Internet DRAFT - draft-ietf-teas-gmpls-lsp-fastreroute
draft-ietf-teas-gmpls-lsp-fastreroute
TEAS Working Group M. Taillon
Internet-Draft T. Saad, Ed.
Updates: 4090 R. Gandhi, Ed.
Intended Status: Standards Track Z. Ali
Expires: March 1, 2018 Cisco Systems, Inc.
M. Bhatia
Nokia
August 28, 2017
Updates to Resource Reservation Protocol For Fast Reroute of
Traffic Engineering GMPLS LSPs
draft-ietf-teas-gmpls-lsp-fastreroute-12
Abstract
This document updates the Resource Reservation Protocol - Traffic
Engineering (RSVP-TE) Fast Reroute (FRR) procedures defined in RFC
4090 to support Packet Switched Capable (PSC) Generalized Multi-
Protocol Label Switching (GMPLS) Label Switched Paths (LSPs). These
updates allow the coordination of a bidirectional bypass tunnel
assignment protecting a common facility in both forward and reverse
directions of a co-routed bidirectional LSP. In addition, these
updates enable the re-direction of bidirectional traffic onto bypass
tunnels that ensure co-routedness of data paths in the forward and
reverse directions after FRR and avoid RSVP soft-state timeout in
control-plane.
Status of this Memo
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Copyright Notice
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Copyright (c) 2017 IETF Trust and the persons identified as the
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Conventions Used in This Document . . . . . . . . . . . . . . 5
2.1. Key Word Definitions . . . . . . . . . . . . . . . . . . . 5
2.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 5
2.3. Abbreviations . . . . . . . . . . . . . . . . . . . . . . 6
3. Fast Reroute For Unidirectional GMPLS LSPs . . . . . . . . . . 6
4. Bypass Tunnel Assignment For Bidirectional GMPLS LSPs . . . . 6
4.1. Bidirectional GMPLS Bypass Tunnel Direction . . . . . . . 7
4.2. Merge Point Labels . . . . . . . . . . . . . . . . . . . . 7
4.3. Merge Point Addresses . . . . . . . . . . . . . . . . . . 7
4.4. RRO IPv4/IPv6 Subobject Flags . . . . . . . . . . . . . . 8
4.5. Bidirectional Bypass Tunnel Assignment Co-ordination . . . 8
4.5.1. Bidirectional Bypass Tunnel Assignment Signaling
Procedure . . . . . . . . . . . . . . . . . . . . . . 8
4.5.2. One-to-one Bidirectional Bypass Tunnel Assignment . . 10
4.5.3. Multiple Bidirectional Bypass Tunnel Assignments . . . 10
5. Fast Reroute For Bidirectional GMPLS LSPs with In-band
Signaling . . . . . . . . . . . . . . . . . . . . . . . . . . 11
5.1. Link Protection for Bidirectional GMPLS LSPs . . . . . . . 12
5.1.1. Behavior After Link Failure . . . . . . . . . . . . . 12
5.1.2. Revertive Behavior After Fast Reroute . . . . . . . . 12
5.2. Node Protection for Bidirectional GMPLS LSPs . . . . . . . 13
5.2.1. Behavior After Link Failure . . . . . . . . . . . . . 14
5.2.2. Behavior After Link Failure To Re-coroute . . . . . . 14
5.2.2.1. Re-coroute in Data-plane After Link Failure . . . 15
5.2.3. Revertive Behavior After Fast Reroute . . . . . . . . 15
5.2.4. Behaviour After Node Failure . . . . . . . . . . . . . 16
5.3. Unidirectional Link Failures . . . . . . . . . . . . . . . 16
6. Fast Reroute For Bidirectional GMPLS LSPs with Out-of-band
Signaling . . . . . . . . . . . . . . . . . . . . . . . . . . 17
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7. Message and Object Definitions . . . . . . . . . . . . . . . . 17
7.1. BYPASS_ASSIGNMENT Subobject . . . . . . . . . . . . . . . 17
7.2. FRR Bypass Assignment Error Notify Message . . . . . . . . 19
8. Compatibility . . . . . . . . . . . . . . . . . . . . . . . . 19
9. Security Considerations . . . . . . . . . . . . . . . . . . . 19
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20
10.1. BYPASS_ASSIGNMENT Subobject . . . . . . . . . . . . . . . 20
10.2. FRR Bypass Assignment Error Notify Message . . . . . . . 20
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 22
11.1. Normative References . . . . . . . . . . . . . . . . . . 22
11.2. Informative References . . . . . . . . . . . . . . . . . 22
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . 23
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 24
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1. Introduction
Packet Switched Capable (PSC) Traffic Engineering (TE) Label Switched
Paths (LSPs) can be setup using Generalized Multi-Protocol Label
Switching (GMPLS) signaling procedures specified in [RFC3473] for
both unidirectional and bidirectional tunnels. The GMPLS signaling
allows sending and receiving the RSVP messages in-band with the data
traffic or out-of-band over a separate control-channel. Fast Reroute
(FRR) [RFC4090] has been widely deployed in the packet TE networks
today and is desirable for TE GMPLS LSPs. Using FRR methods also
allows the leveraging of the existing mechanisms for failure
detection and restoration in deployed networks.
