One document matched: draft-weingarten-mpls-tp-linear-protection-03.xml
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<rfc category="std" docName="draft-weingarten-mpls-tp-linear-protection-03.txt"
ipr="trust200902">
<front>
<title abbrev="MPLS-TP LP">MPLS-TP Linear Protection</title>
<author fullname="Stewart Bryant" initials="S." role="editor"
surname="Bryant">
<organization>Cisco</organization>
<address>
<postal>
<street />
<region />
<code />
<country>United Kingdom</country>
</postal>
<email>stbryant@cisco.com</email>
</address>
</author>
<author fullname="Nurit Sprecher" initials="N." role="editor" surname="Sprecher">
<organization>Nokia Siemens Networks</organization>
<address>
<postal>
<street>3 Hanagar St. Neve Ne'eman B</street>
<city>Hod Hasharon</city>
<region />
<code>45241</code>
<country>Israel</country>
</postal>
<email>nurit.sprecher@nsn.com</email>
</address>
</author>
<author fullname="Huub van Helvoort" initials="H." role="editor" surname="van Helvoort">
<organization>Huawei</organization>
<address>
<postal>
<street>Kolkgriend 38, 1356 BC Almere</street>
<city></city>
<region />
<code></code>
<country>Netherlands</country>
</postal>
<email>hhelvoort@huawei.com</email>
<phone>+31 36 5316076</phone>
</address>
</author>
<author fullname="Annamaria Fulignoli" initials="A." role="" surname="Fulignoli">
<organization>Ericsson</organization>
<address>
<postal>
<street></street>
<city></city>
<region />
<code></code>
<country>Italy</country>
</postal>
<email>annamaria.fulignoli@ericsson.com</email>
<phone></phone>
</address>
</author>
<author fullname="Yaacov Weingarten" initials="Y." role="" surname="Weingarten">
<organization>Nokia Siemens Networks</organization>
<address>
<postal>
<street>3 Hanagar St. Neve Ne'eman B</street>
<city>Hod Hasharon</city>
<region />
<code>45241</code>
<country>Israel</country>
</postal>
<email>yaacov.weingarten@nsn.com</email>
<phone>+972-9-775 1827</phone>
</address>
</author>
<date day="26" month="July" year="2009" />
<abstract>
<t>This document describes mechanisms for linear protection of Multi-Protocol
Label Switching Transport Profile (MPLS-TP) Label Switched Paths (LSP) and
Pseudowires (PW) on multiple layers. Linear protection provides a fast and simple
protection switching mechanism that is especially optimized for a mesh topology.
It provides a clear indication of the protection status. The mechanisms are
described both at the architectural level as well as providing a protocol that is
used to control and coordinate the protection switching.</t>
</abstract>
</front>
<middle>
<section title="Introduction">
<t>As noted in the architecture for Multi-Protocol Label Switching Transport
Profile (MPLS-TP) <xref target='7'/>, the overall architecture framework for
MPLS-TP is based on a profile of the MPLS and Pseudowire (PW) procedures as
specified for the MPLS and (MS-)PW architectures defined in RFC 3031
<xref target='3'/>, RFC 3985 <xref target='5' /> and <xref target='6' />. One
of the basic survivability functions, pointed out by the Survivability Framework
document <xref target='11' />, is that of simple and rapid protection switching
mechanisms for Label Switched Paths (LSP) and Pseudo-wires (PW).</t>
<t>Protection switching is a fully allocated survivability mechanism. It is
fully allocated in the sense that the route and bandwidth of the recovery path
is reserved for a selected working path. It provides a fast and simple
survivability mechanism, that allows the network operator to easily grasp the
active state of the network, compared to other survivability mechanisms.</t>
<t>This draft proposes an architecture and protocol to provide protection for
the different types of point-to-point (p2p) paths supported by MPLS-TP. These
include LSP, PW, Path Segment Tunnels (PST), and Tandem Connections (TC). For
unidirectional protection switching a 1+1 architecture is described. For
bidirectional switching both a 1+1 and a 1:1 architecture are described.</t>
<t>In 1+1 unidirectional architecture, a recovery transport path is dedicated to
each working transport path. Normal traffic is bridged and fed to both the
working and the recovery transport entities by a permanent bridge at the source
of the protection domain. The sink of the protection domain selects which of the
working or recovery entities to receive the traffic from, based on a predetermined
criteria, e.g. server defect indication. When used for bidirectional switching
the 1+1 protection architecture must also support a Protection Switching
Coordination (PSC) protocol. This protocol is used to help synchronize the
decisions of both ends of the protection domain in selecting the proper traffic
flow.</t>
<t>In the 1:1 architecture, a recovery transport path is dedicated to the working
transport path. However, the normal traffic is transmitted only once, on either
the working or the recovery path, by using a selector bridge at the source of the
protection domain. A selector at the sink of the protection domain then selects
the path that carries the normal traffic. Since the source and sink need to be
coordinated to ensure that the selector bridge at both ends select the same path,
this architecture must support the PSC protocol.</t>
<section title="Contributing authors">
<t>Hao Long (Huawei)</t>
</section>
</section>
<section title="Conventions used in this document">
<t>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 <xref target='1' />.</t>
<section title="Acronyms">
<texttable>
<preamble>This draft uses the following acronyms:</preamble>
<ttcol align="left"/>
<ttcol align="left"/>
<c>DNR</c><c>Do not revert</c>
<c>FS</c><c>Forced Switch</c>
<c>GACH</c><c>Generic Associated Channel Header</c>
<c>LSR</c><c>Label Switching relay</c>
<c>MPLS-TP</c><c>Transport Profile for MPLS</c>
<c>MS</c><c>Manual Switch</c>
<c>P2P</c><c>Point-to-point</c>
<c>P2MP</c><c>Point-to-multipoint</c>
<c>PDU</c><c>Packet Data Unit</c>
<c>PSC</c><c>Protection Switching Coordination Protocol</c>
<c>PST</c><c>Path Segment Tunnel</c>
<c>SD</c><c>Signal Degrade</c>
<c>SF</c><c>Signal Fail</c>
<c>SLA</c><c>Service Level Agreement</c>
<c>WTR</c><c>Wait-to-Restore</c>
</texttable>
</section>
<section title="Definitions and Terminology">
<t>Protection domain: Transport path (e.g. LSP, PW, PST, TC) that provides protection
for its normal traffic. The protection domain consists of the following elements –
Two end points (East and West) that in each direction one acts as the source and the
other as the sink, a working path, and a recovery path. </t>
<t>Recovery path: A transport path dedicated to transport normal user traffic in case
of a failure of the Working path.</t>
<t>Working path: A transport path used for transport of normal user traffic,
under normal conditions.</t>
<t>The terminology used in this document is based on the terminology defined in
<xref target='10' />. In addition, we use the term LSR to refer to a MPLS-TP
Network Element, whether it is a LSR, LER, T-PE, or S-PE.</t>
</section>
</section>
<section title="Network objectives">
<t>Linear protection for MPLS-TP should comply with the following network objectives:</t>
<t>
<list style="symbols">
<t>Switch time: protection switching should operate as quickly as possible. A
switching time of less than 50ms has been proposed as a target for certain use cases.
