Pseudowire Redundancy
draft-ietf-pwe3-redundancy-07
The information below is for an old version of the document.
| Document | Type | Active Internet-Draft (pwe3 WG) | |
|---|---|---|---|
| Authors | Praveen Muley , Mustapha Aissaoui , Matthew Bocci | ||
| Last updated | 2012-05-03 (Latest revision 2012-04-23) | ||
| Replaces | draft-muley-pwe3-redundancy | ||
| Stream | Internet Engineering Task Force (IETF) | ||
| Formats | plain text xml htmlized pdfized bibtex | ||
| Reviews | |||
| Stream | WG state | Submitted to IESG for Publication | |
| Document shepherd | Andrew G. Malis | ||
| IESG | IESG state | IESG Evaluation | |
| Consensus boilerplate | Unknown | ||
| Telechat date |
(None)
Needs a YES. |
||
| Responsible AD | Stewart Bryant | ||
| IESG note | Andy Malis (amalis@gmail.com) is the document shepherd. | ||
| Send notices to | pwe3-chairs@tools.ietf.org, draft-ietf-pwe3-redundancy@tools.ietf.org |
draft-ietf-pwe3-redundancy-07
Network Working Group P. Muley
Internet-Draft M. Aissaoui
Intended status: Informational M. Bocci
Expires: October 25, 2012 Alcatel-Lucent
April 23, 2012
Pseudowire Redundancy
draft-ietf-pwe3-redundancy-07
Abstract
This document describes a framework comprised of a number of
scenarios and associated requirements for pseudowire (PW) redundancy.
A set of redundant PWs is configured between provider edge (PE) nodes
in single segment PW applications, or between Terminating PE nodes in
Multi-Segment PW applications. In order for the PE/T-PE nodes to
indicate the preferred PW to use for forwarding PW packets to one
another, a new PW status is required to indicate the preferential
forwarding status of active or standby for each PW in the redundancy
set.
Requirements Language
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].
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on October 25, 2012.
Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
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document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Reference Models . . . . . . . . . . . . . . . . . . . . . . . 5
3.1. PE Architecture . . . . . . . . . . . . . . . . . . . . . 5
3.2. PW Redundancy Network Reference Scenarios . . . . . . . . 5
3.2.1. Single Multi-Homed CE . . . . . . . . . . . . . . . . 5
3.2.2. Multiple Multi-Homed CEs . . . . . . . . . . . . . . . 7
3.2.3. Single-Homed CE With MS-PW Redundancy . . . . . . . . 8
3.2.4. PW Redundancy Between MTU-s in H-VPLS . . . . . . . . 9
3.2.5. PW Redundancy Between VPLS Network Facing PEs
(n-PEs) . . . . . . . . . . . . . . . . . . . . . . . 11
3.2.6. Redundancy in a VPLS Bridge Module Model . . . . . . . 12
4. Generic PW Redundancy Requirements . . . . . . . . . . . . . . 13
4.1. Protection Switching Requirements . . . . . . . . . . . . 13
4.2. Operational Requirements . . . . . . . . . . . . . . . . . 13
5. Security Considerations . . . . . . . . . . . . . . . . . . . 14
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
7. Major Contributing Authors . . . . . . . . . . . . . . . . . . 14
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 15
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15
9.1. Normative References . . . . . . . . . . . . . . . . . . . 15
9.2. Informative References . . . . . . . . . . . . . . . . . . 16
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16
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1. Introduction
The objective of PW redundancy is to provide sparing of attachment
circuits (ACs), Provider Edge nodes (PEs), and Pseudowires (PWs) to
eliminate single points of failure, while ensuring that only one
active path between a pair of Customer Edge nodes (CEs).
