery scheme to which it is
associated. These attributes are part of the PROTECTION object
introduced in Section 14.
4.2.1. LSP Status
The following bits are used in determining resource allocation and
status of the LSP within the group of LSPs forming the protected
entity:
- S (Secondary) bit: enables distinction between primary and
secondary LSPs. A primary LSP is a fully established LSP for which
the resource allocation has been committed at the data plane (i.e.,
full cross-connection has been performed). Both working and
protecting LSPs can be primary LSPs. A secondary LSP is an LSP
that has been provisioned in the control plane only, and for which
resource selection MAY have been done but for which the resource
allocation has not been committed at the data plane (for instance,
no cross-connection has been performed). Therefore, a secondary
LSP is not immediately available to carry any traffic (thus
requiring additional signaling to be available). A secondary LSP
can only be a protecting LSP. The (data plane) resources allocated
for a secondary LSP MAY be used by other LSPs until the primary LSP
fails over to the secondary LSP.
- P (Protecting) bit: enables distinction between working and
protecting LSPs. A working LSP must be a primary LSP whilst a
protecting LSP can be either a primary or a secondary LSP. When
protecting LSP(s) are associated with working LSP(s), one also
refers to the latter as protected LSPs.
Note: The combination "secondary working" is not valid (only
protecting LSPs can be secondary LSPs). Working LSPs are always
primary LSPs (i.e., fully established) whilst primary LSPs can be
either working or protecting LSPs.
- O (Operational) bit: this bit is set when a protecting LSP is
carrying the normal traffic after protection switching (i.e.,
applies only in case of dedicated LSP protection or LSP protection
with extra-traffic; see Section 4.2.2).
In this document, the PROTECTION object uses as a basis the
PROTECTION object defined in [RFC3471] and [RFC3473] and defines
additional fields within it. The fields defined in [RFC3471] and
[RFC3473] are unchanged by this document.
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4.2.2. LSP Recovery
The following classification is used to distinguish the LSP
Protection Type with which LSPs can be associated at end-nodes (a
distinct value is associated with each Protection Type in the
PROTECTION object; see Section 14):
- Full LSP Rerouting: set if a primary working LSP is dynamically
recoverable using (non pre-planned) head-end rerouting.
- Pre-planned LSP Rerouting without Extra-traffic: set if a
protecting LSP is a secondary LSP that allows sharing of the pre-
reserved recovery resources between one or more than one
pair. When the secondary LSPs resources are not
pre-reserved for a single pair, this type is
referred to as "shared mesh" recovery.
- LSP Protection with Extra-traffic: set if a protecting LSP is a
dedicated primary LSP that allows for extra-traffic transport and
thus precludes any sharing of the recovery resources between more
than one pair. This type includes 1:N LSP
protection with extra-traffic.
- Dedicated LSP Protection: set if a protecting LSP does not allow
sharing of the recovery resources nor the transport of extra-
traffic (implying in the present context, duplication of the signal
over both working and protecting LSPs as in 1+1 dedicated
protection). Note also that this document makes a distinction
between 1+1 unidirectional and bidirectional dedicated LSP
protection.
For LSP protection, in particular, when the data plane provides
automated protection-switching capability (see for instance ITU-T
[G.841] Recommendation), a Notification (N) bit is defined in the
PROTECTION object. It allows for distinction between protection
switching signaling via the control plane or the data plane.
Note: this document assumes that Protection Type values have end-to-
end significance and that the same value is sent over the protected
and the protecting path. In this context, shared-mesh (for instance)
appears from the end-nodes perspective as being simply an LSP
rerouting without extra-traffic services. The net result of this is
that a single bit (the S bit alone) does not allow determining
whether resource allocation should be performed with respect to the
status of the LSP within the protected entity. The introduction of
the P bit solves this problem unambiguously. These bits MUST be
processed on a hop-by-hop basis (independently of the LSP Protection
Type context). This allows for an easier implementation of reversion
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signaling (see Section 12) but also facilitates the transparent
delivery of protected services since any intermediate node is not
required to know the semantics associated with the incoming LSP
Protection Type value.
4.3. LSP Association
The ASSOCIATION object, introduced in Section 16, is used to
associate the working and protecting LSPs.
When used for signaling the working LSP, the Association ID of the
ASSOCIATION object (see Section 16) identifies the protecting LSP.
When used for signaling the protecting LSP, this field identifies the
LSP protected by the protecting LSP.
5. 1+1 Unidirectional Protection
One of the simplest notions of end-to-end LSP protection is 1+1
unidirectional protection.
Consider the following network topology:
A---B---C---D
\ /
E---F---G
The paths [A,B,C,D] and [A,E,F,G,D] are node and link disjoint,
ignoring the ingress/egress nodes A and D. A 1+1 protected path is
established from A to D over [A,B,C,D] and [A,E,F,G,D], and traffic
is transmitted simultaneously over both component paths (i.e., LSPs).
During the provisioning phase, both LSPs are fully instantiated (and
thus activated) so that no resource sharing can be done along the
protecting LSP (nor can any extra-traffic be transported). It is
also RECOMMENDED to set the N bit since no protection-switching
signaling is assumed in this case.
When a failure occurs (say, at node B) and is detected at end-node D,
the receiver at D selects the normal traffic from the other LSP.
From this perspective, 1+1 unidirectional protection can be seen as
an uncoordinated protection-switching mechanism acting independently
at both endpoints. Also, for the LSP under failure condition, it is
RECOMMENDED to not set the Path_State_Removed Flag of the ERROR_SPEC
object (see [RFC3473]) upon PathErr message generation.
Note: it is necessary that both paths are SRLG disjoint to ensure
recoverability; otherwise, a single failure may impact both working
and protecting LSPs.
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5.1. Identifiers
To simplify association operations, both LSPs belong to the same
session. Thus, the SESSION object MUST be the same for both LSPs.
The LSP ID, however, MUST be different to distinguish between the two
LSPs.
A new PROTECTION object (see Section 14) is included in the Path
message. This object carries the desired end-to-end LSP Protection
Type -- in this case, "1+1 Unidirectional". This LSP Protection Type
value is applicable to both uni- and bidirectional LSPs.
To allow distinguishing the working LSP (from which the signal is
taken) from the protecting LSP, the working LSP is signaled by
setting in the PROTECTION object the S bit to 0, the P bit to 0, and
in the ASSOCIATION object, the Association ID to the protecting
LSP_ID. The protecting LSP is signaled by setting in the PROTECTION
object the S bit to 0, the P bit to 1, and in the ASSOCIATION object,
the Association ID to the associated protected LSP_ID.
After protection switching completes, and after reception of the
PathErr message, to keep track of the LSP from which the signal is
taken, the protecting LSP SHOULD be signaled with the O bit set. The
formerly working LSP MAY be signaled with the A bit set in the
ADMIN_STATUS object (see [RFC3473]). This process assumes the tail-
end node has notified the head-end node that traffic selection
switchover has occurred.
6. 1+1 Bidirectional Protection
1+1 bidirectional protection is a scheme that provides end-to-end
protection for bidirectional LSPs.
Consider the following network topology:
A---B---C---D
\ /
E---F---G
The LSPs [A,B,C,D] and [A,E,F,G,D] are node and link disjoint,
ignoring the ingress/egress nodes A and D. A bidirectional LSP is
established from A to D over each path, and traffic is transmitted
simultaneously over both LSPs. In this scheme, both endpoints must
receive traffic over the same LSP. Note also that both LSPs are
fully instantiated (and thus activated) so that no resource sharing
can be done along the protection path (nor can any extra-traffic be
transported).
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When a failure is detected by one or both endpoints of the LSP, both
endpoints must select traffic from the other LSP. This action must
be coordinated between node A and D. From this perspective, 1+1
bidirectional protection can be seen as a coordinated protection-
switching mechanism between both endpoints.