The switching time does not include the detection time and the hold-off time.</t>
<t>Hold-off times: to allow protection by the layer that is closest to the detected
defect and retain the stability of the network, a hold-off timer should be employed
when a defect is detected. At the expiration of the hold-off period, the defect
should be rechecked and if still existent the protection mechanism shall be invoked.</t>
<t>Extent of protection: the protection mechanism should restore interrupted
traffic due to a facility (link or node) failure, within a protection domain.
Traffic terminating at a failed node may be disrupted, however, traffic passing
through to other nodes should be protected.</t>
<t>Operation modes: the protection mechanism should provide protection for both
unidirectional and bidirectional transport entities. The protection mechanism should
support both revertive and non-revertive modes of operation.</t>
<t>Manual control: administrative commands may be provided for manual control of the
protection switching operations. The following are examples of possible manual
commands: Clear, Forced Switch, Manual Switch (see definitions in <xref target='10' />).</t>
</list>
</t>
</section>
<section title="Protection architectures">
<t>The protection mechanism defined here supports transport paths (as defined in
<xref target='2' />') within a mesh-based network. This includes support for
unidirectional, both point-to-point and point-to-multipoint, and bidirectional
point-to-point paths. This protection may be supported by different protection
architectures as described in the following subsections.</t>
<section title="1+1 Protection architecture">
<t>The 1+1 protection architecture provides for a fully dedicated recovery path in
addition to the configured working path. Both the recovery and working path MUST support
the full SLA requirements for the traffic between the two end points of the protection
domain.</t>
<t>In this architecture (see <xref target="figure 1"/>), all traffic from LSR A to LSR Z
is bridged, using the permanent bridge at LSR A, to both transport entities, and LSR Z
employs a selector bridge to receive the data from the working path, discarding the
packets from the recovery path.</t>
<t>In case of a condition, e.g. a failure condition or an operator command, where
protection switching is indicated, LSR Z SHOULD select the data packets from the
recovery path and discard any data packets from the working path.</t>
<t>It should be further noted that OAM packets for monitoring the protection domain,
or control plane packets, may be transmitted on the "non-active" transport path.
These packets SHALL NOT be discarded.</t>
<figure anchor="figure 1" title="1+1 Unidirectional protection architecture">
<artwork>
|-------------Protection Domain-----------------|
==============================
/**********Working path************\
+--------+ ============================== +--------+
| LSR /| |\ LSR |
| A {< | | >} Z |
| PB \| | SB |
+--------+ ============================== +--------+
\***********Recovery path***********/
==============================
PB: Permanent Bridge SB: Selector Bridge
</artwork>
</figure>
<t>When using the 1+1 architecture for bidirectional switching, each of the end-points
would have both a permanent bridge and a selector bridge one for each direction.</t>
</section>
<section title="1:1 Protection architecture">
<t>Another option to protect a bidirectional connection is a 1:1 architecture. This
architecture provides for a fully allocated recovery transport path in addition to the
working transport path used for normal user data. In principle, this recovery path
MUST support the full capacity and bandwidth of the SLA but may be degraded from the
normal working path.</t>
<t>In this architecture both ends of the protection domain employ a Selector bridge
(SB) that selects the transport path to transmit the data packets over. Under normal
conditions the SB selects the working path for transmission of the data packets. When
a condition that triggers protection switching is active, the SB at either end need to
select the recovery path for data transmission.</t>
<figure anchor="figure 2" title="1:1 Bidirectional protection architecture using working path">
<artwork>
|-------------Protection Domain-----------------|
==============================
/**********Working path***********\
+--------+ ============================== +--------+
| LSR /| |\ LSR |
| A {< | | >} Z |
| SB | | SB |
+--------+ ============================== +--------+
Recovery path
==============================
SB: Selector Bridge
</artwork>
</figure>
<t>In principle, the recovery path could be used for "extra traffic", i.e. preemptible
traffic. However, if protection switching is in force then this traffic SHALL be pre-empted
by the protected data that is being transmitted on this path. In any case, the recovery
path MUST support OAM and protection coordination traffic (see section 6).</t>
<t>This architecture requires communication between the end-points of the protection
domain to coordinate the protection state. In general bidirectional protection
switching requires coordination between the end-points and verification that both
transmission directions remain on a co-routed bidirectional path.</t>
</section>
<section title="Protection of P2MP networks">
<t><xref target='2' /> specifies that all P2MP MPLS-TP connections are
unidirectional by nature. It further requires that these connections should be
supported by both 1+1 and 1:1 protection architectures.</t>
<t>When protecting a P2MP network using a 1+1 protection architecture, the basic
protection mechanism is still relevant. The root LSR will bridge the user traffic
(using a permanent bridge) to both the working and recovery transport entities. Each
leaf LSR will select the traffic from one transport path according to its own local
triggers. This may lead to a situation where, due to a failure condition on one branch
of the network, that some leaf LSRs may select the working transport path, while other
leaf LSRs may select traffic from the recovery transport path.</t>
<t>When protecting a P2MP network using 1:1 protection architecture, there is a need
for the root LSR to identify the existence of a failure condition on any of the branches
of the network.</t>
<t>Editor's note: This requires the use of tools from the OAM toolset <xref target='9' />,
and also a return path that can pass the indication back to the root LSR. This protection
architecture, in the P2MP case, also requires that each leaf LSR selects the traffic
from the same incoming transport entity that was selected by the root LSR. When
protection switching is triggered, the root LSR selects the recovery transport path
to transfer the traffic and each leaf LSR needs to select this same transmission.
