Re: Thoughts about layering multi-addressing

[Pekka Nikander <pekka.nikander@nomadiclab.com>]

> And *if* it turns out that we need the ability for the app on A to  
> affect how B sends it packets, then this can be viewed as a locator  
> pair preference mechanism which is layered on top of the shim  
> proper. There isn't a need to have different contexts to do this,  
> and it doesn't help because the granularity would be finer than the  
> ULID pair.

Agreed.

> Could this be something passed down from the ULP (prefer a given  
> locator pair) for ULPs that are aware of multiple locators? Or a  
> "locator pair preference sub-layer" for other ULPs?

Something like the following?

                 +----------------+  +--------------+
                 | SHIM unaware UL|  | SHIM aware UL|
                 +----------------+  +--------------+
                         ^                   ^
                         | ULIDs only        |
                         v                   |
     Admin       +----------------+          |
     interface-->| "Policy" subL  |          | ULIDs+locators
                 +----------------+          |
                         ^                   |
                         | ULIDs+locators    |
                         v                   v
                 +----------------------------------+
                 |               SHIM               |
                 +----------------------------------+
                                  ^
                                  | locators only


The admin interface could then used to implement policy negotiation
on the top of the basic SHIM, at some later point, if needed.  SHIM
aware ULPs (like SCTP++?) could implement similar functionality
themselves.

--Pekka Nikander