RSVP Setup Protection
draft-shen-mpls-rsvp-setup-protection-00
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| Authors | Yimin Shen , Yuji Kamite | ||
| Last updated | 2012-03-05 | ||
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draft-shen-mpls-rsvp-setup-protection-00
Internet Engineering Task Force Y. Shen
Internet-Draft Juniper Networks
Intended status: Standards Track Y. Kamite
Expires: September 6, 2012 NTT Communications Corporation
March 5, 2012
RSVP Setup Protection
draft-shen-mpls-rsvp-setup-protection-00
Abstract
RFC 4090 specifies an RSVP facility-backup fast reroute mechanism
that can protect LSPs against link and node failures. This document
extends the mechanism to provide "setup protection" for LSPs during
initial Path message signaling time. In particular, it enables a
router to reroute an LSP via a bypass LSP, when there is a link or
node failure along the desired path.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on September 6, 2012.
Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
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to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
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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
2. Specification of Requirements . . . . . . . . . . . . . . . . 4
3. Theory of Operation . . . . . . . . . . . . . . . . . . . . . 4
3.1. New RSVP Attributes TLVs . . . . . . . . . . . . . . . . . 5
3.1.1. Protected LSP Sender IPv4 Address TLV . . . . . . . . 5
3.1.2. Protected LSP Sender IPv6 Address TLV . . . . . . . . 6
3.2. PLR behavior . . . . . . . . . . . . . . . . . . . . . . . 6
3.3. MP behavior . . . . . . . . . . . . . . . . . . . . . . . 8
3.4. Local Revertive Mode . . . . . . . . . . . . . . . . . . . 9
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
5. Security Considerations . . . . . . . . . . . . . . . . . . . 9
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 9
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9
7.1. Normative References . . . . . . . . . . . . . . . . . . . 9
7.2. Informative References . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10
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1. Introduction
In RSVP facility-backup fast reroute (FRR) [RFC 4090], the router at
a point of local repair (PLR) of an LSP can redirect traffic onto a
bypass LSP upon a failure of the immediate downstream link or node.
The establishment of such protection is normally triggered by
receiving a Resv message. In link protection, the PLR must learn the
label and address of the nexthop router, before it can set up or
select a bypass LSP to protect the LSP. Likewise, in node
protection, the PLR must learn the label and address of the next-
nexthop router. The information is carried in Resv message.
Imagine a scenario where an LSP is being signaled, but its Path
message carries an EXPLICIT_ROUTE object (ERO) that is pre-computed,
statically configured, or computed based on a topology that may not
reflect the current state of every link or node of the network. If a
link or node on this path has already failed, the signaling will halt
at the router immediate upstream of the failure. This will still be
the case even if there is an existing bypass LSP protecting the link
or node for some other P2P or P2MP LSP. In other words, the LSP is
not protected during initial Path message signaling time.
In this situation, the network would rely on IGP to flood the up-to-
date traffic engineering (TE) information, and the router immediate
upstream of the failure to originate a PathErr message, so that the
ingress router of the LSP can compute and signal a new path to avoid
the failed link or node. However, this approach may not always be
possible or desirable, as can be seen in the scenarios described
below.
1. Pre-computed or explicitly defined paths. If the path is pre-
computed or fixed, or the ingress router is incapable of re-
computing the path, an alternative path will not be set up.
2. Requirements for LSP setup time. Control protocol convergence
and path computation may introduce a significant delay, which may
impact signaling performance for services that have a specific
requirement for LSP setup time.
3. Sibling sub-LSPs of a P2MP LSP sharing the failed link. In this
case, the existing bypass LSP will not be used, even if it is the
preferred alternative path. For example, the LSP being signaled
is a sub-LSP of a P2MP LSP, and it is expected to share the same
downstream link with an existing sibling sub-LSP (sub-LSP of the
same P2MP LSP). If the new sub-LSP is rerouted through another
path, unnecessary traffic will be generated on the network.
This document extends the RSVP facility-backup fast reroute mechanism
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to provide so-called "setup protection" for LSPs. During the initial
Path message signaling of an LSP, if there is a link or node failure
on the desired path, and there is a bypass LSP protecting the link or
node, the LSP will be signaled through the bypass LSP. The LSP will
be established as if it was originally set up along its primary path
and then failed over to the bypass LSP after the link or node
failure. When the link or node is restored, the LSP MAY be reverted
to the primary path. The mechanism supports both P2P and P2MP LSPs.
2. Specification of Requirements
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 RFC 2119.
3. Theory of Operation
When an LSP is being signaled by RSVP, a Path message is sent hop by
hop from the ingress router to the egress router, following the path
defined by an ERO. The setup protection mechanism in this document
allows an ingress or transit router to reroute the LSP via a bypass
LSP, if the router detects a failure of the immediate downstream link
or node represented by the next hop in the ERO (i.e. next ERO hop).
This router is referred to as a PLR.
The mechanism is relevant when the Path message carries the "local
protection desired" flag, and optionally the "node protection
desired" and "bandwidth protection desired" flags in the
SESSION_ATTRIBUTE object.
