Questions about multicast replicators
Ahmed A-G Helmy
Wed, 7 Oct 1998 14:44:58 -0700 (PDT)
> I have the following questions about multiclassifier and replicators:
> - Multiclassifier and replicators are (S,G) designed, this means:
> -- If we have (*,G) entries we need to create several replicators in
> place of one.
yes,... unless you change the classifier (and basically the multicast
lookup mechanism) you get S,Gs in the forwarding state ...
currently the pim (or a variant thereof) implementation in ns does
support *,G and it does create corresponding S,Gs for the active sources
[this is how it's implemented in pimd in reality].
> -- Same if we want support masks, in S and/or G.
hmm,.. I haven't tried that (actually I haven't seen any solid proposals
for good aggregation methods for multicast state ! have you ?),... in any
case, the classifier lookup is based on a mask and shift parameters, so I
would presume that supporting S and G masks would be readily natural and
probably not hard to implement.
> - Checking of iif is (S,G) oriented. In the case of protocols without
> notion of source, such as CBT, Multiclassifier upcalls WRONG_IIF each
> time a packet arrives through an interface different to iif. In this
> case, WRONG_IIF must only occurs
> if iif not belongs to the set of interfaces asociated with the entry
> (parent + children)
yes... the iif doesn't have to point to the source,..in pim it points
towards the RP for the shared tree and the src for source specific trees.
Also, there's a hook in the iif check mechanism (by setting it to -1) to
avoid the RPF check altogether ... which may be useful for bidirectional
trees as in CBT, or BGMP... but there's probably a bit more to do for the
complete support of bidir. states.
hope this helps,
> - Add masks in Multiclassifier entries and forward packets using longest
> match prefix?
> - Provide different options for iif checking?
> Any comment will be appreciated
> Guillermo Rigotti
> Computer Sciences Departament
> Universidad Nacional del Centro