Internet DRAFT - draft-ali-mpls-inter-domain-p2mp-rsvp-te-lsp
draft-ali-mpls-inter-domain-p2mp-rsvp-te-lsp
MPLS Working Group Zafar Ali
Internet-Draft Rakesh Gandhi
Intended status: Standards Track Tarek Saad
Expires: April 18, 2013 Cisco Systems, Inc.
Robert H. Venator
Defense Information Systems Agency
Yuji Kamite
NTT Communications Corporation
October 15, 2012
Signaling RSVP-TE P2MP LSPs in an Inter-domain Environment
draft-ali-mpls-inter-domain-p2mp-rsvp-te-lsp-09
Abstract
Point-to-MultiPoint (P2MP) Multiprotocol Label Switching (MPLS) and
Generalized MPLS (GMPLS) Traffic Engineering Label Switched Paths (TE
LSPs) are established using signaling procedures defined in
[RFC4875]. However, [RFC4875] does not address several issues that
arise when a P2MP-TE LSP is signaled in inter-domain networks. One
such issue is the computation of a loosely routed inter-domain P2MP-
TE LSP paths that are re-merge free. Another issue is the
reoptimization of the inter-domain P2MP-TE LSP tree vs. an individual
destination(s), since the loosely routing domain ingress border node
is not aware of the reoptimization scope. This document defines the
required protocol extensions needed for establishing and reoptimizing
P2MP MPLS and GMPLS TE LSPs in inter-domain networks.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on April 18, 2013.
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Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Summary of Solutions . . . . . . . . . . . . . . . . . . . 4
1.2. Path Computation Techniques . . . . . . . . . . . . . . . 5
1.3. Use cases . . . . . . . . . . . . . . . . . . . . . . . . 5
2. Conventions used in this document . . . . . . . . . . . . . . 6
3. Control Plane Solution For Re-merge Handling . . . . . . . . . 6
3.1. Single Border Node For All S2Ls . . . . . . . . . . . . . 6
3.2. Crankback and PathErr Signaling Procedure . . . . . . . . 6
4. Data Plane Solution For Re-merge Handling . . . . . . . . . . 8
4.1. P2MP-TE Re-merge Recording Request Flag . . . . . . . . . 8
4.2. P2MP-TE Re-merge Present Flag . . . . . . . . . . . . . . 8
4.3. Signaling Procedure . . . . . . . . . . . . . . . . . . . 9
5. Intra-domain P2MP-TE LSP Re-merge Handling . . . . . . . . . . 10
6. Reoptimization Handling . . . . . . . . . . . . . . . . . . . 11
6.1. P2MP-TE Tree Re-evaluation Request Flag . . . . . . . . . 11
6.2. Preferable P2MP-TE Tree Exists Flag . . . . . . . . . . . 11
6.3. Signaling Procedure . . . . . . . . . . . . . . . . . . . 11
7. Compatibility . . . . . . . . . . . . . . . . . . . . . . . . 13
8. Security Considerations . . . . . . . . . . . . . . . . . . . 13
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 14
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 15
11.1. Normative References . . . . . . . . . . . . . . . . . . 15
11.2. Informative References . . . . . . . . . . . . . . . . . 15
Author's Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16
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1. Introduction
[RFC4875] describes procedures to set up Point-to-Multipoint (P2MP)
Traffic Engineering Label Switched Paths (TE LSPs) for use in
MultiProtocol Label Switching (MPLS) and Generalized MPLS (GMPLS)
networks.
As with Point-to-Point (P2P) TE LSPs, P2MP TE LSP state is managed
using RSVP messages. While the use of RSVP messages is mostly similar
to their P2P counterpart, P2MP LSP state differs from P2P LSP in a
number of ways. In particular, the P2MP LSP must also handle the
"re-merge" problem described in [RFC4875] section 18.
The term "re-merge" refers to the situation when two source-to-leaf
(S2L) sub-LSPs branch at some point in the P2MP tree, and then
intersect again at a another node further downstream the tree. This
may occur due to discrepancies in the routing algorithms used by
different nodes, errors in path calculation or manual configuration,
or network topology changes during the establishment of the P2MP LSP.