Endof Editor's note!!</t>
</section>
<section title="Extension to 1:n protection">
<t>This is for further study</t>
<t>Editor's note: definition of 1:n protection should be that there is one recovery path
that is given a different label relative to each working path that is being protected.
When any one of the working paths indicates a failure, then the traffic is redirected
to the recovery path, using the dedicated recovery label. When more than one working
path reports a failure, then the path with the highest priority will have its traffic
redirected to the recovery path and traffic from other paths will not be protected.
It should be noted further that 1:n protection cannot be supported using a single phase
protocol, since the coordination of which is the highest priority path and notification
to other paths needs acknowledgement, i.e. at least a second phase.</t>
<t>There is a suggestion to have a separate draft for the extension to 1:n protection,
that would include a definition to the two-phased protocol. This draft should only
prepare the groundwork of the protocol so as not to preclude the 1:n protection.</t>
<t>This is still under discussion. End of Editor's note</t>
</section>
<section title="Revertive and non-revertive switching">
<t>In revertive operation, the normal traffic signal is restored to the working transport
path after the condition that triggered the switching has cleared. When a manual operator
command (e.g. Forced Switch) has cleared, then the reversion happens immediately. When
a failure or degradation of service has cleared, the reversion may be delayed until the
expiry of a Wait-to-restore timer, used to neutralize the effect of intermittent
defects.</t>
<t>In non-revertive mode of operation, the normal traffic continues to use the recovery
transport path, even after the condition that triggered has cleared. Eventually, the
network may be reverted to use the working transport path, by using an explicit operator
command (see section 6.3.5).</t>
<t>The 1+1 protection architecture is often provisioned to operate as non-revertive,
since the recovery transport path is fully dedicated in any case and continuing to select
it on the sink avoids a second disturbance to the traffic. There may, however, be
certain operator policies that dictate provisioning revertive operation for 1+1
protection.</t>
<t>The 1:1 protection architecture is often provisioned to operate in revertive mode.
This takes advantage of the (typically) more optimized working transport path, even at
the cost of the additional disturbance to traffic from the additional switch.</t>
<t>The configuration of revertive or non-revertive operation SHOULD be the same at
both ends of the protection domain.</t>
</section>
</section>
<section title="Protection switching logic">
<section title="Protection switching trigger mechanisms">
<t>The protection switching should be initiated in reaction to any of the following
triggers:</t>
<t>
<list style="symbols">
<t>Server layer indication – if any of the lower layers (e.g. the physical
layer) raises an interrupt indicating that a failure has been detected.</t>
<t>OAM signalling – if the OAM continuity and connectivity verification tools
detect that there is a loss of continuity or mis-connectivity or the performance
monitoring indicates a degradation of the utility of the working path for the
current transport path. In cases of signal degradation, switching to the recovery
path SHOULD only be activated if the recovery path can guarantee better conditions
than the degraded working path.</t>
<t>Control plane – if there is a control plane active in the network (either
signalling or routing), it may send an indication of problems on the working path.
Protection switching should be initiated as a result , until the problems are
signalled to have cleared. If the control-plane is based on GMPLS
<xref target='13' /> then the recovery process should comply with the process
described in <xref target='12' />.</t>
<t>Operator command – the network operator may issue commands that trigger
protection switching. The commands that are supported include – Forced Switch,
Manual Switch, Clear, Lockout of Protection, (see definitions in <xref target='10' />).</t>
</list> </t>
</section>
<section title="Hold-off timer">
<t>In order to coordinate timing of protection switches at multiple layers, a
hold-off timer may be required. Its purpose is to allow, for example, a server
layer protection switch to have a chance to fix the problem before switching at
a client layer.</t>
<t>Each protection group should have a provisionable holdoff timer. The suggested
range of the holdoff timer is 0 to 10 seconds in steps of 100 ms with an accuracy
within 5 ms. The default duration for the holdoff timer is 0 seconds.</t>
<t>When a failure condition is detected, this will not immediately activate
protection switching if the provisioned hold-off timer value is non-zero. Rather,
the hold-off timer will be started. When the hold-off timer expires, we check if
a failure condition is still present. If there is still a failure condition, then
the protection switching is activated, regardless if it is the same failure
condition that caused the activation the hold-off timer.</t>
</section>
<section title="Protection switching control logical architecture">
<t>Protection switching processes the triggers described above together with the
inputs received from the far-end LSR. These inputs cause the LSR to take certain
actions, e.g. switching the Selector Bridge to select the working or recovery path,
and to transmit different protocol messages.</t>
<figure anchor="figure 3" title="Protection switching control logic">
<artwork>
+-------------+ Operator Command Local PSC +-----------+
| External |-----------------+ +-----------------| PSC Status|
| Interface | | | request +---| Module |
+-------------+ | | | +-----------+
V V V Prot. Stat. ^
+----------+ Local OAM +---------------+Highest +------------+ |
| OAM |----------->| Local Request |------->| PSC Mess. | |
| Module | request | logic |local R.| Generator | |
+----------+ +------->+---------------+ +------------+ |
+----------+ | | | |
| Svr/CP |---+ Highest local|request | |
+----------+ V V |
+-------------+ +-----------------+ PSC Message |
| Remote Req. | Remote PSC | global Request | |
| Receiver |------------>| logic | |
+-------------+ Request +-----------------+ |
^ | |
| Highest global request| |
| V |
| +-----------------+ PSC status |
Remote PSC message | PSC Process |-----------------+
| logic |--------> Action
| |
+-----------------+
</artwork>
</figure>
<t><xref target="figure 3" /> describes the logical architecture of the protection
switching control. The Local Request logic unit accepts the triggers from the OAM,
external operator commands, and from the local control plane (when present) and
determines the highest priority request. This high-priority request is passed to
both the PSC Message generator, that will generate the appropriate protocol message
to be sent to the far-end LSR, and the Global Request logic, that will cross-check
this local request with the information received from the far-LSR. The Global
Request logic then processes these two PSC requests that determines the highest
priority request that is passed to the PSC Process logic. The PSC Process logic uses
this input to determine what actions need to be taken, e.g. switching the Selector
Bridge, and the current status of the protection domain.</t>
<section title="PSC Status Module">
<t>The PSC Control Logic must retain the status of the protection domain. The
possible different states indicate the current status of the protection environment,
and can be in one of three states:</t>
<t><list style="symbols">
<t>Normal (Idle) state – When both the recovery and the working paths are
fully allocated and active, data traffic is being transmitted over the working
path, and there are no events being reported within the domain.</t>
<t>Protecting state – When the working path has reported a signal failure
or degradation of signal and the data traffic has been redirected to the recovery
path.</t>
<t>Unavailable state – When the recovery path is unavailable, either as a
result of reporting a SF or SD condition, or as a result of an administrative
Lockout command.</t>
