Internet Engineering Task Force H. Chen
Internet-Draft Huawei Technologies
Intended status: Standards Track N. So
Expires: September 14, 2012 Verizon Inc.
A. Liu
Ericsson
O. Komolafe
Cisco Systems
L. Liu
KDDI R&D Lab Inc.
March 13, 2012
Extensions to RSVP-TE for P2MP LSP Ingress Local Protection
draft-chen-mpls-p2mp-ingress-protection-05.txt
Abstract
This document describes extensions to Resource Reservation Protocol -
Traffic Engineering (RSVP-TE) for locally protecting the ingress node
of a Traffic Engineered (TE) Point-to-MultiPoint (P2MP) Label
Switched Path (LSP) in a Multi-Protocol Label Switching (MPLS) and
Generalized MPLS (GMPLS) network.
Status of this Memo
This Internet-Draft is submitted to IETF 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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This Internet-Draft will expire on September 14, 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
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Conventions Used in This Document . . . . . . . . . . . . . . 4
4. Mechanism . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4.1. An Example of Ingress Local Protection . . . . . . . . . . 4
4.2. Set up of Backup P2MP sub Tree . . . . . . . . . . . . . . 5
4.3. Forwarding State for Backup P2MP sub Tree . . . . . . . . 5
4.4. Detection of Failure around Ingress . . . . . . . . . . . 6
5. Ingress Local Protection with FRR . . . . . . . . . . . . . . 7
6. LSP Information Message . . . . . . . . . . . . . . . . . . . 7
6.1. Format of LSP Information Message . . . . . . . . . . . . 8
6.2. Processing of LSP Information Message . . . . . . . . . . 8
6.3. Discussions on Other Approaches . . . . . . . . . . . . . 9
7. PATH Messages for Backup P2MP sub Tree . . . . . . . . . . . . 9
7.1. Construction of PATH Messages . . . . . . . . . . . . . . 9
7.2. Processing of PATH Messages . . . . . . . . . . . . . . . 10
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
9. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 10
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
10.1. Normative References . . . . . . . . . . . . . . . . . . . 11
10.2. Informative References . . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12
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1. Introduction
RFC4090 "Fast Reroute Extensions to RSVP-TE for LSP Tunnels"
describes two methods to protect P2P LSP tunnels or paths at local
repair points. The first method is a one-to-one backup method, where
a detour backup P2P LSP for each protected P2P LSP is created at each
potential point of local repair, which is an intermediate node
between the ingress node and the egress node of the protected LSP.
The second method is a facility bypass backup protection method,
where a bypass backup P2P LSP tunnel is created using MPLS label
stacking to protect a potential failure point for a set of P2P LSP
tunnels. The bypass backup tunnel can protect a set of P2P LSPs that
have similar backup constraints.
RFC4875 "Extensions to RSVP-TE for P2MP TE LSPs" describes how to use
the one-to-one backup method and facility bypass backup method to
protect a link or intermediate node failure on the path of a P2MP
LSP. However, there is no mention of locally protecting an ingress
node failure in a protected P2MP LSP.
There exist two methods for protecting an ingress node of a P2MP LSP.
The first method deploys a backup P2MP LSP from a backup ingress node
to the destination nodes to protect the ingress node. The main
disadvantage of this method is that the backup P2MP LSP consumes
additional network bandwidth along the entire LSP paths. The impact
on network efficiency can be significant in case of large P2MP
deployments. In addition, the backup LSP often has to be manually
constructed so that the backup P2MP LSP does not route through the
unprotected ingress node, and it has to be linked to the primary LSP
logically at the head-end to allow the fast switching in case of
ingress failure.
The second method extends the existing ways of protecting an
intermediate node of a P2P LSP to protect an ingress node of a P2MP
LSP. The disadvantages of this method include extra work for
refreshing PATH messages and processing RESV messages for the P2MP
LSP in the backup ingress node.
This document defines extensions to RSVP-TE for locally protecting an
ingress node of a Traffic Engineered (TE) point-to-multipoint (P2MP)
Label Switched Path (LSP) through using a backup P2MP sub tree. The
new method overcomes the disadvantages described above. It can also
be applied for protecting an ingress node of a TE point-to-point
(P2P) LSP since a TE P2P LSP can be considered as a special case of a
TE P2MP LSP.
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2. Terminology
This document uses terminologies defined in RFC2205, RFC3031,
RFC3209, RFC3473, RFC4090, RFC4461, and RFC4875.
3. 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 RFC 2119.
4. Mechanism
This section briefly describes a solution that locally protects an
ingress node of a P2MP LSP through using a backup P2MP sub tree. We
start with a simple example, and then present different parts of the
solution, which includes the creation of the backup P2MP sub tree,
the forwarding state for the backup P2MP sub tree, and the detection
of a failure in the ingress node.
