RSVP Setup Protection
draft-shen-mpls-rsvp-setup-protection-02
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| Last updated | 2013-02-08 | ||
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draft-shen-mpls-rsvp-setup-protection-02
Internet Engineering Task Force Y. Shen
Internet-Draft Juniper Networks
Intended status: Standards Track Y. Kamite
Expires: August 12, 2013 NTT Communications Corporation
February 8, 2013
RSVP Setup Protection
draft-shen-mpls-rsvp-setup-protection-02
Abstract
RFC 4090 specifies an RSVP facility-backup fast reroute mechanism for
protecting established LSPs against link and node failures. This
document extends the mechanism to provide so-called "setup
protection" for LSPs during their initial Path message signaling
time. In particular, it enables a router to reroute an LSP via an
existing bypass LSP, when there is a failure of the immediate
downstream link or node along the desired path. Therefore, it can be
used to reduce LSP setup time in such a situation, or allow LSPs with
strict paths to be established successfully when alternative paths
are unavailable in the network or unable to be computed by ingress.
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
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and may be updated, replaced, or obsoleted by other documents at any
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on August 12, 2013.
Copyright Notice
Copyright (c) 2013 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
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publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Specification of Requirements . . . . . . . . . . . . . . . . 4
3. Theory of Operation . . . . . . . . . . . . . . . . . . . . . 4
3.1. New RSVP Attribute Flag . . . . . . . . . . . . . . . . . 5
3.2. New RSVP Attributes TLVs . . . . . . . . . . . . . . . . . 5
3.2.1. Protected LSP Sender IPv4 Address TLV . . . . . . . . 6
3.2.2. Protected LSP Sender IPv6 Address TLV . . . . . . . . 6
3.3. PLR behavior . . . . . . . . . . . . . . . . . . . . . . . 7
3.4. MP behavior . . . . . . . . . . . . . . . . . . . . . . . 9
3.5. Local Revertive Mode . . . . . . . . . . . . . . . . . . . 10
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
5. Security Considerations . . . . . . . . . . . . . . . . . . . 10
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
7.1. Normative References . . . . . . . . . . . . . . . . . . . 10
7.2. Informative References . . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11
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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 via a
bypass LSP upon a failure of the immediate downstream link or node.
Such protection is normally established after the LPS has been set
up. This is because the PLR must know the label and address of the
next-hop router (in the case of link protection) or those of the
next-next-hop router (in the case of node protection), before it can
select or signal a bypass LSP to protect the LSP. The information of
the label and the address is carried in a Resv message.
Imagine a scenario where a new LSP is being signaled, but its Path
message carries an EXPLICIT_ROUTE object (ERO) with a strict path
that is statically configured or computed offline based on a topology
that assumes no failure in the network. In such a case, if a link or
node along the path happens to be in a failure condition, RSVP
signaling will stop at the router upstream adjacent to the failure.
This will be the case even if there is an existing bypass LSP
protecting the link or node for some existing LSPs. In other words,
this new LSP is not protected during this setup phase, i.e. the
initial Path message signaling time.
In this situation, the network would normally rely on IGP to update
traffic engineering (TE) information throughout the network, and the
router upstream adjacent to the failure to send a PathErr message to
trigger the ingress router to compute and signal a new path.
However, this approach may not always be possible, desirable, or even
relevant in the following scenarios:
1. Static strict path. As described above, if the ERO carries an
explicit path with a sequence of strict hops that are statically
configured or computed offline based on a topology assuming no
network failure, the LSP will never be established.
2. LSPs with a strict requirement for setup time. IGP TE
information flooding, PathErr message propagation, and path re-
computation and re-signaling may introduce a significant delay to
LSP establishment. This may impact on the setup time of services
that have a strict requirement for it, such as on-demand
transport services for real-time data.
3. Sibling P2MP sub-LSPs sharing a common link. In this case, the
new LSP is a sub-LSP of a P2MP LSP, and its desired path is
supposed to share the failed link with an existing sibling sub-
LSP, i.e. another sub-LSP of the same P2MP LSP, which is being
protected by a bypass LSP. If the new sub-LSP is rerouted via a
different path, it will not be able to share the data flow over
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the bypass LSP with that sibling sub-LSP, creating unnecessary
traffic flow in the network.