Note: it is necessary that both paths are SRLG disjoint to ensure
recoverability; otherwise, a single failure may impact both working
and protecting LSPs.
6.1. Identifiers
To simplify association operations, both LSPs belong to the same
session. Thus, the SESSION object MUST be the same for both LSPs.
The LSP ID, however, MUST be different to distinguish between the two
LSPs.
A new PROTECTION object (see Section 14) is included in the Path
message. This object carries the desired end-to-end LSP Protection
Type -- in this case, "1+1 Bidirectional". This LSP Protection Type
value is only applicable to bidirectional LSPs.
It is also desirable to allow distinguishing the working LSP (from
which the signal is taken) from the protecting LSP. This is achieved
for the working LSP by setting in the PROTECTION object the S bit to
0, the P bit to 0, and in the ASSOCIATION object, the Association ID
to the protecting LSP_ID. The protecting LSP is signaled by setting
in the PROTECTION object the S bit to 0, the P bit to 1, and in the
ASSOCIATION object the Association ID to the associated protected
LSP_ID.
6.2. End-to-End Switchover Request/Response
To coordinate the switchover between endpoints, an end-to-end
switchover request/response exchange is needed since a failure
affecting one of the LSPs results in both endpoints switching to the
other LSP (resulting in receiving traffic from the other LSP) in
their respective directions.
The procedure is as follows:
1. If an end-node (A or D) detects the failure of the working LSP
(or a degradation of signal quality over the working LSP) or
receives a Notify message including its SESSION object within
the (see [RFC3473]), and the
new error code/sub-code "Notify Error/ LSP Locally Failed" in
the (IF_ID)_ERROR_SPEC object, it MUST begin receiving on the
protecting LSP. Note that the or is also present in the Notify message that resolves
any ambiguity and race condition since identifying (together
with the SESSION object) the LSP under failure condition.
Note: (IF_ID)_ERROR_SPEC indicates that either the
ERROR_SPEC (C-Type 1/2) or the ERROR_SPEC (C-Type 3/4,
defined in [RFC3473]) can be used.
This node MUST reliably send a Notify message, including the
MESSAGE_ID object, to the other end-node (D or A, respectively)
with the new error code/sub-code "Notify Error/LSP Failure"
(Switchover Request) indicating the failure of the working LSP.
This Notify message MUST be sent with the ACK_Desired flag set
in the MESSAGE_ID object to request the receiver to send an
acknowledgment for the message (see [RFC2961]).
This (switchover request) Notify message MAY indicate the
identity of the failed link or any other relevant information
using the IF_ID ERROR_SPEC object (see [RFC3473]). In this
case, the IF_ID ERROR_SPEC object replaces the ERROR_SPEC
object in the Notify message; otherwise, the corresponding
(data plane) information SHOULD be received in the
PathErr/ResvErr message.
2. Upon receipt of the (switchover request) Notify message, the
end-node (D or A, respectively) MUST begin receiving from the
protecting LSP.
This node MUST reliably send a Notify message, including the
MESSAGE_ID object, to the other end-node (A or D,
respectively). This (switchover response) Notify message MUST
also include a MESSAGE_ID_ACK object to acknowledge reception
of the (switchover request) Notify message.
This (switchover response) Notify message MAY indicate the
identity of the failed link or any other relevant information
using the IF_ID ERROR_SPEC object (see [RFC3473]).
Note: upon receipt of the (switchover response) Notify message,
the end-node (A or D, respectively) MUST send an Ack message to
the other end-node to acknowledge its reception.
Since the intermediate nodes (B, C, E, F, and G) are assumed to be
GMPLS RSVP-TE signaling capable, each node adjacent to the failure
MAY generate a Notify message directed either to the LSP head-end
(upstream direction), or the LSP tail-end (downstream direction), or
even both. Therefore, it is expected that these LSP terminating
nodes (that MAY also detect the failure of the LSP from the data
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plane) provide either the right correlation mechanism to avoid
repetition of the above procedure or just discard subsequent Notify
messages corresponding to the same Session. In addition, for the LSP
under failure condition, it is RECOMMENDED to not set the Path_State_
Removed Flag of the ERROR_SPEC object (see [RFC3473]) upon PathErr
message generation.
After protection switching completes (step 2), and after reception of
the PathErr message, to keep track of the LSP from which the signal
is taken, the protecting LSP SHOULD be signaled with the O bit set.
The formerly working LSP MAY be signaled with the A bit set in the
ADMIN_STATUS object (see [RFC3473]).
Note: when the N bit is set, the end-to-end switchover request/
response exchange described above only provides control plane
coordination (no actions are triggered at the data plane level).
7. 1:1 Protection with Extra-Traffic
The most common case of end-to-end 1:N protection is to establish,
between the same endpoints, an end-to-end working LSP (thus, N = 1)
and a dedicated end-to-end protecting LSP that are mutually link/
node/SRLG disjoint. This protects against working LSP failure(s).
The protecting LSP is used for switchover when the working LSP fails.
GMPLS RSVP-TE signaling allows for the pre-provisioning of protecting
LSPs by indicating in the Path message (in the PROTECTION object; see
Section 14) that the LSPs are of type protecting. Here, working and
protecting LSPs are signaled as primary LSPs; both are fully
instantiated during the provisioning phase.
Although the resources for the protecting LSP are pre-allocated,
preemptable traffic may be carried end-to-end using this LSP. Thus,
the protecting LSP is capable of carrying extra-traffic with the
caveat that this traffic will be preempted if the working LSP fails.
The setup of the working LSP SHOULD indicate that the LSP head-end
and tail-end node wish to receive Notify messages using the NOTIFY
REQUEST object. The node upstream to the failure (upstream in terms
of the direction an Path message traverses) SHOULD send a Notify
message to the LSP head-end node, and the node downstream to the
failure SHOULD send an Notify message to the LSP tail-end node. Upon
receipt of the Notify messages, both the end-nodes MUST switch the
(normal) traffic from the working LSP to the pre-configured
protecting LSP (see Section 7.2). Moreover, some coordination is
required if extra-traffic is carried over the end-to-end protecting
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LSP. Note that if the working and the protecting LSP are established
between the same end-nodes, no further notification is required to
indicate that the working LSPs are no longer protected.
Consider the following topology:
A---B---C---D
\ /
E---F---G
The working LSP [A,B,C,D] could be protected by the protecting LSP
[A,E,F,G,D]. Both LSPs are fully instantiated (resources are
allocated for both working and protecting LSPs) and no resource
sharing can be done along the protection path since the primary
protecting LSP can carry extra-traffic.
Note: it is necessary that both paths are SRLG disjoint to ensure
recoverability; otherwise, a single failure may impact both working
and protecting LSPs.
7.1. Identifiers
To simplify association operations, both LSPs belong to the same
session. Thus, the SESSION object MUST be the same for both LSPs.
The LSP ID, however, MUST be different to distinguish between the
protected LSP carrying working traffic and the protecting LSP that
can carry extra-traffic.
A new PROTECTION object (see Section 14) is included in the Path
message used to set up the two LSPs. This object carries the desired
end-to-end LSP Protection Type -- in this case, "1:N Protection with
Extra-Traffic". This LSP Protection Type value is applicable to both
uni- and bidirectional LSPs.
The working LSP is signaled by setting in the new PROTECTION object
the S bit to 0, the P bit to 0, and in the ASSOCIATION object, the
Association ID to the protecting LSP_ID.
The protecting LSP is signaled by setting in the new PROTECTION
object the S bit to 0, the P bit to 1, and in the ASSOCIATION object,
the Association ID to the associated protected LSP_ID.
