Internet DRAFT - draft-avantika-pce-multi-src-dest
draft-avantika-pce-multi-src-dest
PCE Working Group U. Palle
Internet-Draft Avantika. S
Intended status: Experimental D. Dhody
Expires: August 18, 2014 Huawei Technologies
February 14, 2014
PCEP Extensions for Supporting Multiple Sources and Destinations
draft-avantika-pce-multi-src-dest-01
Abstract
The Path Computation Element (PCE) provides functions of path
computation in support of traffic engineering in networks controlled
by Multi-Protocol Label Switching (MPLS) and Generalized MPLS
(GMPLS).
This document provides extensions for the Path Computation Element
Protocol (PCEP) to support multiple sources and destinations in a
single path request.
Status of This Memo
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on August 18, 2014.
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to this document. Code Components extracted from this document must
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.1. Example . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. PCEP Requirements . . . . . . . . . . . . . . . . . . . . . . 6
5. Extension to PCEP . . . . . . . . . . . . . . . . . . . . . . 6
5.1. The New MP2MP END-POINTS Object . . . . . . . . . . . . . 6
6. Other Considerations . . . . . . . . . . . . . . . . . . . . 8
6.1. Identification of Source-Destination Pair in PCRep
Message . . . . . . . . . . . . . . . . . . . . . . . . . 8
6.2. Request-ID . . . . . . . . . . . . . . . . . . . . . . . 9
6.3. Backward Compatibility . . . . . . . . . . . . . . . . . 9
6.4. Overloading the PCE . . . . . . . . . . . . . . . . . . . 9
7. Security Considerations . . . . . . . . . . . . . . . . . . . 9
8. Manageability Considerations . . . . . . . . . . . . . . . . 9
8.1. Control of Function and Policy . . . . . . . . . . . . . 9
8.2. Information and Data Models . . . . . . . . . . . . . . . 10
8.3. Liveness Detection and Monitoring . . . . . . . . . . . . 10
8.4. Verify Correct Operations . . . . . . . . . . . . . . . . 10
8.5. Requirements On Other Protocols . . . . . . . . . . . . . 10
8.6. Impact On Network Operations . . . . . . . . . . . . . . 10
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
9.1. New END-POINTS Object Types . . . . . . . . . . . . . . . 10
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 10
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
11.1. Normative References . . . . . . . . . . . . . . . . . . 11
11.2. Informative References . . . . . . . . . . . . . . . . . 11
Appendix A. Evaluation of Message Size Reduction . . . . . . . . 12
1. Introduction
[RFC5440] specifies the Path Computation Element Communication
Protocol (PCEP) for communications between a Path Computation Client
(PCC) and a Path Computation Element (PCE), or between two PCEs, in
compliance with [RFC4657].
As per [RFC5440], a single Path Computation Request (PCReq) message
may carry more than one path computation request. Each request is
uniquely identified by a request-id number. In some scenarios (refer
Section 3), there is a need to send multiple requests with the same
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constraints and attributes to the PCE. Currently these requests are
either sent in a separate PCReq messages or clubbed together in one
(or more) PCReq messages. In either case, the constraints and
attributes need to be encoded separately for each request even though
they are exactly identical.
Also note that, the PCE may choose to respond to each of the request
independently in a separate Path Computation Reply (PCRep) messages
or choose to bundle them in one (or more) PCRep messages. In some
scenarios (refer Section 3) one should wait for responses for all
request before proceeding further.
A mechanism to request path computation between multiple sources and
destinations in a single path computation request would be helpful.
Note that the scope of this work is point-to-point (P2P) path
computation and is unrelated to MP2MP LSP ([RFC6388]).
1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
2. Terminology
The following terminology is used in this document.
LSR: Label Switch Router.
MPLS: Multiprotocol Label Switching.
NMS: Network Management System.
P2P: Point-to-Point.
PCC: Path Computation Client. Any client application requesting a
path computation to be performed by a Path Computation Element.