The FRR procedures defined in [RFC4090] describe the behavior of the
Point of Local Repair (PLR) to reroute traffic and signaling onto the
bypass tunnel in the event of a failure for protected LSPs. Those
procedures are applicable to the unidirectional protected LSPs
signaled using either RSVP-TE [RFC3209] or GMPLS procedures
[RFC3473]. When using the FRR procedures defined in [RFC4090] with
co-routed bidirectional GMPLS LSPs, it is desired that same PLR and
Merge Point (MP) pairs are selected in each direction and both PLR
and MP assign the same bidirectional bypass tunnel. This document
updates the FRR procedures defined in [RFC4090] to coordinate the
bidirectional bypass tunnel assignment and to exchange MP labels
between upstream and downstream PLRs of the protected co-routed
bidirectional LSP.
When using FRR procedures with co-routed bidirectional GMPLS LSPs, it
is possible in some cases for the RSVP signaling refreshes to stop
reaching certain nodes along the protected LSP path after the PLRs
finish rerouting of the signaling messages. This can occur after a
failure event when using node protection bypass tunnels. As shown in
Figure 2, this is possible even with selecting the same bidirectional
bypass tunnels in both directions and the same PLR and MP pairs.
This is caused by the asymmetry of paths that may be taken by the
bidirectional LSP's signaling in the forward and reverse directions
due to upstream and downstream PLRs independently triggering FRR. In
such cases, after FRR, the RSVP soft-state timeout causes the
protected bidirectional LSP to be torn down, with subsequent traffic
loss.
Protection State Coordination Protocol [RFC6378] is applicable to FRR
[RFC4090] for local protection of co-routed bidirectional LSPs in
order to minimize traffic disruptions in both directions. However,
this does not address the above mentioned problem of RSVP soft-state
timeout that can occur in the control-plane.
This document defines a solution to the RSVP soft-state timeout issue
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by providing mechanisms in the control-plane to complement the FRR
procedures of [RFC4090]. The solution allows to maintain the RSVP
soft-state for co-routed bidirectional protected GMPLS LSPs in the
control-plane and achieve co-routedness of the paths followed by the
traffic in the forward and reverse directions after FRR.
The procedures defined in this document apply to GMPLS signaled PSC
TE co-routed bidirectional protected LSPs and co-routed bidirectional
FRR bypass tunnels. Unless otherwise specified in this document, the
FRR procedures defined in [RFC4090] are not modified by this
document. The FRR mechanism for associated bidirectional GMPLS LSPs
where two unidirectional GMPLS LSPs are bound together by using the
association signaling [RFC7551] is outside the scope of this
document.
2. Conventions Used in This Document
2.1. Key Word Definitions
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 [RFC2119].
2.2. Terminology
The reader is assumed to be familiar with the terminology in
[RFC2205], [RFC3209], [RFC3471], [RFC3473], and [RFC4090].
Downstream PLR: Downstream Point of Local Repair. The PLR that
locally detects a failure in the downstream direction of the
traffic flow and reroutes traffic in the same direction of the
protected bidirectional LSP RSVP Path signaling. A downstream PLR
has a corresponding downstream MP.
Downstream MP: Downstream Merge Point. The LSR where one or more
backup tunnels rejoin the path of the protected LSP in the
downstream direction of the traffic flow. The same LSR can be
both a downstream MP and an upstream PLR simultaneously.
Upstream PLR: Upstream Point of Local Repair. The PLR that locally
detects a failure in the upstream direction of the traffic flow
and reroutes traffic in the opposite direction of the protected
bidirectional LSP RSVP Path signaling. An upstream PLR has a
corresponding upstream MP.
Upstream MP: Upstream Merge Point. The LSR where one or more backup
tunnels rejoin the path of the protected LSP in the upstream
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direction of the traffic flow. The same LSR can be both an
upstream MP and a downstream PLR simultaneously.
Point of Remote Repair (PRR): A downstream MP that assumes the role
of upstream PLR upon receiving protected LSP's rerouted Path
message and triggers reroute of traffic and signaling in the
upstream direction of the traffic flow using the procedures
described in this document.
2.3. Abbreviations
GMPLS: Generalized Multi-Protocol Label Switching
LSP: Label Switched Path
LSR: Label Switching Router
MP: Merge Point
MPLS: Multi-Protocol Label Switching
PLR: Point of Local Repair
PSC: Packet Switched Capable
RSVP: Resource ReSerVation Protocol
TE: Traffic Engineering
3. Fast Reroute For Unidirectional GMPLS LSPs
The FRR procedures defined in [RFC4090] for RSVP-TE signaling
[RFC3209] are equally applicable to the unidirectional protected LSPs
signaled using GMPLS [RFC3473] and are not modified by the updates
defined in this document except the following.
When using the GMPLS out-of-band signaling [RFC3473], after a link
failure event, the RSVP messages are not rerouted over the bypass
tunnel by the downstream PLR but instead rerouted over a
control-channel to the downstream MP.
4. Bypass Tunnel Assignment For Bidirectional GMPLS LSPs
This section describes signaling procedures for FRR bidirectional
bypass tunnel assignment for GMPLS signaled PSC co-routed
bidirectional TE LSPs for both in-band and out-of-band signaling.
