Network Working Group F. Zhang, Ed.
Internet-Draft D. Li
Intended status: Standards Track Huawei
Expires: December 28, 2012 O. Gonzalez de Dios, Ed.
Telefonica I+D
C. Margaria
Nokia Siemens Networks
June 26, 2012
RSVP-TE Extensions for Collecting SRLG Information
draft-ietf-ccamp-rsvp-te-srlg-collect-00
Abstract
This document provides extensions for the Resource ReserVation
Protocol-Traffic Engineering (RSVP-TE) to support automatic
collection of Shared Risk Link Group (SRLG) Information for the TE
link formed by a LSP.
Status of this Memo
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include Simplified BSD License text as described in Section 4.e of
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. RSVP-TE Requirements . . . . . . . . . . . . . . . . . . . . . 3
2.1. SRLG Collection Indication . . . . . . . . . . . . . . . . 3
2.2. SRLG Collection . . . . . . . . . . . . . . . . . . . . . . 3
2.3. SRLG Update . . . . . . . . . . . . . . . . . . . . . . . . 3
3. RSVP-TE Extensions (Encoding) . . . . . . . . . . . . . . . . . 3
3.1. SRLG Collection Flag . . . . . . . . . . . . . . . . . . . 3
3.2. SRLG sub-object . . . . . . . . . . . . . . . . . . . . . . 4
4. Signaling Procedures . . . . . . . . . . . . . . . . . . . . . 5
4.1. SRLG Collection . . . . . . . . . . . . . . . . . . . . . . 5
4.2. SRLG Update . . . . . . . . . . . . . . . . . . . . . . . . 6
5. Manageability Considerations . . . . . . . . . . . . . . . . . 6
5.1. Policy Configuration . . . . . . . . . . . . . . . . . . . 6
5.2. Coherent SRLG IDs . . . . . . . . . . . . . . . . . . . . . 6
6. Security Considerations . . . . . . . . . . . . . . . . . . . . 6
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7
7.1. RSVP Attribute Bit Flags . . . . . . . . . . . . . . . . . 7
7.2. ROUTE_RECORD Object . . . . . . . . . . . . . . . . . . . . 7
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 7
9. Normative References . . . . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 8
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1. Introduction
It is important to understand which TE links in the network might be
at risk from the same failures. In this sense, a set of links may
constitute a 'shared risk link group' (SRLG) if they share a resource
whose failure may affect all links in the set [RFC4202].
On the other hand, as described in [RFC4206] and [RFC6107], H-LSP
(Hierarchical LSP) or S-LSP (stitched LSP) can be used for carrying
one or more other LSPs. Both of the H-LSP and S-LSP can be formed as
a TE link. In such cases, it is important to know the SRLG
information of the LSPs that will be used to carry further LSPs.
This document provides an automatic mechanism to collect the SRLG for
the TE link formed by a LSP. Note that how to use the collected SRLG
information is out of scope of this document
2. RSVP-TE Requirements
2.1. SRLG Collection Indication
The head nodes of the LSP must be capable of indicating whether the
SRLG information of the LSP should be collected during the signaling
procedure of setting up an LSP.
2.2. SRLG Collection
The SRLG information can be collected during the setup of an LSP.
Then the endpoints of the LSP can get the SRLG information and use it
for routing, sharing and TE link configuration purposes.
2.3. SRLG Update
When the SRLG information changes, the endpoints of the LSP need to
be capable of updating the SRLG information of the path. It means
that the signaling should be capable of updating the newly SRLG
information to the endpoints.
3. RSVP-TE Extensions (Encoding)
3.1. SRLG Collection Flag
In order to indicate nodes that SRLG collection is desired, this
document defines a new flag in the Attribute Flags TLV, which is
carried in an LSP_REQUIRED_ATTRIBUTES Object:
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o Bit Number (to be assigned by IANA, recommended bit zero): SRLG
Collection flag
The SRLG Collection flag is meaningful on a Path message. If the
SRLG Collection flag is set to 1, it means that the SRLG information
should be reported to the head and tail node along the setup of the
LSP.
The rules of the processing of the Attribute Flags TLV are not
changed.
3.2. SRLG sub-object
This document defines a new RRO sub-object (ROUTE_RECORD sub-object)
to record the SRLG information of the LSP. Its format is modeled on
the RRO sub-objects defined in RFC 3209 [RFC3209].
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SRLG ID 1 (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ...... ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SRLG ID n (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type
The type of the sub-object, to be assigned by IANA, which is
recommended 34.
Length
The Length contains the total length of the sub-object in bytes,
including the Type and Length fields. The Length depends on the
number of SRLG IDs.
SRLG Id
The 32-bit identifier of the SRLG.
Reserved
This field is reserved. It SHOULD be set to zero on transmission and
MUST be ignored on receipt.
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The rules of the processing of the LSP_REQUIRED_ATTRIBUTES Object and
ROUTE_RECORD Object are not changed.
4. Signaling Procedures
4.1. SRLG Collection
Typically, the head node gets the route information of an LSP by
adding a RRO which contains the sender's IP addresses in the Path
message. If a head node also desires SRLG recording, it sets the
SRLG Collection Flag in the Attribute Flags TLV which can be carried
in an LSP_REQUIRED_ATTRIBUTES Object.
