Internet DRAFT - draft-ietf-mpls-rsvp-ingress-protection
draft-ietf-mpls-rsvp-ingress-protection
Internet Engineering Task Force H. Chen, Ed.
Internet-Draft Huawei Technologies
Intended status: Standards Track R. Torvi, Ed.
Expires: April 29, 2015 Juniper Networks
October 26, 2014
Extensions to RSVP-TE for LSP Ingress Local Protection
draft-ietf-mpls-rsvp-ingress-protection-02.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) 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.
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This Internet-Draft will expire on April 29, 2015.
Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the
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Table of Contents
1. Co-authors . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. An Example of Ingress Local Protection . . . . . . . . . . 3
2.2. Ingress Local Protection with FRR . . . . . . . . . . . . 4
3. Ingress Failure Detection . . . . . . . . . . . . . . . . . . 4
3.1. Source Detects Failure . . . . . . . . . . . . . . . . . . 4
3.2. Backup and Source Detect Failure . . . . . . . . . . . . . 5
4. Backup Forwarding State . . . . . . . . . . . . . . . . . . . 5
4.1. Forwarding State for Backup LSP . . . . . . . . . . . . . 5
5. Protocol Extensions . . . . . . . . . . . . . . . . . . . . . 6
5.1. INGRESS_PROTECTION Object . . . . . . . . . . . . . . . . 6
5.1.1. Subobject: Backup Ingress IPv4/IPv6 Address . . . . . 7
5.1.2. Subobject: Ingress IPv4/IPv6 Address . . . . . . . . . 8
5.1.3. Subobject: Traffic Descriptor . . . . . . . . . . . . 8
5.1.4. Subobject: Label-Routes . . . . . . . . . . . . . . . 9
6. Behavior of Ingress Protection . . . . . . . . . . . . . . . . 9
6.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . 9
6.1.1. Relay-Message Method . . . . . . . . . . . . . . . . . 9
6.1.2. Proxy-Ingress Method . . . . . . . . . . . . . . . . . 10
6.1.3. Comparing Two Methods . . . . . . . . . . . . . . . . 11
6.2. Ingress Behavior . . . . . . . . . . . . . . . . . . . . . 11
6.2.1. Relay-Message Method . . . . . . . . . . . . . . . . . 12
6.2.2. Proxy-Ingress Method . . . . . . . . . . . . . . . . . 12
6.3. Backup Ingress Behavior . . . . . . . . . . . . . . . . . 13
6.3.1. Backup Ingress Behavior in Off-path Case . . . . . . . 14
6.3.2. Backup Ingress Behavior in On-path Case . . . . . . . 16
6.3.3. Failure Detection and Refresh PATH Messages . . . . . 17
6.4. Revertive Behavior . . . . . . . . . . . . . . . . . . . . 17
6.4.1. Revert to Primary Ingress . . . . . . . . . . . . . . 18
6.4.2. Global Repair by Backup Ingress . . . . . . . . . . . 18
7. Security Considerations . . . . . . . . . . . . . . . . . . . 18
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19
9. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 19
10. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 20
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 20
11.1. Normative References . . . . . . . . . . . . . . . . . . . 20
11.2. Informative References . . . . . . . . . . . . . . . . . . 21
A. Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 21
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1. Co-authors
Ning So, Autumn Liu, Alia Atlas, Yimin Shen, Tarek Saad, Fengman Xu,
Mehmet Toy, Lei Liu
2. Introduction
For MPLS LSPs it is important to have a fast-reroute method for
protecting its ingress node as well as transit nodes. This is not
covered either in the fast-reroute method defined in [RFC4090] or in
the P2MP fast-reroute extensions to fast-reroute in [RFC4875].
An alternate approach to local protection (fast-reroute) is to use
global protection and set up a second backup LSP (whether P2MP or
P2P) from a backup ingress to the egresses. The main disadvantage of
this is that the backup LSP may reserve additional network bandwidth.
This specification defines a simple extension to RSVP-TE for local
protection of the ingress node of a P2MP or P2P LSP.
2.1. An Example of Ingress Local Protection
Figure 1 shows an example of using a backup P2MP LSP to locally
protect the ingress of a primary P2MP LSP, which is from ingress R1
to three egresses: L1, L2 and L3. The backup LSP is from backup
ingress Ra to the next hops R2 and R4 of ingress R1.