Such re-merges are inefficient due to the unnecessary duplication of
data and also consume additional network resources. Consequently one
of the requirements for signaling P2MP LSPs is to choose a P2MP path
that is re-merge free. In some deployments, it may also be required
to signal P2MP-TE LSPs that are both re-merge and crossover free
[RFC4875].
For the purposes of this document, a domain is considered to be any
collection of network elements within a common sphere of address
management or path computational responsibility. Examples of such
domains include Interior Gateway Protocol (IGP) areas and Autonomous
Systems (ASes). A border node is a node between different routing
domains.
The re-merge free requirement becomes more acute to address when P2MP
LSP spans multiple domains. This is because in an inter-domain
environment, the ingress node may not have topological visibility
into other domains to be able to compute and signal a re-merge free
P2MP LSP. In that case, the border node for a new domain will be
given loose next hops for one or more destinations in a P2MP LSP. A
border node computes paths in its domain by individually expanding
the loose next hops for the destinations when signaled to it. A
border node can ensure that it computes the re-merge free paths while
performing loose hop ERO expansions by individually grafting
destinations. Note that the computed P2MP tree by a border node in
this case may not be optimal. When processing a Path message, the
border node may not have knowledge of all the destinations of the
P2MP LSP; for example, in the case when not all S2L sub-LSPs pass
through this border node. In that case, existing protocol mechanisms
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do not provide sufficient information for it to be able to expand the
loose hop(s) such that the overall P2MP LSP tree is guaranteed to be
re-merge free.
[RFC4875] specifies two approaches to handle re-merge conditions. The
first method is based on control plane handling the re-merge. In this
case the node detecting the re-merge condition, i.e. the re-merge
node initiates the removal of the re-merge sub-LSP(s) by sending a
PathErr message(s) towards the ingress node. However, this can lead
to a deadlock in setting up the P2MP LSP in certain cases; for
example, when the first S2L setup causes the re-merge with all
subsequent S2Ls in the tree. The second method is based on the data
plane handling the re-merge condition. In this case, the re-merge
node allows the re-merge condition to persist, but data from all but
one incoming interface is dropped at the re-merge node. This ensures
that duplicate data is not sent on any outgoing interface. However,
network resources (such as bandwidth capacity) are wasted as long as
re-merge condition persists which is inefficient.
[RFC4736] defines procedures and signaling extensions for
reoptimizing an inter-domain P2P LSP. Specifically, an ingress node
sends a "path re-evaluation request" to a border node by setting a
flag (0x20) in SESSION_ATTRIBUTES object in a Path message. A border
node sends a PathErr code 25 (notify error defined in [RFC3209]) with
sub-code 6 to indicate "preferable path exists" to the ingress node.
The ingress node upon receiving this PathErr may initiate
reoptimization of the LSP. [RFC4736] however does not define a
procedure to reoptimize the entire P2MP LSP as a whole tree.
As per [RFC4875] Section 14, for a P2MP LSP, an ingress node may
reoptimize the entire P2MP LSP by resignaling all destinations
(Section 14.1, "Make-before-Break") or may reoptimize individual the
destinations (Section 14.2 "Sub-Group-Based Re-Optimization").
Generally speaking make-before-break is considered available for
"whole" P2MP LSP reoptimization, but it can also be used for
reoptimizing physical routes for specific sub-LSP(s). The
Sub-Group-Based reoptimization is not always applicable because it
can lead to data duplication inside the backbone.
1.1. Summary of Solutions
This document defines RSVP-TE signaling procedures for P2MP LSP to
handle the re-merge condition when using either the control plane or
data plane approach. The procedures are applicable to both MPLS TE
and GMPLS networks.
The control plane solution for the re-merge problem makes use of the
crankback signaling mechanism of the RSVP protocol. [RFC5151]
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describes such mechanisms for applying crankback to inter-domain P2P
LSPs, but does not cover P2MP LSPs. Also, crankback mechanisms for
P2MP LSPs are not addressed by [RFC4875]. This document describes how
crankback signaling extensions for MPLS and GMPLS RSVP-TE defined in
[RFC4920] can be used for setting up P2MP TE LSPs to resolve
re-merges.
