Internet Engineering Task Force (IETF) M. Taillon

Internet Engineering Task Force (IETF) M. Taillon
Request for Comments: 8796 Cisco Systems, Inc.
Updates: 4090 T. Saad, Ed.
Category: Standards Track Juniper Networks
ISSN: 2070-1721 R. Gandhi
Cisco Systems, Inc.
A. Deshmukh
Juniper Networks
M. Jork
128 Technology
V. Beeram
Juniper Networks
July 2020

RSVP-TE Summary Fast Reroute Extensions for Label Switched Path (LSP)
Tunnels

Abstract

This document updates RFC 4090 for the Resource Reservation Protocol
(RSVP) Traffic Engineering (TE) procedures defined for facility
backup protection. The updates include extensions that reduce the
amount of signaling and processing that occurs during Fast Reroute
(FRR); as a result, scalability when undergoing FRR convergence after
a link or node failure is improved. These extensions allow the RSVP
message exchange between the Point of Local Repair (PLR) and the
Merge Point (MP) nodes to be independent of the number of protected
Label Switched Paths (LSPs) traversing between them when facility
bypass FRR protection is used. The signaling extensions are fully
backwards compatible with nodes that do not support them.

Status of This Memo

This is an Internet Standards Track document.

This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.

Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc8796.

Copyright Notice

Copyright (c) 2020 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
(https://trustee.ietf.org/license-info) in effect on the date of
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
2. Conventions Used in This Document
2.1. Terminology
2.2. Acronyms and Abbreviations
3. Extensions for Summary FRR Signaling
3.1. B-SFRR-Ready Extended ASSOCIATION Object
3.1.1. IPv4 B-SFRR-Ready Extended Association ID
3.1.2. IPv6 B-SFRR-Ready Extended Association ID
3.1.3. Processing Rules for B-SFRR-Ready Extended ASSOCIATION
Object
3.2. B-SFRR-Active Extended ASSOCIATION Object
3.2.1. IPv4 B-SFRR-Active Extended Association ID
3.2.2. IPv6 B-SFRR-Active Extended Association ID
3.3. Signaling Procedures prior to Failure
3.3.1. PLR Signaling Procedure
3.3.2. MP Signaling Procedure
3.4. Signaling Procedures Post-Failure
3.4.1. PLR Signaling Procedure
3.4.2. MP Signaling Procedure
3.5. Refreshing Summary FRR Active LSPs
4. Backwards Compatibility
5. Security Considerations
6. IANA Considerations
7. References
7.1. Normative References
7.2. Informative References
Acknowledgments
Contributors
Authors' Addresses

1. Introduction

The Fast Reroute (FRR) procedures defined in [RFC4090] describe the
mechanisms for the Point of Local Repair (PLR) to reroute traffic and
signaling of a protected RSVP-TE Label Switched Path (LSP) onto the
bypass tunnel in the event of a TE link or node failure. Such
signaling procedures are performed individually for each affected
protected LSP. This may eventually lead to control-plane scalability
and latency issues on the PLR and/or the Merge Point (MP) nodes due
to limited memory and CPU processing resources. This condition is
exacerbated when the failure affects a large number of protected LSPs
that traverse the same PLR and MP nodes.

For example, in a large-scale deployment of RSVP-TE LSPs, a single
Label Switching Router (LSR) acting as a PLR node may host tens of
thousands of protected RSVP-TE LSPs egressing the same protected link
and also act as an MP node for a similar number of LSPs that ingress
on the same link. In the event of the failure of the link or
neighbor node, the RSVP-TE control plane of the node (when acting as
a PLR node) becomes busy rerouting protected LSPs over the bypass
tunnel(s) in one direction and (when acting as an MP node) becomes
busy merging RSVP states from signaling received over bypass tunnels
for one or more LSPs in the reverse direction. Subsequently, the
head-end Label Edge Routers (LERs) that are notified of the local
repair at any downstream LSRs will attempt to (re)converge the
affected RSVP-TE LSPs onto newly computed paths -- possibly
traversing the same previously affected LSR(s). As a result, the
RSVP-TE control plane becomes overwhelmed (1) by the amount of FRR
RSVP-TE processing overhead following the link or node failure and
(2) due to other control-plane protocols (e.g., IGP) that undergo
convergence on the same node at the same time.