This document extends the RSVP facility-backup fast reroute mechanism
to provide so-called "setup protection". During the initial Path
message signaling of an LSP, if there is a link or node failure along
the desired path, and if 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 the desired path
(aka. primary path) and then failed over to the bypass LSP after the
failure. After the failure is resolved, the LSP MAY be reverted to
the primary path. The mechanism is applicable to 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
enables 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, called "next ERO
hop". In this case, the current router is referred to as a PLR.
The mechanism is relevant when the Path message carries the "local
protection desired" flag in the SESSION_ATTRIBUTE object [RFC 4090]
and a new "setup protection desired" flag defined in this document
(Section 3.1).
On a PLR, the mechanism is only applicable when the next ERO hop is a
strict hop, and in the 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 along the
desired path, and hence reliably detect its status. In link
protection, the strict next ERO hop also indicates the merge point
(MP), i.e. the destination of the bypass LSP to be used to reroute
the LSP. In node protection, the strict next-next ERO hop indicates
the MP.
When performing setup protection, the PLR signals a backup LSP by
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tunneling Path message through the bypass LSP. Like the Path message
of a backup LSP in the normal facility-backup FRR ([RFC 4090]), this
Path message carries an address of the PLR as the sender address in
SENDER_TEMPLATE object. In addition, the Path message also carries
the information of the protected LSP (Section 3.2). When the MP
receives the Path message, it terminates the backup LSP, and re-
creates the protected LSP. If the MP is the egress router of the
protected LSP, it terminates the protected LSP as well. If the MP is
a transit router of the protected LSP, it signals the LSP further
downstream.
Eventually, the LSP will be established end to end, with the backup
LSP tunneled through the bypass LSP from the PLR to the MP. The RSVP
state on the PLR and the MP and the RSVP messages generated by these
routers are no different than those in a post-failure situation of a
normal facility-backup FRR.
Later, when the failure is resolved, the PLR MAY revert the LSP to
the primary path, in the same manner as the local revertive mode
specified in [RFC 4090].
The setup protection 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 the PLR but disabled
on the MP, the MP SHOULD reject the Path message of the backup LSP
and send a PathErr message, as described Section 3.4.
3.1. New RSVP Attribute Flag
In order for an LSP to explicit request for setup protection, this
document defines a new "setup protection desired" flag in the
Attribute Flags TLV of the LSP_ATTRIBUTES object [RFC5420]. It is
carried in the Path message of the LSP, i.e. the protected LSP.
3.2. 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 in
the SENDER_TEMPLATE object of a protected LSP. Both TLVs are carried
in the LSP_REQUIRED_ATTRIBUTES object in the Path message of a backup
LSP.
o Protected LSP Sender IPv4 Address TLV
o Protected LSP Sender IPv6 Address TLV
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3.2.1. Protected LSP Sender IPv4 Address TLV
The Protected LSP Sender IPv4 Address TLV is defined with type TBD.
It is allowed on LSP_REQUIRED_ATTRIBUTES object, and not allowed on
LSP_ATTRIBUTES object. The encoding is as below.
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
TBD
Length
8
Value
Original sender address in the IPv4 SENDER_TEMPLATE object of the
protected LSP.
3.2.2. Protected LSP Sender IPv6 Address TLV
The Protected LSP Sender IPv6 Address TLV is defined with type TBD.
It is allowed on LSP_REQUIRED_ATTRIBUTES object, and not allowed on
LSP_ATTRIBUTES object. The encoding is as below.
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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.
3.3. PLR behavior
When a router has a Path message to send out, if the Path message
carries the "local protection desired" flag in the SESSION_ATTRIBUTE
object and the "setup protection desired" flag in the LSP_ATTRIBUTES
object, and if the next ERO hop is a strict IPv4 or IPv6 prefix, the
router SHOULD validate the reachability of the prefix against routing
tables, traffic engineering (TE) database, and/or any database that
reflects the current status of the network topology. If the prefix
is reachable and is one hop away from the current router, the router
should send out the Path message as it is. Otherwise, there is a
possibility that the link or node associated by the prefix has
experienced a failure.
