[spring] follow-up answer on sr-redundancy-protection

"Yangfan (IP Standard)" <shirley.yangfan@huawei.com> Tue, 27 July 2021 07:09 UTC

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From: "Yangfan (IP Standard)" <shirley.yangfan@huawei.com>
To: spring <spring@ietf.org>
CC: "draft-geng-spring-sr-redundancy-protection@ietf.org" <draft-geng-spring-sr-redundancy-protection@ietf.org>
Thread-Topic: follow-up answer on sr-redundancy-protection
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Date: Tue, 27 Jul 2021 07:09:14 +0000
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Subject: [spring] follow-up answer on sr-redundancy-protection
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Due to limited presentation time today, I’d like to give the clarification to the questions brought by Greg at IETF 110 and 111.

From today’s meeting minutes:
Suggest to analyze why this is more beneficial than just 1+1 protection when you select the working source and protection source and do the switchover not per packet but source.

I first compare the two mechanisms in case people need background.
The common part of 1+1 protection and redundancy protection is that source duplicates the packets and sends two or multiple replicas via different disjoint paths.
The difference is,
regarding 1+1 protection, receiver only receives one copy of traffic from either path, which is determined by a local state machine on receiver.
regarding redundancy protection, two copies of traffic from both paths are received by receiver, and receiver eliminates the redundant packets per packet.

The benefit of redundancy protection is obvious. Since 1+1 protection needs switchover either at source or sink, when there is a failure on either path, the failure detection and switchover could cause the packet loss. With redundancy protection, failures on either path will not result in any packet loss, which brings significant value to service needs ultra reliable transmission.

Thanks again for the discussion.