4.1. An Example of Ingress Local Protection
Figure 1 below illustrates an example of using a backup P2MP sub tree
to locally protect the ingress of a P2MP LSP. The P2MP LSP to be
protected is from ingress node R1 to three egress/leaf nodes: L1, L2
and L3. The backup P2MP sub tree used to protect the ingress node R1
is from backup ingress node Ra to the next hop nodes R2 and R4 of the
ingress node R1 along the P2MP LSP.
The traffic from source S may be delivered to both R1 and Ra. R1
introduces the traffic into the P2MP LSP, which is sent to the
egress/leaf nodes L1, L2 and L3 along the P2MP LSP. Ra normally does
not put the traffic into the backup P2MP sub tree, which is from Ra
to R2 and R4.
There may be a BFD session between ingress node R1 and backup ingress
node Ra. Ra uses this BFD session to detect the failure of ingress
R1. When Ra detects the failure of R1, it imports the traffic from
the source S into the backup P2MP sub tree. The traffic from the sub
tree is merged into the P2MP LSP at R2 and R4, and then sent to the
egress/leaf nodes L1, L2 and L3 along the P2MP LSP. The time for
switching the traffic after R1 fails is within tens of milliseconds.
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[R2]======[R3]=====[L1]
// |
// |
// |
// |
// /
// /
// /
+---[R1]======[R4]====[R5]=====[L2]
| ! / / \\
| ! / / \\
[S]--| ! / / \\
| ! / / \\
| !/ / \\
+---[Ra]---[Rb] \\
\\
\\
[L3]
Figure 1: P2MP sub Tree for Locally Protecting Ingress
After the failure of the ingress node R1, the refresh of the PATH
messages for the ingress node is not needed. Each of the next-hop
nodes of the ingress node will receive the PATH messages and the
refresh of the PATH messages for the backup P2MP sub tree from the
backup ingress node Ra, which make the P2MP LSP alive.
4.2. Set up of Backup P2MP sub Tree
For the ingress node of the P2MP LSP, a backup ingress node is
designated to protect it. The ingress node sends the P2MP LSP
information to the backup ingress node. The backup ingress node
initiates the creation of the backup P2MP sub tree from itself to the
next-hop nodes of the ingress node.
The backup ingress node sets up the backup P2MP sub tree in a way
similar to setting up a P2MP tree or LSP from the signaling's point
of view. It constructs and sends RSVP-TE PATH messages along the
path for the backup P2MP sub tree with the final destinations (i.e,
egress/leaf nodes) matching the P2MP LSP. It receives and processes
RSVP-TE RESV messages that response to the PATH messages.
4.3. Forwarding State for Backup P2MP sub Tree
The forwarding state for the backup P2MP sub tree is different from
that for a P2MP LSP. After receiving the RSVP-TE RESV messages for
the backup P2MP sub tree, the backup ingress node creates a
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forwarding entry with an inactive state or flag. This forwarding
entry with an inactive state or flag is called an inactive forwarding
entry. In a normal operation, this inactive forwarding entry is not
used to forward any data traffic to be transported by the P2MP LSP,
even though the data traffic may be delivered to the backup ingress
node from an external node such as source node S in the above example
or network. The forwarding entry for the P2MP LSP is with an active
state or flag. Thus when the data traffic from the external node or
network reaches the ingress node of the P2MP LSP, it is imported into
the P2MP LSP tunnel through the active forwarding entry on the
ingress node.
When the ingress node fails, the inactive forwarding entry on the
backup ingress node is changed to active. Thus when the data traffic
from the external node reaches the backup ingress node, it is
imported into the backup P2MP sub tree. When the traffic arrives at
the next-hop nodes through the backup P2MP sub tree, it is merged
into the P2MP LSP to be transported to the destinations.
4.4. Detection of Failure around Ingress
There can be two different failure scenarios involving the ingress
node of a P2MP LSP that need to be detected.
o The failure of the ingress node (e.g. R1 of figure 1).
o The failure of the link between the source node and the ingress
node (e.g. the link between node S and node R1 in figure 1).
A failure of the ingress node can be detected through a BFD session
between the ingress node and the backup ingress node in MPLS
networks. A failure of the link between the source node and the
ingress node can be detected by a BFD session running over the link
and to the backup ingress via the ingress.
In the GMPLS networks where the control plane and data plane are
physically separated, the detection and localization of failures in
the physical layer can be achieved by introducing the link management
protocol (LMP) or assisting by performance monitoring devices.
After the backup ingress node detects any failure involving the
ingress node, it imports the traffic from the source node into the
backup P2MP sub tree. The traffic from the backup ingress node via
the sub tree is merged into the P2MP LSP on the next-hop nodes of the
ingress of the P2MP LSP, and then transported to the egress/leaf
nodes of the P2MP LSP.