The router SHOULD determine this by searching for an existing bypass
LSP that is protecting the prefix. If the protected LSP desires link
protection, the destination of the bypass LSP (i.e. MP) is
considered as the router that owns the prefix. If the LSP desires
node protection with the "node protection desired" flag set in the
SESSION_ATTRIBUTE object and the next-next ERO hop of the LSP is also
a strict prefix, the MP is considered as the router that owns this
prefix.
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If a bypass LSP is not found by the above criteria, 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 for setup
protection, and reroute the protected LSP via the bypass LSP. If
multiple satisfactory bypass LSPs exist, the PLR MAY select one based
on bandwidth constraints or local policies. Specifically, 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, in order to
minimize traffic duplication in the network.
The PLR SHOULD NOT send the Path message of the protected LSP any
further. Instead, it MUST create a backup LSP, and send a Path
message of the backup LSP to the MP 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 the
SENDER_TEMPLATE object set to an address of the PLR. It MUST also
carry an LSP_REQUIRED_ATTRIBUTES object with a Protected LSP Sender
IPv4 Address TLV or Protected LSP Sender IPv6 Address TLV.
Upon receiving a Resv message of the backup LSP from the MP, the PLR
SHOULD 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 for the protected LSP, 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 SHOULD
originate a PathErr message with code = 25 (notify error) and sub-
code = 3 (tunnel locally repaired).
The PLR SHOULD also install a forwarding entry for the protected LSP.
In the typical case, the forwarding entry should result in two
outgoing labels for packets. The inner label is the backup LSP's
label, and the outer label is the bypass LSP's label. However, the
forwarding entry may result in one or no label, if either or both of
the backup LSP and the bypass LSP have the Implicit NULL label.
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 send a
PathErr message upstream for the protected LSP. Likewise, if the PLR
receives a PathErr message of the backup LSP after the backup LSP and
the primary LSP have previously been brought up, and the PLR is a
transit router of the protected LSP, it MUST also send a PathErr
message upstream for the protected LSP.
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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 for the protected LSP.
In any cases where the PLR needs to bring down the protected LSP due
to a received PathTear message, an RSVP state time-out, a
configuration change, an administrative command, etc, the PLR MUST
also bring down the backup LSP by sending a PathTear message through
the bypass LSP.
3.4. MP behavior
When an MP receives the Path message of a backup LSP, it MUST realize
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 setup protection mode is disabled on the MP, it MUST reject the
Path message, by sending a PathErr with code = 2 (policy control
failure) to the PLR.
Otherwise, the MP MUST terminate the backup LSP and re-create the
protected LSP. If the MP is the egress router of the protected LSP,
it MUST also terminate the protected LSP. If the MP is a transit
router of the LSP, it MUST send a Path message downstream for the
protected LSP. 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 Protected LSP Sender IPv4 Address
TLV or Protected LSP Sender IPv6 Address TLV. The Path message MUST
NOT carry any Protected LSP Sender IPv4 Address TLV or Protected LSP
Sender IPv6 Address TLV in LSP_REQUIRED_ATTRIBUTES object.
The MP MUST allocate a label for the backup LSP, and distribute it to
the PLR via Resv message of the backup LSP. If the protected LSP is
a sub-LSP of a P2MP LSP and there is an existing sibling sub-LSP
whose backup LSP is tunneled through the same bypass LSP, the MP MUST
allocate the same label as the sibling sub-LSP, in order to avoid
traffic duplication at the PLR.
When the MP receives a PathTear message for the backup LSP, it MUST
bring 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 for the protected LSP.
In any cases where the MP receives or originates a PathErr or
ResvTear message for the protected LSP, the MP MUST translate the
message to a same type of message for the backup LSP and send it to
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the PLR.
3.5. Local Revertive Mode
When the failed link or node is restored, the PLR MAY revert the
protected LSP to its desired primary path, by following the procedure
of local revertive mode described in [RFC 4090].
4. IANA Considerations
This document defines a new flag for the Attribute Flags TLV, which
is carried in the LSP_ATTRIBUTES Object of Path message. This flag
is used to communicate whether setup protection is desired for an
LSP. The value of the new flag needs to be assigned by IANA.
Setup Protection Desired: TBD
This document defines two new RSVP Attributes TLVs, which are carried
in the LSP_REQUIRED_ATTRIBUTES object of Path message. The values of
the new types need to be assigned 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.,
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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.
[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
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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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