[R2]******[R3]*****[L1]
* | **** Primary LSP
* | ---- Backup LSP
* / .... BFD Session
* / $ Link
....[R1]*******[R4]****[R5]*****[L2] $
: $ $ / / * $
: $ $ / / *
[S] $ / / *
$ $ / / *
$ $/ / *
[Ra]----[Rb] [L3]
Figure 1: Backup P2MP LSP for Locally Protecting Ingress
In normal operations, source S sends the traffic to primary ingress
R1. R1 imports the traffic into the primary LSP.
When source S detects the failure of R1, it switches the traffic to
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backup ingress Ra, which imports the traffic from S into the backup
LSP to R1's next hops R2 and R4, where the traffic is merged into the
primary LSP, and then sent to egresses L1, L2 and L3.
Source S should be able to detect the failure of R1 and switch the
traffic within 10s of ms.
Note that the backup ingress must be one logical hop away from the
ingress. A logical hop is a direct link or a tunnel such as a GRE
tunnel, over which RSVP-TE messages may be exchanged.
2.2. Ingress Local Protection with FRR
Through using the ingress local protection and the FRR, we can
locally protect the ingress, all the links and the transit nodes of
an LSP. The traffic switchover time is within 10s of ms whenever the
ingress, any of the links and the transit nodes of the LSP fails.
The ingress node of the LSP can be locally protected through using
the ingress local protection. All the links and all the transit
nodes of the LSP can be locally protected through using the FRR.
3. Ingress Failure Detection
Exactly how to detect the failure of the ingress is out of scope.
However, it is necessary to discuss different modes for detecting the
failure because they determine what is the required behavior for the
source and backup ingress.
3.1. Source Detects Failure
Source Detects Failure or Source-Detect for short means that the
source is responsible for fast detecting the failure of the primary
ingress of an LSP. The backup ingress is ready to import the traffic
from the source into the backup LSP after the backup LSP is up.
In normal operations, the source sends the traffic to the primary
ingress. When the source detects the failure of the primary ingress,
it switches the traffic to the backup ingress, which delivers the
traffic to the next hops of the primary ingress through the backup
LSP, where the traffic is merged into the primary LSP.
For a P2P LSP, after the primary ingress fails, the backup ingress
must use a method to reliably detect the failure of the primary
ingress before the PATH message for the LSP expires at the next hop
of the primary ingress. After reliably detecting the failure, the
backup ingress sends/refreshes the PATH message to the next hop
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through the backup LSP as needed.
After the primary ingress fails, it will not be reachable after
routing convergence. Thus checking whether the primary ingress
(address) is reachable is a possible method.
3.2. Backup and Source Detect Failure
Backup and Source Detect Failure or Backup-Source-Detect for short
means that both the backup ingress and the source are concurrently
responsible for fast detecting the failure of the primary ingress.
In normal operations, the source sends the traffic to the primary
ingress. It switches the traffic to the backup ingress when it
detects the failure of the primary ingress.
The backup ingress does not import any traffic from the source into
the backup LSP in normal operations. When it detects the failure of
the primary ingress, it imports the traffic from the source into the
backup LSP to the next hops of the primary ingress, where the traffic
is merged into the primary LSP.
The source-detect is preferred. It is simpler than the backup-
source-detect, which needs both the source and the backup ingress
detect the ingress failure quickly.
4. Backup Forwarding State
Before the primary ingress fails, the backup ingress is responsible
for creating the necessary backup LSPs. These LSPs might be multiple
bypass P2P LSPs that avoid the ingress. Alternately, the backup
ingress could choose to use a single backup P2MP LSP as a bypass or
detour to protect the primary ingress of a primary P2MP LSP.
The backup ingress may be off-path or on-path of an LSP. If a backup
ingress is not any node of the LSP, we call it is off-path. If a
backup ingress is a next-hop of the primary ingress of the LSP, we
call it is on-path. If it is on-path, the primary forwarding state
associated with the primary LSP SHOULD be clearly separated from the
backup LSP(s) state.
4.1. Forwarding State for Backup LSP
A forwarding entry for a backup LSP is created on the backup ingress
after the LSP is set up. Depending on the failure-detection mode
(e.g., source-detect), it may be used to forward received traffic or
simply be inactive (e.g., backup-source-detect) until required. In
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either case, when the primary ingress fails, this entry is used to
import the traffic into the backup LSP to the next hops of the
primary ingress, where the traffic is merged into the primary LSP.