In single-segment PW (SS-PW) applications, protection for the PW is
provided by the Packet Switched Network (PSN) layer. This may be a
Resource Reservation Protocol with Traffic Engineering (RSVP-TE)
labeled switched path (LSP) with a fast-Reroute (FRR) backup or an
end-to-end backup LSP. It is assumed that these mechanisms can
restore PSN connectivity rapidly enough to avoid triggering
protection by PW redundancy. PSN protection mechanisms cannot
protect against failure of the a PE node or the failure of the remote
AC. Typically, this is supported by dual-homing a Customer Edge (CE)
node to different PE nodes which provide a pseudowire emulated
service across the PSN. A set of PW mechanisms is therefore required
that enables a primary and one or more backup PWs to terminate on
different PE nodes.
In multi-segment PW (MS-PW) applications, PSN protection mechanisms
cannot protect against the failure of a switching PE (S-PE). A set
of mechanisms that support the operation of a primary and one or more
backup PWs via a different set of S-PEs is therefore required. The
paths of these PWs are diverse in the sense that they are switched at
different S-PE nodes.
In both of these applications, PW redundancy is important to maximise
the resiliency of the emulated service.
This document describes framework for these applications and its
associated operational requirements. The framework utilizes a new PW
status, called the Preferential Forwarding Status of the PW. This is
separate from the operational states defined in RFC4447 [RFC4447].
The mechanisms for PW redundancy are modeled on general protection
switching principles.
2. Terminology
o Up PW: A PW which has been configured (label mapping exchanged
between PEs) and is not in any of the PW defect states specified
in [RFC4447]. Such a PW is is available for forwarding traffic.
o Down PW: A PW that has either not been fully configured, or has
been configured and is in any one of the PW defect states
specified in [RFC4447]. Such a PW is not available for forwarding
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traffic.
o Active PW. An UP PW used for forwarding user, OAM and control
plane traffic.
o Standby PW. An UP PW that is not used for forwarding user traffic
but may forward OAM and specific control plane traffic.
o PW Endpoint: A PE where a PW terminates on a point where Native
Service Processing is performed, e.g., A Single Segment PW (SS-PW)
PE, a Multi-Segment Pseudowire (MS-PW) Terminating PE (T-PE), or a
Hierarchical VPLS MTU-s or PE-rs.
o Primary PW: the PW which a PW endpoint activates (i.e. uses for
forwarding) in preference to any other PW when more than one PW
qualifies for active state. When the primary PW comes back up
after a failure and qualifies for the active state, the PW
endpoint always reverts to it. The designation of Primary is
performed by local configuration for the PW at the PE and is only
required when revertive behaviour is used.
o Secondary PW: when it qualifies for the active state, a Secondary
PW is only selected if no Primary PW is configured or if the
configured primary PW does not qualify for active state (e.g., is
DOWN). By default, a PW in a redundancy PW set is considered
secondary. There is no Revertive mechanism among secondary PWs.
o Revertive protection switching. Traffic will be carried by the
primary PW if it is UP and a wait-to-restore timer expires and the
primary PW is made the Active PW.
o Non-revertive protection switching. Traffic will be carried by
the last PW selected as a result of previous active PW entering
Operationally DOWN state.
o Manual selection of PW. The ability for the operator to manually
select the primary/secondary PWs.
o MTU-s: A hierarchical virtual private LAN service Multi-Tenant
Unit switch, as defined in RFC4762 [RFC4762].
o PE-rs: A hierarchical virtual private LAN service switch, as
defined in RFC4762.
o n-PE: A network facing provider edge node, as defined in RFC4026
[RFC4026].
This document uses the term 'PE' to be synonymous with both PEs as
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per RFC3985[RFC3985] and T-PEs as per RFC5659 [RFC5659].
This document uses the term 'PW' to be synonymous with both PWs as
per RFC3985 and SS-PWs, MS-PWs, and PW segments as per RFC5659.
3. Reference Models
The following sections describe show the reference architecture of
the PE for PW redundancy and its usage in different topologies and
applications.
3.1. PE Architecture
Figure 1 shows the PE architecture for PW redundancy, when more than
one PW in a redundant set is associated with a single AC. This is
based on the architecture in Figure 4b of RFC3985 [RFC3985]. The
forwarder selects which of the redundant PWs to use based on the
criteria described in this document.