On a given PLR, the mechanism is only applicable when the next ERO
hop is a strict hop, and in case of node protection, the next-next
ERO hop is also a strict hop. A strict next ERO hop allows the PLR
to unambiguously decide the intended downstream link or node, and
hence reliably detect its status. For link protection, the strict
nexthop also indicates the merge point (MP), i.e. the egress router
of the bypass LSP to be used for rerouting the LSP. For node
protection, the strict next-next ERO hop indicates the MP.
During setup protection operation, the PLR signals a backup LSP by
tunneling a Path message through the bypass LSP. Unlike the normal
facility-backup FRR, this Path message carries additional information
of the protected LSP (Section 3.1). When the MP receives the Path
message, it terminates the backup LSP, and also re-creates the
protected LSP. If the MP is a transit router of the protected LSP,
it signals the LSP further downstream.
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Eventually, the LSP is established end to end, with the backup LSP
being tunneled through the bypass LSP from the PLR to the MP. The
RSVP states on the PLR and the MP and the RSVP messages generated by
these routers are the same as those in a normal facility-backup FRR
scenario.
After the failed link or node is restored, the PLR MAY revert the LSP
to the primary path. This is referred to as local revertive mode, as
described in [RFC 4090].
The setup protection mode MAY be enabled and disabled on a router
based on configuration. For an LSP to be setup-protected, the mode
MUST be enabled on both PLR and MP. If it is enabled on a PLR but
disabled on an MP, the MP SHOULD reject the Path message of the
backup LSP and send a PathErr message, as described Section 3.3.
3.1. New RSVP Attributes TLVs
This document defines two new RSVP Attributes TLVs [RFC 5420]. They
are used by a PLR to convey to an MP the original sender address of a
protected LSP.
o Protected LSP Sender IPv4 Address TLV
o Protected LSP Sender IPv6 Address TLV
Both TLVs are carried by the LSP_REQUIRED_ATTRIBUTES object in the
Path message of a backup LSP.
3.1.1. Protected LSP Sender IPv4 Address TLV
The Protected LSP Sender IPv4 Address TLV is defined with type 2. It
is allowed on LSP_REQUIRED_ATTRIBUTES object, and not allowed on
LSP_ATTRIBUTES object. It is encoded as the following.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type (TBD) | Length (8) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1
Type
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TBD
Length
8
Value
Original sender address in the IPv4 SENDER_TEMPLATE object of the
protected LSP.
3.1.2. Protected LSP Sender IPv6 Address TLV
The Protected LSP Sender IPv6 Address TLV is defined with type 3. It
is allowed on LSP_REQUIRED_ATTRIBUTES object, and not allowed on
LSP_ATTRIBUTES object. It is encoded as the following.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type (TBD) | Length (20) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// Value //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2
Type
TBD
Length
20
Value
Original sender address in the IPv6 SENDER_TEMPLATE object of the
protected LSP.
3.2. PLR behavior
When a router has a Path message to send out and the next ERO hop is
a strict IPv4 or IPv6 prefix, the router validates the hop against
the routing table, traffic engineering (TE) database, and/or a
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topology database. If the hop is reachable and one hop away from the
router, the Path message is sent as it is. Otherwise, there is a
possibility that the hop has experienced a link or node failure.
The router determines this by searching for an existing bypass LSP
that is protecting the hop. If the LSP being signaled desires link
protection, the egress router of the bypass LSP (i.e. MP) must be
the router that owns the IP prefix of the hop. If the LSP desires
node protection, the next-next ERO hop of the LSP must also be a
strict IP prefix, and the MP must be the router that owns this IP
prefix.
If a bypass LSP is not found, the router MUST originate a PathErr
with code = 24 (routing problem) and sub-code = 2 (bad strict node).
If a bypass LSP is found, the router MUST act as a PLR of setup
protection, and reroute the LSP via the bypass LSP. If multiple such
bypass LSPs exist, the PLR MAY select one based on bandwidth
constraints or policy. If the protected LSP is a sub-LSP of a P2MP
LSP, a bypass LSP that is protecting an existing sibling sub-LSP MUST
be preferred. This helps against generating duplicate traffic on two
separate bypass LSPs.
The PLR SHOULD NOT send the Path message of the protected LSP.
Instead, it MUST create a backup LSP, and send a Path message for the
backup LSP via the bypass LSP. The Path message is constructed by
using the sender template specific method [RFC 4090]. In particular,
it has the sender address in SENDER_TEMPLATE object set to an address
of the PLR. It MUST also carried a LSP_REQUIRED_ATTRIBUTES object
containing a Protected LSP Sender IPv4 Address TLV or Protected LSP
Sender IPv6 Address TLV.
Upon receiving a Resv message from the MP, the PLR brings up both of
the backup LSP and the protected LSP. If the PLR is the ingress
router of the protected LSP, the LSP has been set up successfully.