The data plane solution for the re-merge problem described in
[RFC4875] is extended by using a new flag in the LSP_ATTRIBUTES TLV
(in a Path message) and a new flag in RRO Attributes Sub-object (in a
Resv message) in RSVP. The LSP_ATTRIBUTES TLV (in a Path message) and
RRO Attributes Sub-object (in a Resv message) have been defined in
[RFC5420]. This document describes how these new flags can be used to
handle P2MP re-merge conditions efficiently.
For P2MP LSP, a border node may have loosely routed entire or part of
the P2MP LSP by expanding EROs in Path messages of the destinations.
Border node does not know with the signaling procedure defined in
[RFC4736] if an ingress node is requesting a reoptimization for an
individual destination(s) or reoptimization of the entire P2MP tree.
Signaling extension and procedure are defined in this document to
handle reoptimization of an individual destination(s) and the
reoptimization of the entire P2MP tree. Basically, a new query
message is defined in LSP_ATTRIBUTES TLV to request for a "P2MP-TE
Tree Re-evaluation" and a new sub-code is defined for PathErr message
to indicate "Preferable P2MP-TE Tree Exists".
1.2. Path Computation Techniques
This document focuses on the case where the ingress node does not
have full visibility of the topology of all domains and is therefore
not able to compute the complete P2MP tree. Rather, it includes loose
hops to traverse the domains for which it does not have full
visibility and ingress border nodes(s) of each transit domain is
responsible for expanding those loose hops.
The solution presented in this document do not guarantee optimization
of the overall P2MP tree across all domains. Path Computation Element
(PCE) can be used, instead, to address global optimization of the
overall P2MP tree.
1.3. Use cases
Service providers having a network with multiple routing domains are
interested to use the network for P2MP-TE LSPs. This allows the
service providers to use the network to carry multicast and broadcast
traffic (such as video). Service providers can deploy the VPLS and
MVPN services in the network using inter-domain P2MP TE LSPs. The use
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case is for P2MP TE LSPs across multiple routing domains that belong
to a single administrative area. Use case for the Multiple
administrative domains (e.g. autonomous systems) is outside the scope
of this document.
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].
3. Control Plane Solution For Re-merge Handling
It is RECOMMENDED that boundary re-routing is requested for P2MP LSPs
traversing multiple domains. This is because border nodes that are
expanding loose hops are typically best placed to correct any re-
merge errors that occur within their domain, not the ingress node.
3.1. Single Border Node For All S2Ls
It is RECOMMENDED that the ingress node of a P2MP LSP selects the
same ingress border node in the loose hop ERO for all sibling S2L
sub-LSPs that transit through a given domain. The reason is that it
will increase the possibility of re-merge downstream if two or more
border nodes have roles simultaneously to expand loose EROs. An
ingress border node that performs the loose ERO expansion for
individual sub-LSP(s) has the necessary state information for the
destinations transiting through its domain to ensure computed P2MP
tree is re-merge free.
3.2. Crankback and PathErr Signaling Procedure
As mentioned in [RFC4875], in order to avoid duplicate traffic, the
re-merge node MAY initiate the removal of the re-merge S2L sub-LSPs
by sending a PathErr message to the ingress node of the S2L sub-LSP.
Crankback procedures for rerouting around failures for P2P RSVP-TE
LSPs are defined in [RFC4920]. These techniques can also be applied
to P2MP LSPs to handle re-merge conditions, as described in this
section.
If an ingress border node on the path of the P2MP LSP is unable to
find a route that can supply the required resources or that is re-
merge free, it MUST generate a PathErr message for the subset of the
S2L sub-LSPs which it is not able to route. For this purpose the
ingress border node SHOULD try to find a minimum subset of S2L sub-
LSPs for which the PathErr needs to be generated towards the ingress
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node. These are the S2L sub-LSPs on an incoming interface that has
less number of S2L sub-LSPs compared to the second incoming interface
that is causing the re-merge condition.
The RSVP-TE Notify messages do not include S2L_SUB_LSP objects and
cannot be used to send errors for a subset of the S2L sub-LSPs in a
Path message. For that reason, the error generating node SHOULD use a
PathErr message rather than a Notify message to communicate the
error. In the case of a re-merge error, the node SHOULD use the error
code "Routing Problem" and the error value "ERO resulted in re-merge"
as specified in [RFC4875].
