Redundancy SID and Merging SID for Redundancy Protection
draft-geng-spring-redundancy-protection-sid-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 replication, elimination and ordering. This document defines Redundancy SID and Merging SID 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. Terminology and Conventions
• 3. Redundancy Protection Introduction
• 4. Redundancy SID
• 5. Merging SID
• 6. IANA Considerations
• 7. Security Considerations
• 8. Acknowledgements
• 9. Normative References
• Authors' Addresses

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 replication, elimination and ordering. This document defines Redundancy SID and Merging SID 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 redundancy protection, which is a network device that could implement packet replication.

Merging Node: the end point of redundancy 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].

3. Redundancy Protection Introduction

The figure shows how to provide redundancy protection in an Segment Routing Domain.

             |                                         |
             |<---------------SR Domain--------------->|
             |                                         |
             |             +------+T2+----+            |
   +---+    +---+        +-+-+          +-+-+        +---+    +---+
   | E1+----| In|--+T1+--+Red|          |Mer|--+T4+--| Eg+----+ E2|
   +---+    +---+        +-+-+          +-+-+        +---+    +---+
                           +-----+T3+-----+

The process of redundancy protection is as follows: 1) The flow is replicated in Red(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.

In this document, we introduces Redundancy SID and Merging SID to implement redundancy protection. The newly defined SIDs apply equally to both SR-MPLS and SRv6.

4. Redundancy SID

Redundancy SID is a variation of binding SID defined in [I-D.ietf-spring-segment-routing-policy]

Redundancy SID indicates the following operations:

• Steering the packet into the corresponding redundancy policy
• Packet replication based on the redundancy policy, e.g., the number of replication copies
• Encapsulate the packet with necessary meta data (e.g., flow identification, sequence number) if it is not included in the original packet

5. Merging SID

Merging SID indicates the following operations:

• Packet elimination: forward the first received packets and eliminate the redundant packets.
• Packet ordering(optional): reorder the packets if the packet arrives out of order

6. IANA Considerations

TBD

7. Security Considerations

TBD

8. Acknowledgements

Thank you for valuable comments from James Guichard and Andrew Mail

9. Normative References

Authors' Addresses