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4.1. Bidirectional GMPLS Bypass Tunnel Direction
This document defines procedures where bidirectional GMPLS bypass
tunnels are signaled in the same direction as the protected GMPLS
LSPs. In other words, the bidirectional GMPLS bypass tunnels
originate on the downstream PLRs and terminate on the corresponding
downstream MPs. As the originating downstream PLR has the policy
information about the locally provisioned bypass tunnels, it always
initiates the bypass tunnel assignment. The bidirectional GMPLS
bypass tunnels originating from the upstream PLRs and terminating on
the corresponding upstream MPs are outside the scope of this
document.
4.2. Merge Point Labels
To correctly reroute data traffic over a node protection bypass
tunnel, the downstream and upstream PLRs have to know, in advance,
the downstream and upstream MP labels of the protected LSP so that
data in the forward and reverse directions can be redirected through
the bypass tunnel after FRR respectively.
[RFC4090] defines procedures for the downstream PLR to obtain the
protected LSP's downstream MP label from recorded labels in the
RECORD_ROUTE Object (RRO) of the RSVP Resv message received at the
downstream PLR.
To obtain the upstream MP label, the procedures specified in
[RFC4090] are used to record the upstream MP label in the RRO of the
RSVP Path message of the protected LSP. The upstream PLR obtains the
upstream MP label from the recorded labels in the RRO of the received
RSVP Path message.
4.3. Merge Point Addresses
To correctly assign a bidirectional bypass tunnel, the downstream and
upstream PLRs have to know, in advance, the downstream and upstream
MP addresses.
[RFC4561] defines procedures for the downstream PLR to obtain the
protected LSP's downstream MP address from the recorded Node-IDs in
the RRO of the RSVP Resv message received at the downstream PLR.
To obtain the upstream MP address, the procedures specified in
[RFC4561] are used to record upstream MP Node-ID in the RRO of the
RSVP Path message of the protected LSP. The upstream PLR obtains the
upstream MP address from the recorded Node-IDs in the RRO of the
received RSVP Path message.
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4.4. RRO IPv4/IPv6 Subobject Flags
RRO IPv4/IPv6 subobject flags are defined in [RFC4090], Section 4.4
and are equally applicable to the FRR procedure for the protected
bidirectional GMPLS LSPs.
The procedures defined in [RFC4090] are used by the downstream PLR to
signal the IPv4/IPv6 subobject flags upstream in the RRO of the RSVP
Resv message of the protected LSP. Similarly, those procedures are
used by the downstream PLR to signal the IPv4/IPv6 subobject flags
downstream in the RRO of the RSVP Path message of the protected LSP.
4.5. Bidirectional Bypass Tunnel Assignment Co-ordination
This document defines signaling procedures and a new
BYPASS_ASSIGNMENT subobject in the RSVP RECORD_ROUTE Object (RRO)
used to co-ordinate the bidirectional bypass tunnel assignment
between the downstream and upstream PLRs.
4.5.1. Bidirectional Bypass Tunnel Assignment Signaling Procedure
It is desirable to coordinate the bidirectional bypass tunnel
selected at the downstream and upstream PLRs so that the rerouted
traffic flows on co-routed paths after FRR. To achieve this, a new
RSVP subobject is defined for RRO that identifies a bidirectional
bypass tunnel that is assigned at a downstream PLR to protect a
bidirectional LSP.
When the procedures defined in this document are in use, the
BYPASS_ASSIGNMENT subobject MUST be added by each downstream PLR in
the RSVP Path RRO message of the GMPLS signaled bidirectional
protected LSP to record the downstream bidirectional bypass tunnel
assignment. This subobject is sent in the RSVP Path RRO message
every time the downstream PLR assigns or updates the bypass tunnel
assignment. The downstream PLR can assign a bypass tunnel when
processing the first Path message of the protected LSP as long as it
has a topological view of the downstream MP and the traversed path
information in ERO. For the protected LSP where the downstream MP
cannot be determined from the first Path message (e.g. when using
loose hops in ERO), the downstream PLR needs to wait for Resv message
with RRO in order to assign a bypass tunnel. However, in both cases,
the downstream PLR cannot update the data-plane until it receives
Resv messages containing the MP labels.
The upstream PLR (downstream MP) simply reflects the bypass tunnel
assignment in the reverse direction. The absence of
BYPASS_ASSIGNMENT subobject in Path RRO means that the relevant node
or interface is not protected by a bidirectional bypass tunnel.
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Hence, the upstream PLR need not assign a bypass tunnel in the
reverse direction.
When the BYPASS_ASSIGNMENT subobject is added in the Path RRO:
o The IPv4 or IPv6 subobject containing Node-ID address MUST also be
added [RFC4561]. The Node-ID address MUST match the source
address of the bypass tunnel selected for this protected LSP.
o The BYPASS_ASSIGNMENT subobject MUST be added immediately after
the Node-ID address.
o The Label subobject MUST also be added [RFC3209].