PCE: Path Computation Element. An entity (component, application,
or network node) that is capable of computing a network path or
route based on a network graph and applying computational
constraints.
PCEP: Path Computation Element Communication Protocol.
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3. Motivation
Following key scenarios are identified where a mechanism to request
path computation between multiple sources and destinations in a
single path computation request would be helpful.
Hierarchical PCE: [RFC6805] describes the procedure for inter-domain
path computation using Hierarchical PCE. In case of end to end
path computation by Parent PCE, it needs to issue multiple path
computation requests to child PCEs. In case of transit domain(s),
the Parent PCE issues requests from each entry boundary node to
each exit boundary node to the child PCE(s). Similarly for
ingress domain, the Parent PCE issues requests from source to each
exit boundary node, where as for egress domain, the Parent PCE
issues requests from each entry boundary node to the destination.
All requests to a particular child PCE, need to be encoded
separately even though they are exactly identical (they have the
same constraints and attributes). Also the Parent PCE needs to
wait for responses for all requests before proceeding further.
Inter-Layer PCE: [RFC5623] describes inter-layer path computation
framework. In case of cooperating PCEs per layer, where each PCE
has topology visibility restricted to its own layer and
collaborate to compute an end-to-end path across layers. The
higher layer PCE may need to issue multiple requests to lower
layer PCE requesting paths from each entry boundary node to each
exit boundary node. All these requests need to be encoded
separately even though they are exactly identical (they have the
same constraints and attributes). Also the higher layer PCE needs
to wait for responses for all requests before proceeding further.
Management-Based PCE: [RFC4655] describes a case where PCC is not
necessarily an LSR, but for example, maybe a NMS or a planning
tool etc. Such a PCC may issue multiple requests to PCE with
identical constraints and attributes to select among the several
source-destination pairs.
Using Multiple P2P Path Computations for MP2MP TE LSP: In case
where, for establishing a MP2MP TE LSP tunnel, multiple P2P path
computation requests are sent to the PCE, one for each source-
destination pair with identical constraints and attributes.
In these scenarios, a mechanism to request path computation between
multiple sources and destinations in a single path computation
request would be helpful.
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3.1. Example
Consider the topology example mentioned in Section 4.6 of [RFC6805] -
-----------------------------------------------------------------
| Domain 5 |
| ----- |
| |PCE 5| |
| ----- |
| |
| ---------------- ---------------- ---------------- |
| | Domain 1 | | Domain 2 | | Domain 3 | |
| | | | | | | |
| | ----- | | ----- | | ----- | |
| | |PCE 1| | | |PCE 2| | | |PCE 3| | |
| | ----- | | ----- | | ----- | |
| | | | | | | |
| | ----| |---- ----| |---- | |
| | |BN11+---+BN21| |BN23+---+BN31| | |
| | - ----| |---- ----| |---- - | |
| | |S| | | | | |D| | |
| | - ----| |---- ----| |---- - | |
| | |BN12+---+BN22| |BN24+---+BN32| | |
| | ----| |---- ----| |---- | |
| | | | | | | |
| | ---- | | | | ---- | |
| | |BN13| | | | | |BN33| | |
| -----------+---- ---------------- ----+----------- |
| \ / |
| \ ---------------- / |
| \ | | / |
| \ |---- ----| / |
| ----+BN41| |BN42+---- |
| |---- ----| |
| | | |
| | ----- | |
| | |PCE 4| | |
| | ----- | |
| | | |
| | Domain 4 | |
| ---------------- |
| |
-----------------------------------------------------------------
Figure 1: An example topology
The following 11 individual requests are generated by parent PCE (PCE
5) -
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Domain 1: S-BN11; S-BN12; S-BN13;
Domain 2: BN21-BN23; BN21-BN24; BN22-BN23; BN22-BN24;
Domain 3: BN31-D; BN32-D; BN33-D;
Domain 4: BN41-BN42;
The above requests for each domain, need to be encoded separately
even though they are exactly identical. A mechanism to request them
together in a single path computation request would be helpful, in
which case total 4 requests would be generated by parent PCE.
