TEAS Working Group J. He
Internet-Draft I. Busi
Intended status: Standards Track Huawei Technologies
Expires: January 6, 2020 J. Ryoo
B. Yoon
ETRI
P. Park
KT
July 5, 2019
GMPLS Signaling Extensions for Shared Mesh Protection
draft-ietf-teas-gmpls-signaling-smp-01
Abstract
ITU-T Recommendation G.808.3 [G808.3] defines the generic aspects of
a Shared Mesh Protection (SMP) mechanism, where the difference
between SMP and Shared Mesh Restoration (SMR) is also identified.
ITU-T Recommendation G.873.3 [G873.3] defines the protection
switching operation and associated protocol for SMP at the Optical
Data Unit (ODU) layer. RFC 7412 [RFC7412] provides requirements for
any mechanism that would be used to implement SMP in a Multi-Protocol
Label Switching - Transport Profile (MPLS-TP) network.
This document updates RFC 4872 [RFC4872] to provide the extensions to
the Generalized Multi-Protocol Label Switching (GMPLS) signaling to
support the control of the shared mesh protection.
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 https://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 January 6, 2020.
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Copyright Notice
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document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions Used in This Document . . . . . . . . . . . . . . 3
3. SMP Definition . . . . . . . . . . . . . . . . . . . . . . . 3
4. GMPLS Signaling Extension for SMP . . . . . . . . . . . . . . 4
4.1. Identifiers . . . . . . . . . . . . . . . . . . . . . . . 5
4.2. Signaling Primary LSPs . . . . . . . . . . . . . . . . . 6
4.3. Signaling Secondary LSPs . . . . . . . . . . . . . . . . 6
4.4. SMP APS Configuration . . . . . . . . . . . . . . . . . . 8
5. Updates to PROTECTION Object . . . . . . . . . . . . . . . . 8
5.1. New Protection Type . . . . . . . . . . . . . . . . . . . 8
5.2. Other Updates . . . . . . . . . . . . . . . . . . . . . . 8
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
7. Security Considerations . . . . . . . . . . . . . . . . . . . 9
8. Contributor . . . . . . . . . . . . . . . . . . . . . . . . . 9
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
9.1. Normative References . . . . . . . . . . . . . . . . . . 9
9.2. Informative References . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction
RFC 4872 [RFC4872] defines extension of Resource Reservation Protocol
- Traffic Engineering (RSVP-TE) to support Shared Mesh Restoration
(SMR) mechanism. SMR can be seen as a particular case of pre-planned
Label Switched Path (LSP) rerouting that reduces the recovery
resource requirements by allowing multiple protecting LSPs to share
common link and node resources. The recovery resources for the
protecting LSPs are pre-reserved during the provisioning phase, and
an explicit restoration signaling is required to activate (i.e.,
commit resource allocation at the data plane) a specific protecting
LSP instantiated during the provisioning phase.
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ITU-T Recommendation G.808.3 [G808.3] defines the generic aspects of
a shared mesh protection (SMP) mechanism. ITU-T Recommendation
G.873.3 [G873.3] defines the protection switching operation and
associated protocol for SMP at the Optical Data Unit (ODU) layer.
RFC 7412 [RFC7412] provides requirements for any mechanism that would
be used to implement SMP in a Multi-Protocol Label Switching -
Transport Profile (MPLS-TP) network.
SMP differs from SMR in the activation/protection switching
operation. The former activates a protecting LSP via the automatic
protection switching (APS) protocol in the data plane when the
working LSP fails, while the latter does it via the control plane
signaling. It is therefore necessary to distinguish SMP from SMR
during provisioning so that each node involved behaves appropriately
in the recovery phase when activation of a protecting LSP is done.
This document updates [RFC4872] to provide the extensions to the
Generalized Multi-Protocol Label Switching (GMPLS) signaling to
support the control of the SMP mechanism. Only the generic aspects
for signaling SMP are addressed by this document. The technology-
specific aspects are expected to be addressed by other drafts.
2. Conventions Used in This Document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
In addition, the reader is assumed to be familiar with the
terminology used in [RFC4872] and RFC 4426 [RFC4426].
3. SMP Definition
[G808.3] defines the generic aspects of a SMP mechanism. [G873.3]
defines the protection switching operation and associated protocol
for SMP at the ODU layer. [RFC7412] provides requirements for any
mechanism that would be used to implement SMP in a MPLS-TP network.