The rules for adding an IPv4 or IPv6 Interface address subobject and
Unnumbered Interface ID subobject as specified in [RFC3209] and
[RFC4090] are not modified by the above procedure. The options
specified in Section 6.1.3 in [RFC4990] are also applicable as long
as above mentioned rules are followed when using the FRR procedures
defined in this document.
An upstream PLR (downstream MP) SHOULD check all BYPASS_ASSIGNMENT
subobjects in the Path RRO to see if the destination address in the
BYPASS_ASSIGNMENT matches the address of the upstream PLR. For each
BYPASS_ASSIGNMENT subobject that matches, the upstream PLR looks for
a tunnel that has a source address matching the downstream PLR that
inserted the BYPASS_ASSIGNMENT, as indicated by the Node-ID address,
and the same tunnel-ID as indicated in the BYPASS_ASSIGNMENT. The
RRO can contain multiple addresses to identify a node, however, the
upstream PLR relies on the Node-ID address preceding the
BYPASS_ASSIGNMENT subobject for identifying the bypass tunnel. If
the bypass tunnel is not found, the upstream PLR SHOULD send a Notify
message [RFC3473] with Error-code - FRR Bypass Assignment Error
(value: TBA1) and Sub-code - Bypass Tunnel Not Found (value: TBA3) to
the downstream PLR. Upon receiving this error, the downstream PLR
SHOULD remove the bypass tunnel assignment and select an alternate
bypass tunnel if one available. The RRO containing BYPASS_ASSIGNMENT
subobject(s) is then simply forwarded downstream in the RSVP Path
message.
A downstream PLR may add, remove or change bypass tunnel assignment
for a protected LSP resulting in addition, removal or modification of
BYPASS_ASSIGNMENT subobject in the Path RRO, respectively. In this
case, the downstream PLR SHOULD generate modified Path message and
forward it downstream. The downstream MP SHOULD check the RRO in the
received Path message and update the bypass tunnel assignment in the
reverse direction accordingly.
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4.5.2. One-to-one Bidirectional Bypass Tunnel Assignment
The bidirectional bypass tunnel assignment co-ordination procedure
defined in this document can be used for both facility backup
described in Section 3.2 of [RFC4090] and one-to-one backup described
in Section 3.1 of [RFC4090]. As specified in [RFC4090], Section 4.2,
the DETOUR_OBJECT can be used in one-to-one backup method to identify
the detour LSPs. In one-to-one backup method, if the bypass tunnel
is already in-use at the upstream PLR, it SHOULD send a Notify
message [RFC3473] with Error-code - FRR Bypass Assignment Error
(value: TBA1) and Sub-code - One-to-one Bypass Already In-use (value:
TBA4) to the downstream PLR. Upon receiving this error, the
downstream PLR SHOULD remove the bypass tunnel assignment and select
an alternate bypass tunnel if one available.
4.5.3. Multiple Bidirectional Bypass Tunnel Assignments
The upstream PLR may receive multiple bypass tunnel assignments for a
protected LSP from different downstream PLRs leading to an asymmetric
bypass tunnel assignment as shown in the following two examples.
As shown in Example 1 and Example 2, for the protected bidirectional
GMPLS LSP R4-R5-R6, the upstream PLR R6 receives multiple bypass
tunnel assignments, one from downstream PLR R4 for node protection
and one from downstream PLR R5 for link protection. In Example 1, R6
prefers the link protection bypass tunnel from downstream PLR R5
whereas in Example 2, R6 prefers the node protection bypass tunnel
from downstream PLR R4.
+------->>-------+
/ +->>--+ \
/ / \ \
/ / \ \
[R4]--->>---[R5]--->>---[R6]
PATH -> \ /
\ /
+-<<--+
Example 1: Link protection is preferred on downstream MP
+------->>--------+
/ +->>--+ \
/ / \ \
/ / \ \
[R4]--->>---[R5]--->>---[R6]
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\ PATH -> /
\ /
\ /
+-------<<--------+
Example 2: Node protection is preferred on downstream MP
The asymmetry of bypass tunnel assignments can be avoided by using
the flags in the SESSION_ATTRIBUTES Object defined in Section 4.3 of
[RFC4090]. In particular, the "node protection desired" flag is
signaled by the head-end node to request node protection bypass
tunnels. When this flag is set, both downstream PLR and upstream PLR
nodes assign node protection bypass tunnels as shown in Example 2.
In the absence of "node protection desired" flag set, the downstream
PLR nodes may only signal the link protection bypass tunnels avoiding
the asymmetry of bypass tunnel assignments shown in Example 1.
When multiple bypass tunnel assignments are received, the upstream
PLR SHOULD send a Notify message [RFC3473] with Error-code - FRR
Bypass Assignment Error (value: TBA1) and Sub-code - Bypass
Assignment Cannot Be Used (value: TBA2) to the downstream PLR to
indicate that it cannot use the bypass tunnel assignment in the
reverse direction. Upon receiving this error, the downstream PLR MAY
remove the bypass tunnel assignment and select an alternate bypass
tunnel if one available.
If multiple bypass tunnel assignments are present on the upstream PLR
R6 at the time of a failure, any resulted asymmetry gets corrected
using the re-coroute procedure after FRR as specified in Section
5.2.2 of this document.