The forwarding entry for a backup LSP is a local implementation
issue. In one device, it may have an inactive flag. This inactive
forwarding entry is not used to forward any traffic normally. When
the primary ingress fails, it is changed to active, and thus the
traffic from the source is imported into the backup LSP.
5. Protocol Extensions
A new object INGRESS_PROTECTION is defined for signaling ingress
local protection. It is backward compatible.
5.1. INGRESS_PROTECTION Object
The INGRESS_PROTECTION object with the FAST_REROUTE object in a PATH
message is used to control the backup for protecting the primary
ingress of a primary LSP. The primary ingress MUST insert this
object into the PATH message to be sent to the backup ingress for
protecting the primary ingress. It has the following format:
Class-Num = TBD C-Type = TBD
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length (bytes) | Class-Num | C-Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Secondary LSP ID | Flags | Options |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ (Subobjects) ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Flags
0x01 Ingress local protection available
0x02 Ingress local protection in use
0x04 Bandwidth protection
Options
0x01 Revert to Ingress
0x02 P2MP Backup
The Secondary LSP ID in the object is an LSP ID that the primary
ingress has allocated for a protected LSP tunnel. The backup ingress
may use this LSP ID to set up a new LSP from the backup ingress to
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the destinations of the protected LSP tunnel. This allows the new
LSP to share resources with the old one.
The flags are used to communicate status information from the backup
ingress to the primary ingress.
o Ingress local protection available: The backup ingress sets this
flag after backup LSPs are up and ready for locally protecting the
primary ingress. The backup ingress sends this to the primary
ingress to indicate that the primary ingress is locally protected.
o Ingress local protection in use: The backup ingress sets this flag
when it detects a failure in the primary ingress. The backup
ingress keeps it and does not send it to the primary ingress since
the primary ingress is down.
o Bandwidth protection: The backup ingress sets this flag if the
backup LSPs guarantee to provide desired bandwidth for the
protected LSP against the primary ingress failure.
The options are used by the primary ingress to specify the desired
behavior to the backup ingress.
o Revert to Ingress: The primary ingress sets this option indicating
that the traffic for the primary LSP successfully re-signaled will
be switched back to the primary ingress from the backup ingress
when the primary ingress is restored.
o P2MP Backup: This option is set to ask for the backup ingress to
use P2MP backup LSP to protect the primary ingress. Note that one
spare bit of the flags in the FAST-REROUTE object can be used to
indicate whether P2MP or P2P backup LSP is desired for protecting
an ingress and transit node.
The INGRESS_PROTECTION object may contain some sub objects below.
5.1.1. Subobject: Backup Ingress IPv4/IPv6 Address
When the primary ingress of a protected LSP sends a PATH message with
an INGRESS_PROTECTION object to the backup ingress, the object may
have a Backup Ingress IPv4/IPv6 Address sub object containing an
IPv4/IPv6 address belonging to the backup ingress. The Type of the
sub object is TBD-1/TBD-2 for Backup Ingress IPv4/IPv6 Address. The
body of the sub object is given 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4/IPv6 address (4/16 bytres) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
IPv4/IPv6 address: A 32/128-bit unicast, host address.
5.1.2. Subobject: Ingress IPv4/IPv6 Address
The INGRESS_PROTECTION object may have an Ingress IPv4/IPv6 Address
sub object containing an IPv4/IPv6 address belonging to the primary
ingress. The Type of the sub object is TBD-3/TBD-4 for Ingress IPv4/
IPv6 Address. The sub object has the following body:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4/IPv6 address (4/16 bytres) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
IPv4/IPv6 address: A 32/128-bit unicast, host address.
5.1.3. Subobject: Traffic Descriptor
The INGRESS_PROTECTION object may have a Traffic Descriptor sub
object describing the traffic to be mapped to the backup LSP on the
backup ingress for locally protecting the primary ingress. The Type
of the sub object is TBD-5/TBD-6/TBD-7 for Interface/IPv4/6 Prefix
respectively. The sub object has the following body:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Traffic Element 1 |
~ ~
| Traffic Element n |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The Traffic Descriptor sub object may contain multiple Traffic
Elements of same type as follows:
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o Interface Traffic (Type TBD-5): Each of the Traffic Elements is a
32 bit index of an interface, from which the traffic is imported
into the backup LSP.
o IPv4/6 Prefix Traffic (Type TBD-6/TBD-7): Each of the Traffic
Elements is an IPv4/6 prefix, containing an 8-bit prefix length
followed by an IPv4/6 address prefix, whose length, in bits, was
specified by the prefix length, padded to a byte boundary.
