One document matched: draft-zhang-ccamp-srlg-fa-configuration-03.txt
Differences from draft-zhang-ccamp-srlg-fa-configuration-02.txt
Network Working Group Fatai Zhang
Internet-Draft Dan Li
Intended status: Standards Track Huawei
O. Gonzalez de Dios
Telefonica Investigacion y Desarrollo
C. Margaria. C
Nokia Siemens Networks
Expires: January 8, 2012 July 8, 2011
RSVP-TE Extensions for Configuration SRLG of an FA
draft-zhang-ccamp-srlg-fa-configuration-03.txt
Status of this Memo
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This Internet-Draft will expire on January 8, 2012.
Abstract
This memo provides extensions for the Resource ReserVation Protocol-
Traffic Engineering (RSVP-TE) for the support of the automatic
discovery of SRLG of an LSP.
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Conventions used in this document
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].
Table of Contents
1. Introduction ................................................ 2
2. RSVP-TE Requirements......................................... 4
2.1. SRLG Collection Indication.............................. 4
2.2. SRLG Collection......................................... 4
2.3. SRLG Update ............................................ 4
3. RSVP-TE Extensions .......................................... 4
3.1. SRLG Collection Flag.................................... 4
3.2. SRLG sub-object......................................... 5
4. Signaling Procedures......................................... 6
4.1. SRLG Collection......................................... 6
4.2. SRLG Update ............................................ 6
5. Manageability Considerations................................. 7
5.1. Policy Configuration.................................... 7
5.2. Coherent SRLG IDs....................................... 8
6. IANA Considerations ......................................... 8
6.1. RSVP Attribute Bit Flags................................ 8
6.2. ROUTE_RECORD Object..................................... 8
7. Security Considerations...................................... 9
8. References .................................................. 9
9. Authors' Addresses ......................................... 11
1. Introduction
As described in [RFC4206], H-LSP (Hierarchical LSP) can be used for
carrying one or more other LSPs. [RFC6107] further mentions the
implementation of H-LSP. In packet networks, e.g. MPLS networks, H-
LSP mechanism can be implemented by MPLS label stack. In non-packet
networks where the label is implicit, label stacks are not possible,
and H-LSPs rely on the ability to nest switching technologies. Thus,
for example, a lambda switch capable (LSC) LSP can carry a time
division multiplexing (TDM) LSP, but cannot carry another LSC LSP.
S-LSP (LSP Stitching), which is defined in [RFC5150], is an LSP that
represents a segment of another LSP, i.e., the S-LSP is viewed as
one hop by another LSP. As described in [RFC6107], in the data plane
the LSPs are stitched so that there is no label stacking or nesting.
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Thus, an S-LSP must be of the same switching technology as the end-
to-end LSP that it facilitates.
Therefore, H-LSP mechanism can be used in both multi-domain and
multi-layer scenarios and S-LSP mechanism can only be used in multi-
domain scenario.
Both of the H-LSP and S-LSP can be advertised as a TE link in a
GMPLS routing instance for path computation purpose. As described in
[RFC6107], if the LSP (H-LSP or S-LSP) is advertised in the same
instance of the control plane that advertises the TE links from
which the LSP is constructed, the LSP is called an FA.
In multi-domain or multi-layer context, the path information of an
LSP may not be provided to the ingress node for confidential reasons
and the ingress node may not run the same routing instance with the
intermediate nodes traversed by the path. In such scenarios, the
ingress node can not get the SRLG information of the path
information which the LSP traverse.
Even if the ingress node has the same routing instance with the
intermediate nodes traversed by the path, the path information of
the H-LSP or S-LSP may not be provided to the ingress node. Hence
the ingress node may also not know the SRLG of the path the LSP
traverses.
In the case that the ingress node does not get the SRLG of the path
the LSP traverses(i.e. H-LSP or S-LSP), there are disadvantages as
follows:
o SRLG-disjoint path, for instance in case of end-to-end path
protection, cannot be calculated
o Intermediate nodes of a pre-planned shared restoration LSP cannot
correctly decide on the SRLG-disjointness between two PPRO
(PRIMARY_PATH_ROUTE Object)
o In case that an LSP is advertised as a TE-Link, the ingress node
cannot provide the correct SRLG for the TE-Link automatically
In case that an LSP is advertised as a TE-Link, the SRLG information
of the TE link needs to be configured manually or automatically.
However, for manual configuration, there are some disadvantages
(e.g., require configuration coordination and additional management;
manual errors may be introduced) mentioned in Section 1.3.4 of
[RFC6107].
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In addition, Section 1.2 of [RFC6107] describes it is desirable to
have a kind of automatic mechanism to advertise the FA (i.e., to
signal an LSP and automatically coordinate its use and
advertisement in any of the ways with minimum involvement from an
operator).
Thus, in order to provide the SRLG information to the TE link
automatically when an LSP (H-LSP or S-LSP) is advertised as a TE
link, allow disjoint path calculation at ingress and allow correct
pre-planned shared LSP to correctly share resource, this document
provides an automatic mechanism to collect the SRLG used by a LSP
automatically.
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 needs to be capable of updating the newly SRLG
information to the endpoints.
3. RSVP-TE Extensions
3.1. SRLG Collection Flag
In order to indicate nodes that SRLG collection is desired, a new
flag in the Attribute Flags TLV which can be carried in an
LSP_REQUIRED_ATTRIBUTES Object is needed:
SRLG Collection flag (to be assigned by IANA, recommended bit
zero)
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
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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
A new SRLG sub-object is defined for RRO(ROUTE_RECORD Object) to
record the SRLG information of the LSP. Its format is modeled on the
RRO sub-objects defined in [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.