A border node receiving a PathErr message for a set of S2L sub-LSPs
MAY hold the message and attempt to signal an alternate path that can
avoid re-merge through its domain for those S2L sub-LSPs that pass
through it. However, in the case of a re-merge error for which some
of the re-merging S2L sub-LSPs do not pass through the border node,
it SHOULD propagate the PathErr upstream towards the ingress node. If
the subsequent attempt by the border node is successful, the border
node discards the held PathErr and follows the crankback roles of
[RFC4920] and [RFC5151]. If repeated subsequent attempts by the
border node are unsuccessful, the border node MUST send the held
PathErr upstream towards the ingress node.
If the ingress node receives a PathErr message with error code
"Routing Problem" and error value "ERO resulted in re-merge", then it
SHOULD attempt to signal an alternate path through a different domain
or through a different border node for the affected S2L sub-LSPs. The
ingress node MAY use the error node information from the PathErr for
this purpose.
However, it may be that the ingress node or an ingress border node
does not have sufficient topology information to compute an Explicit
Route that is guaranteed to avoid the re-merge link or node. In this
case, Route Exclusions [RFC4874] may be particularly helpful. To
achieve this, [RFC4874] allows the re-merge information to be
presented as route exclusions to force avoidance of the re-merge link
or node.
As discussed in [RFC4920] section 3.3, border node MAY keep the
history of PathErrs. In case of P2MP LSPs, ingress node and border
nodes may keep re-merge PathErrs in history table until S2L sub-LSPs
have been successfully established or until local timer expires.
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4. Data Plane Solution For Re-merge Handling
As mentioned in [RFC4875], a node may accept the re-merging S2Ls but
only send the data from one of these interfaces to its outgoing
interfaces. That is, the node MUST drop data from all but one
incoming interface causing the re-merge. This ensures that duplicate
data is not sent on any outgoing interface. Note that data plane may
be either programmed to drop the incoming traffic for the S2L sub-LSP
or not programmed at all.
It is desirable to avoid the persistent re-merge condition associated
with data plane based solution in the network in order to optimize
bandwidth resources in the network.
The following sections define the RSVP-TE signaling extensions for
"P2MP- TE Re-merge Recording Request" and "P2MP-TE Re-merge Present"
messages.
4.1. P2MP-TE Re-merge Recording Request Flag
In order to indicate to traversed nodes that P2MP-TE re-merge
recording is desired, a new flag in the Attribute Flags TLV of the
LSP_ATTRIBUTES object defined in [RFC5420] is defined as follows:
Bit Number (to be assigned by IANA): P2MP-TE Re-merge Recording
Request flag
The "P2MP-TE Re-merge Recording Request" flag is meaningful in a Path
message and is inserted by the ingress node or a border node in the
LSP_ATTRIBUTES object.
If the "P2MP-TE Re-merge Recording Request" Flag is set, it implies
that the "P2MP-TE Re-merge Present" flag defined in the next section
MUST be used to indicate to the ingress and ingress border nodes of
the transit domains that a re-merge condition is present for this S2L
sub-LSP but accepted, and that incoming traffic is being dropped for
this S2L sub-LSP.
The rules of the processing of the Attribute Flags TLV of the
LSP_ATTRIBUTES object follow [RFC5420].
4.2. P2MP-TE Re-merge Present Flag
The "P2MP-TE Re-merge Present" Flag is the counter part of the
"P2MP-TE Re-merge Recording Request" flag defined above.
Specifically, RSVP signaling extension is defined to indicate to the
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upstream node of the re-merge condition and that incoming traffic is
being dropped for the given S2L.
When a node accepts a re-merge condition by dropping traffic from an
incoming interface for an S2L due to the re-merge condition, and if
it understands the "P2MP-TE Re-merge Recording Request" in the
Attribute Flags TLV of the LSP_ATTRIBUTES object of the Path message,
the node MUST set the newly defined "P2MP-TE Re-merge Present" flag
in the RRO Attributes sub-object defined in [RFC5420] in RRO.
