CCAMP Working Group CCAMP GMPLS P&R Design Team
Internet Draft
Expiration Date: November 2004 J.P. Lang (Editor)
Y. Rekhter (Editor)
D. Papadimitriou (Editor)
May 2004
RSVP-TE Extensions in support of End-to-End GMPLS-based Recovery
draft-ietf-ccamp-gmpls-recovery-e2e-signaling-01.txt
Status of this Memo
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Abstract
This document describes protocol specific procedures for GMPLS
(Generalized Multi-Protocol Label Switching) RSVP-TE (Resource
ReserVation Protocol - Traffic Engineering) signaling extensions to
support end-to-end LSP recovery (protection and restoration). A
generic functional description of GMPLS recovery can be found in a
companion document.
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Table of Contents
1. Contributors ................................................. 3
2. Conventions .................................................. 3
3. Introduction ................................................. 4
4. Definitions .................................................. 5
4.1 LSP Identification .......................................... 5
4.2 Recovery Attributes ......................................... 6
4.2.1 LSP Status ................................................ 6
4.2.2 LSP Recovery .............................................. 7
4.3 LSP Association ............................................. 8
5. 1+1 Unidirectional Protection ................................ 8
5.1. Identifiers ................................................ 9
6. 1+1 Bi-directional Protection ............................... 10
6.1. Identifiers ............................................... 10
6.2. End-to-End Switchover Request/Response .................... 10
7. 1:1 Protection with Extra-Traffic ........................... 12
7.1 Identifiers ................................................ 13
7.2 End-to-End Switchover Request/Response ..................... 13
7.3 1:N (N > 1) Protection with Extra-Traffic .................. 14
8. Re-routing without Extra-Traffic ............................ 15
8.1 Identifiers ................................................ 16
8.2 Signaling Primary LSPs ..................................... 16
8.3 Signaling Secondary LSPs ................................... 16
9. Shared-Mesh Restoration ..................................... 17
9.1. Identifiers ............................................... 19
9.2 Signaling Primary LSPs ..................................... 19
9.3 Signaling Secondary LSPs ................................... 20
10. LSP Preemption ............................................. 21
11. (Full) LSP Re-routing ...................................... 22
11.1 Identifiers ............................................... 22
11.2 Signaling Re-routable LSPs ................................ 23
12. Reversion .................................................. 24
13. External Commands .......................................... 25
14. PROTECTION Object .......................................... 25
14.1 Format .................................................... 25
14.2 Processing ................................................ 26
15. PRIMARY PATH ROUTE Object .................................. 27
15.1 Format .................................................... 27
15.2 Applicability ............................................. 27
15.3 Subobjects ................................................ 28
15.4 Processing ................................................ 29
16. ASSOCIATION Object ......................................... 29
16.1 Format .................................................... 30
16.2 Processing ................................................ 31
17. Updated RSVP Message Formats ............................... 31
18. Security Considerations .................................... 32
19. IANA Considerations ........................................ 32
20. Acknowledgments ............................................ 33
21. Intellectual Property Consideration ........................ 33
21.1 IPR Disclosure Acknowledgement ............................ 33
22. References ................................................. 34
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22.1 Normative References ...................................... 34
23. Author's Addresses ......................................... 35
1. Contributors
This document is the result of the CCAMP Working Group Protection
and Restoration design team joint effort. The following are the
authors that contributed to the present document:
Deborah Brungard (AT&T)
Rm. D1-3C22 - 200 S. Laurel Ave.
Middletown, NJ 07748, USA
EMail: dbrungard@att.com
Sudheer Dharanikota
EMail: sudheer@ieee.org
Jonathan Lang (Rincon Networks)
EMail: jplang@ieee.org
Guangzhi Li (AT&T)
180 Park Avenue,
Florham Park, NJ 07932, USA
EMail: gli@research.att.com
Eric Mannie
EMail: eric_mannie@hotmail.com
Dimitri Papadimitriou (Alcatel)
Fr. Wellesplein, 1
B-2018, Antwerpen, Belgium
EMail: dimitri.papadimitriou@alcatel.be
Bala Rajagopalan
EMail: braj@earthlink.net
Yakov Rekhter (Juniper)
1194 N. Mathilda Avenue
Sunnyvale, CA 94089, USA
EMail: yakov@juniper.net
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 [GMPLS-ARCH], [RFC3471], [RFC3473] and
referenced as well as [TERM] and [FUNCT].