The SMP mechanism is based on pre-computed protection transport
entities that are pre-configured into the network elements. Pre-
configuration here means pre-reserving resources for the protecting
LSPs without activating a particular protecting LSP (e.g. in circuit
networks, the cross-connects in the intermediate nodes of the
protecting LSP are not pre-established). Pre-configuring but not
activating the protecting LSP allows the common link and node
resources in a protecting LSP to be shared by multiple working LSPs
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that are physically (i.e., link, node, Shared Risk Link Group (SRLG),
etc.) disjoint. Protecting LSPs are activated in response to
failures of working LSPs or operator's commands by means of the APS
protocol that operates in the data plane. The APS protocol messages
are exchanged along the protecting LSP. SMP is always revertive.
SMP has a lot of similarity to SMR except that the activation in case
of SMR is achieved by control plan signaling during the recovery
operation while SMP is done by APS protocol in the data plane. SMP
has advantages with regard to the recovery speed compared with SMR.
4. GMPLS Signaling Extension for SMP
Consider the following network topology:
A---B---C---D
\ /
E---F---G
/ \
H---I---J---K
Figure 1: An example of SMP topology
The working LSPs [A,B,C,D] and [H,I,J,K] could be protected by
[A,E,F,G,D] and [H,E,F,G,K], respectively. Per RFC 3209 [RFC3209],
in order to achieve resource sharing during the signaling of these
protecting LSPs, they must have the same Tunnel Endpoint Address (as
part of their SESSION object). However, these addresses are not the
same in this example. Similar to SMR, a new LSP Protection Type of
the secondary LSP is defined as "Shared Mesh Protection" (see
PROTECTION object defined in [RFC4872]) to allow resource sharing
along nodes E, F, and G. In this case, the protecting LSPs are not
merged (which is useful since the paths diverge at G), but the
resources along E, F, G can be shared.
When a failure, such as Signal Fail (SF) and Signal Degrade (SD),
occurs on one of the working LSPs (say working LSP [A,B,C,D]), the
end-node (say node A) that detects the failure initiates the
protection switching operation. The end-node A will send a
protection switching request APS message (for example SF) to its
adjacent (downstream) intermediate node (say node E) to activate
setting up the corresponding protecting LSP and will wait for a
confirmation message from node E. If the protection resource is
available, node E will send the confirmation APS message to the end-
node A and forward the switching request APS message to its adjacent
(downstream) node (say node F). When the confirmation APS message is
received by node A, the cross-connection on node A is established.
At this time the traffic is bridged to and selected from the
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protecting LSP at node A. After forwarding the switching request APS
message, node E will wait for a confirmation APS message from node F,
which triggers node E to set up the cross-connection for the
protecting LSP being activated. If the protection resource is not
available (due to failure or being used by higher priority
connections), the switching will not be successful; the intermediate
node may send a message to notify the end node, or may keep trying
until the resource is available or the switching request is
cancelled. If the resource is in use by a lower priority protecting
LSP, the lower priority service will be removed and then the
intermediate node will follow the procedure as described for the case
when the protection resource is available for the higher priority
protecting LSP.
The following subsections detail how LSPs using SMP can be signaled
in an interoperable fashion using GMPLS RSVP-TE extensions (see RFC
3473 [RFC3473]). This includes;
(1) the ability to identify a "secondary protecting LSP" (hereby
called the "secondary LSP") used to recover another primary
working LSP (hereby called the "protected LSP"),
(2) the ability to associate the secondary LSP with the protected
LSP,
(3) the capability to include information about the resources used
by the protected LSP while instantiating the secondary LSP,
(4) the capability to instantiate during the provisioning phase
several secondary LSPs in an efficient manner, and
(5) the capability to support activation of a secondary LSP after
failure occurrence via APS protocol in the data plane.
4.1. Identifiers
To simplify association operations, both LSPs (i.e., the protected
and the secondary LSPs) belong to the same session. Thus, the
SESSION object MUST be the same for both LSPs. The LSP ID, however,
MUST be different to distinguish between the protected LSP carrying
working traffic and the secondary LSP.
A new LSP Protection Type "Shared Mesh Protection" is introduced to
the LSP Flags of PROTECTION object (see [RFC4872]) to set up the two
LSPs. This LSP Protection Type value is applicable only to
bidirectional LSPs as required in [G808.3].