Today, each protected RSVP-TE LSP is signaled individually over the
bypass tunnel after FRR. The changes introduced in this document
allow the PLR node to assign multiple protected LSPs to a bypass
tunnel group and to communicate this assignment to the MP, such that
upon failure, the signaling over the bypass tunnel happens on one or
more bypass tunnel groups. This document defines new extensions that

1. update the procedures defined in [RFC4090] for facility backup
protection, to enable the MP node to become aware of the PLR
node's bypass tunnel assignment group or groups.

2. allow FRR procedures between the PLR and the MP nodes to be
signaled and processed on one or more per-bypass tunnel groups.

As defined in [RFC2961], summary refresh procedures use MESSAGE_ID to
refresh the RSVP Path and Resv states to help with scaling. The
Summary FRR procedures introduced in this document build on those
concepts to allow the MESSAGE_ID(s) to be exchanged on one or more
per-bypass tunnel assignment groups and continue to use summary
refresh procedures while reducing the amount of messaging that occurs
after rerouting signaling over the bypass tunnel post-FRR.

2. Conventions Used in This Document

2.1. Terminology

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.

2.2. Acronyms and Abbreviations

It is assumed that the reader is familiar with the terms and
abbreviations used in [RFC3209] and [RFC4090].

The following abbreviations are also used in this document:

LSR: Label Switching Router

LER: Label Edge Router

MPLS: Multiprotocol Label Switching

LSP: Label Switched Path

MP: Merge Point node as defined in [RFC4090]

PLR: Point of Local Repair node as defined in [RFC4090]

FRR: Fast Reroute as defined in [RFC4090]

B-SFRR-Ready: Bypass Summary FRR Ready Extended ASSOCIATION object.
Added by the PLR node for each LSP protected by the bypass tunnel

B-SFRR-Active: Bypass Summary FRR Active Extended ASSOCIATION
object. Used to notify the MP node that one or more groups of
protected LSPs have been rerouted over the associated bypass
tunnel

MTU: Maximum Transmission Unit

3. Extensions for Summary FRR Signaling

The RSVP ASSOCIATION object is defined in [RFC4872] as a means to
associate LSPs with each other. For example, in the context of one
or more GMPLS-controlled LSPs, the ASSOCIATION object is used to
associate a recovery LSP with the LSP(s) it is protecting. The
Extended ASSOCIATION object is introduced in [RFC6780] to expand on
the possible usage of the ASSOCIATION object and generalize the
definition of the Extended Association ID field.

This document defines the use of the Extended ASSOCIATION object to
carry the Summary FRR information and associate the protected LSP or
LSPs with the bypass tunnel that protects them. Two new Association
Types for the Extended ASSOCIATION object, and new Extended
Association IDs, are defined in this document to describe the Bypass
Summary FRR Ready (B-SFRR-Ready) and Bypass Summary FRR Active
(B-SFRR-Active) associations.

The PLR node creates and manages the Summary FRR LSP groups
(identified by Bypass_Group_Identifiers) and shares the group
identifiers with the MP via signaling.

A PLR node SHOULD assign the same Bypass_Group_Identifier to all
protected LSPs provided that the protected LSPs:

* share the same outgoing protected interface,

* are protected by the same bypass tunnel, and

* are assigned the same tunnel sender address that is used for
backup path identification after FRR as described in [RFC4090].

This minimizes the number of bypass tunnel Summary FRR groups and
optimizes the amount of signaling that occurs between the PLR and the
MP nodes after FRR.

A PLR node that supports Summary FRR procedures adds an Extended
ASSOCIATION object with a B-SFRR-Ready Extended Association ID in the
RSVP Path message of the protected LSP. The PLR node adds the
protected LSP Bypass_Group_Identifier, information from the assigned
bypass tunnel, and a MESSAGE_ID object into the B-SFRR-Ready Extended
Association ID. The MP uses the information contained in the
received B-SFRR-Ready Extended Association ID to refresh and merge
the protected LSP Path state after FRR occurs.