The following new flag for RRO Attributes Sub-object is defined as
follows:
Bit Number (same as bit number assigned for "P2MP-TE Re-merge
Recording Request" flag): P2MP-TE Re-merge Present flag
The "P2MP-TE Re-merge Present" flag indicates that the S2L is causing
a re-merge. The re-merge has been accepted but the incoming traffic
on this S2L is dropped by the reporting node.
The rules of the processing of the RRO Attribute Sub-object in the
Resv message follow [RFC5420].
4.3. Signaling Procedure
When a node that does not support data plane based re-merge handling
receives an S2L sub-LSP Path message with LSP Attributes sub-object
that has "P2MP-TE Re-merge Recording Request" Flag set, and if the
S2L is causing a re-merge condition, the node MUST reject the S2L
sub-LSP Path message and send the PathErr with the error code
"Routing Problem" and the error value "ERO resulted in re-merge" as
specified in [RFC4875]. If a node is capable of data plane based re-
merge handling but operator may have disabled it via a configuration,
the the node MUST also reject the re-merge and send this PathErr.
When a Path message is received at a transit node for an S2L sub-LSP
and "P2MP-TE Re-merge Recording Request" Flag is set in the LSP
Attributes sub-object, the node MAY decide to accept the re-merge S2L
sub-LSP based on the local policy and node capability. In this case,
before the Resv message is sent to the upstream node for this S2L
sub-LSP, the node MUST add the RRO Attributes sub-object in the Resv
RRO if not already present and set the "P2MP-TE Re-merge Present"
Flag if traffic from the incoming interface of this S2L sub-LSP will
be dropped. This same incoming interface can still be used for a
different S2L sub-LSP in the P2MP LSP to forward traffic and "P2MP-TE
Re-merge Present" flag will not be set for that S2L sub-LSP. Note
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that rules for adding or modifying the other RRO sub-objects do not
change due to this flag.
When a transit node receives a Resv message for an S2L that is
causing a re-merge condition, the node MUST set the "P2MP-TE Re-merge
Present" flag in the RRO Attributes sub-object in the Resv message if
it decides to drop the incoming traffic of this S2L. The "P2MP-TE Re-
merge Present" flag in RRO Attribute sub-object is not set for the
S2L(s) whose incoming interface is selected to receive and forward
the traffic.
An ingress node MAY immediately start sending traffic on all S2Ls in
up state even when re-merge conditions are present on some S2Ls of
the P2MP LSP.
The proposed signaling extensions allow an ingress node and an
ingress border node to have a complete view of the re-merge
conditions on the entire S2L path and on all S2Ls of the P2MP tree.
The ingress or ingress border node in this case can take appropriate
actions to resolve the re-merge conditions and optimize network
bandwidth resources usage. This can be achieved by computing and
selecting alternate path(s) for the S2L(s) bypassing the re-merge
node(s).
The proposed signaling extensions are equally applicable to single
domain scenarios.
A node where re-merge is present, may decide to select a different
incoming interface to forward traffic from in the future. In that
case, a Resv change message with updated "P2MP-TE Re-merge Present"
flag in the RRO is sent upstream for all effected S2Ls. For the new
set of S2L sub-LSPs whose traffic from the incoming interface is
dropped, "P2MP-TE Re-merge Present" flag will bet set.
A border node due to local policy MAY remove the record route object
from the Resv message of the S2L sub-LSP and propagate Resv message
towards the ingress node. When such a policy is provisioned, the
border node may attempt to correct the re-merge condition in its
domain. If the border node is not able to resolve the re-merge
condition, the border node SHOULD send the PathErr with the error
code "Routing Problem" and the error value "ERO resulted in re-merge"
as specified in [RFC4875].
5. Intra-domain P2MP-TE LSP Re-merge Handling
Re-merges between S2Ls in a single domain can occur due to
provisioning errors or path computation errors in the environment
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where IGP-TE or PCE is used. Re-merges can also happen in the
environment where static routing or static path selection policy is
applied at ingress (e.g., CSPF calculation is disabled due to some
operational reasons), regardless of using loose or static hops. In
either case, procedures described in this document are equally
applicable to the intra-domain (i.e. single domain) P2MP-TE LSPs.