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3. Introduction
Generalized Multi-Protocol Label Switching (GMPLS) extends MPLS to
include support for Layer-2 (L2SC), Time-Division Multiplex (TDM),
Lambda Switch Capable (LSC), and Fiber Switch Capable (FSC)
interfaces. GMPLS-based recovery uses control plane mechanisms
(i.e., signaling, routing, 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 [TERM]).
A functional description of GMPLS-based recovery is provided in
[FUNCT] and should be considered as a companion document to this
memo which describes the protocol specific procedures for GMPLS
RSVP-TE (Resource ReSerVation Protocol - Traffic Engineering)
signaling (see [RFC3473]) to support end-to-end recovery of an
entire LSP from the head-end to the tail-end. The present memo
addresses four types of end-to-end LSP recovery: 1+1 unidirectional/
1+1 bi-directional protection, LSP protection with extra-traffic
(including 1:N protection with extra-traffic), pre-planned LSP re-
routing without extra-traffic (including shared mesh), and full LSP
re-routing.
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 traffic
from the valid LSP. No coordination is required between the end
nodes when a failure/switchover occurs.
In 1+1 bi-directional 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 co-ordination
between the end-nodes when switching to the protecting LSP.
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 to the protecting
LSP. Note that M:N protection is out of scope of this document
(though mechanisms it defines may be extended to cover it).
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Pre-planned LSP re-routing (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 and 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 can not
carry any extra-traffic (note that this does not mean that the
corresponding resources can not 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 re-routing that reduces the recovery resource
requirements by allowing multiple protecting LSPs to share common
link and node resources. The recovery resources are pre-reserved and
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. Note that in both
cases, any lower priority LSP that would use the pre-reserved
resources for the protecting LSP(s) MUST be preempted during the
activation of the protecting LSP.
Full LSP re-routing (or restoration) switches normal traffic to an
alternate LSP that is fully established only after 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.
Note that crankback signaling (see [CRANK]) and LSP segment recovery
are further detailed in dedicated companion documents. Also, there
is no impact to Fast Reroute [FRR] introduced by end-to-end
GMPLS-based recovery i.e. it is possible to use either method
defined in FRR with end-to-end GMPLS-based recovery. The objects
used and/or newly introduced by end-to-end recovery will be ignored
by [FRR] conformant implementations, and FRR can operate on a per
LSP basis as defined in [FRR].
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 end point address
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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 LSP tunnels that belong to the same session.
4.2 Recovery Attributes
The recovery attributes includes all the parameters that determine
the status of a 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
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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 (requiring
thus 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 memo.
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 Re-routing: set if a primary working LSP is dynamically
recoverable using (non pre-planned) head-end re-routing.
- Pre-planned LSP Re-routing 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
<sender;receiver> pair. When the secondary LSPs resources are not
pre-reserved for a single <sender;receiver> 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 <sender;receiver> pair. This type includes 1:N LSP
protection with extra-traffic.
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- 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 bi-directional 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 via 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 re-
routing 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 and this *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 signaling (see Section 12) but also
facilitates the transparent delivery of protected services since any
intermediate node is not required to know the semantic 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 the working LSP signaling, the Association ID of the
ASSOCIATION object (see Section 16) identifies the protecting LSP.
When used for the protecting LSP signaling, 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
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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).
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 end-points. Note also that 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. Also, for the protected LSP under
failure condition, the Path_State_Removed Flag of the ERROR_SPEC
object (see [RFC3473]) SHOULD NOT be set upon PathErr message
generation.
Note: one should assume that both paths are SRLG disjoint otherwise,
a failure would impact both working and protecting LSPs.
5.1. Identifiers
Since both LSPs belong to the same session, 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 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 bi-directional 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.
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.
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6. 1+1 Bi-directional Protection
1+1 bi-directional protection is another scheme that provides end-
to-end LSP protection.
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 bi-directional LSP is
established from A to D over each path and traffic is transmitted
simultaneously over both LSPs. In this scheme, both end-points must
receive traffic over the same LSP. When a failure is detected by one
or both end-points of the LSP, both end-points must select traffic
from the other LSP. This action must be coordinated between node A
and D. From this perspective, 1+1 bi-directional protection can be
seen as a coordinated protection switching mechanism between both
end-points. 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).
Note: one should assume that both paths are SRLG disjoint otherwise
a failure would impact both working and protecting LSPs.