The rules of the processing of the LSP_REQUIRED_ATTRIBUTES Object
and ROUTE_RECORD Object are not changed.
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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.
4.2. SRLG Update
When the SRLG information of a link is changed, the LSPs (RSVP
sessions) using that link should be aware of the changes. Note that,
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as stated in RFC 3209, the RRO collects up-to-date detailed path
information hop-by- hop about RSVP sessions, providing valuable
information to the sender or receiver. Thus, in a similar way, the
RRO should also collect the up-to-date SRLG information. The
procedure for the update is described below.
When the SRLG of a link is changed, the endpoints of the link need
to check the information of all the LSPs that traverse the link in
order to find out the LSPs which have requested theSRLG recording.
The new SRLG information needs to be updated if the SRLG Collection
flag is set on a Path message.
When an endpoint of the link finds out an LSP has requested SRLG
recording, it should send a NOTIFY message to the head node of the
LSP informing that SRLG information needs to be recollected.
Then, the head node must send a path message with the SRLG recording
bit set that should be process by the intermediate nodes. As
described in [RFC2961 ] section 4.5, changes the message_id of the
path message would force the intermediate nodes to fully process the
message. Then, the intermediate nodes will all update the SRLG
information in the SRLG sub-object. Then the tail node receives the
new Path message, fully processes the message and gets the new SRLG
information of the LSP from it.
After the tail node of the LSP gets the new SRLG information, it
should update the SRLG information in the corresponding Resv message
which will be sent to the upstream node as a trigger message. The
new Resv message should be fully processed and forwarded in the
upstream direction until it arrives at the head node. Then the head
node receives the new Resv message, fully processes the message and
gets the new SRLG information of the LSP from it.
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.
If the SRLG IDs should not be exposed to the nodes outside of the
domain or specific layer network by policy, the border node should
reject the Path message desiring SRLG recording and send a PathErr
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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. IANA Considerations
6.1. 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:
- Bit number: TBD (0)
- Defining RFC: this I-D
- Name of bit: SRLG Collection Flag
- The meaning of the Attribute Flags TLV on a Path is defined in
this I-D
6.2. 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 [RFC3209]
portions of this registry.
This document introduces a new RRO sub-object:
Type Name Reference
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--------- ---------------------- ---------
TBD (34) SRLG sub-object This I-D
7. Security Considerations
TBD.
8. Acknowledgements
The authors would like to thank Igor Bryskin and Ramon Casellas for
their useful comments to the document.
9. References
[RFC2119] S. Bradner, "Key words for use in RFCs to indicate
requirements levels", RFC 2119, March 1997.
[RFC2961] L. Berger, D. Gan, G. Swallow, P. Pan, F. Tommasi and S.
Molendini, "RSVP Refresh Overhead Reduction Extensions",
RFC 2961, April 2001.
[RFC3477] K. Kompella, Y. Rekhter, "Signalling Unnumbered Links in
Resource ReSerVation Protocol - Traffic Engineering (RSVP-
TE)", rfc3477, January 2003.
[RFC4206] K. Kompella, Y. Rekhter, "Label Switched Paths (LSP)
Hierarchy with Generalized Multi-Protocol Label Switching
(GMPLS) Traffic Engineering (TE)", RFC 4206, October 2005.
[RFC4208] G. Swallow, J. Drake, Boeing, H. Ishimatsu, and Y. Rekhter,
"Generalized Multiprotocol Label Switching (GMPLS) User-
Network Interface (UNI): Resource ReserVation Protocol-
Traffic Engineering (RSVP-TE) Support for the Overlay
Model", RFC 4208, October 2005.
[RFC4874] CY. Lee, A. Farrel, S. De Cnodder, " Exclude Routes -
Extension to Resource ReserVation Protocol-Traffic
Engineering (RSVP-TE) ", RFC 4874, April 2007.
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[RFC5150] Ayyangar, A., Vasseur, J.P, and Farrel, A., "Label
Switched Path Stitching with Generalized Multiprotocol
Label Switching Traffic Engineering (GMPLS TE)", RFC 5150,
February 2008.
[RFC5420] A. Farrel, D. Papadimitriou, J.P, and A. Ayyangar,
"Encoding of Attributes for MPLS LSP Establishment Using
Resource Reservation Protocol Traffic Engineering (RSVP-
TE)", RFC 5420, February 2009.
[RFC6107] K. Shiomoto, A. Farrel, " Procedures for Dynamically
Signaled Hierarchical Label Switched Paths ", RFC 6107,
February 2011.
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10. Authors' Addresses
Fatai Zhang
Huawei Technologies
F3-5-B R&D Center, Huawei Base
Bantian, Longgang District
Shenzhen 518129 P.R.China
Phone: +86-755-28972912
Email: zhangfatai@huawei.com
Dan Li
Huawei Technologies
F3-5-B R&D Center, Huawei Base
Bantian, Longgang District
Shenzhen 518129 P.R.China
Phone: +86-755-28970230
Email: danli@huawei.com
Oscar Gonzalez de Dios
Telefonica Investigacion y Desarrollo
Emilio Vargas 6
Madrid, 28045
Spain
Phone: +34 913374013
Email: ogondio@tid.es
Cyril Margaria
Nokia Siemens Networks
St Martin Strasse 76
Munich, 81541
Germany
Phone: +49 89 5159 16934
Email: cyril.margaria@nsn.com
Xiaobing Zi
Huawei Technologies
F3-5-B R&D Center, Huawei Base
Bantian, Longgang District
Shenzhen 518129 P.R.China
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Phone: +86-755-28973229
Email: zixiaobing@huawei.com
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