5. Fast Reroute For Bidirectional GMPLS LSPs with In-band Signaling
When a bidirectional bypass tunnel is used, after a link failure,
following procedure is followed when using the in-band signaling:
o The downstream PLR reroutes protected LSP traffic and RSVP Path
signaling over the bidirectional bypass tunnel using the
procedures defined in [RFC4090]. The RSVP Path messages are
modified as described in Section 6.4.3 of [RFC4090].
o The upstream PLR reroutes protected LSP traffic upon detecting the
link failure or upon receiving RSVP Path message over the
bidirectional bypass tunnel.
o The upstream PLR also reroutes protected LSP RSVP Resv signaling
after receiving the modified RSVP Path message over the
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bidirectional bypass tunnel. The upstream PLR uses the procedure
defined in Section 7 of [RFC4090] to detect that RSVP Path
messages have been rerouted over the bypass tunnel by the
downstream PLR. The upstream PLR does not modify the RSVP Resv
message before sending it over the bypass tunnel.
The above procedure allows both traffic and RSVP signaling to flow on
symmetric paths in the forward and reverse directions of a protected
bidirectional GMPLS LSP. The following sections describe the
handling for link protection and node protection bypass tunnels.
5.1. Link Protection for Bidirectional GMPLS LSPs
<- RESV
[R1]----[R2]----[R3]-----x-----[R4]----[R5]----[R6]
PATH -> \ /
\ /
+<<----->>+
T3
PATH ->
<- RESV
Protected LSP: {R1-R2-R3-R4-R5-R6}
R3's Bypass T3: {R3-R4}
Figure 1: Flow of RSVP signaling after link failure and FRR
Consider the TE network shown in Figure 1. Assume every link in the
network is protected with a link protection bypass tunnel (e.g.,
bypass tunnel T3). For the protected co-routed bidirectional LSP
whose head-end is on node R1 and tail-end is on node R6, each
traversed node (a potential PLR) assigns a link protection co-routed
bidirectional bypass tunnel.
5.1.1. Behavior After Link Failure
Consider the link R3-R4 on the protected LSP path fails. The
downstream PLR R3 and upstream PLR R4 independently trigger fast
reroute to redirect traffic onto bypass tunnel T3 in the forward and
reverse directions. The downstream PLR R3 also reroutes RSVP Path
messages onto the bypass tunnel T3 using the procedures described in
[RFC4090]. The upstream PLR R4 reroutes RSVP Resv messages onto the
reverse bypass tunnel T3 upon receiving RSVP Path message over bypass
tunnel T3.
5.1.2. Revertive Behavior After Fast Reroute
The revertive behavior defined in [RFC4090], Section 6.5.2, is
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applicable to the link protection of bidirectional GMPLS LSPs. When
using the local revertive mode, after the link R3-R4 (in Figure 1) is
restored, following node behaviors apply:
o The downstream PLR R3 starts sending the Path messages and traffic
flow of the protected LSP over the restored link and stops sending
them over the bypass tunnel.
o The upstream PLR R4 starts sending the traffic flow of the
protected LSP over the restored link and stops sending it over the
bypass tunnel.
o When upstream PLR R4 receives the protected LSP Path messages over
the restored link, if not already done, it starts sending Resv
messages and traffic flow of the protected LSP over the restored
link and stops sending them over the bypass tunnel.
5.2. Node Protection for Bidirectional GMPLS LSPs
T1
+<<------->>+
/ \
/ \ <- RESV
[R1]----[R2]----[R3]--x--[R4]----[R5]----[R6]
PATH -> \ /
\ /
+<<------->>+
T2
Protected LSP: {R1-R2-R3-R4-R5-R6}
R3's Bypass T2: {R3-R5}
R4's Bypass T1: {R4-R2}
Figure 2: Flow of RSVP signaling after link failure and FRR
Consider the TE network shown in Figure 2. Assume every link in the
network is protected with a node protection bypass tunnel. For the
protected co-routed bidirectional LSP whose head-end is on node R1
and tail-end is on node R6, each traversed node (a potential PLR)
assigns a node protection co-routed bidirectional bypass tunnel.
The solution introduces two phases to invoking FRR procedures by the
PLR after the link failure. The first phase comprises of FRR
procedures to fast reroute data traffic onto bypass tunnels in the
forward and reverse directions. The second phase re-coroutes the
data and signaling in the forward and reverse directions after the
first phase.
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5.2.1. Behavior After Link Failure
Consider a link R3-R4 (in Figure 2) on the protected LSP path fails.
The downstream PLR R3 and upstream PLR R4 independently trigger fast
reroute procedures to redirect the protected LSP traffic onto
respective bypass tunnels T2 and T1 in the forward and reverse
directions. The downstream PLR R3 also reroutes RSVP Path messages
over the bypass tunnel T2 using the procedures described in
[RFC4090]. Note, at this point, node R4 stops receiving RSVP Path
refreshes for the protected bidirectional LSP while protected traffic
continues to flow over bypass tunnels. As node R4 does not receive
Path messages over bypass tunnel T1, it does not reroute RSVP Resv
messages over the reverse bypass tunnel T1.