6.1. Identifiers
Since both LSPs belong to the same session, 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 Bi-directional"). This LSP Protection Type
value is only applicable to bi-directional 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 co-ordinate the switchover between end-points, an end-to-end
switchover request is needed since a failure affecting one the LSPs
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results in both end-points switching to the other LSP (resulting in
receiving traffic from the other LSP) in their respective
directions. This is done using the Notify message with a new Error
Code indicating "Working LSP Failure (Switchover Request)". The
Notify Ack message MUST be sent to confirm the reception of the
Notify message (see [RFC3473], Section 4.3).
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 <upstream/downstream session list> (see
[RFC3473]), it MUST begin receiving on the protecting LSP
and send a Notify message reliably to the other end-node (D
or A, respectively). This message MAY indicate the identity
of the failed working link and other relevant information
using the IF_ID ERROR_SPEC (see [RFC3473]).
Note: in this case, the IF_ID ERROR_SPEC replaces the
ERROR_SPEC in the Notify message, otherwise the
corresponding (data plane) information SHOULD be received
in the PathErr/ResvErr message.
2. Upon receipt of the switchover message, the end-node
(D or A, respectively) MUST begin receiving from the
protection LSP and send a (Notify) Ack message to the other
end-node (A or D, respectively) using reliable message
delivery (see [RFC2961]).
Since the intermediate nodes (B,C,E,F and G) are assumed to be GMPLS
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 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 working LSP
under failure, the Path_State_Remove Flag of the ERROR_SPEC object
(see [RFC3473]) SHOULD NOT be set 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).
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7. 1:1 Protection with Extra-Traffic
The most common case of end-to-end 1:N protection is to establish,
between the same end-points, 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 fast switchover when the working LSP
fails. GMPLS 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 (i.e.
the protecting LSP is capable of carrying extra-traffic) with the
caveat that this traffic will be preempted if the working LSP fails.
Also, if extra-traffic is carried over the protecting LSP, the
corresponding end-nodes may be notified of the failure in order to
complete the switchover.
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 RSVP Path message traverses) SHOULD send an RSVP
Notify message to the LSP head-end node, and the node downstream to
the failure SHOULD send an RSVP 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 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: one should assume that both paths are SRLG disjoint otherwise
a failure would impact both working and protecting LSPs.
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7.1 Identifiers
Since both LSPs belong to the same session, 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 setup 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 bi-directional 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.
7.2 End-to-End Switchover Request/Response
To co-ordinate the switchover between end-points, an end-to-end
switchover request is needed such that the affected LSP(s) are 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).
This operation may be done using a Notify message exchange with a
new Error Code indicating "(Working) LSP Failure (Switchover
Request)". The Notify Ack message MUST be sent to confirm the
reception of the Notify message.
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 <upstream/downstream session list> (see
[RFC3473]), it disconnects the extra-traffic from the
protecting LSP and sends a Notify message reliably to the
other end-node (D or A, respectively). This message MAY
indicate the identity of the failed working link and other
relevant information using the IF_ID ERROR_SPEC (see [RFC
3473]).
Note: in this case, the IF_ID ERROR_SPEC replaces the
ERROR_SPEC in the Notify message, otherwise the corresponding
information SHOULD be received in the PathErr/ResvErr message
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2. Upon receipt of the switchover (i.e. end-to-end 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
and send a (Notify) Ack message to the other end-node (A or
D, respectively) using reliable message delivery (see [RFC
2961]). Also, the Notify message generated by the end-node
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 Notify
message from an intermediate node.
3. Upon receipt of the switchover (Notify) Ack message, the
end-node (A or D, respectively) MUST begin receiving normal
traffic from the protecting LSP.
Note 1: a 2-phase protection switching signaling is used in the
present context, a 3-phase signaling (see [FUNCT]) that would imply
a notification message and a switchover request/response messages,
is not considered here. Also, when the protecting LSPs do not carry
extra-traffic, a 1-Phase protection switching signaling as defined
in Section 6.2 MAY be used instead of the 2-Phase described here
above.
Note 2: when the N bit is set, the above end-to-end switchover
request/response exchange does only provide 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 LSP from the N
working LSPs. This protecting LSP allows thus for carrying extra-
traffic. In addition, the N working LSPs (considered as identical in
terms of traffic parameters) MAY be 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 Flag is set to 0x04 (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 Flag is set to 0x04
(during LSP setup). The Association ID MUST be set by default to the
LSP ID of the protected LSP corresponding to N = 1.