When a node receives a Path message which carries an
LSP_REQUIRED_ATTRIBUTES Object and the SRLG Collection Flag is set,
if local policy determines that the SRLG information should not be
provided to the endpoints, it must return a PathErr message to reject
the Path message. Otherwise, it must add an SRLG sub-object to the
RRO to carry the local SRLG information. Then it forwards the Path
message to the next node in the downstream direction.
Following the steps described above, the intermediate nodes of the
LSP can collect the SRLG information in the RRO during the forwarding
of the Path message hop by hop. When the Path message arrives at the
tail node, the tail node can get the SRLG information from the RRO.
Before the Resv message is sent to the upstream node, the tail node
adds an SRLG sub-object to the RRO. The collected SRLG information
can be carried in the SRLG sub-object. Therefore, during the
forwarding of the Resv message in the upstream direction, the SRLG
information is not needed to be collected hop by hop.
Based on the above procedure, the endpoints can get the SRLG
information automatically. Then the endpoints can for instance
advertise it as a TE link to the routing instance based on the
procedure described in [RFC6107] and configure the SRLG information
of the FA automatically.
It is noted that a node (e.g. the edge node of a domain) may edit the
RRO to remove the route information (e.g. node, interface identifier
information) before forwarding it due to some reasons (e.g.
confidentiality or reduce the size of RRO), but the SRLG information
should be retained if it is desirable for the endpoints of the LSP.
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4.2. SRLG Update
When the SRLG information of a link is changed, the LSPs using that
link should be aware of the changes. The procedures defined in
Section 4.4.3 of RFC 3209 [RFC3209] MUST be used to refresh the SRLG
information.
5. Manageability Considerations
5.1. Policy Configuration
In a border node of inter-domain or inter-layer network, the
following SRLG processing policy should be capable of being
configured:
o Whether the SRLG IDs of the domain or specific layer network can
be exposed to the nodes outside the domain or layer network.
o If the SRLG IDs must not be exposed to the nodes outside of the
domain or specific layer network by policy, the border node must
reject the Path message desiring SRLG recording and send a PathErr
message with the defined error code 'Policy Control
Failure'/'Inter-domain policy failure'.
5.2. Coherent SRLG IDs
In a multi-layer multi-domain scenario, SRLG ids may be configured by
different management entities in each layer/domain. In such
scenarios, maintaining a coherent set of SRLG IDs is a key
requirement in order to be able to use the SRLG information properly.
Thus, SRLG IDs must be unique. Note that current procedure is
targeted towards a scenario where the different layers and domains
belong to the same operator, or to several coordinated administrative
groups.
Further scenarios, where coherence in the SRLG IDs cannot be
guaranteed are out of the scope of the present document and are left
for further study.
6. Security Considerations
TBD.
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7. IANA Considerations
7.1. RSVP Attribute Bit Flags
The IANA has created a registry and manages the space of attributes
bit flags of Attribute Flags TLV as described in section 11.3 of
[RFC5420]. It is requested that the IANA makes assignments from the
Attribute Bit Flags.
This document introduces a new Attribute Bit Flag:
o Bit number: TBD (0)
o Defining RFC: this I-D
o Name of bit: SRLG Collection Flag
o The meaning of the Attribute Flags TLV on a Path is defined in
this I-D
7.2. ROUTE_RECORD Object
IANA has made the following assignments in the "Class Names, Class
Numbers, and Class Types" section of the "RSVP PARAMETERS" registry
located at http://www.iana.org/assignments/rsvp-parameters. We
request that IANA make assignments from the ROUTE_RECORD RFC 3209
[RFC3209] portions of this registry.
This document introduces a new RRO sub-object:
Type Name Reference
--------- ---------------------- ---------
TBD (34) SRLG sub-object This I-D
8. Acknowledgements
The authors would like to thank Igor Bryskin, Ramon Casellas and Lou
Berger for their useful comments to the document.
9. Normative References
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
Tunnels", RFC 3209, December 2001.
[RFC4202] Kompella, K. and Y. Rekhter, "Routing Extensions in
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Support of Generalized Multi-Protocol Label Switching
(GMPLS)", RFC 4202, October 2005.
[RFC4206] Kompella, K. and Y. Rekhter, "Label Switched Paths (LSP)
Hierarchy with Generalized Multi-Protocol Label Switching
(GMPLS) Traffic Engineering (TE)", RFC 4206, October 2005.
[RFC5150] Ayyangar, A., Kompella, K., Vasseur, JP., and A. Farrel,
"Label Switched Path Stitching with Generalized
Multiprotocol Label Switching Traffic Engineering (GMPLS
TE)", RFC 5150, February 2008.
[RFC6107] Shiomoto, K. and A. Farrel, "Procedures for Dynamically
Signaled Hierarchical Label Switched Paths", RFC 6107,
February 2011.
Authors' Addresses
Fatai Zhang (editor)
Huawei
F3-5-B RD Center
Bantian, Longgang District, Shenzhen 518129
P.R.China
Phone:
Email: zhangfatai@huawei.com
Dan Li
Huawei
F3-5-B RD Center
Bantian, Longgang District, Shenzhen 518129
P.R.China
Phone:
Email: danli@huawei.com
Oscar Gonzalez de Dios (editor)
Telefonica I+D
Don Ramon de la Cruz
Madrid, 28006
Spain
Phone: +34 913328832
Email: ogondio@tid.es
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Cyril Margaria
Nokia Siemens Networks
St Martin Strasse 76
Munich, 81541
Germany
Phone: +49 89 5159 16934
Email: cyril.margaria@nsn.com
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