+----------------------------------------+
| PE Device |
+----------------------------------------+
Single | | Single | PW Instance
AC | + PW Instance X<===========>
| | |
| |----------------------|
<------>o | Single | PW Instance
| Forwarder + PW Instance X<===========>
| | |
| |----------------------|
| | Single | PW Instance
| + PW Instance X<===========>
| | |
+----------------------------------------+
Figure 1: PE Architecture for PW redundancy
3.2. PW Redundancy Network Reference Scenarios
This section presents a set of reference scenarios for PW redundancy.
3.2.1. Single Multi-Homed CE
The following figure illustrates an application of single segment
pseudowire redundancy. This scenario is designed to protect the
emulated service against a failure of one of the PEs or ACs attached
to the multi-homed CE. Protection against failures of the PSN
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tunnels is provided using PSN mechanisms such as MPLS Fast Reroute,
so that these failures do not impact the PW.
CE1 is dual-homed to PE1 and PE3. A dual homing control protocol,
the details of which are outside the scope of this document, selects
which AC CE1 should use to forward towards the PSN, and which PE (PE1
or PE3) should forward towards CE1.
|<-------------- Emulated Service ---------------->|
| |
| |<------- Pseudo Wire ------>| |
| | | |
| | |<-- PSN Tunnels-->| | |
| V V V V |
V AC +----+ +----+ AC V
+-----+ | | PE1|==================| | | +-----+
| |----------|....|...PW1.(active)...|....|----------| |
| | | |==================| | | CE2 |
| CE1 | +----+ |PE2 | | |
| | +----+ | | +-----+
| | | |==================| |
| |----------|....|...PW2.(standby)..| |
+-----+ | | PE3|==================| |
AC +----+ +----+
Figure 2: PW Redundancy with One Multi-Homed CE
In this scenario, only one of the PWs should be used for forwarding
between PE1 / PE3, and PE2. PW redundancy determines which PW to
make active based on the forwarding state of the ACs so that only one
path is available from CE1 to CE2.
Consider the example where the AC from CE1 to PE1 is initially active
and the AC from CE1 to PE3 is initially standby. PW1 is made active
and PW2 is made standby in order to complete the path to CE2.
On failure of the AC between CE1 and PE1, the forwarding state of the
AC on PE3 transitions to Active. The preferential forwarding state
of PW2 therefore needs to become active, and PW1 standby, in order to
reestablish connectivity between CE1 and CE2. PE3 therefore uses PW2
to forward towards CE2, and PE2 uses PW2 instead of PW1 to forward
towards CE1. PW redundancy in this scenario requires that the
forwarding status of the ACs at PE1 and PE3 be signaled to PE2 so
that PE2 can choose which PW to make active.
Changes occurring on the dual homed side of network due to a failure
of the AC or PE are not propagated to the ACs on the other side of
the network. Furthermore, failures in the PSN are not be propagated
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to the attached CEs.
3.2.2. Multiple Multi-Homed CEs
This scenario, illustrated in Figure 3, is also designed to protect
the emulated service against failures of the ACs and failures of the
PEs. Here, both CEs, CE1 and CE2, are dual-homed to their respective
PEs, PE1 and PE2, and PE3 and PE4. The method used by the CEs to
choose which AC to use to forward traffic towards the PSN is
determined by a dual-homing control protocol. The details of this
protocol are outside the scope of this document.
Note that the PSN tunnels are not shown in this figure for clarity.