An MP node that supports Summary FRR procedures adds the B-SFRR-Ready
Extended ASSOCIATION object and respective Extended Association ID in
the RSVP Resv message of the protected LSP to acknowledge the PLR's
bypass tunnel assignment and provide the MESSAGE_ID object that the
MP node will use to refresh the protected LSP Resv state after FRR
occurs.

The MP maintains the PLR node group assignments learned from
signaling and acknowledges the group assignments to the PLR node via
signaling. Once the PLR node receives the group assignment
acknowledgment from the MP, the FRR signaling can proceed based on
Summary FRR procedures as described in this document.

The B-SFRR-Active Extended ASSOCIATION object with Extended
Association ID is sent by the PLR node after activating the Summary
FRR procedures. The B-SFRR-Active Extended ASSOCIATION object with
Extended Association ID is sent within the RSVP Path message of the
bypass tunnel to inform the MP node that one or more groups of
protected LSPs protected by the bypass tunnel are now being rerouted
over the bypass tunnel.

3.1. B-SFRR-Ready Extended ASSOCIATION Object

The Extended ASSOCIATION object is populated using the rules defined
below to associate a protected LSP with the bypass tunnel that is
protecting it when Summary FRR procedures are enabled.

The Association Type, Association ID, and Association Source MUST be
set as defined in [RFC4872] for the ASSOCIATION object. More
specifically:

Association Source:
The Association Source is set to an address of the PLR node.

Association Type:
A new Association Type is defined for B-SFRR-Ready as follows:

+=======+=====================================================+
| Value | Type |
+=======+=====================================================+
| 5 | Bypass Summary FRR Ready Association (B-SFRR-Ready) |
+-------+-----------------------------------------------------+

Table 1: The B-SFRR-Ready Association Type

The Extended ASSOCIATION object's Global Association Source MUST be
set according to the rules defined in [RFC6780].

The B-SFRR-Ready Extended Association ID is populated by the PLR node
when performing Bypass Summary FRR Ready association for a protected
LSP. The rules governing its population are described in the
subsequent sections.

3.1.1. IPv4 B-SFRR-Ready Extended Association ID

The IPv4 Extended Association ID for the B-SFRR-Ready Association
Type is carried inside the IPv4 Extended ASSOCIATION object and has
the following format:

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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Bypass_Tunnel_ID | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Bypass_Source_IPv4_Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Bypass_Destination_IPv4_Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Bypass_Group_Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MESSAGE_ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 1: The IPv4 Extended Association ID for B-SFRR-Ready

Bypass_Tunnel_ID: 16 bits

The bypass tunnel identifier.

Reserved: 16 bits

Reserved for future use. MUST be set to zero when sending and
ignored on receipt.

Bypass_Source_IPv4_Address: 32 bits

The bypass tunnel source IPv4 address.

Bypass_Destination_IPv4_Address: 32 bits

The bypass tunnel destination IPv4 address.

Bypass_Group_Identifier: 32 bits

The bypass tunnel group identifier that is assigned to the LSP.

MESSAGE_ID: A MESSAGE_ID object as defined by [RFC2961].

3.1.2. IPv6 B-SFRR-Ready Extended Association ID

The IPv6 Extended Association ID for the B-SFRR-Ready Association
Type is carried inside the IPv6 Extended ASSOCIATION object and has
the following format:

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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Bypass_Tunnel_ID | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Bypass_Source_IPv6_Address +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Bypass_Destination_IPv6_Address +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Bypass_Group_Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MESSAGE_ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 2: The IPv6 Extended Association ID for B-SFRR-Ready

Bypass_Tunnel_ID: 16 bits

The bypass tunnel identifier.

Reserved: 16 bits

Reserved for future use. MUST be set to zero when sending and
ignored on receipt.

Bypass_Source_IPv6_Address: 128 bits

The bypass tunnel source IPv6 address.

Bypass_Destination_IPv6_Address: 128 bits

The bypass tunnel destination IPv6 address.

Bypass_Group_Identifier: 32 bits

The bypass tunnel group identifier that is assigned to the LSP.

MESSAGE_ID: A MESSAGE_ID object as defined by [RFC2961].

