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Re: flow label demultiplexing




El 19/04/2005, a las 16:15, Iljitsch van Beijnum escribió:

On 19-apr-05, at 15:35, marcelo bagnulo braun wrote:

If we want to use the flow label for this we only need to change the flow label sematics every so slightly so the flow label is unique for a set of source/dest locators belonging to the same source and dest hosts rather than source/dest addresses. Not too unreasonable, IMO.

Right, but i guess that what Pekka was pointing out is that, in the case that the locator set are dynamic, you don't know when the locator set will overlap in the future (because an locator that is already present in one context is added to another one in the future), so it is not possible to make sure that the flow id is not repeated in two different contexts whose locator set overlap. Hence the problem.

Well, there are 1048575 possible flow label values so it's not necessary to reuse the same one for a new session all that quickly. The limitation is that the same flow label can't be used for a different session to the same shim-enabled destination host (regardless of address), for sessions to the same source/dest address pair for non-shim-enabled hosts and for sessions to ANY host where the shim-enabled status is unknown. Since presumably, we're going to find out whether a certain correspondent host is shim-enabled or not sooner rather than later, I don't see how this set of limitations can lead to trouble other than the general downside of adding some complexity.



so quoting Pekka's initial mail on the thread:

 - in step 3. above, an implementation could also perform two-tiered
   reservation: first reserve the flow label for any communication,
   but when in the danger of running out, start using it also for
   those destinations that don't belong to the locator set.  This way
   this would not be an issue (albeit difficult to debug) until the
   hosts are so loaded that they're running out of the flow label
   space for their sessions.


seems the reasonable choice if the flow id approach imho

regards, marcelo



Iljitsch