5.2.2. Behavior After Link Failure To Re-coroute
The downstream MP R5 that receives rerouted protected LSP RSVP Path
message through the bypass tunnel, in addition to the regular MP
processing defined in [RFC4090], gets promoted to a Point of Remote
Repair (PRR) role and performs the following actions to re-coroute
signaling and data traffic over the same path in the reverse
direction:
o Finds the bypass tunnel in the reverse direction that terminates
on the downstream PLR R3. Note: the downstream PLR R3's address
can be extracted from the "IPV4 tunnel sender address" in the
SENDER_TEMPLATE Object of the protected LSP (see [RFC4090],
Section 6.1.1).
o If reverse bypass tunnel is found and the protected LSP traffic is
not already rerouted over the found bypass tunnel T2, the PRR R5
activates FRR reroute procedures to direct traffic over the found
bypass tunnel T2 in the reverse direction. In addition, the PRR
R5 also reroutes RSVP Resv over the bypass tunnel T2 in the
reverse direction. This can happen when the downstream PLR has
changed the bypass tunnel assignment but the upstream PLR has not
yet processed the updated Path RRO and programmed the data-plane
when link failure occurs.
o If reverse bypass tunnel is not found, the PRR R5 immediately
tears down the protected LSP.
<- RESV
[R1]----[R2]----[R3]--X--[R4]----[R5]----[R6]
PATH -> \ /
\ /
+<<------->>+
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Bypass Tunnel T2
traffic + signaling
Protected LSP: {R1-R2-R3-R4-R5-R6}
R3's Bypass T2: {R3-R5}
Figure 3: Flow of RSVP signaling after FRR and re-coroute
Figure 3 describes the path taken by the traffic and signaling after
completing re-coroute of data and signaling in the forward and
reverse paths described above. Node R4 will stop receiving the Path
and Resv messages and it will timeout the RSVP soft-state, however,
this will not cause the LSP to be torn down. RSVP signaling at node
R2 is not affected by the FRR and re-corouting.
If downstream MP R5 receives multiple RSVP Path messages through
multiple bypass tunnels (e.g., as a result of multiple failures), the
PRR SHOULD identify a bypass tunnel that terminates on the farthest
downstream PLR along the protected LSP path (closest to the protected
bidirectional LSP head-end) and activate the reroute procedures
mentioned above.
5.2.2.1. Re-coroute in Data-plane After Link Failure
The downstream MP (upstream PLR) MAY optionally support re-corouting
in data-plane as follows. If the downstream MP has assigned a
bidirectional bypass tunnel, as soon as the downstream MP receives
the protected LSP packets on the bypass tunnel, it MAY switch the
upstream traffic on to the bypass tunnel. In order to identify the
protected LSP packets through the bypass tunnel, Penultimate Hop
Popping (PHP) of the bypass tunnel MUST be disabled. The downstream
MP checks whether the protected LSP signaling is rerouted over the
found bypass tunnel, and if not, it performs the signaling procedure
described in Section 5.2.2 of this document.
5.2.3. Revertive Behavior After Fast Reroute
The revertive behavior defined in [RFC4090], Section 6.5.2, is
applicable to the node protection of bidirectional GMPLS LSPs. When
using the local revertive mode, after the link R3-R4 (in Figures 2
and 3) is restored, following node behaviors apply:
o The downstream PLR R3 starts sending the Path messages and traffic
flow of the protected LSP over the restored link and stops sending
them over the bypass tunnel.
o The upstream PLR R4 (when the protected LSP is present) starts
sending the traffic flow of the protected LSP over the restored
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link towards downstream PLR R3 and forwarding the Path messages
towards PRR R5 and stops sending the traffic over the bypass
tunnel.
o When upstream PLR R4 receives the protected LSP Path messages over
the restored link, if not already done, the node R4 (when the
protected LSP is present) starts sending Resv messages and traffic
flow over the restored link towards downstream PLR R3 and
forwarding the Path messages towards PRR R5 and stops sending them
over the bypass tunnel.
o When PRR R5 receives the protected LSP Path messages over the
restored path, it starts sending Resv messages and traffic flow
over the restored path and stops sending them over the bypass
tunnel.
5.2.4. Behaviour After Node Failure
Consider the node R4 (in Figure 3) on the protected LSP path fails.
The downstream PLR R3 and upstream PLR R5 independently trigger fast
reroute procedures to redirect the protected LSP traffic onto bypass
tunnel T2 in forward and reverse directions. The downstream PLR R3
also reroutes RSVP Path messages over the bypass tunnel T2 using the
procedures described in [RFC4090]. The upstream PLR R5 reroutes RSVP
Resv signaling after receiving the modified RSVP Path message over
the bypass tunnel T2.
5.3. Unidirectional Link Failures
Unidirectional link failures can result in the traffic flowing on
asymmetric paths in the forward and reverse directions. In addition,
unidirectional link failures can cause RSVP soft-state timeout in the
control-plane in some cases. As an example, if the unidirectional
link failure is in the upstream direction (from R4 to R3 in Figures 1
and 2), the downstream PLR (node R3) can stop receiving the Resv
messages of the protected LSP from the upstream PLR (node R4 in
Figures 1 and 2) and this can cause RSVP soft-state timeout to occur
on the downstream PLR (node R3).
