PCEP Extension for SRv6 Unified SIDs
draft-xiong-pce-segment-routing-ipv6-complement-00
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| Document | Type |
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| Authors | Quan Xiong , Shaofu Peng | ||
| Last updated | 2020-03-08 | ||
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draft-xiong-pce-segment-routing-ipv6-complement-00
PCE Q. Xiong
Internet-Draft S. Peng
Intended status: Standards Track ZTE Corporation
Expires: September 9, 2020 March 8, 2020
PCEP Extension for SRv6 Unified SIDs
draft-xiong-pce-segment-routing-ipv6-complement-00
Abstract
This document proposes PCEP extensions for SRv6 Path (i.e. ERO)
which applied to the use of SRv6 Unified SIDs.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions used in this document . . . . . . . . . . . . . . 3
2.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2.2. Requirements Language . . . . . . . . . . . . . . . . . . 3
3. PCEP Extensions . . . . . . . . . . . . . . . . . . . . . . . 3
3.1. The OPEN Object . . . . . . . . . . . . . . . . . . . . . 3
3.2. The ERO Object . . . . . . . . . . . . . . . . . . . . . 4
4. Operations . . . . . . . . . . . . . . . . . . . . . . . . . 5
5. Security Considerations . . . . . . . . . . . . . . . . . . . 5
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
7.1. New SR PCE Capability Flag Registry . . . . . . . . . . . 5
7.2. Extension for SRv6-ERO Registry . . . . . . . . . . . . . 6
8. Normative References . . . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction
[RFC5440] describes the Path Computation Element Protocol (PCEP)
which is used between a Path Computation Element (PCE) and a Path
Computation Client (PCC) (or other PCE) to enable computation of
Multi-protocol Label Switching (MPLS) for Traffic Engineering Label
Switched Path (TE LSP). PCEP Extensions for the Stateful PCE Model
[RFC8231] describes a set of extensions to PCEP to enable active
control of MPLS-TE and Generalized MPLS (GMPLS) tunnels. [RFC8281]
describes the setup and teardown of PCE-initiated LSPs under the
active stateful PCE model, without the need for local configuration
on the PCC, thus allowing for dynamic centralized control of a
network.
Segment Routing (SR) leverages the source routing paradigm. Segment
Routing can be instantiated on MPLS data plane which is referred to
as SR-MPLS [RFC8660]. SR-MPLS leverages the MPLS label stack to
construct the SR path. PCEP Extensions for Segment Routing [RFC8664]
specifies extensions to the PCEP that allow a stateful PCE to compute
and initiate TE paths in SR networks. Segment Routing can be applied
to the IPv6 architecture which is called SRv6 with the Segment
Routing Header (SRH) [I-D.ietf-6man-segment-routing-header].
[I-D.ietf-pce-segment-routing-ipv6] extends the PCEP to support SRv6.
[I-D.ietf-spring-srv6-network-programming] proposes the SRv6 Network
Programming to specify a packet processing program by encoding a
sequence of instructions in the IPv6 packet header. It defined the
SID as two parts, LOC:FUNCT or a complete structure is
B:N:FUNCT:ARGS. However, the size of SRv6 SID faces a scaling
challenge to use topological instructions.
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[I-D.mirsky-6man-unified-id-sr] proposed an extension of SRH that
enables the use of a shorter segment identifier which is referred to
as unified SID, such as 32-bits Label format SID or 32-bits IP
address format SID. The SIDs which allocated by SRv6 nodes are in
the same SRv6 SID Locator Block, SRH only needs to store the
difference between SIDs (N:FUNCT:ARGS), and does not need to contain
the SRv6 SID Locator Block information. So the controller (i.e.
PCE) should indicate the SRv6 path with SRv6 unified SIDs and the
length of SRv6 SID Locator Block and non-Block in a 128-bit classic
SRv6 SID.
This document proposes PCEP extensions for SRv6 Path (i.e. ERO)
which applied to the use of SRv6 Unified SIDs.
2. Conventions used in this document
2.1. Terminology
The terminology is defined as [RFC5440], [RFC8660],
[I-D.ietf-spring-srv6-network-programming] and
[I-D.ietf-pce-segment-routing-ipv6].
2.2. Requirements Language
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.
3. PCEP Extensions
3.1. The OPEN Object
As defined in [I-D.ietf-pce-segment-routing-ipv6], PCEP speakers use
SRv6 PCE Capability sub-TLV to exchange information about their SRv6
capability carried in Open object. This document defined a new flag
(U-flag) for SRv6 PCE Capability sub-TLV as shown in Figure 1.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=TBD1 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Flags |U|N|X|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MSD-Type | MSD-Value | MSD-Type | MSD-Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// ... //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MSD-Type | MSD-Value | Padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: U-flag in SRv6-PCE-CAPABILITY sub-TLV
U (SRv6 unified SIDs is supported) : A PCE sets this flag bit to 1
carried in Open message to indicate that it supports the
configuration of SRv6 path with unified SIDs. A PCC sets this flag
to 1 to indicate that it supports the capability of processing the
unified SIDs and and supports the results of SRv6 path with unified
SIDs.