3.1.3. Processing Rules for B-SFRR-Ready Extended ASSOCIATION Object

A PLR node assigns a bypass tunnel and Bypass_Group_Identifier for
each protected LSP. The same Bypass_Group_Identifier is used for the
set of protected LSPs that share the same bypass tunnel, traverse the
same egress link, and are not already rerouted. The PLR node MUST
generate a MESSAGE_ID object with Epoch and Message_Identifier set
according to [RFC2961]. The MESSAGE_ID object Flags MUST be cleared
when transmitted by the PLR node and ignored when received at the MP
node.

A PLR node MUST generate a new Message_Identifier each time the
contents of the B-SFRR-Ready Extended Association ID change (e.g.,
when the PLR node changes the bypass tunnel assignment).

A PLR node notifies the MP node of the bypass tunnel assignment via
adding a B-SFRR-Ready Extended ASSOCIATION object and Extended
Association ID in the RSVP Path message for the protected LSP, using
the procedures described in Section 3.3.

An MP node acknowledges the assignment to the PLR node by signaling
the B-SFRR-Ready Extended ASSOCIATION object and Extended Association
ID within the RSVP Resv message of the protected LSP. With the
exception of the MESSAGE_ID object, all other fields from the
received B-SFRR-Ready Extended Association ID in the RSVP Path
message are copied into the B-SFRR-Ready Extended Association ID to
be added in the Resv message. The MESSAGE_ID object is set according
to [RFC2961]. The MESSAGE_ID object Flags MUST be cleared when
transmitted by the MP node and ignored when received at the PLR node.
A new Message_Identifier MUST be used to acknowledge an updated PLR
node's assignment.

A PLR node considers the protected LSP as Summary FRR capable only if
all the fields in the B-SFRR-Ready Extended Association ID that are
sent in the RSVP Path message match the fields received in the RSVP
Resv message (with the exception of the MESSAGE_ID). If the fields
do not match or if the B-SFRR-Ready Extended ASSOCIATION object is
absent in a subsequent refresh, the PLR node MUST consider the
protected LSP as not Summary FRR capable.

A race condition may arise for a previously Summary FRR-capable
protected LSP when the MP node triggers a refresh that does not
contain the B-SFRR-Ready Extended ASSOCIATION object, while at the
same time the PLR triggers Summary FRR procedures due to a fault
occurring concurrently. In this case, it is possible that the PLR
triggers Summary FRR procedures on the protected LSP before it can
receive and process the refresh from the MP node. As a result, the
MP will receive an Srefresh with a Message_Identifier that is not
associated with any state. As per [RFC2961], this results in the MP
generating an Srefresh NACK for this Message_Identifier and sending
it back to the PLR. The PLR processes the Srefresh NACK, replays the
full Path state associated with the Message_Identifier, and
subsequently recovers from this condition.

3.2. B-SFRR-Active Extended ASSOCIATION Object

The Extended ASSOCIATION object for the B-SFRR-Active Association
Type is populated by a PLR node to indicate to the MP node (the
bypass tunnel destination) that one or more groups of Summary
FRR-capable protected LSPs that are being protected by the bypass
tunnel are being rerouted over the bypass tunnel.

The B-SFRR-Active Extended ASSOCIATION object is carried in the RSVP
Path message of the bypass tunnel and signaled downstream towards the
MP (the bypass tunnel destination).

The Association Type, Association ID, and Association Source MUST be
set as defined in [RFC4872] for the ASSOCIATION object. More
specifically:

Association Source:
The Association Source is set to an address of the PLR node.

Association Type:
A new Association Type is defined for B-SFRR-Active as follows:

+=======+=======================================================+
| Value | Type |
+=======+=======================================================+
| 6 | Bypass Summary FRR Active Association (B-SFRR-Active) |
+-------+-------------------------------------------------------+

Table 2: The B-SFRR-Active Association Type

Extended Association ID for B-SFRR-Active:
The B-SFRR-Active Extended Association ID is populated by the PLR
node for the Bypass Summary FRR Active association. The rules to
populate the Extended Association ID in this case are described
below.