A unidirectional link failure in the downstream direction (from R3 to
R4 in Figures 1 and 2), does not cause RSVP soft-state timeout when
using the FRR procedures defined in this document, since the upstream
PLR (node R4 in Figure 1 and node R5 in Figure 2) triggers the
re-coroute procedure (defined in Section 5.2.2 of this document)
after receiving RSVP Path messages of the protected LSP over the
bypass tunnel from the downstream PLR (node R3 in Figures 1 and 2).
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6. Fast Reroute For Bidirectional GMPLS LSPs with Out-of-band Signaling
When using the GMPLS out-of-band signaling [RFC3473], after a link
failure event, the RSVP messages are not rerouted over the
bidirectional bypass tunnel by the downstream and upstream PLRs but
instead rerouted over the control-channels to the downstream and
upstream MPs, respectively.
The RSVP soft-state timeout after FRR as described in Section 5.2 of
this document is equally applicable to the GMPLS out-of-band
signaling as the RSVP signaling refreshes can stop reaching certain
nodes along the protected LSP path after the downstream and upstream
PLRs finish rerouting of the signaling messages. However, unlike
with the in-band signaling, unidirectional link failures as described
in Section 5.3 of this document do not result in soft-state timeout
with GMPLS out-of-band signaling. Apart from this, the FRR procedure
described in Section 5 of this document is equally applicable to the
GMPLS out-of-band signaling.
7. Message and Object Definitions
7.1. BYPASS_ASSIGNMENT Subobject
The BYPASS_ASSIGNMENT subobject is used to inform the downstream MP
of the bypass tunnel being assigned by the PLR. This can be used to
coordinate the bypass tunnel assignment for the protected LSP by the
downstream and upstream PLRs in the forward and reverse directions
respectively prior or after the failure occurrence.
This subobject SHOULD be inserted into the Path RRO by the downstream
PLR. It SHOULD NOT be inserted into an RRO by a node which is not a
downstream PLR. It MUST NOT be changed by downstream LSRs and MUST
NOT be added to a Resv RRO.
The BYPASS_ASSIGNMENT IPv4 subobject in RRO 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type:TBA5 | Length | Bypass Tunnel ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 Bypass Destination Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: BYPASS ASSIGNMENT IPv4 RRO Subobject
Type
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Downstream Bypass Assignment. Value is TBA5 by IANA.
Length
The Length contains the total length of the subobject in bytes,
including the Type and Length fields. The length is 8 bytes.
Bypass Tunnel ID
The bypass tunnel identifier (16 bits).
Bypass Destination Address
The bypass tunnel IPv4 destination address.
The BYPASS_ASSIGNMENT IPv6 subobject in RRO 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type:TBA6 | Length | Bypass Tunnel ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| IPv6 Bypass Destination Address |
+ (16 bytes) +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: BYPASS_ASSIGNMENT IPv6 RRO Subobject
Type
Downstream Bypass Assignment. Value is TBA6 by IANA.
Length
The Length contains the total length of the subobject in bytes,
including the Type and Length fields. The length is 20 bytes.
Bypass Tunnel ID
The bypass tunnel identifier (16 bits).
Bypass Destination Address
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The bypass tunnel IPv6 destination address.
7.2. FRR Bypass Assignment Error Notify Message
New Error-code - FRR Bypass Assignment Error (value: TBA1) and its
sub-codes are defined for the ERROR_SPEC Object (C-Type 6) [RFC2205]
in this document, that is carried by the Notify message (Type 21)
defined in [RFC3473] Section 4.3. This Error message is sent by the
upstream PLR to the downstream PLR to notify a bypass assignment
error. In the Notify message, the IP destination address is set to
the node address of the downstream PLR that had initiated the bypass
assignment. In the ERROR_SPEC Object, IP address is set to the node
address of the upstream PLR that detected the bypass assignment
error. This Error MUST NOT be sent in a Path Error message. This
Error does not cause the protected LSP to be torn down.
8. Compatibility
New RSVP subobject BYPASS_ASSIGNMENT is defined for RECORD_ROUTE
Object in this document that is carried in the RSVP Path message.
Per [RFC3209], nodes not supporting this subobject will ignore the
subobject but forward it without modification. As described in
Section 7 of this document, this subobject is not carried in the RSVP
Resv message and is ignored by sending the Notify message for FRR
Bypass Assignment Error (with Subcode: Bypass Assignment Cannot Be
Used) defined in this document. Nodes not supporting the Notify
message defined in this document will ignore it but forward it
without modification.
9. Security Considerations
This document introduces a new BYPASS_ASSIGNMENT subobject for the
RECORD_ROUTE Object that is carried in an RSVP signaling message.
Thus in the event of the interception of a signaling message, more
information about LSP's fast reroute protection can be deduced than
was previously the case. This is judged to be a very minor security
risk as this information is already available by other means. If a
MP does not find a matching bypass tunnel with given source and
destination addresses locally, it ignores the BYPASS_ASSIGNMENT
subobject. Due to this, security risk introduced by inserting a
random address in this subobject is minimal. The Notify message for
FRR Bypass Assignment Error defined in this document does not result
in tear-down of the protected LSP and is not service affecting.