5.1.4. Subobject: Label-Routes
The INGRESS_PROTECTION object in a PATH message from the primary
ingress to the backup ingress will have a Label-Routes sub object
containing the labels and routes that the next hops of the ingress
use. The Type of the sub object is TBD-8. The sub object has the
following body:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Subobjects ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The Subobjects in the Label-Routes are copied from those in the
RECORD_ROUTE objects in the RESV messages that the primary ingress
receives from its next hops for the primary LSP. They MUST contain
the first hops of the LSP, each of which is paired with its label.
6. Behavior of Ingress Protection
6.1. Overview
There are four parts of ingress protection: 1) setting up the
necessary backup LSP forwarding state; 2) identifying the failure and
providing the fast repair (as discussed in Sections 3 and 4); 3)
maintaining the RSVP-TE control plane state until a global repair can
be done; and 4) performing the global repair(see Section 6.4).
There are two different proposed signaling approaches to obtain
ingress protection. They both use the same new INGRESS_PROTECTION
object. The object is sent in both PATH and RESV messages.
6.1.1. Relay-Message Method
The primary ingress relays the information for ingress protection of
an LSP to the backup ingress via PATH messages. Once the LSP is
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created, the ingress of the LSP sends the backup ingress a PATH
message with an INGRESS_PROTECTION object with Label-Routes
subobject, which is populated with the next-hops and labels. This
provides sufficient information for the backup ingress to create the
appropriate forwarding state and backup LSP(s).
The ingress also sends the backup ingress all the other PATH messages
for the LSP with an empty INGRESS_PROTECTION object. Thus, the
backup ingress has access to all the PATH messages needed for
modification to refresh control-plane state after a failure.
The advantages of this method include: 1) the primary LSP is
independent of the backup ingress; 2) simple; 3) less configuration;
and 4) less control traffic.
6.1.2. Proxy-Ingress Method
Conceptually, a proxy ingress is created that starts the RSVP
signaling. The explicit path of the LSP goes from the proxy ingress
to the backup ingress and then to the real ingress. The behavior and
signaling for the proxy ingress is done by the real ingress; the use
of a proxy ingress address avoids problems with loop detection.
[ traffic source ] *** Primary LSP
$ $ --- Backup LSP
$ $ $$ Link
$ $
[ proxy ingress ] [ backup ]
[ & ingress ] |
* |
*****[ MP ]----|
Figure 2: Example Protected LSP with Proxy Ingress Node
The backup ingress must know the merge points or next-hops and their
associated labels. This is accomplished by having the RSVP PATH and
RESV messages go through the backup ingress, although the forwarding
path need not go through the backup ingress. If the backup ingress
fails, the ingress simply removes the INGRESS_PROTECTION object and
forwards the PATH messages to the LSP's next-hop(s). If the ingress
has its LSP configured for ingress protection, then the ingress can
add the backup ingress and itself to the ERO and start forwarding the
PATH messages to the backup ingress.
Slightly different behavior can apply for the on-path and off-path
cases. In the on-path case, the backup ingress is a next hop node
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after the ingress for the LSP. In the off-path, the backup ingress
is not any next-hop node after the ingress for all associated sub-
LSPs.
The key advantage of this approach is that it minimizes the special
handling code requires. Because the backup ingress is on the
signaling path, it can receive various notifications. It easily has
access to all the PATH messages needed for modification to be sent to
refresh control-plane state after a failure.
6.1.3. Comparing Two Methods
+-------+-----------+------+--------+-----------------+---------+
| |Primary LSP|Simple|Config |PATH Msg from |Reuse |
|Method |Depends on | |Proxy- |Backup to primary|Some of |
| |Backup | |Ingress-|RESV Msg from |Existing |
| |Ingress | |ID |Primary to backup|Functions|
+-------+-----------+------+--------+-----------------+---------+
|Relay- | No |Yes | No | No | Yes- |
|Message| | | | | |
+-------+-----------+------+--------+-----------------+---------+
|Proxy- | Yes |Yes- | Yes | Yes | Yes |
|Ingress| | | | | |
+-------+-----------+------+--------+-----------------+---------+
6.2. Ingress Behavior
The primary ingress must be configured with two or three pieces of
information for ingress protection.
o Backup Ingress Address: The primary ingress must know an IP
address for it to be included in the INGRESS_PROTECTION object.