</list></t>
<t>This state may affect the actions taken by the control logic, and therefore, the
PSC Status Module transfers the current status to the Local Request Logic.</t>
<t>See section 6.3.1 for details on what actions are affected by the PSC state.</t>
</section>
</section>
</section>
<section title="Protection switching coordination (PSC) protocol">
<t>Bidirectional protection switching requires coordination between the two
end-points in determining which of the two possible paths, the working or recovery
path, is operational in any given situation. When protection switching is
triggered as described in section 5.1, the end-points must inform each other of the
switch-over from one path to the other in a coordinated fashion.</t>
<t>There are different possibilities for the type of coordinating protocol. One
possibility is a two-phased coordination in which the MEP that is initiating the
protection switching sends a protocol message indicating the switch but the actual
switch-over is performed only after receiving an 'Ack' from the far-end MEP. The
other possibility is a single-phased coordination, in which the initiating MEP
switches over to the alternate path and informs the far-end of the switch, and the
far-end must complete the switch-over.</t>
<t>In the following sub-sections we describe the protocol messages that should be used
between the two end-points of the protection domain.</t>
<t>For the sake of simplicity of the protocol, this protocol is based on the single-phase
approach described above.</t>
<section title="Transmission and acceptance of PSC control packets">
<t>The PSC control packets should be transmitted over the recovery path only.
This allows the transmission of the messages without affecting the normal
traffic in the most prevalent case, i.e. the idle state. In addition,
limiting the transmission to a single path avoids possible conflicts and race
conditions that could develop if the PSC messages were sent on both paths.</t>
<t>A new PSC control packets must be transmitted immediately when a change in
the transmitted status occurs.</t>
<t>The first three PSC packets should be transmitted as fast as possible only
if the PSC information to be transmitted has been changed so that fast
protection switching is possible even if one or two PSC packets are lost or
corrupted. For protection switching within 50ms, the interval of the
first three PSC signals should be 3.3ms. PSC packets after the first three
should be transmitted with an interval of 5 seconds.</t>
<t>If no valid PSC specific information is received, the last valid received
information remains applicable. In the event a signal fail condition is
detected on the protection transport entity, the received PSC specific
information should be evaluated.</t>
</section>
<section title="Protocol format">
<t>The protocol messages SHALL be sent over the GACH as described in
<xref target='8' />. There is a single channel type for the set of PSC messages,
each message will be identified by the first field of the ACH payload as described
below. PSC messages SHOULD support addressing by use of the method described in
<xref target='8' />. The following figure shows the format for the full PSC message.</t>
<figure anchor="figure 4" title="Format of PSC packet with a GACH header">
<artwork>
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 1|0 0 0 0|0 0 0 0 0 0 0 0| MPLS-TP PSC Channel Code |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ACH TLV Header |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ Addressing TLV +
: ... :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ PSC Control Packet ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
</artwork>
</figure>
<t>Where:
<list style="symbols">
<t>MPLS-TP PSC Channel Code is the GACH channel number assigned to the PSC = TBD</t>
<t>The ACH TLV Header is described in <xref target='8' /></t>
<t>The use of the Addressing TLV are described in section 6.2</t>
<t>The following figure shows the format of the PSC Control message that is the
payload for the PSC packet.</t>
</list>
</t>
<t>Editor's note: There is a suggestion that this format should be aligned with the
format used by G.8031/G.8131/Y.1731 in ITU. The argument being that this would make
it easier to pass review from ITU and allow easier transfer of technology.</t>
<t>The counter-argument is that the ITU format is based upon an attempt to find a
common format for different functionality and therefore involves different fields that
are not necessary for the protection switching. Defining a new dedicated format would
make for a simpler and more intuitive protocol. End of editor's note.</t>
<figure anchor="figure 5" title="Format of the PSC control packet">
<artwork>
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Ver|Request|Typ| FPath | Path | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
</artwork>
</figure>
<t>Where:
<list style="symbols">
<t>Ver: is the version of the protocol, for this version the value SHOULD be 0.</t>
<t>Request: this field indicates the specific PSC request that is being
transmitted, the details are described in section 6.1.1</t>
<t>Typ: indicates the type of protection scheme currently supported, more
details are given in section 6.1.4</t>
<t>FPath: used to indicate the path that is reporting a failure condition,
the possible values are described in section 6.1.2</t>
<t>Path: used to indicate the currently active path, possible values are
described in section 6.1.3</t>
<t>Rsv, Reserved: these fields are reserved for possible future use.</t>
</list>
</t>
<!-- Need to continue from here with section 6.1.1 of document!! -->
<section title="PSC Requests">
<t>The Protection Switching Coordination (PSC) protocol SHALL support
the following request types, in order of priority from highest to lowest:</t>
<list style="symbols">
<t>(1111) Clear</t>
<t>(1110) Lockout protection</t>
<t>(1101) Forced switch</t>
<t>(0110) Signal fault</t>
<t>(0101) Signal degrade</t>
<t>(0100) Manual switch</t>
<t>(0011) Wait to restore</t>
<t>(0010) Do not revert (DNR)</t>
<t>(0000) No request</t>
</list>
<t>See section 6.3 for a description of the operation of the different
requests.</t>
</section>
<!-- This will be the continuation from section 6.2 of document!! -->
<section title="Path Fault Identifier">
<t>The Fpath field of the PSC control SHALL be used only in a Signal fault
(0101) or Signal degrade (0100) control packet. Its value indicates on
which path the signal anomaly was detected. The following are the possible
values:</t>
<list style="symbols">
<t>0: indicates that the fault condition is on the Recovery path </t>
<t>1: indicates that the fault condition is on the Working path</t>
<t>2-255: for future extensions</t>
</list>
</section>
<section title="Active path indicator">
<t>The Path field of the PSC control SHALL be used to indicate which path
the source MEP is currently using for data transmission. The MEP should
compare the value of this bit with the path that is locally selected for
data transmission to verify that there is no inconsistency between the
two end-points of the protected domain. If an inconsistency is detected
then an alarm should be raised. The following are the possible values:</t>
<list style="symbols">
<t>0: indicates that normal traffic is being transmitted on the Working
path.</t>
<t>1: indicates the Recovery path is being used to transmit the normal
traffic from the Working path.</t>
<t>2-255: for future extensions</t>
</list>
</section>
<section title="Current Protection Type">
<t>The Typ field indicates the currently configured protection architecture
type, this should be validated to be consistent for both ends of the
protected domain. If an inconsistency is detected then an alarm should be
raised. The following are the possible values:</t>
<list style="symbols">
<t>11: 1+1 bidirectional switching</t>
<t>10: 1:1 bidirectional switching</t>
<t>01: 1+1 unidirectional switching</t>
<t>00: 1:1 unidirectional switching</t>
</list>
</section>
</section>
<section title="Addressing of PSC requests">
<t>The PSC request should include the following addressing information,
in ACH-TLV fields (as described in <xref target='8' />):</t>
<list style="symbols">
<t>Source address: the address of the LSR that initiated this message.