Security considerations for RSVP-TE and GMPLS signaling extensions
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are covered in [RFC3209] and [RFC3473]. Further, general
considerations for securing RSVP-TE in MPLS-TE and GMPLS networks can
be found in [RFC5920]. This document updates the mechanisms defined
in [RFC4090], which also discusses related security measures and are
also applicable to this document. As specified in [RFC4090], a PLR
and its selected merge point trust RSVP messages received from each
other. The security considerations pertaining to the original RSVP
protocol [RFC2205] also remain relevant to the updates in this
document.
10. IANA Considerations
10.1. BYPASS_ASSIGNMENT Subobject
IANA manages the "RSVP PARAMETERS" registry located at
<http://www.iana.org/assignments/rsvp-parameters>. IANA is requested
to assign a value for the new BYPASS_ASSIGNMENT subobject in the
"Class Type 21 ROUTE_RECORD - Type 1 Route Record" registry.
This document introduces a new subobject for RECORD_ROUTE Object:
+--------+-------------------+---------+---------+---------------+
| Type | Description | Carried | Carried | Reference |
| | | in Path | in Resv | |
+--------+-------------------+---------+---------+---------------+
| TBA5 By| BYPASS_ASSIGNMENT | Yes | No | This document |
| IANA | IPv4 subobject | | | |
+--------+-------------------+---------+---------+---------------+
| TBA6 By| BYPASS_ASSIGNMENT | Yes | No | This document |
| IANA | IPv6 subobject | | | |
+--------+-------------------+---------+---------+---------------+
10.2. FRR Bypass Assignment Error Notify Message
IANA maintains the "Resource Reservation Protocol (RSVP) Parameters"
registry (see <http://www.iana.org/assignments/rsvp-parameters>).
The "Error Codes and Globally-Defined Error Value Sub-Codes"
subregistry is included in this registry.
This registry has been extended for the new Error-code and Sub-codes
defined in this document as follows:
o Error-code TBA1: FRR Bypass Assignment Error
o Sub-code TBA2: Bypass Assignment Cannot Be Used
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o Sub-code TBA3: Bypass Tunnel Not Found
o Sub-code TBA4: One-to-one Bypass Already In-use
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11. References
11.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2205] Braden, R., Ed., Zhang, L., Berson, S., Herzog, S., and S.
Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1
Functional Specification", RFC 2205, September 1997.
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
Tunnels", RFC 3209, December 2001.
[RFC3473] Berger, L., Ed., "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Resource ReserVation Protocol-
Traffic Engineering (RSVP-TE) Extensions", RFC 3473,
January 2003.
[RFC4090] Pan, P., Ed., Swallow, G., Ed., and A. Atlas, Ed., "Fast
Reroute Extensions to RSVP-TE for LSP Tunnels", RFC 4090,
May 2005.
[RFC4561] Vasseur, J.P., Ed., Ali, Z., and S. Sivabalan, "Definition
of a Record Route Object (RRO) Node-Id Sub-Object", RFC
4561, June 2006.
11.2. Informative References
[RFC3471] Berger, L., Editor, "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Functional Description", RFC
3471, January 2003.
[RFC4990] Shiomoto, K., Papneja, R., and R. Rabbat, "Use of
Addresses in Generalized Multiprotocol Label Switching
(GMPLS) Networks", RFC 4990, September 2007.
[RFC5920] Fang, L., Ed., "Security Framework for MPLS and GMPLS
Networks", RFC 5920, July 2010.
[RFC6378] Weingarten, Y., Bryant, S., Osborne, E., Sprecher, N., and
A. Fulignoli, "MPLS Transport Profile (MPLS-TP) Linear
Protection", RFC 6378, October 2011.
[RFC7551] Zhang, F., Ed., Jing, R., and Gandhi, R., Ed., "RSVP-TE
Extensions for Associated Bidirectional LSPs", RFC 7551,
May 2015.
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Acknowledgements
Authors would like to thank George Swallow for many useful comments
and suggestions. Authors would like to thank Lou Berger for the
guidance on this work and for providing review comments. Authors
would also like to thank Nobo Akiya, Loa Andersson, Matt Hartley,
Himanshu Shah, Gregory Mirsky, Mach Chen, Vishnu Pavan Beeram and
Alia Atlas for reviewing this document and providing valuable
comments. A special thanks to Adrian Farrel for his thorough review
of this document.
Contributors
Frederic Jounay
Orange
CH
EMail: frederic.jounay@salt.ch
Lizhong Jin
Shanghai
CN
EMail: lizho.jin@gmail.com
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Authors' Addresses
Mike Taillon
Cisco Systems, Inc.
EMail: mtaillon@cisco.com
Tarek Saad (editor)
Cisco Systems, Inc.
EMail: tsaad@cisco.com
Rakesh Gandhi (editor)
Cisco Systems, Inc.
EMail: rgandhi@cisco.com
Zafar Ali
Cisco Systems, Inc.
EMail: zali@cisco.com
Manav Bhatia
Nokia
Banglore, India
EMail: manav.bhatia@nokia.com
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