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4.2. Signaling Primary LSPs
The PROTECTION object (see [RFC4872]) is included in the Path message
during signaling of the primary working LSPs, with the LSP Protection
Type value set to "Shared Mesh Protection".
Primary working LSPs are signaled by setting in the POTECTION object
the S bit to 0, the P bit to 0, the N bit to 1 and in the ASSOCIATION
object, the Association ID to the associated secondary protecting
LSP_ID.
Note: N bit is set to indicate that the protection switching
signaling is done via data plane.
4.3. Signaling Secondary LSPs
The PROTECTION object (see [RFC4872]) is included in the Path message
during signaling of the secondary protecting LSPs, with the LSP
Protection Type value set to "Shared Mesh Protection".
Secondary protecting LSPs are signaled by setting in the PROTECTION
object the S bit and the P bit to 1, the N bit to 1 and in the
ASSOCIATION object, the Association ID to the associated primary
working LSP_ID, which MUST be known before signaling of the secondary
LSP. Moreover, the Path message used to instantiate the secondary
LSP SHOULD include at least one PRIMARY_PATH_ROUTE object (see
[RFC4872]) that further allows for recovery resource sharing at each
intermediate node along the secondary path.
With this setting, the resources for the secondary LSP SHOULD be pre-
reserved, but not committed at the data plane level, meaning that the
internals of the switch need not be established until explicit action
is taken to activate this LSP. Activation of a secondary LSP and
protection switching to the activated protecting LSP is done using
APS protocol in the data plane.
After protection switching completes the protecting LSP SHOULD be
signaled with the S bit set to 0 and O bit set to 1 in the PROTECTION
object. At this point, the link and node resources must be allocated
for this LSP that becomes a primary LSP (ready to carry normal
traffic). The formerly working LSP MAY be signaled with the A bit
set in the ADMIN_STATUS object (see [RFC3473]).
Support for extra traffic in SMP is for further study. Therefore,
mechanisms to setup LSPs for extra traffic are also for further
study.
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The preemption priority of a protecting LSP that is used to resolve
the competition for the same shared resource among multiple
protecting LSPs, is indicated in the TBD1 field of the TBD2 object in
the Path message of the protecting LSP. In SMP, the Setup and
Holding priorities in the SESSION_ATTRIBUTE object can be used to
configure or pre-configure a LSP, but is irrelevant to resolving the
competition among multiple protecting LSPs, which experience failures
on their working LSPs.
When an intermediate node on the protection LSP receives the Path
message, the preemption priority value in the TBD1 field MUST be
stored for that protection LSP. When resource competition among
multiple protecting LSPs occurs, their priority values will be used
to resolve the competition. Once the preemption priorities are
configured, the preemption of the protecting LSPs is fully controlled
by the APS.
When an APS request for a lower priority protecting LSP is preempted
or cannot be confirmed due to existing higher priority APS request
for another protection LSPs, an intermediate node MAY send PathErr
and ResvErr with the error code/sub-code "Policy Control Failure/Hard
Pre-empted" toward the source nodes of Path and Resv, respectively,
to notify that the lower priority protecting LSP is preempted.
Upon receiving a PathErr or ResvErr message with the error code/sub-
code "Policy Control Failure/Hard Pre-empted," the end node that has
initiated the protection switching for a protecting LSP may cancel it
(and try with another protecting LPS) or may keep trying until the
resource is available.
In SMP, a preempted LSP SHOULD not be torn down. Once the working
LSP and the protecting LSP are configured or pre-configured, the end
node SHOULD keep refreshing both working and protecting LSPs
regardless of failure or preempted situation.
[Editor's note: See if it is ok to add the next sentence at the end
of the previous paragraph.] The Path_State_Removed flag in the
ERROR_SPEC object MUST not be set in PathErr and ResvErr messages
generated due to preemption.
[Editor's note: Check what should be the behavior to notify the end
nodes of the lower priority protecting LSP that is no longer
preempted and therefore it is available for SMP protection switching,
if needed.]
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4.4. SMP APS Configuration
SMP relies on APS protocol messages being exchanged between the nodes
along the path to activate a SMP protecting LSP.
In order to allow exchange of APS protocol messages, an APS channel
has to be configured between adjacent nodes along the path of the SMP
protecting LSP. This should be done before any SMP protecting LSP
has been setup by other means than GMPL signaling which are therefore
outside the scope of this document.
Depending on the APS protocol message format, the APS protocol may
use different identifiers than GMPLS signaling to identify the SMP
protecting LSP.