o Proxy-Ingress-Id (only needed for Proxy-Ingress Method): The
Proxy-Ingress-Id is only used in the Record Route Object for
recording the proxy-ingress. If no proxy-ingress-id is specified,
then a local interface address that will not otherwise be included
in the Record Route Object can be used. A similar technique is
used in [RFC4090 Sec 6.1.1].
o Application Traffic Identifier: The primary ingress and backup
ingress must both know what application traffic should be directed
into the LSP. If a list of prefixes in the Traffic Descriptor
sub-object will not suffice, then a commonly understood
Application Traffic Identifier can be sent between the primary
ingress and backup ingress. The exact meaning of the identifier
should be configured similarly at both the primary ingress and
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backup ingress. The Application Traffic Identifier is understood
within the unique context of the primary ingress and backup
ingress.
With this additional information, the primary ingress can create and
signal the necessary RSVP extensions to support ingress protection.
6.2.1. Relay-Message Method
To protect the ingress of an LSP, the ingress does the following
after the LSP is up.
1. Select a PATH message.
2. If the backup ingress is off-path, then send it a PATH message
with the content from the selected PATH message and an
INGRESS_PROTECTION object; else (the backup ingress is a next
hop, i.e., on-path case) add an INGRESS_PROTECTION object into
the existing PATH message to the backup ingress (i.e., the next
hop). The object contains the Traffic-Descriptor sub-object, the
Backup Ingress Address sub-object and the Label-Routes sub-
object. The flags is set to indicate whether a Backup P2MP LSP
is desired. A second LSP-ID is allocated (if it is not allocated
yet) and used in the object. The Label-Routes sub-object
contains the next-hops of the ingress and their labels.
3. For each of the other PATH messages, send the backup ingress a
PATH message with the content copied from the message and an
empty INGRESS_PROTECTION object, which is an object without any
Traffic-Descriptor sub-object.
6.2.2. Proxy-Ingress Method
The primary ingress is responsible for starting the RSVP signaling
for the proxy-ingress node. To do this, the following is done for
the RSVP PATH message.
1. Compute the EROs for the LSP as normal for the ingress.
2. If the selected backup ingress node is not the first node on the
path (for all sub-LSPs), then insert at the beginning of the ERO
first the backup ingress node and then the ingress node.
3. In the PATH RRO, instead of recording the ingress node's address,
replace it with the Proxy-Ingress-Id.
4. Leave the HOP object populated as usual with information for the
ingress-node.
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5. Add the INGRESS_PROTECTION object to the PATH message. Allocate
a second LSP-ID to be used in the INGRESS-PROTECTION object.
Include the Backup Ingress Address (IPv4 or IPv6) sub-object and
the Traffic-Descriptor sub-object. Set or clear the flag
indicating that a Backup P2MP LSP is desired.
6. Optionally, add the FAST-REROUTE object [RFC4090] to the Path
message. Indicate whether one-to-one backup is desired.
Indicate whether facility backup is desired.
7. The RSVP PATH message is sent to the backup node as normal.
If the ingress detects that it can't communicate with the backup
ingress, then the ingress should instead send the PATH message to the
next-hop indicated in the ERO computed in step 1. Once the ingress
detects that it can communicate with the backup ingress, the ingress
SHOULD follow the steps 1-7 to obtain ingress failure protection.
When the ingress node receives an RSVP PATH message with an INGRESS-
PROTECTION object and the object specifies that node as the ingress
node and the PHOP as the backup ingress node, the ingress node SHOULD
remove the INGRESS_PROTECTION object from the PATH message before
sending it out. Additionally, the ingress node must store that it
will install ingress forwarding state for the LSP rather than
midpoint forwarding.
When an RSVP RESV message is received by the ingress, it uses the
NHOP to determine whether the message is received from the backup
ingress or from a different node. The stored associated PATH message
contains an INGRESS_PROTECTION object that identifies the backup
ingress node. If the RESV message is not from the backup node, then
ingress forwarding state should be set up, and the INGRESS_PROTECTION
object MUST be added to the RESV before it is sent to the NHOP, which
should be the backup node. If the RESV message is from the backup
node, then the LSP should be considered available for use.
If the backup ingress node is on the forwarding path, then a RESV is
received with an INGRESS_PROTECTION object and an NHOP that matches
the backup ingress. In this case, the ingress node's address will
not appear after the backup ingress in the RRO. The ingress node
should set up ingress forwarding state, just as is done if the LSP
weren't ingress-node protected.
