Internet DRAFT - draft-cheng-shorter-srv6-sid-requirement
draft-cheng-shorter-srv6-sid-requirement
SPRING WG W. Cheng
Internet-Draft China Mobile
Intended status: Standards Track R. Chen
Expires: August 19, 2020 A. Liu
G. Mirsk
ZTE Corporation
February 16, 2020
Shorter SRv6 SID Requirements
draft-cheng-shorter-srv6-sid-requirement-00
Abstract
This document describes a list of requirement for Shorter SRv6 SID.
Status of This Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requirements: . . . . . . . . . . . . . . . . . . . . . . . . 2
3. The proposal solutions of shorter SRv6 SID . . . . . . . . . 4
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
5. Security Considerations . . . . . . . . . . . . . . . . . . . 5
6. Normative References . . . . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
Segment Routing [RFC8402]leverages the source routing paradigm. An
ingress node steers a packet through an ordered list of instructions,
called segments.
A segment can be encoded as a Multi-Protocol Label Switching (MPLS)
label, IPv4 address, or IPv6 address. Segment Routing can be
deployed on MPLS data plane by encoding 20-bits SIDs in MPLS label
stack [I-D.ietf-spring-segment-routing-mpls]. It also can be
deployed on the IPv6 data plane by encoding a list of 128-bits SIDs
in IPv6 Segment Routing Extension Header
(SRH)[I-D.ietf-6man-segment-routing-header].
The SRv6 Network Programming
[I-D.ietf-spring-srv6-network-programming]specifies the base set of
SRv6 behaviors that enables the creation of interoperable overlays
with underlay optimization.
However, the size of the IPv6 segment identifier (SID) presents a
scaling challenge to use topological instructions that define a
strict explicitly routed path in combination with service-based
instructions. At the same time, the size of the SRH/SID may be a
challenge for some data plane processors and traffic overhead.
Meanwhile, SR-MPLS currently, more often than SRv6, is used in metro
networks. With the gradual deployment of SRv6 in the core networks,
it becomes necessary to support interworking between SR-MPLS and SRv6
and upgrading to SRv6 from SR-MPLS.It requires some solutions to
resolve these problems.
2. Requirements:
This section list the suggested requirements for Shorter SRv6 SID,
which have been used to help the WG evaluate against the proposed
solutions:
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REQ#1:The Shorter SRv6 solution MUST align with the basic SRv6.
There are three basic Segment Routing over the IPv6 data-plane (SRv6)
documents:
o The Segment Routing (SR) architecture is defined [RFC8402].
o The IPv6 Segment Routing Header (SRH) is defined
[I-D.ietf-6man-segment-routing-header].
o SRv6 Network Programming is defined
[I-D.ietf-spring-srv6-network-programming].
The Shorter SRv6 SID solution MUST align with above basic SRv6
documents.
REQ#2:The Shorter SRv6 SID solution MUST support Efficient SRv6
header compression.
When SRv6 is deployed, the SRv6 header overhead must be considered,
as the size of the SRH may affect the forwarding performance. The
solution MUST reduce the SRv6 SID size effectively.
REQ#3:The Shorter SRv6 SID solution MUST be easy to implement and
hardware-friendly
The Shorter SRv6 SID solution MUST be simple and easy to implement
and MUST use the mature hardware capabilities
REQ#4:The Shorter SRv6 SID solution MUST be compatible with SRv6
header(SRH).
For support of SRv6 network, Segment Routing Header (SRH) has been
defined in [I-D.ietf-6man-segment-routing-header]. The Shorter SRv6
SID solution MUST be compatible with SRH.
REQ#5:The Shorter SRv6 SID solution MUST support Compressed SRv6
Network Programming.
In a SR domain,there will be such the scenario in which some nodes
support Compressed SRv6 while others only support SRv6, the proposed
solution must support this scenario.
REQ#6:The Shorter SRv6 SID solution MUST support super-large-scale
networking and address planning.
Note:The operator suggest to reuse the current address assignment and
planning, thus minimizing the impact on the network.
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REQ#7:The Shorter SRv6 SID solution MUST have the ability to upgrade
smooth from SR-MPLS to SRv6.
2G/3G/4G backhaul networks widely deploy MPLS to connect wireless
services. Many operators are already deploying 5G networks. To
optimize the operation of the network, many operators intent to adopt
the segment routing. Currently, given maturity of SR-MPLS, it has
been deployed on a large scale. Meanwhile the requirements of 5G
super-large-scale number of connections accelerate the deployment of
IPv6 networks. Thus, logically, operators consider SRv6 solution to
fulfill the 5G backhaul requirement. But the backhaul network could
not deploy SRv6 in one day, especially if it has already been using
MPLS and SR-MPLS. It might be reasonable to upgrade from MPLS to SR-
MPLS and then to SRv6
REQ#8:The Shorter SRv6 SID solution MUST support interworking between
SRv6 and SR-MPLS domains in the network.
