PCEP extensions for SR-TP
draft-xiong-pce-pcep-extension-sr-tp-00
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| Authors | Quan Xiong , fangwei hu , Shuangping Zhan | ||
| Last updated | 2018-03-05 | ||
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draft-xiong-pce-pcep-extension-sr-tp-00
PCE WG Quan Xiong
Internet-Draft Fangwei Hu
Intended status: Standards Track Shuangping Zhan
Expires: September 6, 2018 ZTE Corporation
March 5, 2018
PCEP extensions for SR-TP
draft-xiong-pce-pcep-extension-sr-tp-00.txt
Abstract
This document proposes a set of extensions to PCEP for Segment
Routing in MPLS Transport Profile (SR-TP) networks and defines a
mechanism to create the bi-directional SR tunnel in SR-TP networks
with PCE.
Status of This Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 2
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. The SR-TP Architecture with PCE . . . . . . . . . . . . . . . 3
3. PCEP extensions for SR-TP . . . . . . . . . . . . . . . . . . 4
3.1. Bi-directional LSP extension . . . . . . . . . . . . . . 4
3.1.1. The B flag in SRP Object . . . . . . . . . . . . . . 4
3.2. SR-TP ERO extension . . . . . . . . . . . . . . . . . . . 4
3.3. Processing Rules . . . . . . . . . . . . . . . . . . . . 5
4. Security Considerations . . . . . . . . . . . . . . . . . . . 6
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
7.1. Informative References . . . . . . . . . . . . . . . . . 6
7.2. Normative References . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
The Path Computation Element Communication Protocol (PCEP) defined in
[RFC5440] provides mechanisms for Path Computation Elements (PCEs) to
perform path computations in response to Path Computation Clients
(PCCs) requests.
[I-D.ietf-pce-segment-routing] proposes extensions to PCEP that allow
a stateful PCE to compute Traffic Engineering (TE) paths in segment
routing (SR) networks. But it is applicable to Multi-protocol Label
Switching (MPLS) networks. [I-D.hu-spring-sr-tp-use-case] describes
the use case of SR tunnel to be deployed in MPLS Transport Profile
(SR-TP) network. It is required to extend the PCEP protocol to meet
the new requirement for SR-TP.
This document proposes a set of extensions to PCEP for Segment
Routing in MPLS Transport Profile (SR-TP) networks and defines a
mechanism to create the bi-directional SR tunnel in SR-TP networks
with PCE.
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].
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1.2. Terminology
The terminology is defined as [RFC5440],
[I-D.ietf-pce-segment-routing] and [I-D.hu-spring-sr-tp-use-case].
2. The SR-TP Architecture with PCE
As described in [I-D.hu-spring-sr-tp-use-case], in SR-TP networks,
the centralized controller may calculate the end to end SR paths, and
creates the ordered segment list. The centralized controller may be
replaced to PCE as the Figure 1 shown. The PCE can calculate the SR
paths and initiate a SR path on a PCC.
|
|
V
+---+--+
+--------------+ PCE +---------------+
| +---+--+ |
+-------|-------------------------------------|--------+
| | SR-TP network | |
| | | |
| +---+--+ +---+--+ +---+--+ |
| | A +-----------+ B +-----------+ C + |
| +------+ +------+ +------+ |
| |
+------------------------------------------------------+
+------------+ +------------+
| Label A | | Label C |
+------------+ +------------+
| ... | | ... |
+------------+ +------------+
| Label C | | Label A |
+------------+ +------------+
| Path Label | | Path Label |
+------------+ +------------+
Figure 1 The SR-TP Architecture with PCE
It is required to support bi-direction tunnel to meet the requirement
of SP-TP networks. A label named Path segment at both ends of the
paths was defined to identify the direction of the SR paths as
described in [I-D.cheng-spring-mpls-path-segment]. It mainly aims to
bind two unidirectional SR paths to a single bi-directional tunnel.
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3. PCEP extensions for SR-TP
3.1. Bi-directional LSP extension
3.1.1. The B flag in SRP Object
The format of the SRP object is defined in [RFC8231] and included
here for easy reference with the addition of the new B flag.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags |B|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SRP-ID-number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// Optional TLVs //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2 The SRP Object Format
A new flag is defined to indicate a bi-directional LSP operation
initiated by the PCE:
B(Bi-directional -- 1 bit):when set, the PCE specifies that the
request relates to a bi-directional TE LSP that has the same traffic
engineering requirements including fate sharing, protection and
restoration, LSRs, TE links, and resource requirements (e.g., latency
and jitter) in each direction. When cleared, the TE LSP is
unidirectional.