6.3. Backup Ingress Behavior
An LER determines that the ingress local protection is requested for
an LSP if the INGRESS_PROTECTION object is included in the PATH
message it receives for the LSP. The LER can further determine that
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it is the backup ingress if one of its addresses is in the Backup
Ingress Address sub-object of the INGRESS_PROTECTION object. The LER
as the backup ingress will assume full responsibility of the ingress
after the primary ingress fails. In addition, the LER determines
that it is off-path if it is not a next hop of the primary ingress.
6.3.1. Backup Ingress Behavior in Off-path Case
The backup ingress considers itself as a PLR and the primary ingress
as its next hop and provides a local protection for the primary
ingress. It behaves very similarly to a PLR providing fast-reroute
where the primary ingress is considered as the failure-point to
protect. Where not otherwise specified, the behavior given in
[RFC4090] for a PLR should apply.
The backup ingress SHOULD follow the control-options specified in the
INGRESS_PROTECTION object and the flags and specifications in the
FAST-REROUTE object. This applies to providing a P2MP backup if the
"P2MP backup" is set, a one-to-one backup if "one-to-one desired" is
set, facility backup if the "facility backup desired" is set, and
backup paths that support the desired bandwidth, and administrative-
colors that are requested.
If multiple non empty INGRESS_PROTECTION objects have been received
via multiple PATH messages for the same LSP, then the most recent one
MUST be the one used.
The backup ingress creates the appropriate forwarding state for the
backup LSP tunnel(s) to the merge point(s).
When the backup ingress sends a RESV message to the primary ingress,
it should add an INGRESS_PROTECTION object into the message. It
SHOULD set or clear the flags in the object to report "Ingress local
protection available", "Ingress local protection in use", and
"bandwidth protection".
If the backup ingress doesn't have a backup LSP tunnel to all the
merge points, it SHOULD clear "Ingress local protection available".
[Editor Note: It is possible to indicate the number or which are
unprotected via a sub-object if desired.]
When the primary ingress fails, the backup ingress redirects the
traffic from a source into the backup P2P LSPs or the backup P2MP LSP
transmitting the traffic to the next hops of the primary ingress,
where the traffic is merged into the protected LSP.
In this case, the backup ingress keeps the PATH message with the
INGRESS_PROTECTION object received from the primary ingress and the
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RESV message with the INGRESS_PROTECTION object to be sent to the
primary ingress. The backup ingress sets the "local protection in
use" flag in the RESV message, indicating that the backup ingress is
actively redirecting the traffic into the backup P2P LSPs or the
backup P2MP LSP for locally protecting the primary ingress failure.
Note that the RESV message with this piece of information will not be
sent to the primary ingress because the primary ingress has failed.
If the backup ingress has not received any PATH message from the
primary ingress for an extended period of time (e.g., a cleanup
timeout interval) and a confirmed primary ingress failure did not
occur, then the standard RSVP soft-state removal SHOULD occur. The
backup ingress SHALL remove the state for the PATH message from the
primary ingress, and tear down the one-to-one backup LSPs for
protecting the primary ingress if one-to-one backup is used or unbind
the facility backup LSPs if facility backup is used.
When the backup ingress receives a PATH message from the primary
ingress for locally protecting the primary ingress of a protected
LSP, it checks to see if any critical information has been changed.
If the next hops of the primary ingress are changed, the backup
ingress SHALL update its backup LSP(s) accordingly.
6.3.1.1. Relay-Message Method
When the backup ingress receives a PATH message with an non empty
INGRESS_PROTECTION object, it examines the object to learn what
traffic associated with the LSP. It determines the next-hops to be
merged to by examining the Label-Routes sub-object in the object.
The backup ingress stores the PATH message received from the primary
ingress, but does NOT forward it.
The backup ingress MUST respond with a RESV to the PATH message
received from the primary ingress. If the INGRESS_PROTECTION object
is not "empty", the backup ingress SHALL send the RESV message with
the state indicating protection is available after the backup LSP(s)
are successfully established.
6.3.1.2. Proxy-Ingress Method
The backup ingress determines the next-hops to be merged to by
collecting the set of the pair of (IPv4/IPv6 sub-object, Label sub-
object) from the Record Route Object of each RESV that are closest to
the top and not the Ingress router; this should be the second to the
top pair. If a Label-Routes sub-object is included in the
INGRESS_PROTECTION object, the included IPv4/IPv6 sub-objects are
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used to filter the set down to the specific next-hops where
protection is desired. A RESV message must have been received before
the Backup Ingress can create or select the appropriate backup LSP.