4. PCEP Requirements
Following key requirements are identified for PCEP to enable multiple
sources and destinations in a single path computation request:
1. It MUST be possible for a single Path Computation Request to list
multiple sources and destinations.
2. It MUST be possible for a single Path Computation Reply to be
sent for multiple sources and destinations.
3. It MUST NOT be possible to set different constraints, traffic
parameters, or quality-of-service requirements for different
source and destination pair within a single computation request.
5. Extension to PCEP
This document extends the existing END-POINTS object [RFC5440] and
[RFC6006] by defining two new END-POINTS object types.
5.1. The New MP2MP END-POINTS Object
The END-POINTS object is used in a PCReq message to specify the
source IP address and the destination IP address of the path for
which a path computation is requested. This document extends the
existing END-POINT object to support multiple sources and
destinations in a single path request.
Two new MP2MP END-POINTS objects for IPv4 and IPv6 are defined.
The format of the MP2MP END-POINTS object body for IPv4 (Object-
Type=5 (TBD)) is as follows:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| No of Sources (2 bytes) | No of Destinations (2 bytes)|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source IPv4 address 1 (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ...... ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source IPv4 address m (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination IPv4 address 1 (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ...... ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination IPv4 address n (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: The new MP2MP END-POINTS Object Body Format for IPv4
The format of the MP2MP END-POINTS object body for IPv6 (Object-
Type=6 (TBD)) is as follows:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| No of Sources (2 bytes) | No of Destinations (2 bytes)|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Source IPv6 address 1 (16 bytes) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ...... ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Source IPv6 address m (16 bytes) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Destination IPv6 address 1 (16 bytes) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ...... ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Destination IPv6 address n (16 bytes) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: The new MP2MP END-POINTS Object Body Format for IPv6
The MP2MP END-POINTS object body has a variable length. These are
multiples of 4 bytes for IPv4, and multiples of 16 bytes for IPv6,
plus 4 bytes.
On receiving MP2MP END-POINTS object, PCE computes m*n P2P paths,
i.e, point to point path is computed between each combination of
source and destination received in MP2MP END-POINTS object.
6. Other Considerations
6.1. Identification of Source-Destination Pair in PCRep Message
Since the END-POINTS object is not carried in the PCRep message
([RFC5440]), the implementation supporting this extension SHOULD
encode the source and the destination as the first and the last hop
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in the ERO. This is done to easily identify that which ERO
corresponds to which source-destination pair.
6.2. Request-ID
As per [RFC5440], each request is uniquely identified by a request-id
number.
Since a single request is used for multiple sources and destinations
sharing the same request-id number, along with request and response,
the request-id number in RP object used in other PCEP messages
(PCNtf, PCErr ...) applies to all sources and destinations (in the
single request).
6.3. Backward Compatibility
If PCE receives new END-POINTS type in path request and it
understands the END-POINTS type, but the PCE is not capable of/
support multiple sources and destinations in a single path request,
the PCE MUST send a PCErr message with a PCEP-ERROR Object Error-Type
= 4 (Not supported object) [RFC5440]. The path computation request
MUST then be cancelled.
If the PCE does not understand the new END-POINTS type, then the PCE
MUST send a PCErr message with a PCEP-ERROR Object Error-Type = 3
(Unknown object) [RFC5440].
6.4. Overloading the PCE
The new END-POINTS type could be used to issue multiple computations
together hence overloading the PCE. The PCE MUST allow for the use
of policies to accept/reject such a request.
7. Security Considerations
This document defines new END-POINTS types which does not add any new
security concerns beyond those discussed in [RFC5440].
8. Manageability Considerations
8.1. Control of Function and Policy
TBD.
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8.2. Information and Data Models
TBD.
8.3. Liveness Detection and Monitoring
TBD.
8.4. Verify Correct Operations
TBD.
8.5. Requirements On Other Protocols
TBD.