However, it can be assumed that each of the PWs shown is encapsulated
in a separate PSN tunnel. Protection against failures of the PSN
tunnels is provided using PSN mechanisms such as MPLS Fast Reroute,
so that these failures do not impact the PW.
|<-------------- Emulated Service ---------------->|
| |
| |<------- Pseudowire ------->| |
| | | |
| | |<-- PSN Tunnels-->| | |
| V V V V |
V AC +----+ +----+ AC V
+-----+ | |....|.......PW1........|....| | +-----+
| |----------| PE1|...... .........| PE3|----------| |
| CE1 | +----+ \ / PW3 +----+ | CE2 |
| | +----+ X +----+ | |
| | | |....../ \..PW4....| | | |
| |----------| PE2| | PE4|--------- | |
+-----+ | |....|.....PW2..........|....| | +-----+
AC +----+ +----+ AC
Figure 3: Multiple Multi-Homed CEs with PW Redundancy
PW1 and PW4 connect PE1 to PE3 and PE4, respectively. Similarly, PE2
has PW2 and PW3 connect PE2 to PE4 and PE3. PW1, PW2, PW3 and PW4
are all UP. In order to support N:1 or 1:1 protection, only one PW
MUST be selected to forward traffic. This document defines an
additional PW state that reflects this forwarding state, which is
separate from the operational status of the PW. This is the
'Preferential Forwarding Status'.
If a PW has a preferential forwarding status of 'active', it can be
used for forwarding traffic. The actual UP PW chosen by the combined
set of PEs that interconnect the CEs is determined by considering the
preferential forwarding status of each PW at each PE. The mechanisms
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for communicating the preferential forwarding status are outside the
scope of this document. Only one PW is used for forwarding.
The following failure scenario illustrates the operation of PW
redundancy in Figure 2. In the initial steady state, when there are
no failures of the ACs, one of the PWs is chosen as the active PW,
and all others are chosen as standby. The dual-homing protocol
between CE1 and PE1/PE2 chooses to use the AC to PE2, while the
protocol between CE2 and PE3/PE4 chooses to use the AC to PE4.
Therefore the PW between PE2 and PE4 is chosen as the active PW to
complete the path between CE1 and CE2.
On failure of the AC between the dual-homed CE1 and PE2, the
preferential forwarding status of the PWs at PE1, PE2, PE3 and PE4
needs to change so as to re-establish a path from CE1 to CE2.
Different mechanisms can be used to achieve this and these are beyond
the scope of this document. After the change in status the algorithm
for selection of PW needs to revaluate and select PW to forward
traffic. In this application each dual-homing algorithm, i.e., {CE1,
PE1, PE2} and {CE2, PE3, PE4}, selects the active AC independently.
There is therefore a need to signal the active status of each AC such
that the PEs can select a common active PW for forwarding between CE1
and CE2.
Changes occurring on one side of network due to a failure of the AC
or PE are not propagated to the ACs on the other side of the network.
Furthermore, failures in the PSN are not be propagated to the
attached CEs. Note that End-to-end native service protection
switching can also be used to protect the emulated service in this
scenario. In this case, PW3 and PW4 are not necessary.
If the CEs do not perform native service protection switching, they
may instead may use load balancing across the paths between the CEs.
3.2.3. Single-Homed CE With MS-PW Redundancy
This application is shown in Figure 4. The main objective is to
protect the emulated service against failures of the S-PEs.
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Native |<----------- Pseudowires ----------->| Native
Service | | Service
(AC) | |<-PSN1-->| |<-PSN2-->| | (AC)
| V V V V V V |
| +-----+ +-----+ +-----+ |
+----+ | |T-PE1|=========|S-PE1|=========|T-PE2| | +----+
| |-------|......PW1-Seg1.......|.PW1-Seg2......|-------| |
| CE1| | |=========| |=========| | | CE2|
| | +-----+ +-----+ +-----+ | |
+----+ |.||.| |.||.| +----+
|.||.| +-----+ |.||.|
|.||.|=========| |========== .||.|
|.||...PW2-Seg1......|.PW2-Seg2...||.|
|.| ===========|S-PE2|============ |.|
|.| +-----+ |.|
|.|============+-----+============= .|
|.....PW3-Seg1.| | PW3-Seg2......|
==============|S-PE3|===============
| |
+-----+
Figure 4: Single-Homed CE with MS-PW Redundancy
CE1 is connected to PE1 and CE2 to PE2, respectively. There are
three multi-segment PWs. PW1 is switched at S-PE1, PW2 is switched
at S-PE2, and PW3 is switched at S-PE3.
