Network Working Group X. Geng
Internet-Draft M. Chen
Intended status: Experimental Huawei
Expires: September 10, 2020 March 09, 2020
SRH Extension for Redundancy Protection
draft-geng-spring-redundancy-protection-srh-00
Abstract
Redundancy protection is a method of service protection by sending
copies of the same packets of one flow over multiple paths, which
includes packet replicaiton, elimination and ordering. This document
defines SRv6 header(SRH) extensions to support redundancy protection.
Requirements Language
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 .
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology and Conventions . . . . . . . . . . . . . . . . . 2
3. Redundancy Protection Requirement Analysis . . . . . . . . . 3
4. SRH Extensions for Redundancy Protection . . . . . . . . . . 3
4.1. Option 1: seperated TLVs for flow identification and
sequence number . . . . . . . . . . . . . . . . . . . . . 4
4.2. Option 2 unified TLV for flow identification and sequence
number . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
6. Security Considerations . . . . . . . . . . . . . . . . . . . 5
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
8. Normative References . . . . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
Redundancy protection is a method of providing 1+1 protection by
sending copies of the same packets of one flow over multiple paths,
which includes packet replicaiton, elimination and ordering. This
document defines SRv6 header(SRH) extensions to support redundancy
protection.
2. Terminology and Conventions
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].
Redundancy Node: the start point of redudancy protection, which is a
network device that could implement packet replication.
Merging Node: the end point of redudancy protection, which is a
network node that could implement packet elimination and
ordering(optionally).
Editor's Note: Similar mechanism is defined as "Service Protection"
in the [RFC8655]. In this document, we define a new term "Redundancy
Protection" to distinguish with other service protection method.
Some of the terms are the similar as [RFC8655].
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3. Redundancy Protection Requirement Analysis
The figure shows how to provide redundancy protection over SRv6.
| |
----IPv6--->|<---------------SRv6 Domain------------->|<----IPv6---
| |
| +------+T2+----+ |
+---+ +---+ +-+-+ +-+-+ +---+ +---+
| E1+----| In|--+T1+--+Red| |Mer|--+T4+--| Eg+----+ E2|
+---+ +---+ +-+-+ +-+-+ +---+ +---+
+-----+T3+-----+
As the figure shows, an IPv6 flow is sent out from the end station
E1. The packet of the flow is encapsulated in an outer IPv6+SRH
header in the Ingress(In) and transported through an SRv6 domain. In
the Egress(Eg), the outer IPv6 header+SR of the packet is popped, and
the packet is sent to the destination E2.
The process of redundancy protection is as follows: 1) The flow is
replicated in Rep(Redundancy Node); 2) Tow replicated flows go
through different paths till Mer (Merging Node); When there is any
failures happened in one the path, the service continues to deliver
through the other path without break; 3) The first received packet of
the flow is transmitted from Mer (Merging Node) to Eg(Egress), and
the redundant packets are eliminated. 4) Sometimes, the packet will
arrive out of order because of redundancy protection, the function of
reordering may be necessary in the Merging Node.
This document defines Flow Identification and Sequence Number in
Segment Routing Header(SRH) as an extension of the current
draft[I-D.ietf-6man-segment-routing-header] to support redundancy
protection.
Flow Identification is used to distinguish flows and Sequence Number
is used to distinguish packets in the same flow when doing packet
merging and ordering.
4. SRH Extensions for Redundancy Protection
Flow Identification and Sequence Number could be defined in SRH
optional TLV.
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4.1. Option 1: seperated TLVs for flow identification and sequence
number
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 | Length | RESERVED |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RESERVED | Flow Identification |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where:
o Type: 8bits, to be assigned by IONA.
o Length: 8 octets.
o RESERVED: 28 bits, MUST be 0 on transmission and ignored on
receipt.
o Flow Identification: 20 bits, which is used for identifying
redundant protection flow.
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 | Length | RESERVED |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|RESERVED| Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where:
o Type: 8 bits, to be assigned by IONA.
o Length: 8.
o RESERVED: 20 bits. MUST be 0 on transmission and ignored on
receipt.
o Sequence Number: 28 bits, which is used for indicating sequence
number of the redundant protection flow.
4.2. Option 2 unified TLV for flow identification and sequence number
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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 | Length | Flow Identification |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RESERVED |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where:
o Type: 8bits, to be assigned by IANA.
o Length: 8 octets.
o Flow Identification: 20 bits, which is used for identifying the
redundant protection flow.
o Sequence Number: 28 bits, which is used for indicating sequence
number of the redundant protection flow.
o Reserved: 32 bits. MUST be 0 on transmission and ignored on
receipt.
5. IANA Considerations
TBD
6. Security Considerations
TBD
7. Acknowledgements
Thank you for valuable comments from James Guichard and Andrew Mail
8. Normative References
[]
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.
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[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>.
[RFC8655] Finn, N., Thubert, P., Varga, B., and J. Farkas,
"Deterministic Networking Architecture", RFC 8655,
DOI 10.17487/RFC8655, October 2019,
<https://www.rfc-editor.org/info/rfc8655>.
Authors' Addresses
Xuesong Geng
Huawei
Email: gengxuesong@huawei.com
Mach(Guoyi) Chen
Huawei
Email: mach.chen@huawei.com
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