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Any signaling procedure applicable to 1:1 protection with extra-
traffic equally applies to 1:N protection with extra-traffic.
8. Re-routing without Extra-Traffic
End-to-end (pre-planned) re-routing 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 one. However, in this case the protecting LSP is not fully
instantiated, thus, it can not carry any extra-traffic (note that
this does not mean that the corresponding resources can not 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 LSP are established between the same end-nodes no
further notification is required to indicate that the working LSPs
are no longer protected.
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 Setup 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 at least to 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:
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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 can not carry any extra-traffic. When a failure is detected on
the working LSP (say at B), the error is propagated and/or notified
to the ingress node (A), which 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.
8.1 Identifiers
Since both LSPs (i.e. the protected and the secondary LSPs) belong
to the same session, the SESSION object MUST be the same in both
LSPs. The LSP ID, however, MUST be different to distinguish between
the protected LSP carrying working traffic and the secondary LSP
that can not carry extra-traffic.
A new PROTECTION object (see Section 14) is used to setup the two
LSPs. This object carries the desired end-to-end LSP Protection Type
in this case, "Re-routing without Extra-Traffic") as well as the LSP
ID of the association LSP. This LSP Protection Type value is
applicable to both uni- and bi-directional 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 "Re-routing 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 "Re-routing without Extra-Traffic".
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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).
From [GMPLS-ARCH], the secondary LSP is setup 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 re-assigned (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. 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 [FUNCT]. Shared-mesh restoration can be seen as a
particular case of pre-planned LSP re-routing (see Section 8) that
reduces the recovery resource requirements by allowing multiple
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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
numerically higher) than the Setup 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 at least to 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. In order to achieve
resource merging during the signaling of these protecting LSPs (i.e.
resource sharing), the LSPs must have the same Session Ids, but the
Session Id includes the target (egress) IP address. These addresses
are not the same in this example. Resource sharing along E, F, G can
only be achieved if the nodes E, F and G recognize that the LSP Type
setting of the secondary LSPs is for protection (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 can be shared.
When a failure is detected on one of the working LSPs (say at B),
the error is propagated and/or notified to the ingress node (A),
which activates the protecting LSP (see Section 8). At this point,
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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 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 sub-sections details 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
Since both LSPs (i.e. the protected and the secondary LSPs) belong
to the same session, 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 can not carry extra-traffic.
A new PROTECTION object (see Section 14) is used to setup the two
LSPs. This object carries the desired end-to-end LSP Protection Type
in this case, "Re-routing without Extra-Traffic". This LSP
Protection Type value is applicable to both uni- and bi-directional
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 "Re-routing 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 "Re-routing 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 MUST 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 [GMPLS-ARCH], the secondary LSP is setup 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 re-assigned (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 setup lower priority LSPs. In this case,
these resources MUST be preempted when the protecting LSP is
activated. Additional condition raises from mis-connection 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 pre-empting LSP) Path message
reaches a node using the resources for lower priority LSP(s) (i.e.
pre-empted LSP(s)) is as follows:
1. Deallocate resources to be used by the pre-empting LSP and
release the cross-connection. Note that if the pre-empting LSP is
bi-directional, these resources may come from one or two lower
priority LSPs, and if from two LSPs, they may be uni- or bi-
directional. The pre-empting node SHOULD NOT send the Path message
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before the deallocation of resources has completed since this may
lead to the downstream path becoming misconnected if the downstream
node is able to re-assign the resources more quickly.
2. Send PathTear and PathErr with "Policy Control failure"/"Hard
Pre-empted" and the Path_State_Removed flag set for the pre-empted
LSP(s).
3. Reserve the pre-empted resources for the protecting LSP. The pre-
empting node MUST NOT cross-connect the upstream resources of a bi-
directional pre-empting LSP.
4. Send the Path message.
5. Upon reception of a trigger Resv from the downstream node, cross-
connect the downstream path resources and if the pre-empting LSP is
bi-directional, perform cross-connection for the upstream path
resources.
Note that step 1 may cause alarms to be raised for the pre-empted
LSP. If alarm suppression is desired the pre-empting node MAY expand
before applying step 1 act as follows.
1a. Before deallocating resources send a Resv message including an
ADMIN_STATUS object to disable alarms for the pre-empted LSP.
1b. Receive a Path message indicating that alarms are disabled.