Since there is no multi-homing running on the ACs, the T-PE nodes
would advertise 'Active' for the forwarding status based on a
priority for the PW. Priorities associate meaning of 'primary PW'
and 'secondary PW'. These priorities MUST be used in revertive mode
as well and paths must be switched accordingly. The priority can be
configuration or derivation from the PWid. Lower the PWid higher the
priority. However, this does not guarantee selection of same PW by
the T-PEs because, for example, mismatch of the configuration of the
PW priority in each T-PE. The intent of this application is to have
T-PE1 and T-PE2 synchronize the transmit and receive paths of the PW
over the network. In other words, both T-PE nodes are required to
transmit over the PW segment which is switched by the same S-PE.
This is desirable for ease of operation and troubleshooting.
3.2.4. PW Redundancy Between MTU-s in H-VPLS
The following figure (based on the architecture shown in Figure 3 of
[RFC4762]) illustrates the application of use of PW redundancy to
Hierarchical VPLS (H-VPLS). Note that the PSN tunnels are not shown
for clarity, and only one PW of a PW group is shown. Here, a Multi-
Tenant Unit switch (MTU-s) is dual-homed to two PE router switches
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(PE-rs).
PE1-rs
+--------+
| VSI |
Active PW | -- |
Group..........|../ \..|.
CE-1 . | \ / | .
\ . | -- | .
\ . +--------+ .
\ MTU-s . . . PE3-rs
+--------+ . . . +--------+
| VSI | . . H-VPlS .| VSI |
| -- ..|.. . Core |.. -- |
| / \ | . PWs | / \ |
| \ /..|.. . | \ / |
| -- | . . .|.. -- |
+--------+ . . . +--------+
/ . . .
/ . +--------+ .
/ . | VSI | .
CE-2 . | -- | .
..........|../ \..|.
Standby PW | \ / |
Group | -- |
+--------+
PE2-rs
Figure 5: MTU-s Dual Homing in H-VPLS Core
In Figure 5, the MTU-s is dual homed to PE1-rs and PE2-rs and has
spoke PWs to each of them. The MTU-s needs to choose only one of the
spoke PWs ( the active PW) to one of the PE to forward the traffic
and the other to standby status. The MTU-s can derive the status of
the PWs based on local policy configuration. PE1-rs and PE2-rs are
connected to the H-VPLS core on the other side of network. The MTU-s
communicates the status of its member PWs for a set of Virtual
Switching Instances (VSIs) having common status of Active or Standby.
Here the MTU-s controls the selection of PWs to forward the traffic.
Signaling using PW grouping with a common group-id in PWid FEC
Element or Grouping TLV in Generalized PWid FEC Element as defined in
[RFC4447] to PE1-rs and PE2rs respectively, is recommended to scale
better.
Whenever MTU-s performs a switchover, it needs to communicate to
PE2-rs for the Standby PW group the change to the status of active.
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In this scenario, PE devices are aware of switchovers at MTU-s and
could generate MAC Withdraw Messages to trigger MAC flushing within
the H-VPLS full mesh. By default, MTU-s devices should still trigger
MAC Withdraw messages as currently defined in [RFC4762] to prevent
two copies of MAC withdraws to be sent (one by MTU-s and another one
by the PE-rs'). Mechanisms to disable the MAC Withdraw trigger in
certain devices are out of the scope of this document.
3.2.5. PW Redundancy Between VPLS Network Facing PEs (n-PEs)
Following figure illustrates the application of use of PW redundancy
for dual homed connectivity between PE devices in a ring topology.
As above, PSN tunnels are not shown and only one PW of a PW group is
shown for clarity.
PE1 PE2
+--------+ +--------+
| VSI | | VSI |
| -- | | -- |
......|../ \..|.....................|../ \..|.......
| \ / | PW Group 1 | \ / |
| -- | | -- |
+--------+ +--------+
. .
. .