6. Reoptimization Handling
6.1. P2MP-TE Tree Re-evaluation Request Flag
In order to query border nodes to check if a preferable P2MP tree
exists, a new flag is defined in Attributes Flags TLV of the
LSP_ATTRIBUTES object [RFC5420] as follows:
Bit Number (to be assigned by IANA): P2MP-TE Tree Re-evaluation
Request flag
The "P2MP-TE Tree Re-evaluation Request" flag is meaningful in a Path
message of an S2L sub-LSP and is inserted by the ingress node.
6.2. Preferable P2MP-TE Tree Exists Flag
In order to indicate to an ingress node that a preferable P2MP-TE
tree is available, following new sub-code for PathErr code 25 (notify
error) is defined:
Sub-code (to be assigned by IANA): Preferable P2MP-TE Tree Exists
flag
When a preferable P2MP-TE tree is found, the border node MUST send
"Preferable P2MP-TE Tree Exists" to the ingress node in order to
reoptimize the entire P2MP LSP.
6.3. Signaling Procedure
Using signaling procedure defined in [RFC4736], an ingress node MUST
initiate "path re-evaluation request" query to reoptimize a
destination in a P2MP LSP. Note that this message MUST be used to
reoptimize a single or a sub-set of the destinations in a P2MP LSP.
Ingress node MUST send this query in a Path message for each
destination it is reoptimizing.
When a Path message for a destination in a P2MP LSP with "path
re-evaluation request" flag [RFC4736] is received at the border node,
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it MUST re-compute the loose-hop ERO to see if a preferable path
exists for that destination. A border node MUST send PathErr code 25
(notify error defined in [RFC3209]) with "preferable path exists"
sub-code to indicate that a preferable path exists for the requested
destination AND border node is capable of per destination
reoptimization. A border node MUST terminate the path query.
Alternatively, a border node not capable of per destination
reoptimization MAY respond with "Preferable P2MP-TE Tree Exists"
PathErr by checking for a preferable P2MP tree instead of a
preferable single destination.
It is often desired to reoptimize the entire P2MP LSP. In order to
query border nodes to check if a preferable P2MP tree exists, an
ingress node MUST send a Path message with "P2MP-TE Tree
Re-evaluation Request" defined in this document. An ingress node MAY
send this message for all destinations in a P2MP LSP or a sub-set of
the destinations.
A border node receiving the "P2MP-TE Tree Re-evaluation Request" MUST
check for a preferable P2MP LSP for the destinations it is loosely
routing by loose-hop ERO expansions. The border node if a preferable
P2MP-TE tree is found, MUST reply with "Preferable P2MP-TE Tree
Exists" sub-code defined in this document with PathErr 25 (notify
error defined in [RFC3209] and terminate the path query.
Note that a border node MAY send "Preferable P2MP-TE Tree Exists"
with PathErr code 25 to indicate the ingress node in order to
reoptimize the entire P2MP LSP message unsolicited or in a response
to "path re-evaluation query" for a destination or in a response to
"P2MP-TE Tree Re-evaluation Request" message.
If an ingress node initiated a "path re-evaluation request" query for
a single destination for per S2L sub-LSP reoptimization and receives
"Preferable P2MP-TE Tree Exists" PathErr, the ingress node MAY cancel
the per S2L reoptimization and initiate P2MP-TE tree reoptimization.
This may happen in case when a border node is not capable of per
destination reoptimization.
Note that even if per destination reoptimization, not whole P2MP LSP
Tree reoptimization, is sufficient, ingress node often needs to re-
signal whole P2MP LSP tree to complete route optimization for that
destination. In this case, make-before-break reoptimization scheme is
used (see [RFC4875] Section 14.1), and all S2L sub-LSPs are re-
signaled with a different LSP-ID. That is, the procedure of signaling
a re-optimization by an ingress node is separate from the matter if
PathErr reply was "Preferable Path Exists" or "Preferable P2MP-TE
Tree Exists".