Since APS protocol is for further study in [G808.3], it can be
assumed that APS message format and identifiers are technology-
specific and/or vendor-specific. Therefore, additional requirements
for APS configuration are outside the scope of this document.
5. Updates to PROTECTION Object
GMPLS extension requirements for SMP introduce several updates to the
Protection Object (see [RFC4872]).
5.1. New Protection Type
A new LSP protection type "Shared Mesh Protection" is added in the
protection object. This LSP Protection Type value is applicable to
only bidirectional LSPs.
LSP (Protection Type) Flags:
0x11: Shared Mesh Protection
5.2. Other Updates
N bit and O bit in the Protection object as defined in [RFC4872] are
also updated to include applicability to SMP.
Notification (N): 1 bit
When set to 1, this bit indicates that the control plane message
exchange is only used for notification during protection
switching. When set to 0 (default), it indicates that the control
plane message exchanges are used for protection-switching
purposes. The N bit is only applicable when the LSP Protection
Type Flag is set to either 0x04 (1:N Protection with Extra-
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Traffic), or 0x08 (1+1 Unidirectional Protection), or 0x10 (1+1
Bidirectional Protection). In SMP, N bit MUST be set to 1. The N
bit MUST be set to 0 in any other case.
Operational (O): 1 bit
When set to 1, this bit indicates that the protecting LSP is
carrying the normal traffic after protection switching. The O bit
is only applicable when the P bit is set to 1, and the LSP
Protection Type Flag is set to either 0x04 (1:N Protection with
Extra-Traffic), or 0x08 (1+1 Unidirectional Protection), or 0x10
(1+1 Bidirectional Protection), or 0x11 (Shared Mesh Protection).
The O bit MUST be set to 0 in any other case.
6. IANA Considerations
IANA actions required by this document will be described later.
7. Security Considerations
No further security considerations than [RFC4872].
8. Contributor
The following person contributed significantly to the content of this
document and should be considered as a co-author.
Yuji Tochio
Fujitsu
Email: tochio@fujitsu.com
9. References
9.1. Normative References
[G808.3] International Telecommunication Union, "Generic protection
switching - Shared mesh protection", ITU-T Recommendation
G.08.3, October 2012.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001,
<https://www.rfc-editor.org/info/rfc3209>.
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[RFC3473] Berger, L., Ed., "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Resource ReserVation Protocol-
Traffic Engineering (RSVP-TE) Extensions", RFC 3473,
DOI 10.17487/RFC3473, January 2003,
<https://www.rfc-editor.org/info/rfc3473>.
[RFC4426] Lang, J., Ed., Rajagopalan, B., Ed., and D. Papadimitriou,
Ed., "Generalized Multi-Protocol Label Switching (GMPLS)
Recovery Functional Specification", RFC 4426,
DOI 10.17487/RFC4426, March 2006,
<https://www.rfc-editor.org/info/rfc4426>.
[RFC4872] Lang, J., Ed., Rekhter, Y., Ed., and D. Papadimitriou,
Ed., "RSVP-TE Extensions in Support of End-to-End
Generalized Multi-Protocol Label Switching (GMPLS)
Recovery", RFC 4872, DOI 10.17487/RFC4872, May 2007,
<https://www.rfc-editor.org/info/rfc4872>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
9.2. Informative References
[G873.3] International Telecommunication Union, "Optical transport
network - Shared mesh protection", ITU-T Recommendation
G.873.3, September 2017.
[RFC7412] Weingarten, Y., Aldrin, S., Pan, P., Ryoo, J., and G.
Mirsky, "Requirements for MPLS Transport Profile (MPLS-TP)
Shared Mesh Protection", RFC 7412, DOI 10.17487/RFC7412,
December 2014, <https://www.rfc-editor.org/info/rfc7412>.
Authors' Addresses
Jia He
Huawei Technologies
F3-1B, R&D Center, Huawei Industrial Base, Bantian, Longgang District
Shenzhen
China
Email: hejia@huawei.com
Italo Busi
Huawei Technologies
Email: italo.busi@huawei.com
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Jeong-dong Ryoo
ETRI
218 Gajeongno
Yuseong-gu, Daejeon 34129
South Korea
Phone: +82-42-860-5384
Email: ryoo@etri.re.kr
Bin Yeong Yoon
ETRI
Email: byyun@etri.re.kr
Peter Park
KT
Email: peter.park@kt.com
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