3.2. The ERO Object
SRv6-ERO subobject is used for SRv6 path which consists of one or
more SRv6 SIDs as defined in [I-D.ietf-pce-segment-routing-ipv6].
This document extends the SRv6-ERO for supporting the SRv6 unified
SIDs as Figure 2 shown:
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=TBD3 | Length | NT | Flags |U|F|S|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Block Len | Non-Block Len | Function Code |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| SRv6 SID (optional) |
| (128-bit) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// NAI (variable, optional) //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Extension for SRv6-ERO Subobject
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U (SRv6 unified SIDs) : If this flag is set, it means that the SRv6
path is composed of unified SIDs and the SRv6 SIDs should be unified
in PCC for unified SRH.
Block Len (8bit), indicates the bit length of SRv6 SID Locator Block
information of a 128-bit SID.
non-Block Len (8bit), indicates the bit length of SRv6 SID Locator
non-Block information of a 128-bit SID.
4. Operations
The PCC and PCE exchanges the capability of supporting SRv6
compresses SIDs with C bit set to 1 with in SRv6 PCE Capability sub-
TLV carried in Open message. The SRv6 path is initiated by PCE or
PCC with PCReq, PCInitiated or PCUpd messages. The PCC received the
SRv6 path within SRv6-ERO subobjects. When the U flag set to 1, it
indicates the SRv6 SIDs should be unified. Take the length of the
short SID as 32 bits as an example. The PCC analyzes whether the
SRv6 SIDs are in the same block and whether the Block length of
Node:Func does not exceed 32 bits based on the Non-Block length.The
PCC uses a 32-bit short SID optimization SID List for SRH
encapsulation.
5. Security Considerations
TBA
6. Acknowledgements
TBA
7. IANA Considerations
7.1. New SR PCE Capability Flag Registry
SR PCE Capability TLV is defined in
[I-D.ietf-pce-segment-routing-ipv6], and the registry to manage the
Flag field of the SRv6 PCE Capability TLV is requested in
[I-D.ietf-pce-segment-routing-ipv6]. IANA is requested to make
allocations from the registry, as follows:
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+--------+-----------------------------------------+----------------+
| Value | Name | Reference |
+--------+-----------------------------------------+----------------+
| TBD1 | SRv6 unified SIDs is supported is | [this |
| | supported (U) | document] |
+--------+-----------------------------------------+----------------+
Table 1
7.2. Extension for SRv6-ERO Registry
SRv6-ERO subobject is defined in [I-D.ietf-pce-segment-routing-ipv6],
and the registry to manage the Flag field of SR-ERO is requested in
[I-D.ietf-pce-segment-routing-ipv6]. IANA is requested to make
allocations from the registry, as follows:
+---------+------------------------------------+------------------+
| Value | Name | Reference |
+---------+------------------------------------+------------------+
| TBD2 | Extension for SRv6-ERO Subobject | [this document] |
+---------+------------------------------------+------------------+
Table 2
8. Normative References
[I-D.ietf-6man-segment-routing-header]
Filsfils, C., Dukes, D., Previdi, S., Leddy, J.,
Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header
(SRH)", draft-ietf-6man-segment-routing-header-26 (work in
progress), October 2019.
[I-D.ietf-pce-segment-routing-ipv6]
Negi, M., Li, C., Sivabalan, S., Kaladharan, P., and Y.
Zhu, "PCEP Extensions for Segment Routing leveraging the
IPv6 data plane", draft-ietf-pce-segment-routing-ipv6-03
(work in progress), October 2019.
[I-D.ietf-spring-srv6-network-programming]
Filsfils, C., Camarillo, P., Leddy, J., Voyer, D.,
Matsushima, S., and Z. Li, "SRv6 Network Programming",
draft-ietf-spring-srv6-network-programming-10 (work in
progress), February 2020.
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[I-D.mirsky-6man-unified-id-sr]
Cheng, W., Mirsky, G., Peng, S., Aihua, L., Wan, X., Wei,
C., and S. Shay, "Unified Identifier in IPv6 Segment
Routing Networks", draft-mirsky-6man-unified-id-sr-05
(work in progress), February 2020.
[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>.
[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>.
[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>.
[RFC8660] Bashandy, A., Ed., Filsfils, C., Ed., Previdi, S.,
Decraene, B., Litkowski, S., and R. Shakir, "Segment
Routing with the MPLS Data Plane", RFC 8660,
DOI 10.17487/RFC8660, December 2019,
<https://www.rfc-editor.org/info/rfc8660>.
[RFC8664] Sivabalan, S., Filsfils, C., Tantsura, J., Henderickx, W.,
and J. Hardwick, "Path Computation Element Communication
Protocol (PCEP) Extensions for Segment Routing", RFC 8664,
DOI 10.17487/RFC8664, December 2019,
<https://www.rfc-editor.org/info/rfc8664>.
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Authors' Addresses
Quan Xiong
ZTE Corporation
No.6 Huashi Park Rd
Wuhan, Hubei 430223
China
Email: xiong.quan@zte.com.cn
Shaofu Peng
ZTE Corporation
No.50 Software Avenue
Nanjing, Jiangsu 210012
China
Email: peng.shaofu@zte.com.cn
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