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5. Ingress Local Protection with FRR
RFC4875 "Extensions to RSVP-TE for P2MP TE LSPs" describes how to use
RFC 4090 "Fast Reroute Extensions to RSVP-TE for LSP Tunnels" (FFR
for short) to locally protect failures in a link or intermediate node
of a P2MP LSP. However, there is not any standard that locally
protects the ingress of the P2MP LSP. The ingress local protection
mechanism described above fills this gap. Thus, through using the
ingress local protection and the FRR, we can locally protect the
ingress node , all the links and the intermediate nodes of a P2MP
LSP. The traffic switchover time is within tens of milliseconds
whenever the ingress, any of the links and the intermediate nodes of
the P2MP LSP fails.
The ingress node of the P2MP LSP can be locally protected through
using the ingress local protection. All the links and all the
intermediate nodes of the P2MP LSP can be locally protected through
using the FRR.
RFC 4090 defines fast reroute extensions to RSVP-TE for local
protection of P2P TE LSP in MPLS networks. RFC 4090, which is for
local protection of P2P TE LSP, has a few of limitations or issues
when it is used for local protection of P2MP TE LSP.
For example, locally protecting an intermediate node of a P2MP TE LSP
requires, when the protected node is a branch LSR, a set of P2P Next-
Next-Hop (NNHOP) Bypass tunnels toward all LSRs downstream to the
protected node. When the protected node fails, the PLR has to
replicate traffic on each of the P2P bypass tunnels. If there are K
next-next-hops, this may lead to K times of the traffic on some
links, which is not acceptable.
To overcome these limitations, draft "P2MP MPLS-TE Fast Reroute with
P2MP Bypass Tunnels" proposes extensions to FRR procedures defined in
RFC4090 to locally protect links and intermediate nodes of a P2MP TE
LSP with P2MP bypass tunnels.
Note that the methods for locally protecting all the links and the
intermediate nodes of a P2MP LSP are out of scope of this document.
6. LSP Information Message
LSP information messages are used to transfer the information about a
P2MP LSP to a backup ingress node from an ingress node. The
destination address of the LSP information message is that of the
backup ingress node. This section describes the format of an LSP
information message and processing of the message. It also discusses
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other approaches for transferring the information about a P2MP LSP to
a backup ingress from an ingress.
6.1. Format of LSP Information Message
The format of a P2MP LSP information message is illustrated below.
<LSP Information 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> ]
[ <POLICY_DATA> ... ]
<sender descriptor>
[<S2L sub-LSP descriptor list>]
<RECORD_ROUTE>
<S2L sub LSP flow descriptor list>
The formats and values of the objects in a P2MP LSP information
message are similar to or the same as those of the corresponding
objects defined in RFC4875.
The value of the Msg Type field in the common header in the P2MP LSP
information message will be a new number to be assigned by Internet
Assigned Numbers Authority (IANA).
6.2. Processing of LSP Information Message
Similar to sending an existing RSVP-TE message such as a PATH
message, the primary ingress MUST send a updated RSVP-TE LSP
information message to the backup ingress whenever there is a change
in the RSVP-TE LSP information message. It MAY send the same RSVP-TE
LSP information message to the backup ingress every refresh interval
if there is no change.
When the backup ingress receives the RSVP-TE LSP information message
from the primary ingress, it stores the LSP information, constructs
PATH messages, and sends the PATH messages downstream accordingly.
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If it has not received any RSVP-TE LSP information message for an
extended period of time (e.g. a cleanup timeout interval) and the BFD
session between the primary ingress and backup ingress is up, it
SHALL remove the information about the P2MP LSP, constructs PathTear
messages, and send the PathTear messages downstream accordingly.
When the BFD session between the primary ingress and backup ingress
is down, the backup ingress MUST keep the information about the P2MP
LSP and the state of the backup P2MP sub tree even though it has not
received any RSVP-TE LSP information message for an extended period
of time. It refreshes the PATH messages downstream for the backup
P2MP sub tree.
6.3. Discussions on Other Approaches
The information about a P2MP LSP may be transferred through other
approaches from the ingress node of the LSP to the backup ingress
node. One approach is to use OSPF Opaque LSA. The main reason for
giving up this option is that more parts need to be changed. Both
OSPF and RSVP-TE need to be modified.
On the ingress node, RSVP-TE needs to be changed to send the
information to OSPF when there is a change on the information about
the P2MP LSP. OSPF needs to be changed to receive the information
about the P2MP LSP from RSVP-TE and distribute the information in
Opaque LSA to the OSPF on the backup ingress node.
On the backup ingress node, OSPF needs to be changed to receive the
information in Opaque LSA from the ingress ndoe and send the
information to RSVP-TE. RSVP-TE needs to be changed to receive the
information about the P2MP LSP from OSPF.