3.2.1. IPv4 B-SFRR-Active Extended Association ID

The IPv4 Extended Association ID for the B-SFRR-Active Association
Type is carried inside the IPv4 Extended ASSOCIATION object and has
the following format:

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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Num-BGIDs | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Bypass_Group_Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| : |
// : //
| : |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Bypass_Group_Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// RSVP_HOP_Object //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// TIME_VALUES //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 tunnel sender address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 3: The IPv4 Extended Association ID for B-SFRR-Active

Num-BGIDs: 16 bits

Number of Bypass_Group_Identifier fields.

Reserved: 16 bits

Reserved for future use.

Bypass_Group_Identifier: 32 bits each

A Bypass_Group_Identifier that was previously signaled by the PLR
using the Extended ASSOCIATION object in the B-SFRR-Ready Extended
Association ID. One or more Bypass_Group_Identifiers MAY be
included.

RSVP_HOP_Object: Class 3, as defined by [RFC2205]

Replacement RSVP_HOP object to be applied to all LSPs associated
with each of the following Bypass_Group_Identifiers. This
corresponds to C-Type = 1 for IPv4 RSVP_HOP.

TIME_VALUES object: Class 5, as defined by [RFC2205]

Replacement TIME_VALUES object to be applied to all LSPs
associated with each of the preceding Bypass_Group_Identifiers
after receiving the B-SFRR-Active Extended ASSOCIATION object.

IPv4 tunnel sender address:
The IPv4 address that the PLR node sets to identify one or more
backup paths as described in Section 6.1.1 of [RFC4090]. This
address is applicable to all groups identified by any
Bypass_Group_Identifiers carried in the B-SFRR-Active Extended
Association ID.

3.2.2. IPv6 B-SFRR-Active Extended Association ID

The IPv6 Extended Association ID for the B-SFRR-Active Association
Type is carried inside the IPv6 Extended ASSOCIATION object and has
the following format:

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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Num-BGIDs | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Bypass_Group_Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| : |
// : //
| : |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Bypass_Group_Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// RSVP_HOP_Object //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// TIME_VALUES //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ IPv6 tunnel sender address +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 4: The IPv6 Extended Association ID for B-SFRR-Active

Num-BGIDs: 16 bits

Number of Bypass_Group_Identifier fields.

Reserved: 16 bits

Reserved for future use.

Bypass_Group_Identifier: 32 bits each

A Bypass_Group_Identifier that was previously signaled by the PLR
using the Extended ASSOCIATION object in the B-SFRR-Ready Extended
Association ID. One or more Bypass_Group_Identifiers MAY be
included.

RSVP_HOP_Object: Class 3, as defined by [RFC2205]

Replacement RSVP_HOP object to be applied to all LSPs associated
with each of the following Bypass_Group_Identifiers. This
corresponds to C-Type = 2 for IPv6 RSVP_HOP.

TIME_VALUES object: Class 5, as defined by [RFC2205]

Replacement TIME_VALUES object to be applied to all LSPs
associated with each of the following Bypass_Group_Identifiers
after receiving the B-SFRR-Active Extended ASSOCIATION object.

IPv6 tunnel sender address:
The IPv6 address that the PLR node sets to identify one or more
backup paths as described in Section 6.1.1 of [RFC4090]. This
address is applicable to all groups identified by any
Bypass_Group_Identifiers carried in the B-SFRR-Active Extended
Association ID.

3.3. Signaling Procedures prior to Failure

Before Summary FRR procedures can be used, a handshake MUST be
completed between the PLR and MP nodes. This handshake is performed
using the Extended ASSOCIATION object that carries the B-SFRR-Ready
Extended Association ID in both the RSVP Path and Resv messages of
the protected LSP.

The facility backup method introduced in [RFC4090] takes advantage of
MPLS label stacking (the PLR node imposes additional MPLS labels
post-FRR) to allow rerouting of protected traffic over the backup
path. The backup path may have stricter MTU requirements; due to
label stacking at the PLR node, the protected traffic may exceed the
backup path MTU. It is assumed that the operator engineers their
network to allow rerouting of protected traffic and the additional
label stacking at the PLR node in order to not exceed the backup path
MTU.