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7. Compatibility
The LSP_ATTRIBUTES TLV and RRO Attributes sub-object have been
defined [RFC5420] with class numbers in the form 11bbbbbb, which
ensures compatibility with non- supporting nodes. Per [RFC2205],
nodes not supporting this extension will ignore the TLV, sub-object
and the new flags defined in this document but forward it, unexamined
and unmodified, in all messages resulting from this message.
8. Security Considerations
This document does not introduce any additional security issues above
those identified in [RFC3209], [RFC4875], [RFC5151], [RFC4920] and
[RFC5920].
9. IANA Considerations
The following new flag is defined for the Attributes Flags TLV in the
LSP_ATTRIBUTES object [RFC5420]. The numeric values are to be
assigned by IANA.
o P2MP-TE Re-merge Recording Request Flag:
- Bit Number: To be assigned by IANA.
- Attribute flag carried in Path message: Yes
- Attribute flag carried in Resv message: No
The following new flag is defined for the RRO Attributes sub-object
in the RECORD_ROUTE object [RFC5420]. The numeric values are to be
assigned by IANA.
o P2MP-TE Re-merge Present Flag:
- Bit Number: To be assigned by IANA.
- Attribute flag carried in Path message: No
- Attribute flag carried in RRO Attributes sub-object in RRO of
the Resv message: Yes
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The following new flag is defined for the Attributes Flags TLV in the
LSP_ATTRIBUTES object [RFC5420]. The numeric values are to be
assigned by IANA.
o P2MP-TE Tree Re-evaluation Request Flag:
- Bit Number: To be assigned by IANA.
- Attribute flag carried in Path message: Yes
- Attribute flag carried in Resv message: No
As defined in [RFC3209], the Error Code 25 in the ERROR SPEC object
corresponds to a Notify Error PathErr. This document adds a new sub-
code as follows for this PathErr:
o Preferable P2MP-TE Tree Exists sub-code:
- Sub-code for Notify PathErr code 25. To be assigned by
IANA.
10. Acknowledgments
The authors would like to thank N. Neate for his contributions on the
draft.
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11. References
11.1. Normative References
[RFC4875] Aggarwal, R., Papadimitriou, D., and S. Yasukawa,
"Extensions to Resource Reservation Protocol Traffic
Engineering (RSVP-TE) for Point-to-Multipoint TE Label
Switched Paths (LSPs)", RFC 4875, May 2007.
[RFC5151] Farrel, A., Ayyangar, A., and JP. Vasseur, "Inter-Domain
MPLS and GMPLS Traffic Engineering -- Resource Reservation
Protocol-Traffic Engineering (RSVP-TE) Extensions", RFC
5151, February 2008.
[RFC4920] Farrel, A., Satyanarayana, A., Iwata, A., Fujita, N., and
G. Ash, "Crankback Signaling Extensions for MPLS and GMPLS
RSVP-TE", RFC 4920, July 2007.
[RFC5920] L. Fang, Ed., "Security Framework for MPLS and GMPLS
Networks", RFC 5920, July 2010.
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
Tunnels", RFC 3209, December 2001.
[RFC4736] Vasseur, JP., Ikejiri, Y. and Zhang, R, "Reoptimization of
Multiprotocol Label Switching (MPLS) Traffic Engineering
(TE) Loosely Routed Label Switched Path (LSP)", RFC 4736,
November 2006.
[RFC5420] Farrel, A., Papadimitriou, D., Vasseur, JP., and A.
Ayyangarps, "Encoding of Attributes for MPLS LSP
Establishment Using Resource Reservation Protocol Traffic
Engineering (RSVP-TE)", RFC 5420, February 2009.
11.2. Informative References
[RFC4726] Farrel, A., Vasseur, J., and A. Ayyangar, "A Framework for
Inter-Domain Multiprotocol Label Switching Traffic
Engineering", RFC 4726, November 2006.
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Author's Addresses
Zafar Ali
Cisco Systems
Email: zali@cisco.com
Rakesh Gandhi
Cisco Systems
Email: rgandhi@cisco.com
Tarek Saad
Cisco Systems
Email: tsaad@cisco.com
Robert H. Venator
Defense Information Systems Agency
Email: robert.h.venator.civ@mail.mil
Yuji Kamite
NTT Communications Corporation
Email: y.kamite@ntt.com
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