8.6. Impact On Network Operations
TBD.
9. IANA Considerations
IANA assigns values to PCEP parameters in registries defined in
[RFC5440]. IANA is requested to make the following additional
assignments.
9.1. New END-POINTS Object Types
Two new END-POINTS Object-Types are defined in this document. IANA
is requested to make the following Object-Type allocations from the
"PCEP Objects" sub-registry:
Object-Class Value 4
Name END-POINTS
Object-Type 5: MP2MP IPv4
6: MP2MP IPv6
7-15: Unassigned
Reference This.I-D
10. Acknowledgments
Thanks to Quintin Zhao for his suggestions.
11. References
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11.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4657] Ash, J. and J. Le Roux, "Path Computation Element (PCE)
Communication Protocol Generic Requirements", RFC 4657,
September 2006.
11.2. Informative References
[RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation
Element (PCE)-Based Architecture", RFC 4655, August 2006.
[RFC5440] Vasseur, JP. and JL. Le Roux, "Path Computation Element
(PCE) Communication Protocol (PCEP)", RFC 5440, March
2009.
[RFC5623] Oki, E., Takeda, T., Le Roux, JL., and A. Farrel,
"Framework for PCE-Based Inter-Layer MPLS and GMPLS
Traffic Engineering", RFC 5623, September 2009.
[RFC6006] Zhao, Q., King, D., Verhaeghe, F., Takeda, T., Ali, Z.,
and J. Meuric, "Extensions to the Path Computation Element
Communication Protocol (PCEP) for Point-to-Multipoint
Traffic Engineering Label Switched Paths", RFC 6006,
September 2010.
[RFC6388] Wijnands, IJ., Minei, I., Kompella, K., and B. Thomas,
"Label Distribution Protocol Extensions for Point-to-
Multipoint and Multipoint-to-Multipoint Label Switched
Paths", RFC 6388, November 2011.
[RFC6805] King, D. and A. Farrel, "The Application of the Path
Computation Element Architecture to the Determination of a
Sequence of Domains in MPLS and GMPLS", RFC 6805, November
2012.
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Appendix A. Evaluation of Message Size Reduction
Consider the domain 2 in Figure 1, where 4 path requests need to be
encoded (from 2 entry boundary nodes to 2 exit boundary nodes with
the exact same constraints).
Following figure illustrates the existing mechanism of carrying
multiple requests in single PCReq message (as per [RFC5440]):
+--------------+ +--------------+ +--------------+
|RP | |RP | |RP |
+-------+ |END-POINTS(8) | |END-POINTS | |END-POINTS |
|COMMON |+|BANDWIDTH |+|BANDWIDTH |+|BANDWIDTH |
|HEADER | |METRIC | |METRIC | |METRIC |
+-------+ |METRIC | |METRIC | |METRIC |
+--------------+ +--------------+ +--------------+
4 Bytes 36 Bytes 36 Bytes 36 Bytes
+--------------+
|RP |
|END-POINTS(20)|
+ |BANDWIDTH | = 148 Bytes
|METRIC |
|METRIC |
+--------------+
36 Bytes
Combining multiple requests into a single request by using MP2MP END-
POINTS object is illustrated below:
+--------------+
|RP |
+-------+ |END-POINTS(20)|
|COMMON |+|BANDWIDTH | = 54 Bytes
|HEADER | |METRIC |
+-------+ |METRIC |
+--------------+
4 Bytes 48 Bytes
There is message size reduction of 64% in this example for just one
domain.
Authors' Addresses
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Udayasree Palle
Huawei Technologies
Leela Palace
Bangalore, Karnataka 560008
INDIA
EMail: udayasree.palle@huawei.com
Avantika
Huawei Technologies
Leela Palace
Bangalore, Karnataka 560008
INDIA
EMail: avantika.sushilkumar@huawei.com
Dhruv Dhody
Huawei Technologies
Leela Palace
Bangalore, Karnataka 560008
INDIA
EMail: dhruv.ietf@gmail.com
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