7. PATH Messages for Backup P2MP sub Tree
PATH messages for a backup P2MP sub tree has the same format as PATH
messages for a P2MP LSP defined in RFC 4875. This section describes
the construction of the PATH messages for the backup P2MP sub tree,
which is followed by processing of the PATH messages.
7.1. Construction of PATH Messages
When the backup ingress node receives a P2MP LSP information message,
it checks to see if anything has been changed. If the message is a
new message or the information in the message has been changed, then
the PATH messages for the backup P2MP sub tree are to be constructed
as follows.
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First, a path to the next-hop nodes of the ingress node HAS to be
computed. The path MUST satisfy the constraints for the P2MP LSP and
not go through the ingress node.
If a path is computed successfully, then the PATH messages for the
backup P2MP sub tree are constructed based on the computed path and
the information message received, and sent downstream accordingly.
After sending the PATH messages, the backup ingress node receives
RESV messages from downstream nodes responding to the PATH messages.
It then processes the RESV messages and creates forwarding state
based on the information in the RESV messages.
If a path can not be found, the backup ingress node SHALL tear down
the backup P2MP sub tree created based the previous information
message.
The construction of a PATH message on a backup ingress node for a
backup P2MP sub tree is similar to the construction of a normal PATH
message on an ingress node for a P2MP LSP. It is based on LSP
information messages and a computed path for the backup P2MP sub
tree. The backup ingress node refreshes the PATH message to its
downstream nodes when the refresh reduction is not enabled.
The EXPLICIT_ROUTE object and the objects in the S2L sub-LSP
descriptor list for the PATH message may be constructed through
combining the path computed to the next-hop nodes of the ingress node
and the path from the next-hop nodes to the destination nodes of the
P2MP LSP obtained from the RECORD_ROUTE object and the objects for
the S2L sub-LSP flow descriptor list in the LSP information messages.
7.2. Processing of PATH Messages
The processing of PATH messages on the intermediate nodes and the
destination nodes along the backup P2MP sub tree is the same as the
processing of PATH messages for a P2MP LSP.
8. IANA Considerations
TBD
9. Acknowledgement
The authors would like to thank Richard Li, Rahul Aggarwal, Rob
Rennison, Neil Harrison, Kannan Sampath, Yimin Shen, Ronhazli Adam
and Quintin Zhao for their valuable comments and suggestions on this
draft.
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10. References
10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3692] Narten, T., "Assigning Experimental and Testing Numbers
Considered Useful", BCP 82, RFC 3692, January 2004.
[RFC2205] Braden, B., Zhang, L., Berson, S., Herzog, S., and S.
Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1
Functional Specification", RFC 2205, September 1997.
[RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
Label Switching Architecture", RFC 3031, January 2001.
[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.
[RFC3473] Berger, L., "Generalized Multi-Protocol Label Switching
(GMPLS) Signaling Resource ReserVation Protocol-Traffic
Engineering (RSVP-TE) Extensions", RFC 3473, January 2003.
[RFC4090] Pan, P., Swallow, G., and A. Atlas, "Fast Reroute
Extensions to RSVP-TE for LSP Tunnels", RFC 4090,
May 2005.
[RFC4461] Yasukawa, S., "Signaling Requirements for Point-to-
Multipoint Traffic-Engineered MPLS Label Switched Paths
(LSPs)", RFC 4461, April 2006.
[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.
[P2MP FRR]
Le Roux, J., Aggarwal, R., Vasseur, J., and M. Vigoureux,
"P2MP MPLS-TE Fast Reroute with P2MP Bypass Tunnels",
draft-leroux-mpls-p2mp-te-bypass , March 1997.
10.2. Informative References
[RFC2702] Awduche, D., Malcolm, J., Agogbua, J., O'Dell, M., and J.
McManus, "Requirements for Traffic Engineering Over MPLS",
RFC 2702, September 1999.
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[RFC3032] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y.,
Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack
Encoding", RFC 3032, January 2001.
Authors' Addresses
Huaimo Chen
Huawei Technologies
Boston, MA
USA
Email: Huaimochen@huawei.com
Ning So
Verizon Inc.
2400 North Glenville Drive
Richardson, TX 75082
USA
Email: Ning.So@verizonbusiness.com
Autumn Liu
Ericsson
CA
USA
Email: autumn.liu@ericsson.com
Olufemi Komolafe
Cisco Systems
96 Commercial Street
Edinburgh, EH6 6LX
United Kingdom
Email: femi@cisco.com
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Lei Liu
KDDI R&D Lab Inc.
2-1-15
Ohara Fujimino-shi, Saitama
Japan
Email: le-liu@kddilabs.jp
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