At the downstream node (with respect to the pre-empting LSP) the
processing is RECOMMENDED to be as follows:
1. Receive PathTear (and/or PathErr) message for the pre-empted
LSP(s).
2a.Release the resources associated with the LSP on the interface
to the pre-empting LSP, remove any cross-connection and release
all other resources associated with the pre-empted LSP.
2b.Forward the PathTear (and/or PathErr) message per [RFC 3473].
C. Receive the Path message for the pre-empting LSP and process as
normal, forwarding it to the downstream node.
D. Receive the Resv for the pre-empting LSP and process as normal,
forwarding it to the upstream node.
11. (Full) LSP Re-routing
LSP re-routing, 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
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failure. Crankback signaling (see [CRANK]) and route exclusion
techniques (see [XRO]) 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 re-routing) 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 re-routing will be initiated by the head-end node that
has either detected the failure or received a Notify message and/or
a PathErr message indicating that a failure has occurred. The new
LSP resources can be established using the make-before-break
mechanism, where the new LSP is setup 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 re-used by the new alternate LSP.
11.1 Identifiers
The Tunnel End Point Address, Tunnel Id, Extended Tunnel Id, 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 setup 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.
The alternate LSP MAY be setup 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 Re-routable LSPs
A new PROTECTION object is included in the Path message during
signaling of dynamically re-routable LSPs, with the end-to-end LSP
Protection Type value set to "Full Re-routing". These LSPs that can
be either uni- or bi-directional are signaled by setting in the
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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 re-routed at the head-end node after failure occurrence. The
Association_ID value MUST be set to the LSP_ID value of the signaled
LSP.
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 it 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 bi-directional" and "1:N Protection with Extra-traffic"
protection, reversion to the recovered LSP occurs by using the
following sequence:
- first, clear the A bit of the ADMIN_STATUS object if set for the
recovered LSP
- then, apply the reverse 1-phase APS switchover request/response
(or 2-phase APS) described in Section 6.2 (or Section 7.2,
respectively) to switch normal traffic back from the
protecting to the recovered LSP. This is performed by using the
Notify message with a new Error Code indicating "(Working) LSP
Recovered (Switchover Request)". The Notify Ack message MUST be
sent to confirm the reception of the Notify message (see [RFC
3473], Section 4.3).
- finally, clear the O bit of the PROTECTION object sent over the
protecting LSP.
For "Re-routing without Extra-traffic" reversion (including the
shared recovery case) 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:
- first, clear the A bit of the ADMIN_STATUS object if set for the
recovered LSP.
- then, apply the reverse 1-phase APS switchover request/response
described in Section 6.2, to switch normal traffic back from the
protecting to the recovered LSP. This is performed by using the
Notify message with a new Error Code indicating "(Working) LSP
Recovered (Switchover Request)". The Notify Ack message MUST be
sent to confirm the reception of the Notify message (see [RFC
3473], Section 4.3).
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- finally, de-activate the protecting LSP by setting the S bit to 1
in the PROTECTION object sent over the protecting LSP.
13. External Commands
This section specifies the control plane behavior when using several
external commands (see [TERM]), typically issued by an operator
through the Network Management System (NMS)/Element Management
System (EMS), which can be used to influence or command the recovery
operations. Other specific commands may complete the below list.
A. Lockout of recovery LSP:
The Lockout bit (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 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 Flag is set to either 0x04, or 0x08 or 0x10.
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 Flag
is set to either 0x04, or 0x08 or 0x10.
C. Forced switch for normal traffic:
Recovery signaling is initiated externally that switches normal
traffic to the recovery LSP following the procedures defined in
Section 6, 7, 8 and 9.
D. Manual switch for normal traffic:
Recovery signaling operation is initiated externally that switches
normal traffic to the recovery LSP following the procedures defined
in Section 6, 7, 8 and 9. This, unless a fault condition exists on
other LSPs/spans (including the recovery LSP) or an equal or higher
priority switch command is in effect.
E. Manual switch for recovery LSP:
Recovery signaling operation is initiated externally that switches
normal traffic to the working LSP following the procedure defined in
Section 12. This, unless a fault condition exists on the working LSP
or an equal or higher priority switch command is in effect.
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14. PROTECTION Object
This section describes the extensions to the PROTECTION object to
broaden its applicability to end-to-end LSP recovery. In addition to
modifications to the format of the PROTECTION object, we extend its
use so that the object can be included in the Notify message to act
a switchover request for 1+1 bi-directional and 1:1 protection.