There MUST be only one Source address TLV present in the message.</t>
<t>Destination address: the address of the LSR of the far-end MEP that
this message is intended for. There MUST be at least one Destination
address TLV present in the message.</t>
<t>Fault location: the address of the LSR reporting a SF condition,
if known. This TLV is present only in SF or SD messages and only if
the information was provided by the switching trigger.</t>
</list>
<t>The format for the TLV fields are as specified in <xref target='8' />.</t>
</section>
<section title="Principles of Operation">
<t>In all of the following sub-sections, assume a protected domain
between LSR-A and LSR-Z, using paths W (working) and R (recovery).</t>
<section title="PSC States">
<section title="Normal State">
<t>When the protected domain has no special condition in effect, the
ingress LSR SHOULD forward the user data along the working path, and,
in the case of 1+1 protection, the Permanent Bridge will bridge the data
to the recovery path as well. The receiving LSR SHOULD read the data
from the working path.</t>
<t>The ingress LSR MAY transmit a No Request PSC packet with the Path field
set to 0 for the recovery path.</t>
</section>
<section title="Protecting State">
<t>When the protection mechanism has been triggered and the protected domain
has performed a protection switch, the domain is in the protecting state.
In this state the normal traffic is transmitted and received on the recovery
path.</t>
<t>If the protection domain is currently in a protecting state, then the LSRs
SHOULD NOT accept a Manual Switch request.</t>
<t>If the protection domain is currently in a protecting state, and a Forced
Switch is requested then the normal traffic SHALL continue to be transmitted
on the recovery path even if the original protection trigger is cleared.</t>
</section>
<section title="Unavailable State">
<t>When the recovery path is unavailable – either as a result of a Lockout
operator command (see section 6.3.3), or as a result of a SF or SD detected on
the recovery path (see section 6.3.4) – then the protection domain is in the
unavailable state. In this state, the normal traffic is transmitted and
received on the working path.</t>
<t>While in unavailable state any event that would trigger a protection
switching SHOULD be ignored with the following exception – If a Signal Degrade
request is received, then protection switching will be activated only if the
recovery path can guarantee a better signal than the working path.</t>
<t>The protection domain will exit the unavailable state and revert to the
normal state when, either the operator clears the Lockout command or the
recovery path recovers from the signal fault or degraded situation. Both
ends will resume sending the PCS packets over the recovery path, as a result
of this recovery.</t>
</section>
</section>
<section title="Failure or Degraded condition (Working path)">
<t>If one of the LSRs (for example, LSR-A) detects a failure condition or a serious
degradation condition on the working path that warrants invoking protection
switching, then it SHOULD take the following actions:</t>
<list style="symbols">
<t>Switch all traffic for LSR-Z to the recovery path only.</t>
<t>Transmit a PCS control packet, using GACH, with the appropriate Request code
(either Signal fault or Signal degrade), the Fpath set to 1, to indicate that
the fault/degrade was detected on the working path, and the Path set to 0,
indicating that normal traffic is now being transmitted on the recovery path.
</t>
<t>Verify that LSR-Z replies with a PCS control packet indicating that it has
switched to the recovery path. If this is not received after xxx then send an
alarm to the management system.</t>
</list>
<t>When the far-end LSR (in this example LSR-Z) receives the PCS packet informing
it that other LSR (LSR-A) has switched, it SHOULD perform the following actions:</t>
<list style="symbols">
<t>Check priority of the request</t>
<t>Switch all traffic addressed to LSR-A to the recovery path only.</t>
<t>Begin transmission of a PCS control packet, using GACH, with the appropriate
Request code (either Signal fault or Signal degrade), the Fpath set to 1, to
indicate that the fault/degrade was detected on the working path, and the Path
set to 1, indicating that traffic is now being transmitted on the recovery path.
