From: Mark Lewis (markl11@xxxxxxxxxxx)
Date: Wed Sep 20 2000 - 12:29:41 GMT-3
Right, big question!
Rendezvous Point are a common distribution point for multicast traffic when
using a sparse mode multicast routing protocol (eg. PIM SM/CBT (although
with CBT it has a different name).
With multicast there are three important levels of interaction:
1.Interaction between hosts on subnets and 'local' routers (registration not
of clients (only the last reporter is registered per group),but of multicast
groups (traffic) that hosts on that segment require). This process is
handled by IGMP.
2.There's interaction between switches and local routers via CGMP or IGMP
snooping (registration of multicast clients on the switches so that
multicast traffic is not just flooded (default behavior). This (CGMP/IGMP
snooping) is optional, but recommended.
3.Interaction between routers.
a. Dense mode (eg. DVMRP/PIM DM/MOSPF) : traffic is flooded throughout the
network initially, until 'downstream' routers tell upstream ones that they
don't want the traffic (pruning). Routers use RPF checks to switch over to
SPT (shortest path tree) back to source.
b. Sparse mode: traffic here is not flooded. 'Downstream' routers here
request traffic from the RP intially and then switch over to SPT (shortest
path back to 'real' source (ie. multicast server) when they know where it is
(they find out after they get initial packets from the RP by looking at the
source address of the packets).
It's best to have a few RP candidates on the network (use auto rp instead of
manual rp config on large net.s) for redundancy. Can be in core of net or
close to multcast servers.
Hope that helps,
Mark
>From: "Eddie Parra" <eparra@telocity.com>
>Reply-To: "Eddie Parra" <eparra@telocity.com>
>To: "CCIE Group Study" <ccielab@groupstudy.com>
>Subject: Multicasting Questions...
>Date: Wed, 20 Sep 2000 10:23:34 -0400
>
>Can anyone answer a few multicasting questions. Am I correct in saying
>that
>the RP handles registration for all multicast clients? My other question
>is, where do you place the RP's? Do I need a RP on every segment? Every
>VLAN? Could someone explain this a little better. Thanks...
>
>-Eddie
>
>
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