When using the procedures defined in this document, the PLR node MUST
ensure that the bypass tunnel assignment can satisfy the protected
LSP MTU requirements post-FRR. This prevents any packets from being
dropped due to exceeding the MTU size of the backup path after
traffic is rerouted onto the bypass tunnel post-failure. Section 2.6
of [RFC3209] describes a mechanism to determine whether a node needs
to fragment or drop a packet when it exceeds the path MTU discovered
using RSVP signaling on the primary LSP path. A PLR can leverage the
RSVP-discovered path MTU on the backup and primary LSP paths to
ensure that the MTU is not exceeded before or after rerouting the
protected traffic onto the bypass tunnel.

3.3.1. PLR Signaling Procedure

The B-SFRR-Ready Extended ASSOCIATION object is added by each PLR
node in the RSVP Path message of the protected LSP to record the
bypass tunnel assignment. This object is updated every time the PLR
node updates the bypass tunnel assignment. This results in
triggering an RSVP Path change message.

Upon receiving an RSVP Resv message with a B-SFRR-Ready Extended
ASSOCIATION object, the PLR node checks to see if the expected
subobjects from the B-SFRR-Ready Extended Association ID are present.
If present, the PLR node determines if the MP has acknowledged the
current PLR node's assignment.

To be a valid acknowledgment, the received B-SFRR-Ready Extended
Association ID contents within the RSVP Resv message of the protected
LSP MUST match the latest B-SFRR-Ready Extended ASSOCIATION object
and Association ID contents that the PLR node had sent within the
RSVP Path message (with the exception of the MESSAGE_ID).

Note that when forwarding an RSVP Resv message upstream, the PLR node
SHOULD remove any/all B-SFRR-Ready Extended ASSOCIATION objects whose
Bypass_Source_IPv4_Address or Bypass_Source_IPv6_Address field
matches any of the PLR node addresses.

3.3.2. MP Signaling Procedure

Upon receiving an RSVP Path message with a B-SFRR-Ready Extended
ASSOCIATION object, an MP node processes all (there may be multiple
PLR nodes for a single MP node) B-SFRR-Ready Extended ASSOCIATION
objects that have the MP node address as the bypass destination
address in the Extended Association ID.

The MP node first ensures the existence of the bypass tunnel and that
the Bypass_Group_Identifier is not already FRR Active. That is, an
LSP cannot join a group that is already FRR rerouted.

The MP node builds a mirrored Summary FRR group database per PLR node
by associating the Bypass_Source_IPv4_Address or
Bypass_Source_IPv6_Address that is carried in the IPv4 or IPv6
B-SFRR-Ready Extended Association IDs, respectively.

The MESSAGE_ID is extracted and recorded for the protected LSP Path
state. The MP node signals a B-SFRR-Ready Extended ASSOCIATION
object and Extended Association ID in the RSVP Resv message of the
protected LSP. With the exception of the MESSAGE_ID objects, all
other fields of the received B-SFRR-Ready Extended ASSOCIATION object
in the RSVP Path message are copied into the B-SFRR-Ready Extended
ASSOCIATION object to be added in the Resv message. The MESSAGE_ID
object is set according to [RFC2961] with the Flags cleared.

Note that an MP may receive more than one RSVP Path message with the
B-SFRR-Ready Extended ASSOCIATION object from one or more different
upstream PLR nodes. In this case, the MP node is expected to save
all the received MESSAGE_IDs received from the different upstream PLR
nodes. After a failure, the MP node determines and activates the
state(s) associated with the Bypass_Group_Identifier(s) received in
the RSVP Path message containing the B-SFRR-Active Extended
ASSOCIATION object that is signaled over the bypass tunnel from the
PLR node, as described in Section 3.4.

When forwarding an RSVP Path message downstream, the MP node SHOULD
remove any/all B-SFRR-Ready Extended ASSOCIATION objects whose
Bypass_Destination_IPv4_Address or Bypass_Destination_IPv6_Address
field matches any of the MP node addresses.

3.4. Signaling Procedures Post-Failure

Upon detection of a fault (egress link or node failure), the PLR node
will first perform the object modification procedures described by
Section 6.4.3 of [RFC4090] for all affected protected LSPs. For the
Summary FRR-capable LSPs that are assigned to the same bypass tunnel,
a common RSVP_HOP and SENDER_TEMPLATE MUST be used.