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7.2. End-to-End Switchover Request/Response
To coordinate the switchover between endpoints, an end-to-end
switchover request/response is needed such that the affected LSP is
moved to the protecting LSP. Protection switching from the working
to the protecting LSP (implying preemption of extra-traffic carried
over the protecting LSP) must be initiated by one of the end-nodes (A
or D).
The procedure is as follows:
1. If an end-node (A or D) detects the failure of the working LSP
(or a degradation of signal quality over the working LSP) or
receives a Notify message including its SESSION object within
the (see [RFC3473]), and the
new error code/sub-code "Notify Error/LSP Locally Failed" in
the (IF_ID)_ERROR_SPEC object, it disconnects the extra-traffic
from the protecting LSP. Note that the or
is also present in the Notify message that
resolves any ambiguity and race condition since identifying
(together with the SESSION object) the LSP under failure
condition.
This node MUST reliably send a Notify message, including the
MESSAGE_ID object, to the other end-node (D or A, respectively)
with the new error code/sub-code "Notify Error/LSP Failure"
(Switchover Request) indicating the failure of the working LSP.
This Notify message MUST be sent with the ACK_Desired flag set
in the MESSAGE_ID object to request the receiver to send an
acknowledgment for the message (see [RFC2961]).
This (switchover request) Notify message MAY indicate the
identity of the failed link or any other relevant information
using the IF_ID ERROR_SPEC object (see [RFC3473]). In this
case, the IF_ID ERROR_SPEC object replaces the ERROR_SPEC
object in the Notify message; otherwise, the corresponding
(data plane) information SHOULD be received in the
PathErr/ResvErr message.
2. Upon receipt of the (switchover request) Notify message, the
end-node (D or A, respectively) MUST disconnect the extra-
traffic from the protecting LSP and begin sending/receiving
normal traffic out/from the protecting LSP.
This node MUST reliably send a Notify message, including the
MESSAGE_ID object, to the other end-node (A or D,
respectively). This (switchover response) Notify message MUST
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also include a MESSAGE_ID_ACK object to acknowledge reception
of the (switchover request) Notify message.
This (switchover response) Notify message MAY indicate the
identity of the failed link or any other relevant information
using the IF_ID ERROR_SPEC object (see [RFC3473]).
Note: since the Notify message generated by the other end-node
(A or D, respectively) is distinguishable from the one
generated by an intermediate node, there is no possibility of
connecting the extra-traffic to the working LSP due to the
receipt of a Notify message from an intermediate node.
3. Upon receipt of the (switchover response) Notify message, the
end-node (A or D, respectively) MUST begin receiving normal
traffic from or sending normal traffic out the protecting LSP.
This node MUST also send an Ack message to the other end-node
(D or A, respectively) to acknowledge the reception of the
(switchover response) Notify message.
Note 1: a 2-phase protection-switching signaling is used in the
present context; a 3-phase signaling (see [RFC4426]) that would imply
a notification message, a switchover request, and a switchover
response messages is not considered here. Also, when the protecting
LSPs do not carry extra-traffic, protection-switching signaling (as
defined in Section 6.2) MAY be used instead of the procedure
described in this section.
Note 2: when the N bit is set, the above end-to-end switchover
request/response exchange only provides control plane coordination
(no actions are triggered at the data plane level).
After protection switching completes (step 3), and after reception of
the PathErr message, to keep track of the LSP from which the normal
traffic is taken, the protecting LSP SHOULD be signaled with the O
bit set. In addition, the formerly working LSP MAY be signaled with
the A bit set in the ADMIN_STATUS object (see [RFC3473]).
7.3. 1:N (N > 1) Protection with Extra-Traffic
1:N (N > 1) protection with extra-traffic assumes that the fully
provisioned protecting LSP is resource-disjoint from the N working
LSPs. This protecting LSP thereby allows for carrying extra-traffic.
Note that the N working LSPs and the protecting LSP are all between
the same pair of endpoints. In addition, the N working LSPs
(considered as identical in terms of traffic parameters) MAY be
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mutually resource-disjoint. Coordination between end-nodes is
required when switching from one of the working to the protecting
LSP.
Each working LSP is signaled with both S bit and P bit set to 0. The
LSP Protection Type is set to 0x04 (1:N Protection with Extra-
Traffic) during LSP setup. Each Association ID points to the
protecting LSP ID.
The protecting LSP (carrying extra-traffic) is signaled with the S
bit set to 0 and the P bit set to 1. The LSP Protection Type is set
to 0x04 (1:N Protection with Extra-Traffic) during LSP setup. The
Association ID MUST be set by default to the LSP ID of the protected
LSP corresponding to N = 1.
Any signaling procedure applicable to 1:1 protection with extra-
traffic equally applies to 1:N protection with extra-traffic.
8. Rerouting without Extra-Traffic
End-to-end (pre-planned) rerouting without extra-traffic relies on
the establishment between the same pair of end-nodes of a working LSP
and a protecting LSP that is link/node/SRLG disjoint from the working
LSP. However, in this case the protecting LSP is not fully
instantiated; thus, it cannot carry any extra-traffic (note that this
does not mean that the corresponding resources cannot be used by
other LSPs). Therefore, this mechanism protects against working LSP
failure(s) but requires activation of the protecting LSP after
failure occurrence.
Signaling is performed by indicating in the Path message (in the
PROTECTION object; see Section 14) that the LSPs are of type working
and protecting, respectively. Protecting LSPs are used for fast
switchover when working LSPs fail. In this case, working and
protecting LSPs are signaled as primary LSP and secondary LSP,
respectively. Thus, only the working LSP is fully instantiated
during the provisioning phase, and for the protecting LSPs, no
resources are committed at the data plane level (they are pre-
reserved at the control plane level only). The setup of the working
LSP SHOULD indicate (using the NOTIFY REQUEST object as specified in
Section 4 of [RFC3473]) that the LSP head-end node (and possibly the
tail-end node) wish to receive a Notify message upon LSP failure
occurrence. Upon receipt of the Notify message, the head-end node
MUST switch the (normal) traffic from the working LSP to the
protecting LSP after its activation. Note that since the working and
the protecting LSPs are established between the same end-nodes, no
further notification is required to indicate that the working LSPs
are without protection.
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To make bandwidth pre-reserved for a protecting (but not activated)
LSP available for extra-traffic, this bandwidth could be included in
the advertised Unreserved Bandwidth at priority lower (means
numerically higher) than the Holding Priority of the protecting LSP.
In addition, the Max LSP Bandwidth field in the Interface Switching
Capability Descriptor sub-TLV should reflect the fact that the
bandwidth pre-reserved for the protecting LSP is available for extra
traffic. LSPs for extra-traffic then can be established using the
bandwidth pre-reserved for the protecting LSP by setting (in the Path
message) the Setup Priority field of the SESSION_ATTRIBUTE object to
X (where X is the Setup Priority of the protecting LSP), and the
Holding Priority field to at least X+1. Also, if the resources pre-
reserved for the protecting LSP are used by lower-priority LSPs,
these LSPs MUST be preempted when the protecting LSP is activated
(see Section 10).
Consider the following topology:
A---B---C---D
\ /
E---F---G
The working LSP [A,B,C,D] could be protected by the protecting LSP
[A,E,F,G,D]. Only the protected LSP is fully instantiated (resources
are only allocated for the working LSP). Therefore, the protecting
LSP cannot carry any extra-traffic. When a failure is detected on
the working LSP (say, at B), the error is propagated and/or notified
(using a Notify message with the new error code/sub-code "Notify
Error/LSP Locally Failed" in the (IF_ID)_ERROR_SPEC object) to the
ingress node (A). Upon reception, the latter activates the secondary
protecting LSP instantiated during the (pre-)provisioning phase.
This requires:
(1) the ability to identify a "secondary protecting LSP" (hereby
called the "secondary LSP") used to recover another primary
working LSP (hereby called the "protected LSP")
(2) the ability to associate the secondary LSP with the protected
LSP
(3) the capability to activate a secondary LSP after failure
occurrence.