</t>
</list>
</section>
<section title="Lockout of Protection">
<t>If one of the LSRs (for example, LSR-A) receives a management command indicating
that the protection is disabled, then it SHOULD indicate this to the far-end LSR
(for example, LSR-Z) that it is not possible to use the recovery path. The
following actions MUST be taken:</t>
<list>
<t>Transmit a PCS control packet, using GACH, with the Request code set to Lockout
of protection (1010), the Fpath set to 0, and the Path set to 0.</t>
<t>All normal traffic packets should be transmitted on the working path only.</t>
<t>Verify that the far-end LSR (for example LSR-Z) is forwarding the data packets
on the working path. Raise alarm in case of mismatch.</t>
<t>The PSC control logic should go into Unavailable state.</t>
</list>
<t>When the far-end LSR (in this example LSR-Z) receives the PCS packet informing
it that other LSR (LSR-A) has switched, it SHOULD perform the following actions:</t>
<list style="symbols">
<t>Check priority of request</t>
<t>Switch all normal traffic addressed to LSR-A to the working path only.</t>
<t>The PSC control logic should go into Unavailable status.</t>
<t>Begin transmission of a PCS control packet, using GACH, with the appropriate
Request code (Lockout of protection), the Fpath set to 0, and the Path set to 0,
indicating that traffic is now being transmitted on the working path only.</t>
</list>
</section>
<section title="Failure or Degraded condition (Recovery path)">
<t>If one of the LSRs (for example, LSR-A) detects a failure condition or a serious
degradation condition on the recovery path, then it SHOULD take the following
actions:</t>
<list style="symbols">
<t>Begin transmission of a PCS control packet with the appropriate Request code
(either Signal fault or Signal degrade), the Fpath set to 0, to indicate that
the fault/degrade was detected on the recovery path, and the Path set to 1,
indicating that traffic is now being forwarded on the working path. Note that
this will actually reach the far-end if this is a unidirectional fault or
recovery path is possibly in a degraded situation.</t>
<t>The PSC control logic should go into Unavailable state.</t>
<t>All traffic MUST be transmitted on the working path for the duration of
the SF/SD condition.</t>
</list>
<t>When the far-end LSR (in this example LSR-Z) receives the PCS packet informing
it that other LSR (LSR-A) has become Unavailable, it SHOULD perform the following
actions:</t>
<list style="symbols">
<t>Transmit all traffic on the working path for the duration of the SF/SD
condition</t>
<t>The PSC Control logic should go into Unavailable state.</t>
</list>
</section>
<section title="Operator Controlled Switching">
<t>If the management system indicated to one of the LSRs (for example LSR-A) that a
switch is necessary, e.g. either a Forced Switch or a Manual Switch, then the LSR
SHOULD switch the traffic to the recovery path and perform the following actions:</t>
<list style="symbols">
<t>Switch all data traffic to the recovery path only.</t>
<t>Transmit a PCS control packet, using GACH, with the appropriate Request code
(either Manual switch or Forced switch), the Fpath set to 0, to indicate that the
fault/degrade was detected on the working path, and the Path set to 1, indicating
that traffic is now being forwarded on the recovery path.</t>
<t>Verify that LSR-Z replies with a PCS control packet indicating that it has
switched to the recovery path. If this is not received after xxx then send an alarm
to the management system.</t>
</list>
<t>When the far-end LSR (in this example LSR-Z) receives the PCS packet informing it
that other LSR (LSR-A) has switched, it SHOULD perform the following actions:</t>
<list style="symbols">
<t>Check priority of the request</t>
<t>Switch all normal traffic addressed to LSR-A to the recovery path only.</t>
<t>Begin transmission of a PCS control packet, using GACH, with the appropriate
Request code (either Manual switch of Forced switch), the Fpath set to 1, to
indicate that the fault/degrade was detected on the working path, and the Path set
to 1, indicating that traffic is now being forwarded on the recovery path.</t>
</list>
<section title="Clearing operator commands">
<t>The operator may clear the switching condition by issuing a Clear request.
This command will cause immediate recovery from the switch that was initiated by
any of the previous operator commands, i.e. Forced Switch or Manual Switch. In
addition, a Clear command after a Lockout Protection command should clear the
Unavailable state and return the protection domain to the normal state.</t>
<t>If the Clear request is issued in the absence of a Manual Switch, Forced
Switch, or Lockout protection, then it SHALL be ignored. In the presence of any
of these commands, the Clear request SHALL clear the state affected by the
operator command.</t>
</section>
</section>
<section title="Recovery from switching">
<t>When the condition that triggered the protection switching clears, e.g. the cause
of the failure condition has been corrected, the operator clears a Manual Switch, then
the protection domain SHOULD follow the following procedures:</t>
<list style="symbols">
<t>If the network is configured for non-revertive behaviour, then the two LSRs SHOULD
transmit DNR (Request code 0010) messages. When the operator clears the non-revertive
condition, the two LSRs SHOULD return to use of the working transport path and transmit
No request (Request code 0000) messages.</t>
<t>If the network is recovering from an operator switching command (in revertive mode),
then both LSRs SHOULD return to using the working transport path and transmit No request
(Request code 0000) messages.</t>
<t>If the network is recovering from a failure or degraded condition (in revertive mode),
then the LSR that detects this recovery SHALL activate a local Wait-to-restore (WTR)
timer (see section 6.3.6.1) to verify that there is not an intermittent failure. After
the WTR expires, the LSR SHOULD return to using the working transport path and transmit
No request (Request code 0000) messages.</t>
</list>
<section title="Wait-to-restore timer">
<t>In revertive mode, in order to prevent frequent activation of protection switching due
to an intermittent defect, the working transport path must become stable and fault-free
before reverting to the normal condition. In order to verify that this is the case a
fixed period of time must elapse before the normal traffic uses the working transport path.
