Internet DRAFT - draft-cp-spring-srv6-sid-allocation
draft-cp-spring-srv6-sid-allocation
SPRING WG R. Chen
Internet-Draft Sh. Peng
Intended status: Standards Track ZTE
Expires: 30 September 2023 29 March 2023
SRv6 SID Allocation
draft-cp-spring-srv6-sid-allocation-02
Abstract
This document describes a SRv6 SID allocation method.
Status of This Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions used in this document . . . . . . . . . . . . . . 2
3. Allocating a SRv6 Compressed SID to a node . . . . . . . . . 2
4. The New SR Endpoint Behaviors . . . . . . . . . . . . . . . . 3
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
6. Security Considerations . . . . . . . . . . . . . . . . . . . 5
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
8. Normative References . . . . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction
Segment Routing architecture [RFC8402]leverages the paradigm of
source routing. It can be realized in a network data plane by
prepending the packet with a list of instructions, a.k.a. Segment
Identifiers (SIDs). A segment can be encoded as a Multi-Protocol
Label Switching (MPLS) label, IPv4 address, or IPv6 address. Segment
Routing can be applied in MPLS data plane by encoding 20-bits SIDs in
MPLS label stack [RFC8660]. It also can be applied to IPv6 data
plane by encoding a list of 128-bits SIDs in IPv6 Segment Routing
Extension Header (SRH)[RFC8754].
As we know, several proposals are introduced to reduce the overhead
of SIDs. The main ideas of them are basically to use a Compressed
SID to replace the complete 128 bit SID in the SID list. The
consequence of this is that the SID allocation space provided to each
node will be very limited, which will limit the deployment of
services in the network.
This document describes an SRv6 SID allocation method to increase the
SID allocation space.
2. 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 RFC2119.
3. Allocating a SRv6 Compressed SID to a node
Assign a general global SRv6 SID to the corresponding consumer type,
which is called the container SID. In the SID List, the container
SID is followed by the local index or identification to indicate a
specific segment with complete meaning. The container SID itself is
128bits and can be compressed to a short SID (such as 32 bits or 16
bits). The local index or identifier in general can also be a short
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SID.
For example, END.X SIDs [RFC8986] are allocated to all outbound L3
links on SRv6 nodes, and all these END.X SIDs occupy the global SRv6
SID resource. Now we define a new allocation method: for the
consumer type of L3 link, only one general global container SID
(called END.T.X SID) is allocated, and then allocates a local index
for each specific L3 link, and the combination of END.T.X SID and
local index can express the meaning of the original END.X.
4. The New SR Endpoint Behaviors
This document defines a new set of behaviors. Following is a set of
behaviors that can be associated with a SID.
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END.T.X SID Endpoint with Layer-3 cross-connect.
Only one universal container SID (END.T.X SID) is allocated on each node,
and each outbound L3 link is represented by a local index.
END.T.DX6 SID Endpoint with decapsulation and IPv6 cross-connect.
Only one universal container SID (END.T.DX6 SID) is allocated on each node,
and each L3 link connecting the CE is represented by a local index.
END.T.DX4 SID Endpoint with decaps and IPv4 cross-connect.
Only one universal container SID (END.T.DX4 SID) is allocated on each node,
and each L3 link connecting the CE is represented by a local index.
END.T.DT6 SID Endpoint with decapsulation and IPv6 table lookup.
Only one universal container SID (END.T.DT6 SID) is allocated on each node,
and each L3VPN instance is represented by a local index.
END.T.DT4 SID Endpoint with decapsulation and IPv4 table lookup.
Only one universal container SID (END.T.DT4 SID) is allocated on each node,
and each L3VPN instance is represented by a local index.
END.T.DT46 SID Endpoint with decapsulation and IP table lookup.
Only one universal container SID (END.T.DT46 SID) is allocated on each node,
and each L3VPN instance is represented by a local index.
END.T.DX2 SID Endpoint with decapsulation and L2 cross-connect.
Only one universal container SID (END.T.DX2 SID) is allocated on each node,
and each L2 link connecting the CE is represented by a local index.
END.T.DX2V SID Endpoint with decapsulation and VLAN L2 table lookup.
Only one universal container SID (END.T.DX2V SID) is allocated on each node,
and each L2VPN/EVPN instance is represented by a local index.
END.T.DT2U SID Endpoint with decapsulation and unicast MAC L2table lookup.
Only one universal container SID (END.T.DT2U SID) is allocated on each node,
and each L2VPN/EVPN instance is represented by a local index.
END.T.DT2M SID Endpoint with decapsulation and L2 table flooding
Only one universal container SID (END.T.DT2M SID) is allocated on each node,
and each L2VPN/EVPN instance is represented by a local index.
END.T.B SID Endpoint bound to an SRv6 policy with encapsulation
Only one universal container SID (END.T.B SID) is allocated on each node,
and each SR policy is represented by a local index.
Above the END.T.X, END.T.DX6, END.T.DX4, END.T.DT6, END.T.DT4,
END.T.DT46, END.T.DX2, END.T.DX2V, END.T.DT2U, END.T.DT2M, END.T.B
are all variants of the End T behavior.
The END.T behavior allows the use of the next classic SRv6 SID as the
key value to look up and forward in a specific IPv6 FIB table, and
these variants explicitly use the next short SID of a specific length
(such as 32 or 16 bits) as the key value to look-up table in the
specific consumer type table . These variants can also be combined
with different Flavors, such as PSP, USP and USD Flavors defined in
[RFC8986].
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5. IANA Considerations
TBD.
6. Security Considerations
7. Acknowledgements
TBD.
8. Normative References
[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>.
[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>.
[RFC8754] Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J.,
Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header
(SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020,
<https://www.rfc-editor.org/info/rfc8754>.
[RFC8986] Filsfils, C., Ed., Camarillo, P., Ed., Leddy, J., Voyer,
D., Matsushima, S., and Z. Li, "Segment Routing over IPv6
(SRv6) Network Programming", RFC 8986,
DOI 10.17487/RFC8986, February 2021,
<https://www.rfc-editor.org/info/rfc8986>.
Authors' Addresses
Ran Chen
ZTE
Email: chen.ran@zte.com.cn
Shaofu Peng
ZTE
Email: peng.shaofu@zte.com.cn
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