When the backup ingress receives a PATH message with the
INGRESS_PROTECTION object, the backup ingress examines the object to
learn what traffic associated with the LSP. The backup ingress
forwards the PATH message to the ingress node with the normal RSVP
changes.
When the backup ingress receives a RESV message with the
INGRESS_PROTECTION object, the backup ingress records an IMPLICIT-
NULL label in the RRO. Then the backup ingress forwards the RESV
message to the ingress node, which is acting for the proxy ingress.
6.3.2. Backup Ingress Behavior in On-path Case
An LER as the backup ingress determines that it is on-path if one of
its addresses is a next hop of the primary ingress (and the primary
ingress is not its next hop via checking the PATH message with the
INGRESS_PROTECTION object received from the primary ingress for
Proxy-Ingress Method). The LER on-path sends the corresponding PATH
messages without any INGRESS_PROTECTION object to its next hops. It
creates a number of backup P2P LSPs or a backup P2MP LSP from itself
to the other next hops (i.e., the next hops other than the backup
ingress) of the primary ingress. The other next hops are from the
Label-Routes sub object.
It also creates a forwarding entry, which sends/multicasts the
traffic from the source to the next hops of the backup ingress along
the protected LSP when the primary ingress fails. The traffic is
described by the Traffic-Descriptor.
After the forwarding entry is created, all the backup P2P LSPs or the
backup P2MP LSP is up and associated with the protected LSP, the
backup ingress sends the primary ingress the RESV message with the
INGRESS_PROTECTION object containing the state of the local
protection such as "local protection available" flag set to one,
which indicates that the primary ingress is locally protected.
When the primary ingress fails, the backup ingress sends/multicasts
the traffic from the source to its next hops along the protected LSP
and imports the traffic into each of the backup P2P LSPs or the
backup P2MP LSP transmitting the traffic to the other next hops of
the primary ingress, where the traffic is merged into protected LSP.
During the local repair, the backup ingress continues to send the
PATH messages to its next hops as before, keeps the PATH message with
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the INGRESS_PROTECTION object received from the primary ingress and
the RESV message with the INGRESS_PROTECTION object to be sent to the
primary ingress. It sets the "local protection in use" flag in the
RESV message.
6.3.3. Failure Detection and Refresh PATH Messages
As described in [RFC4090], it is necessary to refresh the PATH
messages via the backup LSP(s). The Backup Ingress MUST wait to
refresh the PATH messages until it can accurately detect that the
ingress node has failed. An example of such an accurate detection
would be that the IGP has no bi-directional links to the ingress node
and the last change was long enough in the past that changes should
have been received (i.e., an IGP network convergence time or
approximately 2-3 seconds) or a BFD session to the primary ingress'
loopback address has failed and stayed failed after the network has
reconverged.
As described in [RFC4090 Section 6.4.3], the backup ingress, acting
as PLR, SHOULD modify and send any saved PATH messages associated
with the primary LSP to the corresponding next hops through backup
LSP(s). Any PATH message sent will not contain any
INGRESS_PROTECTION object. The RSVP_HOP object in the message
contains an IP source address belonging to the backup ingress. The
sender template object has the backup ingress address as its tunnel
sender address.
6.4. Revertive Behavior
Upon a failure event in the (primary) ingress of a protected LSP, the
protected LSP is locally repaired by the backup ingress. There are a
couple of basic strategies for restoring the LSP to a full working
path.
- Revert to Primary Ingress: When the primary ingress is restored,
it re-signals each of the LSPs that start from the primary
ingress. The traffic for every LSP successfully re-signaled is
switched back to the primary ingress from the backup ingress.
- Global Repair by Backup Ingress: After determining that the
primary ingress of an LSP has failed, the backup ingress computes
a new optimal path, signals a new LSP along the new path, and
switches the traffic to the new LSP.
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6.4.1. Revert to Primary Ingress
If "Revert to Primary Ingress" is desired for a protected LSP, the
(primary) ingress of the LSP re-signals the LSP that starts from the
primary ingress after the primary ingress restores. When the LSP is
re-signaled successfully, the traffic is switched back to the primary
ingress from the backup ingress and redirected into the LSP starting
from the primary ingress.