In the following subsections, these features are described in more
detail.
Lang, et al. Standards Track [Page 18]
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8.1. Identifiers
To simplify association operations, both LSPs (i.e., the protected
and the secondary LSPs) belong to the same session. Thus, the
SESSION object MUST be the same for both LSPs. The LSP ID, however,
MUST be different to distinguish between the protected LSP carrying
working traffic and the secondary LSP that cannot carry extra-
traffic.
A new PROTECTION object (see Section 14) is used to set up the two
LSPs. This object carries the desired end-to-end LSP Protection Type
(in this case, "Rerouting without Extra-Traffic"). This LSP
Protection Type value is applicable to both uni- and bidirectional
LSPs.
8.2. Signaling Primary LSPs
The new PROTECTION object is included in the Path message during
signaling of the primary working LSP, with the end-to-end LSP
Protection Type value set to "Rerouting without Extra-Traffic".
Primary working LSPs are signaled by setting in the new PROTECTION
object the S bit to 0, the P bit to 0, and in the ASSOCIATION object,
the Association ID to the associated secondary protecting LSP_ID.
8.3. Signaling Secondary LSPs
The new PROTECTION object is included in the Path message during
signaling of secondary protecting LSPs, with the end-to-end LSP
Protection Type value set to "Rerouting without Extra-Traffic".
Secondary protecting LSPs are signaled by setting in the new
PROTECTION object the S bit and the P bit to 1, and in the
ASSOCIATION object, the Association ID to the associated primary
working LSP_ID, which MUST be known before signaling of the secondary
LSP.
With this setting, the resources for the secondary LSP SHOULD be
pre-reserved, but not committed at the data plane level, meaning that
the internals of the switch need not be established until explicit
action is taken to activate this secondary LSP. Activation of a
secondary LSP is done using a modified Path message with the S bit
set to 0 in the PROTECTION object. At this point, the link and node
resources must be allocated for this LSP that becomes a primary LSP
(ready to carry normal traffic).
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From [RFC3945], the secondary LSP is set up with resource pre-
reservation but with or without label pre-selection (both allowing
sharing of the recovery resources). In the former case (defined as
the default), label allocation during secondary LSP signaling does
not require any specific procedure compared to [RFC3473]. However,
in the latter case, label (and thus resource) re-allocation MAY occur
during the secondary LSP activation. This means that during the LSP
activation phase, labels MAY be reassigned (with higher precedence
over existing label assignment; see also [RFC3471]).
Note: under certain circumstances (e.g., when pre-reserved protecting
resources are used by lower-priority LSPs), it MAY be desirable to
perform the activation of the secondary LSP in the upstream direction
(Resv trigger message) instead of using the default downstream
activation. In this case, any mis-ordering and any mis-
interpretation between a refresh Resv (along the lower-priority LSP)
and a trigger Resv message (along the secondary LSP) MUST be avoided
at any intermediate node. For this purpose, upon reception of the
Path message, the egress node MAY include the PROTECTION object in
the Resv message. The latter is then processed on a hop-by-hop basis
to activate the secondary LSP until reaching the ingress node. The
PROTECTION object included in the Path message MUST be set as
specified in this section. In this case, the PROTECTION object with
the S bit MUST be set to 0 and included in the Resv message sent in
the upstream direction. The upstream activation behavior SHOULD be
configurable on a local basis. Details concerning lower-priority LSP
preemption upon secondary LSP activation are provided in Section 10.
9. Shared-Mesh Restoration
An approach to reduce recovery resource requirements is to have
protection LSPs sharing network resources when the working LSPs that
they protect are physically (i.e., link, node, SRLG, etc.) disjoint.
This mechanism is referred to as shared mesh restoration and is
described in [RFC4426]. Shared-mesh restoration can be seen as a
particular case of pre-planned LSP rerouting (see Section 8) that
reduces the recovery resource requirements by allowing multiple
protecting LSPs to share common link and node resources. Here also,
the recovery resources for the protecting LSPs are pre-reserved
during the provisioning phase, thus an explicit signaling action is
required to activate (i.e., commit resource allocation at the data
plane) a specific protecting LSP instantiated during the (pre-)
provisioning phase. This requires restoration signaling along the
protecting LSP.
To make bandwidth pre-reserved for a protecting (but not activated)
LSP, available for extra-traffic this bandwidth could be included in
the advertised Unreserved Bandwidth at priority lower (means
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numerically higher) than the Holding Priority of the protecting LSP.
In addition, the Max LSP Bandwidth field in the Interface Switching
Capability Descriptor sub-TLV should reflect the fact that the
bandwidth pre-reserved for the protecting LSP is available for extra
traffic. LSPs for extra-traffic then can be established using the
bandwidth pre-reserved for the protecting LSP by setting (in the Path
message) the Setup Priority field of the SESSION_ATTRIBUTE object to
X (where X is the Setup Priority of the protecting LSP) and the
Holding Priority field to at least X+1. Also, if the resources pre-
reserved for the protecting LSP are used by lower priority LSPs,
these LSPs MUST be preempted when the protecting LSP is activated
(see Section 10). Further, if the recovery resources are shared
between multiple protecting LSPs, the corresponding working LSPs
head-end nodes must be informed that they are no longer protected
when the protecting LSP is activated to recover the normal traffic
for the working LSP under failure.
Consider the following topology:
A---B---C---D
\ /
E---F---G
/ \
H---I---J---K
The working LSPs [A,B,C,D] and [H,I,J,K] could be protected by
[A,E,F,G,D] and [H,E,F,G,K], respectively. Per [RFC3209], in order
to achieve resource sharing during the signaling of these protecting
LSPs, they must have the same Tunnel Endpoint Address (as part of
their SESSION object). However, these addresses are not the same in
this example. Resource sharing along E, F, and G can only be
achieved if the nodes E, F, and G recognize that the LSP Protection
Type of the secondary LSP is set to "Rerouting without Extra-Traffic"
(see PROTECTION object, Section 14) and acts accordingly. In this
case, the protecting LSPs are not merged (which is useful since the
paths diverge at G), but the resources along E, F, G can be shared.
When a failure is detected on one of the working LSPs (say, at B),
the error is propagated and/or notified (using a Notify message with
the new error code/sub-code "Notify Error/LSP Locally Failed" in the
(IF_ID)_ERROR_SPEC object) to the ingress node (A). Upon reception,
the latter activates the secondary protecting LSP (see Section 8).
At this point, it is important that a failure on the other LSP (say,
at J) does not cause the other ingress (H) to send the data down the
protecting LSP since the resources are already in use. This can be
achieved by node E using the following procedure. When the capacity
is first reserved for the protecting LSP, E should verify that the
LSPs being protected ([A,B,C,D] and [H,I,J,K], respectively) do not
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share any common resources. Then, when a failure occurs (say, at B)
and the protecting LSP [A,E,F,G,D] is activated, E should notify H
that the resources for the protecting LSP [H,E,F,G,K] are no longer
available.
The following subsections detail how shared mesh restoration can be
implemented in an interoperable fashion using GMPLS RSVP-TE
extensions (see [RFC3473]). This includes:
(1) the ability to identify a "secondary protecting LSP" (hereby
called the "secondary LSP") used to recover another primary
working LSP (hereby called the "protected LSP")
(2) the ability to associate the secondary LSP with the protected
LSP
(3) the capability to include information about the resources used
by the protected LSP while instantiating the secondary LSP.
(4) the capability to instantiate during the provisioning phase
several secondary LSPs in an efficient manner.
(5) the capability to activate a secondary LSP after failure
occurrence.
In the following subsections, these features are described in detail.