14.1 Format
The format of the PROTECTION Object (Class-Num = 37, C-Type = 2,
suggested value, TBA by IANA) 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 (TBA) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|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.
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 Flag is set to either 0x04, or 0x08 or 0x10. 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
Flag is set to either 0x04, or 0x08 or 0x10. The O bit MUST be
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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) Re-routing
0x02 Re-routing without Extra-Traffic
0x04 1:N Protection with Extra-Traffic
0x08 1+1 Unidirectional Protection
0x10 1+1 Bi-directional 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.
Link Flags: 6 bits
Indicates the desired link protection type (see [RFC3471]).
14.2 Processing
Intermediate nodes processing a Path message containing a PROTECTION
object with the LSP Protection Type "0x02" 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 can not, the node MUST generate a PathErr message, with a
"Routing problem/Unsupported LSP Protection" indication.
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 "Routing problem/
Unsupported LSP Protection" error code.
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
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(as specified by the Association ID field). This object MUST be
present in the Path message (for the pre-provisioning of the
secondary protecting LSP) if and only if the LSP Protection Type
value is set to "0x02". 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 MAY 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.
15.1 Format
The primary path route is specified via the PRIMARY_PATH_ROUTE
object (PPRO). The Primary Path Route Class Number of form 0bbbbbbb
is TBA by IANA.
Currently one C-Type (Class-Type) is defined, Type 1, Primary Path
Route. The PRIMARY_PATH_ROUTE object has the following format:
Class-Num = TBA by IANA (of form 0bbbbbbb), C-Type = 1 (suggested)
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. The subobjects are
identical to those that can constitute an EXPLICIT/RECORD ROUTE
object as defined in [RFC3209], [RFC3473] and [RFC3477].
To signal a secondary protecting LSP, the Path message MUST include
at least one or MAY include 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 Applicability
The PRIMARY_PATH_ROUTE object MUST 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
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draft-ietf-ccamp-gmpls-recovery-e2e-signaling-01.txt May 2004
along the path that do not support this object MUST return a PathErr
message with the "Unknown Object Class" error code.
Also, the following restrictions MUST be applied with respect to the
PPRO usage:
- PPROs MUST only be sent over secondary protecting LSPs (S bit = 1
and P bit = 1) and when the LSP Protection Type value is set to
"0x02" in the PROTECTION object (see Section 14.)
- Crossed exchanges of PPROs over primary LSPs are forbidden (i.e.
their usage is restricted to a single set of protected LSPs). If a
PPRO is received with the S bit set to 0 in the PROTECTION object,
the receiving node MUST return a PathErr message with the "Routing
Problem/PRIMARY PATH_ROUTE object not applicable" error code.
- The PPRO's content MUST NOT include subobjects coming from other
PPROs. In particular, received PPROs MUST NOT be re-used to
establish other working or protecting LSPs.
15.3 Subobjects
The PRIMAY_PATH_ROUTE object is defined as a list of variable-length
data items called subobjects. PPR subobjects are derived from the
subobjects of the EXPLICIT ROUTE and/or RECORD ROUTE object of the
primary working LSP(s). Each PPR 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])
An empty PPRO with no subobjects is considered as 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 "Routing Problem/Bad PRIMARY PATH_ROUTE object" error code.
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).
15.4 Processing
The PPRO enables of sharing recovery resources between a given
secondary protecting LSP and one or more secondary protecting LSPs
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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 and protecting 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 messages 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 "Admission Control Failure/LSP Admission
Failure" error code.
- 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, after verifying (also
from its 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 upon
local policy decision no other link is allowed to be allocated for
Q, N SHOULD return a PathErr message with the "Admission Control
Failure/Requested Bandwidth Unavailable" error code. Otherwise (if
no other link is available), N SHOULD return a PathErr message
with the "Admission Control Failure/LSP Admission Failure" error
code.
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.
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. The Association Type,
Association Source and Association ID fields of the object together
uniquely identify an association. The object uses an object class
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draft-ietf-ccamp-gmpls-recovery-e2e-signaling-01.txt May 2004
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 form 11bbbbbb with value =
198, C-Type = 1, suggested values, TBA by IANA) 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(TBD)| C-Type (1) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Association Type | Association ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 Association Source |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The IPv6 ASSOCIATION object (Class-Num of form 11bbbbbb with value =
198, C-Type = 2, suggested values, TBA by IANA) 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(TBD)| C-Type (2) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Association Type | Association ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| IPv6 Association Source |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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 that when combined with Association Type and
Association Source uniquely identifies an association.