If the ingress can resignal the PATH messages for the LSP, then the
ingress can specify the "Revert to Ingress" control-option in the
INGRESS_PROTECTION object. Doing so may cause a duplication of
traffic while the Ingress starts sending traffic again before the
Backup Ingress stops; the alternative is to drop traffic for a short
period of time.
Additionally, the Backup Ingress can set the "Revert To Ingress"
control-option as a request for the Ingress to take over.
6.4.2. Global Repair by Backup Ingress
When the backup ingress has determined that the primary ingress of
the protected LSP has failed (e.g., via the IGP), it can compute a
new path and signal a new LSP along the new path so that it no longer
relies upon local repair. To do this, the backup ingress uses the
same tunnel sender address in the Sender Template Object and uses the
previously allocated second LSP-ID in the INGRESS_PROTECTION object
of the PATH message as the LSP-ID of the new LSP. This allows the
new LSP to share resources with the old LSP. In addition, if the
Ingress recovers, the Backup Ingress SHOULD send it RESVs with the
INGRESS_PROTECTION object where the "Revert to Ingress" is specified.
The Secondary LSP ID should be the unused LSP ID - while the LSP ID
signaled in the RESV will be that currently active. The Ingress can
learn from the RESVs what to signal. Even if the Ingress does not
take over, the RESVs notify it that the particular LSP IDs are in
use. The Backup Ingress can reoptimize the new LSP as necessary
until the Ingress recovers. Alternately, the Backup Ingress can
create a new LSP with no bandwidth reservation that duplicates the
path(s) of the protected LSP, move traffic to the new LSP, delete the
protected LSP, and then resignal the new LSP with bandwidth.
7. Security Considerations
In principle this document does not introduce new security issues.
The security considerations pertaining to RFC 4090, RFC 4875 and
other RSVP protocols remain relevant.
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8. IANA Considerations
TBD
9. Contributors
Renwei Li
Huawei Technologies
2330 Central Expressway
Santa Clara, CA 95050
USA
Email: renwei.li@huawei.com
Quintin Zhao
Huawei Technologies
Boston, MA
USA
Email: quintin.zhao@huawei.com
Zhenbin Li
Huawei Technologies
2330 Central Expressway
Santa Clara, CA 95050
USA
Email: zhenbin.li@huawei.com
Boris Zhang
Telus Communications
200 Consilium Pl Floor 15
Toronto, ON M1H 3J3
Canada
Email: Boris.Zhang@telus.com
Markus Jork
Juniper Networks
10 Technology Park Drive
Westford, MA 01886
USA
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Email: mjork@juniper.net
10. Acknowledgement
The authors would like to thank Nobo Akiya, Rahul Aggarwal, Eric
Osborne, Ross Callon, Loa Andersson, Daniel King, Michael Yue,
Olufemi Komolafe, Rob Rennison, Neil Harrison, Kannan Sampath, and
Ronhazli Adam for their valuable comments and suggestions on this
draft.
11. References
11.1. Normative References
[RFC1700] Reynolds, J. and J. Postel, "Assigned Numbers", RFC 1700,
October 1994.
[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.
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[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.
11.2. 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.
[RFC3032] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y.,
Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack
Encoding", RFC 3032, January 2001.
Appendix A. Authors' Addresses
Huaimo Chen
Huawei Technologies
Boston, MA
USA
Email: huaimo.chen@huawei.com
Raveendra Torvi
Juniper Networks
10 Technology Park Drive
Westford, MA 01886
USA
Email: rtorvi@juniper.net
Ning So
Tata Communications
2613 Fairbourne Cir.
Plano, TX 75082
USA
Email: ningso01@gmail.com
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Autumn Liu
Ericsson
300 Holger Way
San Jose, CA 95134
USA
Email: autumn.liu@ericsson.com
Alia Atlas
Juniper Networks
10 Technology Park Drive
Westford, MA 01886
USA
Email: akatlas@juniper.net
Yimin Shen
Juniper Networks
10 Technology Park Drive
Westford, MA 01886
USA
Email: yshen@juniper.net
Tarek Saad
Cisco Systems
Email: tsaad@cisco.com
Fengman Xu
Verizon
2400 N. Glenville Dr
Richardson, TX 75082
USA
Email: fengman.xu@verizon.com
Mehmet Toy
Comcast
1800 Bishops Gate Blvd.
Mount Laurel, NJ 08054
USA
Email: mehmet_toy@cable.comcast.com
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Lei Liu
UC Davis
USA
Email: liulei.kddi@gmail.com
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