9.1. Identifiers
To simplify association operations, both LSPs (i.e., the protected
and the secondary LSPs) belong to the same session. Thus, the
SESSION object MUST be the same for both LSPs. The LSP ID, however,
MUST be different to distinguish between the protected LSP carrying
working traffic and the secondary LSP that cannot carry extra-
traffic.
A new PROTECTION object (see Section 14) is used to set up the two
LSPs. This object carries the desired end-to-end LSP Protection Type
-- in this case, "Rerouting without Extra-Traffic". This LSP
Protection Type value is applicable to both uni- and bidirectional
LSPs.
9.2. Signaling Primary LSPs
The new PROTECTION object is included in the Path message during
signaling of the primary working LSPs, with the end-to-end LSP
Protection Type value set to "Rerouting without Extra-Traffic".
Primary working LSPs are signaled by setting in the new PROTECTION
object the S bit to 0, the P bit to 0, and in the ASSOCIATION object,
the Association ID to the associated secondary protecting LSP_ID.
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9.3. Signaling Secondary LSPs
The new PROTECTION object is included in the Path message during
signaling of the secondary protecting LSPs, with the end-to-end LSP
Protection Type value set to "Rerouting without Extra-Traffic".
Secondary protecting LSPs are signaled by setting in the new
PROTECTION object the S bit and the P bit to 1, and in the
ASSOCIATION object, the Association ID to the associated primary
working LSP_ID, which MUST be known before signaling of the secondary
LSP. Moreover, the Path message used to instantiate the secondary
LSP SHOULD include at least one PRIMARY_PATH_ROUTE object (see
Section 15) that further allows for recovery resource sharing at each
intermediate node along the secondary path.
With this setting, the resources for the secondary LSP SHOULD be
pre-reserved, but not committed at the data plane level, meaning that
the internals of the switch need not be established until explicit
action is taken to activate this LSP. Activation of a secondary LSP
is done using a modified Path message with the S bit set to 0 in the
PROTECTION object. At this point, the link and node resources must
be allocated for this LSP that becomes a primary LSP (ready to carry
normal traffic).
From [RFC3945], the secondary LSP is set up with resource pre-
reservation but with or without label pre-selection (both allowing
sharing of the recovery resources). In the former case (defined as
the default), label allocation during secondary LSP signaling does
not require any specific procedure compared to [RFC3473]. However,
in the latter case, label (and thus resource) re-allocation MAY occur
during the secondary LSP activation. This means that, during the LSP
activation phase, labels MAY be reassigned (with higher precedence
over existing label assignment; see also [RFC3471]).
10. LSP Preemption
When protecting resources are only pre-reserved for the secondary
LSPs, they MAY be used to set up lower-priority LSPs. In this case,
these resources MUST be preempted when the protecting LSP is
activated. An additional condition raises from misconnection
avoidance between the secondary protecting LSP being activated and
the low-priority LSP(s) being preempted. Procedure to be applied
when the secondary protecting LSP (i.e., the preempting LSP) Path
message reaches a node using the resources for lower-priority LSP(s)
(i.e., preempted LSP(s)) is as follows:
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1. De-allocate resources to be used by the preempting LSP and release
the cross-connection. Note that if the preempting LSP is
bidirectional, these resources may come from one or two lower-
priority LSPs, and if from two LSPs, they may be uni- or bi-
directional. The preempting node SHOULD NOT send the Path message
before the de-allocation of resources has completed since this may
lead to the downstream path becoming misconnected if the
downstream node is able to reassign the resources more quickly.
2. Send PathTear and PathErr messages with the new error code/sub-
code "Policy Control failure/Hard preempted" and the
Path_State_Removed flag set for the preempted LSP(s).
3. Reserve the preempted resources for the protecting LSP. The
preempting node MUST NOT cross-connect the upstream resources of a
bidirectional preempting LSP.
4. Send the Path message.
5. Upon reception of a trigger Resv message from the downstream node,
cross-connect the downstream path resources, and if the preempting
LSP is bidirectional, perform cross-connection for the upstream
path resources.
Note that step 1 may cause alarms to be raised for the preempted LSP.
If alarm suppression is desired, the preempting node MAY insert the
following steps before step 1.
1a. Before de-allocating resources, send a Resv message, including an
ADMIN_STATUS object, to disable alarms for the preempted LSP.
1b. Receive a Path message indicating that alarms are disabled.
At the downstream node (with respect to the preempting LSP), the
processing is RECOMMENDED to be as follows:
1. Receive PathTear (and/or PathErr) message for the preempted
LSP(s).
2a. Release the resources associated with the LSP on the interface to
the preempting LSP, remove any cross-connection, and release all
other resources associated with the preempted LSP.
2b. Forward the PathTear (and/or PathErr) message per [RFC3473].
3. Receive the Path message for the preempting LSP and process as
normal, forwarding it to the downstream node.
4. Receive the Resv message for the preempting LSP and process as
normal, forwarding it to the upstream node.
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11. (Full) LSP Rerouting
LSP rerouting, on the other hand, switches normal traffic to an
alternate LSP that is fully established only after failure
occurrence. The new (alternate) route is selected at the LSP head-
end and may reuse intermediate nodes included in the original route;
it may also include additional intermediate nodes. For strict-hop
routing, TE requirements can be directly applied to the route
computation, and the failed node or link can be avoided. However, if
the failure occurred within a loose-routed hop, the head-end node may
not have enough information to reroute the LSP around the failure.
Crankback signaling (see [CRANK]) and route exclusion techniques (see
[RFC4874]) MAY be used in this case.
The alternate route MAY be either computed on demand (that is, when
the failure occurs; this is referred to as full LSP rerouting) or
pre-computed and stored for use when the failure is reported. The
latter offers faster restoration time. There is, however, a risk
that the alternate route will become out of date through other
changes in the network; this can be mitigated to some extent by
periodic recalculation of idle alternate routes.
(Full) LSP rerouting will be initiated by the head-end node that has
either detected the LSP failure or received a Notify message and/or a
PathErr message with the new error code/sub-code "Notify Error/LSP
Locally Failed" for this LSP. The new LSP resources can be
established using the make-before-break mechanism, where the new LSP
is set up before the old LSP is torn down. This is done by using the
mechanisms of the SESSION_ATTRIBUTE object and the Shared-Explicit
(SE) reservation style (see [RFC3209]). Both the new and old LSPs
can share resources at common nodes.
Note that the make-before-break mechanism is not used to avoid
disruption to the normal traffic flow (the latter has already been
broken by the failure that is being repaired). However, it is
valuable to retain the resources allocated on the original LSP that
will be reused by the new alternate LSP.
11.1. Identifiers
The Tunnel Endpoint Address, Tunnel ID, Extended Tunnel ID, and
Tunnel Sender Address uniquely identify both the old and new LSPs.
Only the LSP_ID value differentiates the old from the new alternate
LSP. The new alternate LSP is set up before the old LSP is torn down
using Shared-Explicit (SE) reservation style. This ensures that the
new (alternate) LSP is established without double-counting resource
requirements along common segments.
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The alternate LSP MAY be set up before any failure occurrence with
SE-style resource reservation, the latter shares the same Tunnel End
Point Address, Tunnel ID, Extended Tunnel ID, and Tunnel Sender
Address with the original LSP (i.e., only the LSP ID value MUST be
different).
In both cases, the Association ID of the ASSOCIATION object MUST be
set to the LSP ID value of the signaled LSP.
11.2. Signaling Reroutable LSPs
A new PROTECTION object is included in the Path message during
signaling of dynamically reroutable LSPs, with the end-to-end LSP
Protection Type value set to "Full Rerouting". These LSPs that can
be either uni- or bidirectional are signaled by setting in the
PROTECTION object the S bit to 0, the P bit to 0, and the Association
ID value to the LSP_ID value of the signaled LSP. Any specific
action to be taken during the provisioning phase is up to the end-
node local policy.