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Association Source: 4 or 16 bytes
The IP address of the node that originated the association.
16.2. Processing
The ASSOCIATION object is used to associate different LSPs with each
other. In the protection and restoration context, the 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
- 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 "LSP Admission Failure/Bad Association Type" error code.
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 "Routing Problem/PROTECTION object
not Applicable" error code.
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:
J.P.Lang et al. - Internet Draft Expires November 2004 31
draft-ietf-ccamp-gmpls-recovery-e2e-signaling-01.txt May 2004
<Path Message> ::= <Common Header> [ <INTEGRITY> ]
[ [<MESSAGE_ID_ACK> | <MESSAGE_ID_NACK>] ... ]
[ <MESSAGE_ID> ]
<SESSION> <RSVP_HOP>
<TIME_VALUES>
[ <EXPLICIT_ROUTE> ]
<LABEL_REQUEST>
[ <PROTECTION> ]
[ <LABEL_SET> ... ]
[ <SESSION_ATTRIBUTE> ]
[ <NOTIFY_REQUEST> ... ]
[ <ADMIN_STATUS> ]
[ <ASSOCIATION> ... ]
[ <PRIMARY_PATH_ROUTE> ... ]
[ <POLICY_DATA> ... ]
<sender descriptor>
The format of the <sender descriptor> for unidirectional and
bidirectional LSPs is not modified by the present document.
18. Security Considerations
This document does not introduce or imply any specific security
consideration.
19. IANA Considerations
IANA assigns values to RSVP protocol parameters. Within the current
document a PROTECTION object (new C-Type) and a PRIMARY PATH ROUTE
object are defined.
One RSVP Class Number (Class-Num) and two Class Types (C-Types)
values have to be defined by IANA in registry:
http://www.iana.org/assignments/rsvp-parameters
- PROTECTION object: Class-Num = 37, C-Type = 2 (suggested)
- PRIMARY PATH ROUTE object: Class-Num = TBA (of form 0bbbbbbb),
C-Type = 1 (suggested)
- ASSOCIATION object: Class-Num = TBA (of form 11bbbbbb, value 198
is suggested), C-Type = 1 (suggested)
- Error values:
o "Admission Control Failure/LSP Admission Failure" (value = TBA)
o "Admission Control Failure/Bad Association Type" (value = TBA)
o "Routing Problem/Unsupported LSP Protection" (value = TBA)
o "Routing Problem/PROTECTION object not applicable" (value = TBA)
o "Routing Problem/Bad PRIMARY PATH_ROUTE object" (value = TBA)
J.P.Lang et al. - Internet Draft Expires November 2004 32
draft-ietf-ccamp-gmpls-recovery-e2e-signaling-01.txt May 2004
o "Routing Problem/PRIMARY PATH_ROUTE object not applicable"
(value = TBA)
o "Notify Error/LSP Failure" (value = TBA)
o "Notify Error/LSP Recovered" (value = TBA)
20. Acknowledgments
The authors would like to thank John Drake for its active
collaboration, Adrian Farrel for his contribution to this document
(in particular, to the Section 10 and 11) and his thorough review of
the document, Bart Rousseau (for editorial review), Dominique
Verchere, and Stefaan De_Cnodder.
The authors would like also to thank Lou Berger for the time and
effort he spent together with the design team, in contributing to
the present document.
21. Intellectual Property Consideration
The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed
to pertain to the implementation or use of the technology
described in this document or the extent to which any license
under such rights might or might not be available; nor does it
represent that it has made any independent effort to identify any
such rights. Information on the procedures with respect to rights
in RFC documents can be found in BCP 78 and BCP 79.
Copies of IPR disclosures made to the IETF Secretariat and any
assurances of licenses to be made available, or the result of an
attempt made to obtain a general license or permission for the use
of such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository
at http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention
any copyrights, patents or patent applications, or other
proprietary rights that may cover technology that may be required
to implement this standard. Please address the information to the
IETF at ietf-ipr@ietf.org.
21.1 IPR Disclosure Acknowledgement
By submitting this Internet-Draft, I certify that any applicable
patent or other IPR claims of which I am aware have been
disclosed, and any of which I become aware will be disclosed, in
accordance with RFC 3668.
