From: D. J. Jones (meganac@xxxxxxxxx)
Date: Fri Jan 04 2002 - 13:43:34 GMT-3
I believe there is a performance impact of token ring mapping of multicast
addresses. According to Beau Williamson (Developing IP Multicast Networks
Volume 1, pp 33-34) "Many Token Ring NICs do not have the capabiity to be
programmed to interrupt the CPU when an arbitrary multicast MAC address is
received. Therefore, the only alternative is to use the all-ones
(0xffff.ffff.ffff)
broadcast MAC address or a functional address for IP multicast to MAC
address
mapping as hown in figure 2.7." Further, on page 34 he states "This means
all
multicast traffic on the ring will cause a Token Ring node's CPU to be
interrupted
for every multicast packet on the ring!"
"In addition to causing this CPU performance impact, the all-into-one
mapping scheme
virtually precludes Token Ring switches from constraining multicast flooding
at the
MAC layer. As a result, Token Ring switches, which operate solely at layer
2, are
powerless to prevent any Token Ring node that joins a multicast group and
begins
receiving multicast traffic from afffecting every other node on the ring."
Bottom line is that you may wish to pursue a course of action that involves
a switched
ethernet environment instead of token ring.
----- Original Message -----
From: "Aiman A. M." <drpower@hotmail.com>
To: <Ron.Kirby@getronics.com>; <ccielab@groupstudy.com>
Sent: Friday, January 04, 2002 3:58 PM
Subject: Multicast over NBMA
> hi all,
> how to do multicasting in token ring enviroment ?, thanx.
>
> Aiman
>
>
> >From: "Kirby, Ron" <Ron.Kirby@getronics.com>
> >Reply-To: "Kirby, Ron" <Ron.Kirby@getronics.com>
> >To: ccielab@groupstudy.com
> >Subject: Multicast over NBMA
> >Date: Fri, 4 Jan 2002 10:44:23 -0500
> >
> >All,
> >
> >I am working with multicasting over a frame cloud. R1 has a multipoint
> >subinterface connected to R3 and R4 which are using physical interfaces
> >(basic hub and spoke design). I am using EIGRP and have split horizon
> >turned
> >off at the hub (R1). The routing table is fine and everything can be
> >pinged.
> >
> >Now, Pim is running on all routers and dense mode on all interfaces. I
> >have
> >pim neighbor relationships between R1 and R3 and R1 and R4. Here's the
> >problem. R1 (the hub) has an mroute entry for the multicast source off
of
> >R3 as shown below:
> >
> >**********************************************
> >r1#sh ip mroute 234.5.6.7
> >IP Multicast Routing Table
> >Flags: D - Dense, S - Sparse, C - Connected, L - Local, P - Pruned
> > R - RP-bit set, F - Register flag, T - SPT-bit set, J - Join SPT
> > M - MSDP created entry, X - Proxy Join Timer Running
> > A - Candidate for MSDP Advertisement
> >Outgoing interface flags: H - Hardware switched
> >Timers: Uptime/Expires
> >Interface state: Interface, Next-Hop or VCD, State/Mode
> >
> >(*, 234.5.6.7), 00:12:31/00:02:59, RP 0.0.0.0, flags: D
> > Incoming interface: Null, RPF nbr 0.0.0.0
> > Outgoing interface list:
> > Ethernet0/0, Forward/Dense, 00:12:09/00:00:00
> > Serial0/0.2, Forward/Dense, 00:12:31/00:00:00
> > Serial0/0.1, Forward/Dense, 00:12:31/00:00:00
> >
> >(192.168.30.2, 234.5.6.7), 00:02:46/00:00:24, flags: PT
> > Incoming interface: Serial0/0.2, RPF nbr 131.5.20.3
> > Outgoing interface list:
> > Serial0/0.1, Prune/Dense, 00:02:46/00:00:19
> > Ethernet0/0, Prune/Dense, 00:02:46/00:00:19
> >***************************************************
> >
> >
> >As you can see, S0/0.2 is not in the outgoing interface list, and I
figure
> >it is because the router does it's RPF check and finds that the upstream
> >interface is S0/0.2 and therefore S0/0.2 is not a candidate for flooding
> >the
> >multicast data. So how do I get the multicast traffic to a host on R4?
I
> >believe my possibilities are a tunnel between R1 and R3 and R1 and R4 for
> >multicast purposes, or moving to frame-relay P-to-P subinterfaces. I
have
> >also worked with the NBMA mode command, but it doesn't look as if it is
> >designed for this. Is there a command line solution available?
> >
> >Thanks
> >Ron
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