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North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical sparse vs dense and multicast
[email protected] wrote: | and are you suggesting that dense-mode (blindly distributing), to coin the | term, is more efficient than say, sparse-mode (multicast?) .. not even in your You are misusing two reasonably well-known terms used in the IP multicast world today. You could easily argue that the PIM use of "sparse" and "dense" is gross and in some way wrong, however they are understood to be very different from dense = "blindly distributing" and "sparse" = "undefined but maybe multicast". In particular, in PIM [DEFJLW 94] a sparse group is one in which only a few widely-scattered receivers have joined a given group, while a dense group is one in which most multicast routers are likely to have at least one receiver joined to the group. The sparseness vs denseness of a group helps one decide if flood-and-prune is efficient or whether it is more efficient for an explicit join towards the root of the [local-]spanning tree to succeed before traffic is sent. Doing the latter on a dense group obviously, can result in a join implosion towards the [local] root of the spanning tree, while doing the former on a sparse group results in the arrival of lots of unnecessary traffic prior to the issuance of [lots of] prune messages. "dense-mode" and "sparse-mode" are PIM terms: with PIM any group can be declared sparse or dense. The use of "ip pim sparse-mode" etc. as an interface command in IOS is often confusing. Making the terms worse by further overloading them is unhelpful. | -danny (who won't waste any additional time in this thread) That's probably wise. Sean.
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