Note: when the end-to-end LSP Protection Type is set to
"Unprotected", both S and P bit MUST be set to 0, and the LSP SHOULD
NOT be rerouted at the head-end node after failure occurrence. The
Association_ID value MUST be set to the LSP_ID value of the signaled
LSP. This does not mean that the Unprotected LSP cannot be re-
established for other reasons such as path re-optimization and
bandwidth adjustment driven by policy conditions.
12. Reversion
Reversion refers to a recovery switching operation, where the normal
traffic returns to (or remains on) the working LSP when it has
recovered from the failure. Reversion implies that resources remain
allocated to the LSP that was originally routed over them even after
a failure. It is important to have mechanisms that allow reversion
to be performed with minimal service disruption and reconfiguration.
For "1+1 bidirectional Protection", reversion to the recovered LSP
occurs by using the following sequence:
1. Clear the A bit of the ADMIN_STATUS object if set for the
recovered LSP.
2. Then, apply the method described below to switch normal traffic
back from the protecting to the recovered LSP. This is performed
by using the new error code/sub-code "Notify Error/LSP Recovered"
(Switchback Request).
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The procedure is as follows:
1) The initiating (source) node sends the normal traffic onto both
the working and the protecting LSPs. Once completed, the
source node sends reliably a Notify message to the destination
with the new error code/sub-code "Notify Error/LSP Recovered"
(Switchback Request). This Notify message includes the
MESSAGE_ID object. The ACK_Desired flag MUST be set in this
object to request the receiver to send an acknowledgment for
the message (see [RFC2961]).
2) Upon receipt of this message, the destination selects the
traffic from the working LSP. At the same time, it transmits
the traffic onto both the working and protecting LSP.
The destination then sends reliably a Notify message to the
source confirming the completion of the operation. This
message includes the MESSAGE_ID_ACK object to acknowledge
reception of the received Notify message. This Notify message
also includes the MESSAGE_ID object. The ACK_Desired flag MUST
be set in this object to request the receiver to send an
acknowledgment for the message (see [RFC2961]).
3) When the source node receives this Notify message, it switches
to receive traffic from the working LSP.
The source node then sends an Ack message to the destination
node confirming that the LSP has been reverted.
3. Finally, clear the O bit of the PROTECTION object sent over the
protecting LSP.
For "1:N Protection with Extra-traffic", reversion to the recovered
LSP occurs by using the following sequence:
1. Clear the A bit of the ADMIN_STATUS object if set for the
recovered LSP.
2. Then, apply the method described below to switch normal traffic
back from the protecting to the recovered LSP. This is performed
by using the new error code/sub-code "Notify Error/LSP Recovered"
(Switchback Request).
The procedure is as follows:
1) The initiating (source) node sends the normal traffic onto both
the working and the protecting LSPs. Once completed, the
source node sends reliably a Notify message to the destination
Lang, et al. Standards Track [Page 27]
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with the new error code/sub-code "Notify Error/LSP Recovered"
(Switchback Request). This Notify message includes the
MESSAGE_ID object. The ACK_Desired flag MUST be set in this
object to request the receiver to send an acknowledgment for
the message (see [RFC2961]).
2) Upon receipt of this message, the destination selects the
traffic from the working LSP. At the same time, it transmits
the traffic onto both the working and protecting LSP.
The destination then sends reliably a Notify message to the
source confirming the completion of the operation. This
message includes the MESSAGE_ID_ACK object to acknowledge
reception of the received Notify message. This Notify message
also includes the MESSAGE_ID object. The ACK_Desired flag MUST
be set in this object to request the receiver to send an
acknowledgment for the message (see [RFC2961]).
3) When the source node receives this Notify message, it switches
to receive traffic from the working LSP, and stops transmitting
traffic on the protecting LSP.
The source node then sends an Ack message to the destination
node confirming that the LSP has been reverted.
4) Upon receipt of this message, the destination node stops
transmitting traffic along the protecting LSP.
3. Finally, clear the O bit of the PROTECTION object sent over the
protecting LSP.
For "Rerouting without Extra-traffic" (including the shared recovery
case), reversion implies that the formerly working LSP has not been
torn down by the head-end node upon PathErr message reception, i.e.,
the head-end node kept refreshing the working LSP under failure
condition. This ensures that the exact same resources are retrieved
after reversion switching (except if the working LSP required re-
signaling). Re-activation is performed using the following sequence:
1. Clear the A bit of the ADMIN_STATUS object if set for the
recovered LSP.
2. Then, apply the method described below to switch normal traffic
back from the protecting to the recovered LSP. This is performed
by using the new error code/sub-code "Notify Error/LSP Recovered"
(Switchback Request).
Lang, et al. Standards Track [Page 28]
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The procedure is as follows:
1) The initiating (source) node sends the normal traffic onto both
the working and the protecting LSPs. Once completed, the
source node sends reliably a Notify message to the destination
with the new error code/sub-code "Notify Error/LSP Recovered"
(Switchback Request). This Notify message includes the
MESSAGE_ID object. The ACK_Desired flag MUST be set in this
object to request the receiver to send an acknowledgment for
the message (see [RFC2961]).
2) Upon receipt of this message, the destination selects the
traffic from the working LSP. At the same time, it transmits
the traffic onto both the working and protecting LSP.
The destination then sends reliably a Notify message to the
source confirming the completion of the operation. This
message includes the MESSAGE_ID_ACK object to acknowledge
reception of the received Notify message. This Notify message
also includes the MESSAGE_ID object. The ACK_Desired flag MUST
be set in this object to request the receiver to send an
acknowledgment for the message (see [RFC2961]).
3) When the source node receives this Notify message, it switches
to receive traffic from the working LSP, and stops transmitting
traffic on the protecting LSP.
The source node then sends an Ack message to the destination
node confirming that the LSP has been reverted.
4) Upon receipt of this message, the destination node stops
transmitting traffic along the protecting LSP.
3. Finally, de-activate the protecting LSP by setting the S bit to 1
in the PROTECTION object sent over the protecting LSP.
13. Recovery Commands
This section specifies the control plane behavior when using several
commands (see [RFC4427]) that can be used to influence the recovery
operations.
A. Lockout of recovery LSP:
The Lockout (L) bit of the ADMIN_STATUS object is used following the
rules defined in Section 8 of [RFC3471] and Section 7 of [RFC3473].
The L bit must be set together with the Reflect (R) bit in the
ADMIN_STATUS object sent in the Path message. Upon reception of the
Lang, et al. Standards Track [Page 29]
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Resv message with the L bit set, this forces the recovery LSP to be
temporarily unavailable to transport traffic (either normal or
extra-traffic). Unlock is performed by clearing the L bit, following
the rules defined in Section 7 of [RFC3473]. This procedure is only
applicable when the LSP Protection Type Flag is set to either 0x04
(1:N Protection with Extra-Traffic), or 0x08 (1+1 Unidirectional
Protection), or 0x10 (1+1 Bidirectional Protection).
The updated format of the ADMIN_STATUS object to include the L bit is
as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | Class-Num(196)| C-Type (1) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|R| Reserved |L|I|C|T|A|D|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Lockout (L): 1 bit
When set, forces the recovery LSP to be temporarily unavailable
to transport traffic (either normal or extra traffic).
The R (Reflect), T (Testing), A (Administratively down), and D
(Deletion in progress) bits are defined in [RFC3471]. The C (Call
control) bit is defined in [GMPLS-CALL], and the I (Inhibit alarm
communication) bit in [RFC4783].