The PLR node MUST signal non-Summary FRR-capable LSPs over the bypass
tunnel before signaling the Summary FRR-capable LSPs. This is needed
to allow for the case where the PLR node recently changed a bypass
assignment and the MP has not processed the change yet.

The B-SFRR-Active Extended ASSOCIATION object is sent within the RSVP
Path message of the bypass tunnel to reroute the RSVP state of
Summary FRR-capable LSPs.

3.4.1. PLR Signaling Procedure

After a failure event, when using the Summary FRR path signaling
procedures, an individual RSVP Path message is not signaled for each
Summary FRR LSP. Instead, to reroute Summary FRR LSPs via the bypass
tunnel, the PLR node adds the B-SFRR-Active Extended ASSOCIATION
object in the RSVP Path message of the RSVP session of the bypass
tunnel.

The RSVP_HOP_Object field in the B-SFRR-Active Extended Association
ID is set to a common object that will be applied to all LSPs
associated with the Bypass_Group_Identifiers that are carried in the
B-SFRR-Active Extended Association ID.

The PLR node adds the Bypass_Group_Identifier(s) of any group or
groups that have common group attributes, including the tunnel sender
address, to the same B-SFRR-Active Extended Association ID. Note
that multiple ASSOCIATION objects, each carrying a B-SFRR-Active
Extended Association ID, can be carried within a single RSVP Path
message of the bypass tunnel and sent towards the MP as described in
[RFC6780].

Any previously received MESSAGE_IDs from the MP are activated on the
PLR. As a result, the PLR starts sending Srefresh messages
containing the specific Message_Identifier(s) for the states to be
refreshed.

3.4.2. MP Signaling Procedure

Upon receiving an RSVP Path message with a B-SFRR-Active Extended
ASSOCIATION object, the MP performs normal merge point processing for
each protected LSP associated with each Bypass_Group_Identifier, as
if it had received an individual RSVP Path message for that LSP.

For each Summary FRR-capable LSP that is being merged, the MP first
modifies the Path state as follows:

1. The RSVP_HOP object is copied from the RSVP_HOP_Object field in
the B-SFRR-Active Extended Association ID.

2. The TIME_VALUES object is copied from the TIME_VALUES field in
the B-SFRR-Active Extended Association ID. The TIME_VALUES
object contains the refresh period of the PLR node, and it is
used to generate periodic refreshes. The TIME_VALUES object
carried in the B-SFRR-Active Extended Association ID matches the
one that would have been exchanged in a full Path message sent to
the MP after the failure when no Summary FRR procedures are used.

3. The tunnel sender address field in the SENDER_TEMPLATE object is
copied from the tunnel sender address field of the B-SFRR-Active
Extended Association ID.

4. The Explicit Route Object (ERO) is modified as per Section 6.4.4
of [RFC4090]. Once the above modifications are completed, the MP
node performs merge processing as per [RFC4090].

5. Any previously received MESSAGE_IDs from the PLR node are
activated. The MP is allowed to send Srefresh messages
containing the specific Message_Identifier(s) for the states to
be refreshed.

A failure during merge processing of any individual rerouted LSP MUST
result in an RSVP PathErr message.

An individual RSVP Resv message for each successfully merged Summary
FRR LSP is not signaled. The MP node SHOULD immediately use summary
refresh procedures to refresh the protected LSP Resv state.

3.5. Refreshing Summary FRR Active LSPs

The refreshing of Summary FRR Active LSPs is performed using summary
refresh as defined by [RFC2961].

4. Backwards Compatibility

The (Extended) ASSOCIATION object is defined in [RFC4872] with a
class number in the form 11bbbbbb, where b=0 or 1. This ensures
compatibility with nodes that do not provide support, in accordance
with the procedures specified in Section 3.10 of [RFC2205] regarding
unknown-class objects. Such nodes will ignore the object and forward
it without any modification.

5. Security Considerations

This document updates an existing RSVP object -- the Extended
ASSOCIATION object as described in Section 3. Thus, in the event of
the interception of a signaling message, slightly more information
could be deduced about the state of the network than was previously
the case.