22. References
22.1 Normative References
J.P.Lang et al. - Internet Draft Expires November 2004 33
draft-ietf-ccamp-gmpls-recovery-e2e-signaling-01.txt May 2004
[FRR] P.Pan (Editor), "Fast Reroute Extensions to RSVP-TE for
LSP Tunnels," Internet Draft, Work in progress, draft-
ietf-mpls-rsvp-lsp-fastreroute-04.txt, June 2003.
[FUNCT] J.P.Lang and B.Rajagopalan (Editors), "Generalized MPLS
Recovery Functional Specification," Internet Draft,
Work in Progress, draft-ietf-ccamp-gmpls-recovery-
functional-02.txt, April 2004.
[GMPLS-ARCH] E.Mannie (Editor), "Generalized Multi-Protocol Label
Switching Architecture," Internet Draft, Work in
progress, draft-ietf-ccamp-gmpls-architecture-07.txt,
May 2003.
[GMPLS-RTG] K.Kompella (Editor), "Routing Extensions in Support of
Generalized MPLS," Internet Draft, Work in Progress,
draft-ietf-ccamp-gmpls-routing-09.txt, October 2003.
[LMP] J.Lang (Editor), "Link Management Protocol (LMP) v1.0,"
Internet Draft, Work in progress, draft-ietf-ccamp-lmp-
10, October 2003.
[RFC2026] S.Bradner, "The Internet Standards Process -- Revision
3," BCP 9, RFC 2026, October 1996.
[RFC2119] S.Bradner, "Key words for use in RFCs to Indicate
Requirement Levels," BCP 14, RFC 2119, March 1997.
[RFC2961] L.Berger et al., "RSVP Refresh Overhead Reduction
Extensions," RFC 2961, April 2001.
[RFC3209] D.Awduche et al., "RSVP-TE: Extensions to RSVP for
LSP Tunnels," RFC 3209, December 2001.
[RFC3471] L.Berger (Editor) et al., "Generalized Multi-Protocol
Label Switching (GMPLS) Signaling Functional
Description," RFC 3471, January 2003.
[RFC3473] L.Berger (Editor) et al., "Generalized Multi-Protocol
Label Switching (GMPLS) Signaling Resource
Reservation Protocol - Traffic Engineering (RSVP-TE)
Extensions," RFC 3473, January 2003.
[RFC3477] K.Kompella, and Y.Rekhter, "Signaling Unnumbered Links
in Resource Reservation Protocol - Traffic Engineering
(RSVP-TE)," RFC 3477, January 2003.
[RFC3667] S.Bradner, "IETF Rights in Contributions", BCP 78,
RFC 3667, February 2004.
[RFC3668] S.Bradner, Ed., "Intellectual Property Rights in IETF
J.P.Lang et al. - Internet Draft Expires November 2004 34
draft-ietf-ccamp-gmpls-recovery-e2e-signaling-01.txt May 2004
Technology", BCP 79, RFC 3668, February 2004.
[TERM] E.Mannie and D.Papadimitriou (Editors), "Recovery
(Protection and Restoration) Terminology for GMPLS,"
Internet Draft, Work in progress, draft-ietf-ccamp-
gmpls-recovery-terminology-04.txt, April 2004.
[XRO] C.Y.Lee et al. "Exclude Routes - Extension to RSVP-TE,"
Internet Draft, Work in progress, draft-ietf-ccamp-
rsvp-te-exclude-route-01.txt, November 2003.
23. Author's Addresses
Jonathan Lang (Rincon Networks)
EMail: jplang@ieee.org
Yakov Rekhter (Juniper)
1194 N. Mathilda Avenue
Sunnyvale, CA 94089, USA
EMail: yakov@juniper.net
Dimitri Papadimitriou (Alcatel)
Fr. Wellesplein, 1
B-2018, Antwerpen, Belgium
EMail: dimitri.papadimitriou@alcatel.be
J.P.Lang et al. - Internet Draft Expires November 2004 35
draft-ietf-ccamp-gmpls-recovery-e2e-signaling-01.txt May 2004
Full Copyright Statement
Copyright (C) The Internet Society (2004). This document is subject
to the rights, licenses and restrictions contained in BCP 78 and
except as set forth therein, the authors retain all their rights.
This document and the information contained herein are provided on
an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE
REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE
INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR
IMPLIED,INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
J.P.Lang et al. - Internet Draft Expires November 2004 36
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