3.2. SR-TP ERO extension
As described in [I-D.hu-spring-sr-tp-use-case], it is required to
support bi-directional tunnel to meet the requirement of SP-TP
networks. But it is the uni-directional tunnel for SR and
engineering traffic network as discussed in
[I-D.ietf-pce-segment-routing]. The SR path is carried in the
Segment Routing Explicit Route Object (SR-ERO), which consists of a
sequence of SR subobjects. This document proposes the extension of
the SR-ERO Subobject to carry the bi-directional tunnel information
as the Figure 3 shown.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|L| Type | Length | ST | Flags |R|F|S|C|M|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// Path Label information (variable) //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3 Extension of SR-ERO Subobject format
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Path Label | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4 Path Label information
ST (SID Type -- 4 bit):TBD, indicates the type of information
associated with the Path Label contained in the object body. when the
ST indicates the Path Label type, the NAI is filled with the Path
Label information as the Figure 4 shown.
R (Reverse Flag -- 1 bit): indicates the SR path direction, when it
is clear, it indicates the forward direction and when it is set, it
indicates the reverse direction.
The definition of other fields is the same with
[I-D.ietf-pce-segment-routing].
3.3. Processing Rules
As discussed in [I-D.cheng-spring-mpls-path-segment], the bi-
directional SR tunnel is created from two binding unidirectional SR
paths. As defined in [RFC8281], the stateful PCE calculates the SR
paths and initiates the bi-directional LSP with Initiate Request
message (PCInitiate).
The B bit in SRP Object MUST be set and the two unidirectional SR
paths may be computed from the forward and reverse direction and sent
to the source and destination PCC respectively in SR-ERO object. The
path labels which binding the paths may be generated in PCE and sent
to the related PCC carried in the bottom of the SR-ERO. When the
PCCs at both ends receiving the PCInitiate message with the labels in
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SR-ERO subobjects, they may forward the packets from bi-directional
tunnel in SR-TP networks.
4. Security Considerations
TBD.
5. IANA Considerations
TBD.
6. Acknowledgements
TBD.
7. References
7.1. Informative References
[I-D.hu-spring-sr-tp-use-case]
hu, f., Xiong, Q., Mirsky, G., and W. Cheng, "Segment
Routing Transport Profile Use Case", draft-hu-spring-sr-
tp-use-case-01 (work in progress), March 2018.
7.2. Normative References
[I-D.cheng-spring-mpls-path-segment]
Cheng, W., Wang, L., Li, H., Chen, M., Zigler, R., and S.
Zhan, "Path Segment in MPLS Based Sement Routing Network",
draft-cheng-spring-mpls-path-segment-01 (work in
progress), March 2018.
[I-D.ietf-pce-segment-routing]
Sivabalan, S., Filsfils, C., Tantsura, J., Henderickx, W.,
and J. Hardwick, "PCEP Extensions for Segment Routing",
draft-ietf-pce-segment-routing-11 (work in progress),
November 2017.
[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>.
[RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation
Element (PCE) Communication Protocol (PCEP)", RFC 5440,
DOI 10.17487/RFC5440, March 2009,
<https://www.rfc-editor.org/info/rfc5440>.
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[RFC8231] Crabbe, E., Minei, I., Medved, J., and R. Varga, "Path
Computation Element Communication Protocol (PCEP)
Extensions for Stateful PCE", RFC 8231,
DOI 10.17487/RFC8231, September 2017,
<https://www.rfc-editor.org/info/rfc8231>.
[RFC8281] Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "Path
Computation Element Communication Protocol (PCEP)
Extensions for PCE-Initiated LSP Setup in a Stateful PCE
Model", RFC 8281, DOI 10.17487/RFC8281, December 2017,
<https://www.rfc-editor.org/info/rfc8281>.
Authors' Addresses
Quan Xiong
ZTE Corporation
No.6 Huashi Park Rd
Wuhan, Hubei 430223
China
Phone: +86 27 83531060
Email: xiong.quan@zte.com.cn
Fangwei Hu
ZTE Corporation
No.889 Bibo Rd
Shanghai 201203
China
Phone: +86 21 68896273
Email: hu.fangwei@zte.com.cn
Shuangping Zhan
ZTE Corporation
Liuxian Rd
Shenzhen 518057
China
Phone: +86 755 26773770
Email: zhan.shuangping@zte.com.cn
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