[spring] follow up explanations on I-D.geng-spring-redundancy-policy

["Yangfan(Fan,IP Standards)" <[e-mail]>]

Hi SPRING,

Thank you for the comments to I-D.geng-spring-redundancy-policy. Some follow-up explanations to the questions in meeting.


1.       Redundancy at Candidate path level or SID-List level?
There are two reasons to define the redundancy paths at SID-List level. Firstly, looking at the use cases, e2e load balance and redundancy protection has very limited chance to be used together. If there is a partial network needs load balancing, loose path can be used. Secondly, there is a scenario shown in the slide, (due to the limited time I didn't emphasize and explain it in the session), where the redundancy protection is protected by the third best effort path in green. It actually provides different levels of protections to the service.

As discussed in meeting, either way is doable for redundancy policy. IMHO the choice is more dependent on the scenarios and requirements.


2.       Redundancy SID acts as the BSID of Redundancy Policy
In I-D.ietf-spring-redundancy-protection, Redundancy SID is defined as the variation of Binding SID (BSID) and the operations defined as:
Redundancy Segment is associated with service instructions,
   indicating the following operations:
   *  Steers the packet into the corresponding redundancy policy
   *  Encapsulates flow identification and sequence number in packets if
      the two information is not carried in packets
   *  Packet replication and segment encapsulation based on the
      information of redundancy policy, e.g., the number of replication
      copies, an ordered list of segments with a topological instruction
Thanks again for the comments.
Best regards,
Fan