Comparison of SRv6 Extensions uSID, SRv6+, C-SRH

SRv6 Consortium @Tokyo
Comparison of SRv6 Extensions
uSID, SRv6+, C-SRH
2019/08/23
Kentaro Ebisawa
Twitter: @ebiken
SRv6 Consortium @Tokyo, Japan

• Around IETF 105 Montreal, some Internet-Drafts proposing
extensions to SRv6 were submitted. Since some extensions are not
compatible with the existing SRv6 specifications (drafts), one need
good understanding of what each proposal extends to compare them.
• This document aims to describes overview of each proposal to build a
basic understanding to study difference of each proposal.
Comparison of SRv6 Extensions ... uSID, SRv6+, C-SRH | 2019/08/23 | Kentaro Ebisawa @ebiken
Motivation

• uSID … Network Programming extension: SRv6 uSID instruction
• draft-filsfils-spring-net-pgm-extension-srv6-usid-01
• SRv6+ … IPv6 Support for Segment Routing: SRv6+
• draft-bonica-spring-srv6-plus-04
• Compressed Routing Header (CRH): draft-bonica-6man-comp-rtg-hdr-05
• Per-Segment Service Instruction (PSSI) option: draft-bonica-6man-seg-end-opt-04
• Per-Path Service Instruction (PPSI) option: draft-bonica-6man-vpn-dest-opt-06
• C-SRH … Compressed SRv6 Network Programming
• draft-li-spring-compressed-srv6-np-00
Related Internet-Drafts

SRv6 Consortium @TokyoComparison of SRv6 Extensions ... uSID, SRv6+, C-SRH | 2019/08/23 | Kentaro Ebisawa @ebiken
Authors as of 2019/08/19
uSID: Network Programming extension: SRv6 uSID instruction
draft-filsfils-spring-net-pgm-extension-srv6-usid-01
C-SRH … Compressed SRv6 Network Programming
draft-li-spring-compressed-srv6-np-00
SRv6+ … IPv6 Support for Segment Routing: SRv6+
draft-bonica-spring-srv6-plus-04

Overview of Concepts,
what are extended

uSID & C-SRH
• No Conceptual change from SRv6
• How to update IPv6 DA based on SID value has changed
• Segment … a single node.
• Source SR Node, Transit Node, SR Segment Endpoint Node
• No concept of “Ingress / Egress Segment node”
• Adjacency SID … Described as SID of End function. (ex: End.X)
C-SRH
• SRH format was enhanced
uSID and Compressed SRH (C-SRH)

SRv6+
• SRv6+ consist of “Segment” and “Path”
• Path consists of multiple Segments.
• Segment consists of multiple nodes,
• Segment Ingress node, Transit node, Segment Egress node
• or a single node which has both Ingress/Egress Node.
SRv6+

SRv6+
Path and Segment Ingress/Egress/Transit Node
Segment Ingress
(Seg A-C)
Segment Egress (Seg A-C)Transit
(Seg A-C) Segment Ingress (Seg C-D)
SRv6+ Path = {
Segment A-C,
Segment C-D,
Segment D-F
}
Path Ingress
Path Egress

SRv6+
Path and Segment Ingress/Egress/Transit Node
SRv6+ Path = {
Segment A-C,
Segment C-D,
Segment D-F
}
Path Ingress
Path Egress
A segment provides
unidirectional connectivity from its ingress node to its egress node.
Segment
Ingress
Segment
Egress In Eg In Eg In Eg
Segment

SRv6+
“per-segment” Topological / Service Instructions
In Eg In Eg In Eg
T S T S T S
Topological
Instructions
Service
Instructions
=> determines the segment egress node
=> augment a segment

SRv6+
“per-path” Service Instructions
“per-path”
Service Instruction

SRv6+
• Loosely Routed
• IPv6 address of Segment Egress node.
• (Follow IGP shortest path)
• Strictly Routed
• IPv6 address of Segment Egress node.
• Interface a packet would be forwarded (on Segment Ingress node)
• (Follow IGP shortest path after sent out from the interface)
Topology Segments … Loosely / Strictly Routed

SRv6+
SID
10
3
1
2
11
129
129
129
130
129
Policy
Loosely Routed
SID[0] = 11
SID[1] = 3

SRv6+
SID
10
3
1
2
11
129
129
129
130
129
Policy
Strictly Routed
SID[0] = 129
SID[1] = 129
Interface ::1

Segment ID & Header format comparison

Compressed SRv6 Network Programming
The IPv6 Compressed Routing Header (CRH)
draft-bonica-6man-comp-rtg-hdr-05
16- or 32-bit value
uSID block
Active
uSID
Next
uSID
...
uSID
Last
uSID
End of
Carrier
...
End of
Carrier
Network Programming extension: SRv6 uSID instruction
draft-filsfils-spring-net-pgm-extension-srv6-usid-01
32b 16b 0000 0000 0000

Compressed SRv6 Network Programming
IPv6 Segment Routing Header (SRH)
draft-ietf-6man-segment-routing-header-22

SRv6+ Headers for Instruction (IPv6 options)
PSSI, PPSI is Destination Options header defined in RFC8200 (IPv6)
Opt Type Data Len
PSSI/PPSI identifier
Total 8 bytes
The Per-Path Service Instruction (PPSI) Option
draft-bonica-6man-vpn-dest-opt-06
The Per-Segment Service Instruction (PSSI) Option
draft-bonica-6man-seg-end-opt-04

Tables maintained by
SRv6, SRv6+ and SR-MPLS

• SRv6 (uSID, C-SRH)
• SR Policy Table (SRv6 Path Ingress Node)
• My SID Table (All Segments)
• No SID to IPv6 mapping table
• SRv6+
• SR Policy Table (SRv6+ Path Ingress Node)
• My SID Table (All Segments)
• Segment Forwarding Information Base (SFIB) (All Segments)
• SR-MPLS
• SID to IPv6 mapping table required
SRv6 (uSID, C-SRH), SRv6+, SR-MPLS Tables

Segment Forwarding Information Base (SFIB)
[Segment Type] = Strictly-routed

Appendix

Acronyms
SRv6+
• CRH ... Compressed Routing Header
• SFIB ... Segment Forwarding Information Base
• PSSI ... Per-Segment Service Instruction
• PPSI ... Per-Path Service Instruction
C-SRH
• C-SID ... Compressed Segment Identifier
• C-SRH ... Compressed SRH
• C-Tag ... Compressed Tag

Comparison of SRv6 Extensions uSID, SRv6+, C-SRH

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Similar to Comparison of SRv6 Extensions uSID, SRv6+, C-SRH

Similar to Comparison of SRv6 Extensions uSID, SRv6+, C-SRH (20)

More from Kentaro Ebisawa

More from Kentaro Ebisawa (20)

Recently uploaded

Recently uploaded (20)

Comparison of SRv6 Extensions uSID, SRv6+, C-SRH