When using the procedures defined in this document, FRR signaling for
rerouting of the states of one or more protected LSPs onto the bypass
tunnel can be performed on a group of protected LSPs with a single
RSVP message. This allows an intruder to potentially impact and
manipulate a set of protected LSPs that are assigned to the same
bypass tunnel group. Note that such an attack is possible even
without the mechanisms defined in this document, albeit at an extra
cost resulting from the excessive per-LSP signaling that will occur.

Existing mechanisms for maintaining the integrity and authenticity of
RSVP messages [RFC2747] can be applied. Other considerations
mentioned in [RFC4090] and [RFC5920] also apply.

6. IANA Considerations

IANA maintains the "Generalized Multi-Protocol Label Switching
(GMPLS) Signaling Parameters" registry. The "Association Type"
subregistry is included in this registry.

This registry has been updated with the new Association Types for the
Extended ASSOCIATION objects defined in this document as follows:

+=======+===========================+=============+
| Value | Name | Reference |
+=======+===========================+=============+
| 5 | B-SFRR-Ready Association | Section 3.1 |
+-------+---------------------------+-------------+
| 6 | B-SFRR-Active Association | Section 3.2 |
+-------+---------------------------+-------------+

Table 3: New Extended ASSOCIATION Object
Association Types

7. References

7.1. Normative References

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.

[RFC2205] Braden, R., Ed., Zhang, L., Berson, S., Herzog, S., and S.
Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1
Functional Specification", RFC 2205, DOI 10.17487/RFC2205,
September 1997, <https://www.rfc-editor.org/info/rfc2205>.

[RFC2747] Baker, F., Lindell, B., and M. Talwar, "RSVP Cryptographic
Authentication", RFC 2747, DOI 10.17487/RFC2747, January
2000, <https://www.rfc-editor.org/info/rfc2747>.

[RFC2961] Berger, L., Gan, D., Swallow, G., Pan, P., Tommasi, F.,
and S. Molendini, "RSVP Refresh Overhead Reduction
Extensions", RFC 2961, DOI 10.17487/RFC2961, April 2001,
<https://www.rfc-editor.org/info/rfc2961>.

[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001,
<https://www.rfc-editor.org/info/rfc3209>.

[RFC4090] Pan, P., Ed., Swallow, G., Ed., and A. Atlas, Ed., "Fast
Reroute Extensions to RSVP-TE for LSP Tunnels", RFC 4090,
DOI 10.17487/RFC4090, May 2005,
<https://www.rfc-editor.org/info/rfc4090>.

[RFC4872] Lang, J.P., Ed., Rekhter, Y., Ed., and D. Papadimitriou,
Ed., "RSVP-TE Extensions in Support of End-to-End
Generalized Multi-Protocol Label Switching (GMPLS)
Recovery", RFC 4872, DOI 10.17487/RFC4872, May 2007,
<https://www.rfc-editor.org/info/rfc4872>.

[RFC6780] Berger, L., Le Faucheur, F., and A. Narayanan, "RSVP
ASSOCIATION Object Extensions", RFC 6780,
DOI 10.17487/RFC6780, October 2012,
<https://www.rfc-editor.org/info/rfc6780>.

[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.

7.2. Informative References

[RFC5920] Fang, L., Ed., "Security Framework for MPLS and GMPLS
Networks", RFC 5920, DOI 10.17487/RFC5920, July 2010,
<https://www.rfc-editor.org/info/rfc5920>.

Acknowledgments

The authors would like to thank Alexander Okonnikov, Loa Andersson,
Lou Berger, Eric Osborne, Gregory Mirsky, and Mach Chen for reviewing
and providing valuable comments on this document.

Contributors

Nicholas Tan
Arista Networks

Email: [email protected]

Authors' Addresses

Mike Taillon
Cisco Systems, Inc.

Email: [email protected]

Tarek Saad (editor)
Juniper Networks

Email: [email protected]

Rakesh Gandhi
Cisco Systems, Inc.

Email: [email protected]

Abhishek Deshmukh
Juniper Networks

Email: [email protected]

Markus Jork
128 Technology

Email: [email protected]

Vishnu Pavan Beeram
Juniper Networks

Email: [email protected]