Hi,

When reading RFC8990 and draft-ietf-anima-grasp-distribution, I found RFC8990 
allows Flood Synchronization Message (section 2.8.11) to be *unsolicited* but 
Synchronization Message does not allow so. I guess that's why 
unsolicited_synch-message is defined in section 5.1 in 
draft-ietf-anima-grasp-distribution.

So why not simply allow the synch-message (M_SYNCH) to be sent unsolicitedly 
instead of define a new message type? It looks like more straight forward.
BTW section 5.1 in draft-ietf-anima-grasp-distribution is quite different from 
the rest subsections as it defines a new message type and the rest are for 
objectives. Some re-structure of the subsection titles may make it more 
self-descriptive.

I am trying to figure out what would be the best messages to be used to 
distribute mapping info from IP address/prefix to access control group IDs as 
suggested in draft-yizhou-anima-ip-to-access-control-groups. Both the Objective 
providers (i.e. access authentication point, AAP in this case) and Objective 
consumers (i.e. policy enforcement point, PEP in this case) are supporting the 
same ASA/Objective. However, it would be ideal when the Syn message is flooded 
unsolicitedly, the message is only moving towards the Objective consumers but 
not the other Objective providers. I had thought the selective flooding can be 
leveraged here. However current selective flooding seems not quite for this 
purpose. Consider the following topology, if I understand it correctly, when 
the selective flood flows from node1 to node 2 and then node 3, it would stop 
at node 2 if the matching condition fails at node 2. Then even node 3 meets the 
matching rules, the message would not reach it.

Node 1 (ASA 1) --- Node 2(ASA 2)---Node 3(ASA1)

Come back to the IP prefix to group id mapping information distribute case, 
there might be nodes not supporting this specific ASA/objective in between of 
the objective providers and consumers. It would be expected that the message 
can pass through such intermediate nodes. Certainly, multiple unicast syn 
messages can be used since the nodes supporting this objective would have been 
discovered at the discovery stage. I am wondering if flooding like approach is 
also a good option here.

Thanks,
Yizhou




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