If the PLR is a transit router, it MUST send a Resv message upstream,
with the "local protection available", "local protection in use", and
optionally "node protection" and "bandwidth protection" flags set to
1 in the RRO hop corresponding to the PLR [RFC 4090]. The PLR MUST
originate a PathErr message with code = 25 (notify error) and sub-
code = 3 (tunnel locally repaired).
The PLR also installs a forwarding entry for the LSP. The nexthop of
this entry MAY indicate zero, one or two outgoing labels, depending
on whether any of the backup LSP's label and the bypass LSP's label
is Implicit NULL. In the case of two labels, the inner label is the
backup LSP's label, and the outer label is the bypass LSP's label.
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If the PLR receives a PathErr message when signaling the backup LSP,
the PLR MUST NOT bring up the backup LSP or the protected LSP. If
the PLR is a transit router of the protected LSP, it MUST propagate
the PathErr message upstream. Likewise, if the PLR receives a
PathErr message after the backup LSP and the primary LSP have been
set up, and the PLR is a transit router of the protected LSP, it MUST
also propagate the PathErr message upstream.
When the PLR receives a ResvTear message of the backup LSP, the PLR
MUST bring down both the backup LSP and the protected LSP. If the
PLR is a transit router of the protected LSP, it MUST send a ResvTear
message upstream.
In any case where the PLR tears down the protected LSP due to receipt
of a PathTear message, state time-out, configuration, etc, the PLR
MUST also tear down the backup LSP by sending a PathTear message
through the bypass LSP.
3.3. MP behavior
When a MP receives the Path message of a backup LSP, it detects the
setup protection condition based on the presence of Protected LSP
Sender IPv4 Address TLV or Protected LSP Sender IPv6 Address TLV in
LSP_REQUIRED_ATTRIBUTES object.
If the setup protection mode is disabled on the router, it MUST
reject the Path message. In this case, the router recognizes the
TLV, but does not support it. Therefore, it MUST originate a PathErr
with code = 2 (policy control failure).
The MP then terminates the backup LSP, and re-creates the protected
LSP. If the MP is the egress router of the LSP, it MUST also
terminate the protected LSP. Otherwise, it MUST send a Path message
of the protected LSP downstream. The Path message has the sender
address in SENDER_TEMPLATE object set to the original address of the
ingress router, based on the above received TLV. The Path message
MUST NOT carry a Protected LSP Sender IPv4 Address TLV or Protected
LSP Sender IPv6 Address TLV.
The MP MUST allocate a label for the LSP, and distribute it to the
PLR via the Resv message of the backup LSP. If the protected LSP is
a sub-LSP of a P2MP LSP, the MP MAY allocate the same label as an
existing sibling sub-LSP, in order to avoid traffic duplication.
When the MP receives a PathTear message of the backup LSP, it MUST
tear down both the backup LSP and the protected LSP. If the MP is a
transit router of the protected LSP, it MUST send a PathTear message
downstream.
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In any case where the MP receives or originates a PathErr or ResvTear
message of the protected LSP, it SHOULD translate it into a message
of the backup LSP and send it to the PLR.
3.4. Local Revertive Mode
When the failed link or node is restored, the PLR MAY revert the
protected LSP to its primary path, following the procedure of local
revertive mode described in [RFC 4090].
4. IANA Considerations
This document defines two new RSVP Attributes TLVs. New type values
need to assigned to them by IANA.
Protected LSP Sender IPv4 Address TLV
Protected LSP Sender IPv6 Address TLV
5. Security Considerations
The security considerations discussed in RFC 3209, RFC 4090 and RFC
4875 apply to this document.
6. Acknowledgements
Thanks to Rahul Aggarwal, Disha Chopra, and Nischal Sheth for their
contribution.
7. References
7.1. Normative References
[RFC2205] Braden, B., Zhang, L., Berson, S., Herzog, S., and S.
Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1
Functional Specification", RFC 2205, September 1997.
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
Tunnels", RFC 3209, December 2001.
[RFC4090] Pan, P., Swallow, G., and A. Atlas, "Fast Reroute
Extensions to RSVP-TE for LSP Tunnels", RFC 4090,
May 2005.
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[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.
[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.
[RFC3471] Berger, L., "Generalized Multi-Protocol Label Switching
(GMPLS) Signaling Functional Description", RFC 3471,
January 2003.
[RFC3472] Ashwood-Smith, P. and L. Berger, "Generalized Multi-
Protocol Label Switching (GMPLS) Signaling Constraint-
based Routed Label Distribution Protocol (CR-LDP)
Extensions", RFC 3472, January 2003.
[RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
Label Switching Architecture", RFC 3031, January 2001.
7.2. Informative References
[RFC5920] Fang, L., "Security Framework for MPLS and GMPLS
Networks", RFC 5920, July 2010.
Authors' Addresses
Yimin Shen
Juniper Networks
10 Technology Park Drive
Westford, MA 01886
USA
Phone: +1 9785890722
Email: yshen@juniper.net
Yuji Kamite
NTT Communications Corporation
Granpark Tower 3-4-1 Shibaura, Minato-ku
Tokyo 108-8118
Japan
Email: y.kamite@ntt.com
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