Network G. Mirsky
Internet-Draft ZTE Corp.
Intended status: Standards Track P. Shaofu
Expires: April 13, 2019 ZTE Corporation
October 10, 2018
Unified Identifier in IPv6 Segment Routing Networks
draft-mirsky-6man-unified-id-sr-01
Abstract
Segment Routing architecture 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. segments. 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 segments in MPLS label stack. It also can be
applied to IPv6 data plane by encoding list of segment identifiers in
IPv6 Segment Routing Extension Header (SRH). This document extends
the use of the SRH to segment identifiers encoded as MPLS label and
IPv4 address.
Status of This Memo
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This Internet-Draft will expire on April 13, 2019.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Conventions used in this document . . . . . . . . . . . . 3
1.1.1. Terminology . . . . . . . . . . . . . . . . . . . . . 3
1.1.2. Requirements Language . . . . . . . . . . . . . . . . 3
2. Segment Routing Extension Header: Benefits and Challenges . . 3
3. Support of Multiple SID Lengths in IPv6 Segment Routing
Extension Header . . . . . . . . . . . . . . . . . . . . . . 4
4. Theory of Operation . . . . . . . . . . . . . . . . . . . . . 5
4.1. Egress SR Tunnel Node . . . . . . . . . . . . . . . . . . 5
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
6. Security Considerations . . . . . . . . . . . . . . . . . . . 5
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
8. Normative References . . . . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
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 [I-D.ietf-spring-segment-routing-mpls]. It also can
be applied to IPv6 data plane by encoding list of 128-bits SIDs in
IPv6 Segment Routing Extension Header (SRH)
[I-D.ietf-6man-segment-routing-header]. Applicability of 32-bits SID
that may represent an IPv4 address has not been defined.
SR extensions to Interior Gateway Protocols (IGP), IS-IS
[I-D.ietf-isis-segment-routing-extensions], OSPF
[I-D.ietf-ospf-segment-routing-extensions], and OSPFv3
[I-D.ietf-ospf-ospfv3-segment-routing-extensions], defined how
20-bits and 32-bits SIDs advertised and bound to SR objects and/or
instructions. Extensions to BGP link-state address family
[I-D.ietf-idr-bgp-ls-segment-routing-ext] enabled propagation of
segment information of variable length via BGP.
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This document extends the use of the SRH
[I-D.ietf-6man-segment-routing-header] to SIDs encoded as MPLS label
and IPv4 address.
1.1. Conventions used in this document
1.1.1. Terminology
SR: Segment Routing
SRH: Segment Routing Extension Header
MPLS: Multiprotocol Label Switching
MPLS-SR: Segment Routing in MPLS
SID: Segment Identifier
IGP: Interior Gateway Protocol
OAM: Operation, Administration and Maintenance
TE: Traffic Engineering
SRv6: Segment Routing in IPv6
1.1.2. 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.
2. Segment Routing Extension Header: Benefits and Challenges
Many functions related to Operation, Administration and Maintenance
(OAM) require identification of the SR tunnel ingress and the path,
constructed by segments, between the ingress and the egress SR nodes.
Combination of IPv6 encapsulation [RFC8200] and SRH
[I-D.ietf-6man-segment-routing-header], referred to as SRv6, comply
with this requirements while it is challenging when applying SR in
MPLS networks, also referred to as MPLS-SR.
On the other hand, the size of IPv6 SID presents a scaling challenge
to use topological instructions that define strict explicit traffic
engineered (TE) path in combination with service-based instructions.
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At the same time, that is where MPLS-SR approach provides better
results due to smaller SID length.
[I-D.bryant-mpls-unified-ip-sr] addresses the scaling challenge by
using more compact SID encoding of MPLS-SR. Ability to address OAM
challenge characteristic to MPLS-SR is open for investigation.
3. Support of Multiple SID Lengths in IPv6 Segment Routing Extension
Header
In section 3 of [I-D.ietf-6man-segment-routing-header] SRH format has
been defined as presented in Figure 1
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Next Header | Hdr Ext Len | Routing Type | Segments Left |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Last Entry | Flags | Tag |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Segment List[0] (128 bits IPv6 address) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| |
...
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Segment List[n] (128 bits IPv6 address) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// //
// Optional Type Length Value objects (variable) //
// //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: SRH format
This document defines the new field Size in the Flags field,
presented in Figure 2, as a two-bits field with the following values:
0b00 - 128-bits SID;
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0b01 - 20-bits SID;
0b10 - 32-bits SID
0b11 - reserved for future use.
When the value of the S field is 0b01, the 20-bit SID is encoded in
four octets and occupies the 20 rightmost bits.
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|U|P|O|A|H| S |U|
+-+-+-+-+-+-+-+-+
Figure 2: Flags field format
Entries of the segment list in the SRH MUST be of the same length.
4. Theory of Operation
When the SRH is used to include 20-bits or 32-bits SIDs the ingress
and transit nodes of an SR tunnel act as described in Section 5.1 and
Section 5.2 of [I-D.ietf-6man-segment-routing-header] respectively.
4.1. Egress SR Tunnel Node
TBD
5. IANA Considerations
TBD
6. Security Considerations
This specification inherits all security considerations of [RFC8402]
and [I-D.ietf-6man-segment-routing-header].
7. Acknowledgements
TBD
8. Normative References
[I-D.bryant-mpls-unified-ip-sr]
Bryant, S., Farrel, A., Drake, J., and J. Tantsura, "MPLS
Segment Routing in IP Networks", draft-bryant-mpls-
unified-ip-sr-03 (work in progress), October 2017.
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[]
Filsfils, C., Previdi, S., Leddy, J., Matsushima, S., and
d. daniel.voyer@bell.ca, "IPv6 Segment Routing Header
(SRH)", draft-ietf-6man-segment-routing-header-14 (work in
progress), June 2018.
[I-D.ietf-idr-bgp-ls-segment-routing-ext]
Previdi, S., Talaulikar, K., Filsfils, C., Gredler, H.,
and M. Chen, "BGP Link-State extensions for Segment
Routing", draft-ietf-idr-bgp-ls-segment-routing-ext-08
(work in progress), May 2018.
[I-D.ietf-isis-segment-routing-extensions]
Previdi, S., Ginsberg, L., Filsfils, C., Bashandy, A.,
Gredler, H., Litkowski, S., Decraene, B., and J. Tantsura,
"IS-IS Extensions for Segment Routing", draft-ietf-isis-
segment-routing-extensions-19 (work in progress), July
2018.
[I-D.ietf-ospf-ospfv3-segment-routing-extensions]
Psenak, P., Filsfils, C., Previdi, S., Gredler, H.,
Shakir, R., Henderickx, W., and J. Tantsura, "OSPFv3
Extensions for Segment Routing", draft-ietf-ospf-ospfv3-
segment-routing-extensions-15 (work in progress), August
2018.
[I-D.ietf-ospf-segment-routing-extensions]
Psenak, P., Previdi, S., Filsfils, C., Gredler, H.,
Shakir, R., Henderickx, W., and J. Tantsura, "OSPF
Extensions for Segment Routing", draft-ietf-ospf-segment-
routing-extensions-25 (work in progress), April 2018.
[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-14
(work in progress), June 2018.
[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>.
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[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>.
[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
Greg Mirsky
ZTE Corp.
Email: gregimirsky@gmail.com
Peng Shaofu
ZTE Corporation
No.50 Software Avenue, Yuhuatai District
Nanjing
China
Email: peng.shaofu@zte.com.cn
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