Re: [Dyncast] edge capability feedback

[Carsten Bormann <[e-mail]>]

On 12. Mar 2021, at 03:29, Joel M. Halpern <[e-mail]> wrote:
> 
> If the UE had a way to ask an informed server, there would be no need for the UE to have a "significant amount of new logics".
> And we would not have to worry about overloading routing with behavior and data that it does not need.  And we would naturally get the needed stickiness.

As far as I understand dyncast, I see the following two reasons for not simply falling back to an “ask a server” approach:

* Just-send.  See slide 35 on [1].  This assumes that saving that round-trip is a relevant consideration for some applications.  (It is hard to amortize the round-trip when progress (same slide) is needed; of course the client could proactively ask at the start of each new service period — but that creates a constant load.)
* The server may not know.  Even if the server is reached using anycast, it may not have a way to get input from the routing system that is knowledgeable about the specific network environment of the client.  This becomes relevant when the “last mile” provides choices and there is more than one edge server cluster close to the client.

It seems to me that dyncast has not previously been pursued mainly because there weren’t that many applications that could actually benefit from addressing these two considerations.  

Grüße, Carsten

[1] https://github.com/dyncast/ietf110/blob/main/dyncast-ietf110-side-meeting-full-deck.pdf