VPLS Domain A . . VPLS Domain B
. .
. .
. .
+--------+ +--------+
| VSI | | VSI |
| -- | | -- |
......|../ \..|.....................|../ \..|........
| \ / | PW Group 2 | \ / |
| -- | | -- |
+--------+ +--------+
PE3 PE4
Figure 6: Redundancy in a Ring Topology
In Figure 6, PE1 and PE3 from VPLS domain A are connected to PE2 and
PE4 in VPLS domain B via PW group 1 and group 2. Each of the PEs in
the respective domains is connected to each other as well as forming
the ring topology. Such scenarios may arise in inter-domain H-VPLS
deployments where rapid spanning tree (RSTP) or other mechanisms may
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be used to maintain loop free connectivity of PW groups.
[RFC4762] outlines multi-domain VPLS services without specifying how
multiple redundant border PEs per domain per VPLS instance can be
supported. In the example above, PW group 1 may be blocked at PE1 by
RSTP and it is desirable to block the group at PE2 by virtue of
exchanging the PW preferential forwarding status of Standby. How the
PW grouping should be done here is again deployment specific and is
out of scope of the solution.
3.2.6. Redundancy in a VPLS Bridge Module Model
|<----- Provider ----->|
Core
+------+ +------+
| n-PE |::::::::::::::::::::::| n-PE |
Provider | (P) |.......... .........| (P) | Provider
Access +------+ . . +------+ Access
Network X Network
(1) +------+ . . +------+ (2)
| n-PE |.......... .........| n-PE |
| (B) |......................| (B) |
+------+ +------+
Figure 7: Bridge Module Model
Bridge Module Model
In Figure 7, two provider access networks, each having two n-PEs,
where the n-PEs are connected via a full mesh of PWs for a given VPLS
instance. As shown in the figure, only one n-PE in each access
network is serving as a Primary PE (P) for that VPLS instance and the
other n-PE is serving as the backup PE (B). In this figure, each
primary PE has two active PWs originating from it. Therefore, when a
multicast, broadcast, and unknown unicast frame arrives at the
primary n-PE from the access network side, the n-PE replicates the
frame over both PWs in the core even though it only needs to send the
frames over a single PW (shown with :::: in the figure) to the
primary n-PE on the other side. This is an unnecessary replication
of the customer frames that consumes core-network bandwidth (half of
the frames get discarded at the receiving n-PE). This issue gets
aggravated when there is three or more n-PEs per provider, access
network. For example if there are three n-PEs or four n-PEs per
access network, then 67% or 75% of core-BW for multicast, broadcast
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and unknown unicast are wasted, respectively.
In this scenario, n-PEs can disseminate the status of PWs active/
standby among them and furthermore to have it tied up with the
redundancy mechanism such that per VPLS instance the status of
active/backup n-PE gets reflected on the corresponding PWs emanating
from that n-PE.
4. Generic PW Redundancy Requirements
4.1. Protection Switching Requirements
o Protection architectures such as N:1,1:1 or 1+1 are possible. 1:1
protection MUST be supported. The N:1 protection case is less
efficient in terms of the resources that must be allocated and
hence this SHOULD be supported. 1+1 protection architecture MAY be
suported, but its definition is for further study.
o Non-revertive behavior MUST be supported, while revertive behavior
is OPTIONAL. This avoids the need to designate one PW as primary
unless revertive behavior is explicitly required.
o Protection switchover can be initiated from a PE e.g. using a
Manual lockout/force switchover, or it may be triggered by a
signal failure i.e. a defect in the PW or PSN. Manual switchover
may be necessary if it is required to disable one PW in a
redundant set. Both methods MUST be supported and signal failure
triggers MUST be treated with a higher priority than any local or
far-end manual trigger.
o Note that a PE MAY be able to forward packets received from a
standby status PW in order to avoid black holing of in-flight
packets during switchover. However, in the case of use of VPLS,
all VPLS application packets received from standby PWs MUST be
dropped, except for OAM packets.