B. Lockout of normal traffic:
The O bit of the PROTECTION object is set to 1 to force the recovery
LSP to be temporarily unavailable to transport normal traffic. This
operation MUST NOT occur unless the working LSP is carrying the
normal traffic. Unlock is performed by clearing the O bit over the
protecting LSP. This procedure is only applicable when the LSP
Protection Type Flag is set to either 0x04 (1:N Protection with
Extra-Traffic), or 0x08 (1+1 Unidirectional Protection), or 0x10 (1+1
Bidirectional Protection).
C. Forced switch for normal traffic:
Recovery signaling is initiated that switches normal traffic to the
recovery LSP following the procedures defined in Section 6, 7, 8, and
9.
Lang, et al. Standards Track [Page 30]
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D. Requested switch for normal traffic:
Recovery signaling is initiated that switches normal traffic to the
recovery LSP following the procedures defined in Section 6, 7, 8, and
9. This happens unless a fault condition exists on other LSPs or
spans (including the recovery LSP), or a switch command of equal or
higher priority is in effect.
E. Requested switch for recovery LSP:
Recovery signaling is initiated that switches normal traffic to the
working LSP following the procedure defined in Section 12. This
request is executed except if a fault condition exists on the working
LSP or an equal or higher priority switch command is in effect.
14. PROTECTION Object
This section describes the extensions to the PROTECTION object to
broaden its applicability to end-to-end LSP recovery.
14.1. Format
The format of the PROTECTION Object (Class-Num = 37, C-Type = 2) is
as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | Class-Num(37) | C-Type (2) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|S|P|N|O| Reserved | LSP Flags | Reserved | Link Flags|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Secondary (S): 1 bit
When set to 1, this bit indicates that the requested LSP is a
secondary LSP. When set to 0 (default), it indicates that the
requested LSP is a primary LSP.
Protecting (P): 1 bit
When set to 1, this bit indicates that the requested LSP is a
protecting LSP. When set to 0 (default), it indicates that the
requested LSP is a working LSP. The combination, S set to 1
with P set to 0 is not valid.
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Notification (N): 1 bit
When set to 1, this bit indicates that the control plane
message exchange is only used for notification during
protection switching. When set to 0 (default), it indicates
that the control plane message exchanges are used for
protection-switching purposes. The N bit is only applicable
when the LSP Protection Type Flag is set to either 0x04 (1:N
Protection with Extra-Traffic), or 0x08 (1+1 Unidirectional
Protection), or 0x10 (1+1 Bidirectional Protection). The N bit
MUST be set to 0 in any other case.
Operational (O): 1 bit
When set to 1, this bit indicates that the protecting LSP is
carrying the normal traffic after protection switching. The O
bit is only applicable when the P bit is set to 1, and the LSP
Protection Type Flag is set to either 0x04 (1:N Protection with
Extra-Traffic), or 0x08 (1+1 Unidirectional Protection) or 0x10
(1+1 Bidirectional Protection). The O bit MUST be set to 0 in
any other case.
Reserved: 5 bits
This field is reserved. It MUST be set to zero on transmission
and MUST be ignored on receipt. These bits SHOULD be passed
through unmodified by transit nodes.
LSP (Protection Type) Flags: 6 bits
Indicates the desired end-to-end LSP recovery type. A value of
0 implies that the LSP is "Unprotected". Only one value SHOULD
be set at a time. The following values are defined. All other
values are reserved.
0x00 Unprotected
0x01 (Full) Rerouting
0x02 Rerouting without Extra-Traffic
0x04 1:N Protection with Extra-Traffic
0x08 1+1 Unidirectional Protection
0x10 1+1 Bidirectional Protection
Reserved: 10 bits
This field is reserved. It MUST be set to zero on transmission
and MUST be ignored on receipt. These bits SHOULD be passed
through unmodified by transit nodes.
Lang, et al. Standards Track [Page 32]
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Link Flags: 6 bits
Indicates the desired link protection type (see [RFC3471]).
Reserved field: 32 bits
Encoding of this field is detailed in [RFC4873].
14.2. Processing
Intermediate and egress nodes processing a Path message containing a
PROTECTION object MUST verify that the requested LSP Protection Type
can be satisfied by the incoming interface. If it cannot, the node
MUST generate a PathErr message, with the new error code/sub-code
"Routing problem/Unsupported LSP Protection".
Intermediate nodes processing a Path message containing a PROTECTION
object with the LSP Protection Type 0x02 (Rerouting without Extra-
Traffic) value set and a PRIMARY_PATH_ROUTE object (see Section 15)
MUST verify that the requested LSP Protection Type can be supported
by the outgoing interface. If it cannot, the node MUST generate a
PathErr message with the new error code/sub-code "Routing
problem/Unsupported LSP Protection".
15. PRIMARY_PATH_ROUTE Object
The PRIMARY_PATH_ROUTE object (PPRO) is defined to inform nodes along
the path of a secondary protecting LSP about which resources
(link/nodes) are being used by the associated primary protected LSP
(as specified by the Association ID field). If the LSP Protection
Type value is set to 0x02 (Rerouting without Extra-Traffic), this
object SHOULD be present in the Path message for the pre-provisioning
of the secondary protecting LSP to enable recovery resource sharing
between one or more secondary protecting LSPs (see Section 9). This
document does not assume or preclude any other usage for this object.
PRIMARY_PATH_ROUTE objects carry information extracted from the
EXPLICIT ROUTE object and/or the RECORD ROUTE object of the primary
working LSPs they protect. Selection of the PPRO content is up to
local policy of the head-end node that initiates the request.
Therefore, the information included in these objects can be used as
policy-based admission control to ensure that recovery resources are
only shared between secondary protecting LSPs whose associated
primary LSPs have link/node/SRLG disjoint paths.
Lang, et al. Standards Track [Page 33]
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15.1. Format
The primary path route is specified via the PRIMARY_PATH_ROUTE object
(PPRO). The Primary Path Route Class Number (Class-Num) of form
0bbbbbbb 38.
Currently one C-Type (Class-Type) is defined, Type 1, Primary Path
Route. The PRIMARY_PATH_ROUTE object has the following format:
Class-Num = 38 (of the form 0bbbbbbb), C-Type = 1
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// (Subobjects) //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The contents of a PRIMARY_PATH_ROUTE object are a series of
variable-length data items called subobjects (see Section 15.3).
To signal a secondary protecting LSP, the Path message MAY include
one or multiple PRIMARY_PATH_ROUTE objects, where each object is
meaningful. The latter is useful when a given secondary protecting
LSP must be link/node/SRLG disjoint from more than one primary LSP
(i.e., is protecting more than one primary LSP).
15.2. Subobjects
The PRIMARY_PATH_ROUTE object is defined as a list of variable-length
data items called subobjects. These subobjects are derived from the
subobjects of the EXPLICIT ROUTE and/or RECORD ROUTE object of the
primary working LSP(s).
Each subobject has its own length field. The length contains the
total length of the subobject in bytes, including the Type and Length
fields. The length MUST always be a multiple of 4, and at least 4.
The following subobjects are currently defined for the
PRIMARY_PATH_ROUTE object:
- Sub-Type 1: IPv4 Address (see [RFC3209])
- Sub-Type 2: IPv6 Address (see [RFC3209])
- Sub-Type 3: Label (see [RFC3473])
- Sub-Type 4: Unnumbered Interface (see [RFC3477])
Lang, et al. Standards Track [Page 34]
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An empty PPRO with no subobjects is considered illegal. If there is
no first subobject, the corresponding Path message is also in error,
and the receiving node SHOULD return a PathErr message with the new
error code/sub-code "Routing Problem/Bad PRIMARY_PATH_ROUTE object".
Note: an intermediate node processing a PPRO can derive SRLG
identifiers from the local IGP-TE database using its Type 1, 2, or 4
subobject values as pointers to the corresponding TE Links (assuming
each of them has an associated SRLG TE attribute).