This period, called the WTR period, should be configurable by the operator in 1-minute
intervals within the range 1-12 minutes. The default value is 5 minutes.</t>
<t>During this period, if a failure condition is detected on the working transport path,
then the WTR timer is stopped and the normal traffic SHALL continue to be transported over
the recovery transport path. If the WTR timer expires without being pre-empted by a failure,
then the traffic SHOULD be returned to use the working transport path (as above).</t>
</section>
</section>
</section>
</section>
<section anchor="IANA" title="IANA Considerations">
<t>This document makes no request of IANA.</t>
<t>Note to RFC Editor: this section may be removed on publication as an
RFC.</t>
</section>
<section anchor="Security" title="Security Considerations">
<t>This document does not by itself raise any particular security
considerations.</t>
</section>
<section anchor="Acknowledgements" title="Acknowledgements">
<t>The authors would like to thank all members of the teams (the Joint
Working Team, the MPLS Interoperability Design Team in IETF and the T-MPLS
Ad Hoc Group in ITU-T) involved in the definition and specification of MPLS
Transport Profile.</t>
</section>
</middle>
<back>
<references title="Normative References">
<!-- Begin inclusion reference.RFC.2116.xml. -->
<reference anchor="1">
<front>
<title abbrev="KeyW">Key words for use in RFCs to Indicate Requirement Levels</title>
<author fullname="S. Bradner" initials="S." surname="Bradner">
<organization />
</author>
<date month="March" year="1997" />
<abstract>
<t>Defines the normative terms used in RFCs.</t>
</abstract>
</front>
<seriesInfo name="BCP" value="14" />
<seriesInfo name="RFC" value="792" />
</reference>
<!-- End inclusion reference.RFC.2116.xml. -->
<!-- Begin inclusion reference.draft.MPLS.TP.Reqs -->
<reference anchor="2">
<front>
<title>Requirements for the Trasport Profile of MPLS</title>
<author initials="B." surname="Niven-Jenkins" fullname="Ben Niven-Jenkins">
<organization> BT </organization>
</author>
<author initials="D." surname="Brungard" fullname="Deborah Brungard">
<organization> AT&T </organization>
</author>
<author initials="M." surname="Betts" fullname="Malcolm Betts">
<organization />
</author>
<author initials="N." surname="Sprecher" fullname="Nurit Sprecher">
<organization> NSN </organization>
</author>
<author initials="S." surname="Ueno" fullname="S.Ueno">
<organization />
</author>
<date year="2009" month="June" />
<abstract>
<t>Lists the requirements for MPLS-TP with cross reference </t>
</abstract>
</front>
<seriesInfo name="ID" value="draft-ietf-mpls-tp-requirements-09" />
</reference>
<!-- End inclusion reference.draft.MPLS.TP.Reqs -->
</references>
<references title="Informative References">
<!-- Begin inclusion reference.RFC.3031.xml. -->
<reference anchor="3">
<front>
<title abbrev="MPLS-Arch">Multiprotocol Label Switching Architecture</title>
<author fullname="E. Rosen" initials="E." surname="Rosen">
<organization />
</author>
<author fullname="A. Viswanathan" initials="A." surname="Viswanathan">
<organization />
</author>
<author fullname="Ross Callon" initials="R." surname="Callon">
<organization />
</author>
<date month="Jan" year="2001" />
<abstract>
<t>Describes the architecture of MPLS and the use of LSP tunnels.</t>
</abstract>
</front>
<seriesInfo name="RFC" value="3031" />
</reference>
<!-- End inclusion reference.RFC.3031.xml. -->
<!--Begin inclusion reference.RFC.3032 -->
<reference anchor="4">
<front>
<title>MPLS Label Stack Encoding", RFC 3032, January 2001</title>
<author initials="E." surname="Rosen" fullname="E. Rosen">
<organization />
</author>
<author initials="D." surname="Tappan" fullname="D. Tappan">
<organization />
</author>
<author initials="G." surname="Fedorkow" fullname="G. Fedorkow">
<organization />
</author>
<author initials="Y." surname="Rekhter" fullname="Yakov Rechter">
<organization />
</author>
<author initials="T." surname="Li" fullname="T. Li">
<organization />
</author>
<date year="2001" month="Jan" />
<abstract>
<t>"Multi-Protocol Label Switching (MPLS)" requires a set of procedures
for augmenting network layer packets with "label stacks",thereby turning
them into "labeled packets". Routers which support MPLS are known as
"Label Switching Routers", or "LSRs". In order to transmit a labeled
packet on a particular data link, an LSR must support an encoding
technique which, given a label stack and a network layer packet, produces
a labeled packet. This document specifies the encoding to be used by an
LSR in order to transmit labeled packets on Point-to-Point Protocol (PPP)
data links, on LAN data links, and possibly on other data links as well.
On some data links, the label at the top of the stack may be encoded in
a different manner, but the techniques described here MUST be used to
encode the remainder of the label stack. This document also specifies
rules and procedures for processing the various fields of the label stack
encoding.</t>
</abstract>
</front>
<seriesInfo name="RFC" value="3032" />
<format type="TXT" octets="116872" target="ftp://ftp.isi.edu/in-notes/rfc3032.txt" />
</reference>
<!-- End inclusion reference.RFC.3032 -->
<!-- Begin inclusion reference.RFC.3985 -->
<reference anchor="5">
<front>
<title>Pseudowire Emulation Edge-to-Edge (PWE3) Architecture</title>
<author initials="S." surname="Bryant" fullname="S. Bryant">
<organization />
</author>
<author initials="P." surname="Pate" fullname="P. Pate">
<organization />
</author>
<date year="2005" month="March" />
<abstract>
<t>This document describes an architecture for Pseudo Wire Emulation Edge-to-
Edge (PWE3). It discusses the emulation of services such as Frame Relay, ATM,
Ethernet, TDM, and SONET/SDH over packet switched networks (PSNs) using IP
or MPLS. It presents the architectural framework for pseudo wires (PWs),
defines terminology, and specifies the various protocol elements and their
functions. </t>
</abstract>
</front>
<seriesInfo name="RFC" value="3985" />
<format type="TXT" octets="22440" target="ftp://ftp.isi.edu/in-notes/rfc3985.txt" />
</reference>
<!-- End inclusion reference.RFC.4385 -->
<!-- Begin inclusion reference.RFC.5085 -->
<reference anchor="6">
<front>
<title>Pseudowire Virtual Circuit Connectivity Verification (VCCV): A Control Channel for Pseudowires</title>
<author initials="T." surname="Nadeau" fullname="T. Nadeau">
<organization />
</author>
<author initials="C." surname="Pignataro" fullname="C. Pignataro">
<organization />
</author>
<date year="2007" month="December" />
<abstract>
<t>This document describes Virtual Circuit Connectivity Verification (VCCV), which
provides a control channel that is associated with a pseudowire (PW), as well as
the corresponding operations and management functions (such as connectivity
verification) to be used over that control channel. VCCV applies to all supported