4.2. Operational Requirements
o (T-)PEs involved in protecting a PW SHOULD automatically discover
and attempt to resolve inconsistencies in the configuration of
primary/secondary PW.
o (T-)PEs involved in protecting a PW SHOULD automatically discover
and attempt to resolve inconsistencies in the configuration of
revertive/non-revertive protection switching mode.
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o (T-)PEs that do not automatically discover or resolve
inconsistencies in the configuration of primary/secondary,
revertive/non-revertive, or other parameters MUST generate an
alarm upon detection of an inconsistent configuration.
o (T-)PEs participating in PW redundancy MUST support the
configuration of revertive or non-revertive protection switching
modes if both modes are supported.
o (T-)PEs participating in PW redundancy SHOULD support the local
invocation of protection switching.
o (T-)PEs participating in PW redundancy SHOULD support the local
invocation of a lockout of protection switching.
5. Security Considerations
This document requires extensions to the Label Distribution Protocol
(LDP) that are needed for protecting pseudowires. These will inherit
at least the same security properties as LDP [RFC5036] and the PW
control protocol [RFC4447].
6. IANA Considerations
This document has no actions for IANA.
7. Major Contributing Authors
The editors would like to thank Pranjal Kumar Dutta, Marc Lasserre,
Jonathan Newton, Hamid Ould-Brahim, Olen Stokes, Dave Mcdysan, Giles
Heron and Thomas Nadeau who made a major contribution to the
development of this document.
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Pranjal Dutta
Alcatel-Lucent
Email: pranjal.dutta@alcatel-lucent.com
Marc Lasserre
Alcatel-Lucent
Email: marc.lasserre@alcatel-lucent.com
Jonathan Newton
Cable & Wireless
Email: Jonathan.Newton@cw.com
Olen Stokes
Extreme Networks
Email: ostokes@extremenetworks.com
Hamid Ould-Brahim
Nortel
Email: hbrahim@nortel.com
Dave McDysan
Verizon
Email: dave.mcdysan@verizon.com
Giles Heron
Cisco Systems
Email: giles.heron@gmail.com
Thomas Nadeau
Computer Associates
Email: tnadeau@lucidvision.com
8. Acknowledgements
The authors would like to thank Vach Kompella, Kendall Harvey,
Tiberiu Grigoriu, Neil Hart, Kajal Saha, Florin Balus and Philippe
Niger for their valuable comments and suggestions.
9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3985] Bryant, S. and P. Pate, "Pseudo Wire Emulation Edge-to-
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Edge (PWE3) Architecture", RFC 3985, March 2005.
[RFC4026] Andersson, L. and T. Madsen, "Provider Provisioned Virtual
Private Network (VPN) Terminology", RFC 4026, March 2005.
[RFC4447] Martini, L., Rosen, E., El-Aawar, N., Smith, T., and G.
Heron, "Pseudowire Setup and Maintenance Using the Label
Distribution Protocol (LDP)", RFC 4447, April 2006.
[RFC4762] Lasserre, M. and V. Kompella, "Virtual Private LAN Service
(VPLS) Using Label Distribution Protocol (LDP) Signaling",
RFC 4762, January 2007.
[RFC5036] Andersson, L., Minei, I., and B. Thomas, "LDP
Specification", RFC 5036, October 2007.
[RFC5659] Bocci, M. and S. Bryant, "An Architecture for Multi-
Segment Pseudowire Emulation Edge-to-Edge", RFC 5659,
October 2009.
9.2. Informative References
[RFC6073] Martini, L., Metz, C., Nadeau, T., Bocci, M., and M.
Aissaoui, "Segmented Pseudowire", RFC 6073, January 2011.
Authors' Addresses
Praveen Muley
Alcatel-Lucent
Email: praveen.muley@alcatel-lucent.com
Mustapha Aissaoui
Alcatel-Lucent
Email: mustapha.aissaoui@alcatel-lucent.com
Matthew Bocci
Alcatel-Lucent
Email: matthew.bocci@alcatel-lucent.com
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