SR-MPLS currently, more often than SRv6, is used in metro networks.
With the gradual deployment of SRv6 in the core networks, it becomes
necessary to support interworking between SR-MPLS and SRv6.
3. The proposal solutions of shorter SRv6 SID
As we know, there are a number of proposals in the called 'shorter
SRv6 SID' topic. This document tries to summarize these proposals
here. Then we can discuss whether all the proposals can meet the
requirements. And then we can look at merits and costs of each
solution. After that, we will possibly refine them, possibly
converge on a single one, and probably drop multiples.
Here are the solutions that have been proposed:
o [I-D.mirsky-6man-unified-id-sr]extends the use the flag of the SRH
to unified identifiers encoded as shorter SID (such as 32-bits).
It can be interworking with SR-MPLS. It is the earliest one,
simple, and compatible well with original SRH.
o [I-D.filsfils-spring-net-pgm-extension-srv6-usid] extends SRv6
Network Programming with a new type of SRv6 SID behavior. A uSID
carrier can be encoded in the Destination Address of an IPv6
header or at any position in the Segment List of an SRH.
o [I-D.decraene-spring-srv6-vlsid]extends SRH and SRv6 Network
Programming to allow for SIDs of variable length, from 1 up to 128
bits. It is required to extend the control plane to advertise the
SID length.
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o [I-D.bonica-6man-comp-rtg-hdr]defines two new Routing header
types. Collectively, they are called the Compressed Routing
Headers (CRH). Individually,they are called CRH-16 and CRH-32.
In the CRH, the Type-specific data field contains a list of
Segment Identifiers (SIDs)(16bits/32bits).
o [I-D.cl-spring-generalized-srv6-np]proposes Generalized Segment
Routing over IPv6 (G-SRv6) Networking Programming, which supports
to encode multiple types of Segments in a SRH, called Generalized
SRH (G-SRH). These Segments can be called Generalized Segment,
and the ID can be Generalized Segment Identifier (G-SID), which
may include an SRv6 SID(128 bits),C-SIDs, MPLS labels, or IPv4
tunnel information.
4. IANA Considerations
This document has no requests to IANA.
5. Security Considerations
This document does not change the security considerations of SRv6,
please refers to [RFC8402], [I-D.ietf-6man-segment-routing-header]
and [I-D.ietf-spring-srv6-network-programming].
6. Normative References
[I-D.bonica-6man-comp-rtg-hdr]
Bonica, R., Kamite, Y., Niwa, T., Alston, A., and N. So,
"The IPv6 Compressed Routing Header (CRH)", draft-bonica-
6man-comp-rtg-hdr-11 (work in progress), February 2020.
[I-D.cl-spring-generalized-srv6-np]
Cheng, W., Li, Z., Li, C., Xie, C., Cong, L., Tian, H.,
and F. Zhao, "Generalized SRv6 Network Programming",
draft-cl-spring-generalized-srv6-np-00 (work in progress),
February 2020.
[I-D.decraene-spring-srv6-vlsid]
Decraene, B. and R. Raszuk, "SRv6 vSID: Network
Programming extension for variable length SIDs", draft-
decraene-spring-srv6-vlsid-02 (work in progress), February
2020.
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[I-D.filsfils-spring-net-pgm-extension-srv6-usid]
Filsfils, C., Camarillo, P., Cai, D., Voyer, D., Meilik,
I., Patel, K., Henderickx, W., Jonnalagadda, P., and D.
Melman, "Network Programming extension: SRv6 uSID
instruction", draft-filsfils-spring-net-pgm-extension-
srv6-usid-03 (work in progress), February 2020.
[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-spring-segment-routing-mpls]
Bashandy, A., Filsfils, C., Previdi, S., Decraene, B.,
Litkowski, S., and R. Shakir, "Segment Routing with MPLS
data plane", draft-ietf-spring-segment-routing-mpls-22
(work in progress), May 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-09 (work in
progress), February 2020.
[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-04
(work in progress), November 2019.
[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>.
[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>.
[RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", STD 86, RFC 8200,
DOI 10.17487/RFC8200, July 2017,
<https://www.rfc-editor.org/info/rfc8200>.
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[RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
Decraene, B., Litkowski, S., and R. Shakir, "Segment
Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
July 2018, <https://www.rfc-editor.org/info/rfc8402>.
Authors' Addresses
Weiqiang Cheng
China Mobile
Email: chengweiqiang@chinamobile.com
Ran Chen
ZTE Corporation
Email: chen.ran@zte.com.cn
Aihua Liu
ZTE Corporation
Email: liu.aihua@zte.com.cn
Greg Mirsk
ZTE Corporation
Email: gregimirsky@gmail.com
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