access circuit and transport types currently defined for PWs.</t>
</abstract>
</front>
<seriesInfo name="RFC" value="5085" />
<format type="TXT" octets="67847" target="ftp://ftp.isi.edu/in-notes/rfc5085.txt" />
</reference>
<!-- End inclusion reference.RFC.5085 -->
<!-- Begin inclusion reference.draft.MPLS-TP.FWK -->
<reference anchor="7">
<front>
<title>A Framework for MPLS in Transport Networks</title>
<author initials="M." surname="Bocci" fullname="Matthew Bocci">
<organization />
</author>
<author initials="S." surname="Bryant" fullname="Stewart Bryant">
<organization> Cisco </organization>
</author>
<author initials="L." surname="Levrau" fullname="Lieven Levrau">
<organization> Cisco </organization>
</author>
<date year="2009" month="July" />
<abstract>
<t>This document specifies an architectural framework for the application of MPLS
in transport networks. It describes a profile of MPLS that enables operational
models typical in transport networks , while providing additional OAM,
survivability and other maintenance functions not currently supported by MPLS. </t>
</abstract>
</front>
<seriesInfo name="ID" value="draft-ietf-mpls-tp-framework-02.txt" />
</reference>
<!-- End inclusion reference.draft.MPLS-TP.FWK -->
<!-- Begin inclusion reference.draft.MPLS.BFD -->
<reference anchor="8">
<front>
<title>MPLS Generic Associated Channel</title>
<author initials="M." surname="Vigoureux," fullname="Martin Vigoureux,">
<organization />
</author>
<author initials="M." surname="Bocci" fullname="Matthew Bocci">
<organization />
</author>
<author initials="G." surname="Swallow" fullname="George Swallow">
<organization />
</author>
<author initials="R." surname="Aggarwal" fullname="Rahul Aggarwal">
<organization />
</author>
<author initials="D." surname="Ward" fullname="David Ward">
<organization />
</author>
<date year="2009" month="May" />
<abstract>
<t>This document generalizes the applicability of the pseudowire (PW)
Associated Channel Header (ACH), enabling the realization of a control
channel associated to MPLS Label Switched Paths (LSPs) and MPLS Sections
in addition to MPLS pseudowires. In order to identify the presence of
this Associated Channel Header in the label stack, this document also
assigns one of the reserved MPLS label values to the Generic Associated
Channel Label (GAL), to be used as a label based exception mechanism. </t>
</abstract>
</front>
<seriesInfo name="RFC" value="5586" />
</reference>
<!-- End inclusion reference.draft.MPLS.BFD -->
<!-- Begin inclusion reference.draft.MPLS.TP.OAM.Reqs -->
<reference anchor="9">
<front>
<title>Requirements for OAM in MPLS Transport Networks</title>
<author initials="M." surname="Vigoureux" fullname="Martin Vigoureux">
<organization />
</author>
<author initials="M." surname="Betts" fullname="Malcolm Betts">
<organization />
</author>
<author initials="D." surname="Ward" fullname="Dave Ward">
<organization />
</author>
<date year="2009" month="April" />
<abstract>
<t>Lists the requirements for the OAM functionality in support of MPLS-TP.</t>
</abstract>
</front>
<seriesInfo name="ID" value="draft-ietf-mpls-tp-oam-requirements-01" />
</reference>
<!-- End inclusion reference.draft.MPLS.TP.OAM.Reqs -->
<!-- Begin inclusion reference.rfc.4427 -->
<reference anchor="10">
<front>
<title>Recovery Terminology for Generalized Multi-Protocol Label Switching</title>
<author initials="E." surname="Mannie" fullname="E. Mannie">
<organization />
</author>
<author initials="D." surname="Papadimitriou" fullname="D. Papadimitriou">
<organization />
</author>
<date year="2006" month="Mar" />
<abstract>
<t>This document defines a common terminology for Generalized Multi-Protocol
Label Switching (GMPLS)-based recovery mechanisms (i.e.,protection and
restoration). The terminology is independent of the underlying transport
technologies covered by GMPLS</t>
</abstract>
</front>
<seriesInfo name="RFC" value="4427" />
</reference>
<!-- End inclusion reference.rfc.4427 -->
<!-- Begin inclusion reference.draft.survive.fwk -->
<reference anchor="11">
<front>
<title>Multi-protocol Label Switching Transport Profile Survivability Framework</title>
<author initials="N." surname="Sprecher" fullname="Nurit Sprecher">
<organization />
</author>
<author initials="A." surname="Farrel" fullname="Adrian Farrel">
<organization />
</author>
<author initials="H." surname="Shah" fullname="Himanshu Shah">
<organization />
</author>
<date year="2009" month="Feb" />
<abstract>
<t>Network survivability is the network's ability to restore traffic following
failure or attack; it plays a critical factor in the delivery of reliable
services in transport networks. Guaranteed services in the form of Service
Level Agreements (SLAs) require a resilient network that detects facility or
node failures very rapidly, and immediately starts to restore network
operations in accordance with the terms of the SLA. The Transport Profile of
Multiprotocol Label Switching (MPLS-TP) is a packet transport technology that
combines the packet experience of MPLS with the operational experience of
transport networks like SONET/SDH. It provides survivability mechanisms such
as protection and restoration, with similar function levels to those found in
established transport networks such as in SONET/SDH networks. Some of the
MPLS-TP survivability mechanisms are data plane-driven and are based on MPLS-TP
OAM fault management functions which are used to trigger protection switching
in the absence of a control plane. Other survivability mechanisms utilize the
MPLS-TP control plane. This document provides a framework for MPLS-TP
survivability. </t>
</abstract>
</front>
<seriesInfo name="ID" value="draft-ietf-mpls-tp-survive-fwk-00.txt" />
</reference>
<!-- End inclusion reference.draft.survive.fwk -->
<!-- Begin inclusion reference.draft.RFC.4872 -->
<reference anchor="12">
<front>
<title>RSVP-TE Extensions in Support of End-to-End Generalized Multi-Protocol
Label Switching (GMPLS) Recovery</title>
<author initials="J.P." surname="Lang" fullname="J.P. Lang">
<organization />
</author>
<author initials="D." surname="Papadimitriou" fullname="D. Papadimitriou">
<organization />
</author>
<author initials="Y." surname="Rekhter" fullname="Yakov Rekhter">
<organization />
</author>
<date year="2007" month="May" />
<abstract>
<t></t>
</abstract>
</front>
<seriesInfo name="RFC" value="4872" />
</reference>
<!-- End inclusion reference.RFC.4872 -->
<!-- Begin inclusion reference.RFC.3945 -->
<reference anchor="13">
<front>
<title>Generalized Multi-Protocol Label Switching (GMPLS) Architecture</title>
<author initials="E." surname="Mannie" fullname="E. Mannie">
<organization />
</author>
<date year="2004" month="Oct" />
<abstract>
<t></t>
</abstract>
</front>
<seriesInfo name="RFC" value="3945" />
</reference>
<!-- End inclusion reference.RFC.3945 -->
</references>
</back>
</rfc>| PAFTECH AB 2003-2026 | 2026-04-24 02:55:16 |