15.3. Applicability
The PRIMARY_PATH_ROUTE object MAY only be used when all GMPLS nodes
along the path support the PRIMARY_PATH_ROUTE object and a secondary
protecting LSP is being requested. The PRIMARY_PATH_ROUTE object is
assigned a class value of the form 0bbbbbbb. Receiving GMPLS nodes
along the path that do not support this object MUST return a PathErr
message with the "Unknown Object Class" error code (see [RFC2205]).
Also, the following restrictions MUST be applied with respect to the
PPRO usage:
- PPROs MAY only be included in Path messages when signaling
secondary protecting LSPs (S bit = 1 and P bit = 1) and when the
LSP Protection Type value is set to 0x02 (without Rerouting Extra-
Traffic) in the PROTECTION object (see Section 14).
- PRROs SHOULD be present in the Path message for the pre-
provisioning of the secondary protecting LSP to enable recovery
resource sharing between one or more secondary protecting LSPs (see
Section 15.4).
- PPROs MUST NOT be used in any other conditions. In particular, if
a PPRO is received when the S bit is set to 0 in the PROTECTION
object, the receiving node MUST return a PathErr message with the
new error code/sub-code "Routing Problem/PRIMARY_PATH_ROUTE object
not applicable".
- Crossed exchanges of PPROs over primary LSPs are forbidden (i.e.,
their usage is restricted to a single set of protected LSPs).
- The PPRO's content MUST NOT include subobjects coming from other
PPROs. In particular, received PPROs MUST NOT be reused to
establish other working or protecting LSPs.
Lang, et al. Standards Track [Page 35]
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15.4. Processing
The PPRO enables sharing recovery resources between a given secondary
protecting LSP and one or more secondary protecting LSPs if their
corresponding primary working LSPs have mutually (link/node/SRLG)
disjoint paths. Consider a node N through which n secondary
protecting LSPs (say, P[1],...,P[n]) have already been established
that protect n primary working LSPs (say, P'[1],...,P'[n]). Suppose
also that these n secondary working LSPs share a given outgoing link
resource (say r).
Now, suppose that node N receives a Path message for an additional
secondary protecting LSP (say, Q, protecting Q'). The PPRO carried
by this Path message is processed as follows:
- N checks whether the primary working LSPs P'[1],...,P'[n]
associated with the LSPs P[1],...,P[n], respectively, have any
link, node, and SLRG in common with the primary working Q'
(associated with Q) by comparing the stored PPRO subobjects
associated with P'[1],...,P'[n] with the PPRO subobjects associated
with Q' received in the Path message.
- If this is the case, N SHOULD NOT attempt to share the outgoing
link resource r between P[1],...,P[n] and Q. However, upon local
policy decision, N MAY allocate another available (shared) link
other than r for use by Q. If this is not the case (upon the local
policy decision that no other link is allowed to be allocated for
Q) or if no other link is available for Q, N SHOULD return a
PathErr message with the new error code/sub-code "Admission Control
Failure/LSP Admission Failure".
- Otherwise (if P'[1],...,P'[n] and Q' are fully disjoint), the link
r selected by N for the LSP Q MAY be exactly the same as the one
selected for the LSPs P[1],...,P[n]. This happens after verifying
(from the node's local policy) that the selected link r can be
shared between these LSPs. If this is not the case (for instance,
the sharing ratio has reached its maximum for that link), and if
upon local policy decision, no other link is allowed to be
allocated for Q, N SHOULD return a PathErr message with the error
code/sub-code "Admission Control Failure/Requested Bandwidth
Unavailable" (see [RFC2205]). Otherwise (if no other link is
available), N SHOULD return a PathErr message with the new error
code/sub-code "Admission Control Failure/LSP Admission Failure".
Note that the process, through which m out of the n (m =< n)
secondary protecting LSPs' PPROs may be selected on a local basis to
perform the above comparison and subsequent link selection, is out of
scope of this document.
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16. ASSOCIATION Object
The ASSOCIATION object is used to associate LSPs with each other. In
the context of end-to-end LSP recovery, the association MUST only
identify LSPs that support the same Tunnel ID as well as the same
tunnel sender address and tunnel endpoint address. The Association
Type, Association Source, and Association ID fields of the object
together uniquely identify an association. The object uses an object
class number of the form 11bbbbbb to ensure compatibility with non-
supporting nodes.
The ASSOCIATION object is used to associate LSPs with each other.
16.1. Format
The IPv4 ASSOCIATION object (Class-Num of the form 11bbbbbb with
value = 199, C-Type = 1) has the format:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | Class-Num(199)| C-Type (1) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Association Type | Association ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 Association Source |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The IPv6 ASSOCIATION object (Class-Num of the form 11bbbbbb with
value = 199, C-Type = 2) has the format:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | Class-Num(199)| C-Type (2) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Association Type | Association ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| IPv6 Association Source |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Lang, et al. Standards Track [Page 37]
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Association Type: 16 bits
Indicates the type of association being identified. Note that
this value is considered when determining association. The
following are values defined in this document.
Value Type
----- ----
0 Reserved
1 Recovery (R)
Association ID: 16 bits
A value assigned by the LSP head-end. When combined with the
Association Type and Association Source, this value uniquely
identifies an association.
Association Source: 4 or 16 bytes
An IPv4 or IPv6 address, respectively, that is associated to
the node that originated the association.
16.2. Processing
In the end-to-end LSP recovery context, the ASSOCIATION object is
used to associate a recovery LSP with the LSP(s) it is protecting or
a protected LSP(s) with its recovery LSP. The object is carried in
Path messages. More than one object MAY be carried in a single Path
message.
Transit nodes MUST transmit, without modification, any received
ASSOCIATION object in the corresponding outgoing Path message.
An ASSOCIATION object with an Association Type set to the value
"Recovery" is used to identify an LSP-Recovery-related association.
Any node associating a recovery LSP MUST insert an ASSOCIATION object
with the following setting:
- The Association Type MUST be set to the value "Recovery" in the
Path message of the recovery LSP.
- The (IPv4/IPv6) Association Source MUST be set to the tunnel sender
address of the LSP being protected.
Lang, et al. Standards Track [Page 38]
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- The Association ID MUST be set to the LSP ID of the LSP being
protected by this LSP or the LSP protecting this LSP. If unknown,
this value is set to its own signaled LSP_ID value (default).
Also, the value of the Association ID MAY change during the
lifetime of the LSP.
Terminating nodes use received ASSOCIATION object(s) with the
Association Type set to the value "Recovery" to associate a recovery
LSP with its matching working LSP. This information is used to bind
the appropriate working and recovery LSPs together. Such nodes MUST
ensure that the received Path messages, including ASSOCIATION
object(s), are processed with the appropriate PROTECTION object
settings, if present (see Section 14 for PROTECTION object
processing). Otherwise, this node MUST return a PathErr message with
the new error code/sub-code "LSP Admission Failure/Bad Association
Type". Similarly, terminating nodes receiving a Path message with a
PROTECTION object requiring association between working and recovery
LSPs MUST include an ASSOCIATION object. Otherwise, such nodes MUST
return a PathErr message with the new error code/sub-code "Routing
Problem/PROTECTION object not Applicable".
17. Updated RSVP Message Formats
This section presents the RSVP message-related formats as modified by
this document. Unmodified RSVP message formats are not listed.
The format of a Path message is as follows:
::= [ ]
[ [ | ] ... ]
[ ]
[ ]
[ ]
[ ... ]
[ ]
[ ... ]
[ ]
[ ... ]
[ ... ]
[ ... ]
The format of the for unidirectional and
bidirectional LSPs is not modified by the present document.
Lang, et al. Standards Track [Page 39]
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The format of a Resv message is as follows:
::= [ ]
[ [ | ] ... ]
[ ]
[ ] [ ]
[ ]
[ ]
[ ]
[ ... ]
