Subject: RE: packet loss between mbone2.UU.Net & SanFrancisco.mci.net

From: Arlie Davis <[email-masked]>
Date: Mon, 17 Feb 1997 10:00:39 -0500

We are using Ciscos to connect to the MBONE.  Our up-stream provider is
using mrouted.  The first tunnel from our provider terminates at a Cisco
7000 running 11.0(10).  After some configuration dinking, I've found
Cisco's implementation to be solid and well-behaved.  (The biggest
problem was that multicast fast switching had to be disabled for
everything to work.)

A quick verbal sketch of our network:  Network provider running mrouted
to Cisco 7000 #1.  This machine has several local-area networks which
use multicast.  This machine also has tunnels to several LANs using
mrouted.  Also, this machine has a GRE tunnel to Cisco 7000 #2.  (All of
the tunnels are required because intermediate routers do not support
multicast routing.)  This machine has many local area interfaces which
use multicast, as well as a few mrouted tunnels hanging off of it.

Until recently, the first 7000 ran with a full DVMRP table from the
global MBONE.  Recently, however, I have changed this so that the router
does not accept any routes whatsoever from the MBONE and as a static
default mroute pointing toward the tunnel connected to our up-stream
provider.  Also, on all of the down-stream tunnels and interfaces on
this router, I am using the "ip dvmrp default-information only".  The
net effect of this configuration is that each router in the distribution
tree has a DVMRP table that contains only the network addresses of those
networks below it on the tree.  This makes my network completely immune
to the massive route fluctuations so common in the MBONE.  I highly
reccomend it.

This only works if your multicast routing topology is a tree.  Anywhere
where you have loops, you must not use "ip dvmrp default-information
only"; just turn this off and let DVMRP do its thing.  If you have a
tree structure below a loop (even if it is just a single branch) you can
use the default-information option again.

All of this works very well.  I'm Happy.

I'm going to experiment soon with Ascend's IGMP proxy support.  The
first support for the Pipeline 50s was just released; we have a lot of
these in the field.  I'll post a summary soon.

-- arlie

>-----Original Message-----
>From:	Dave Hayes [SMTP:[email-masked]]
>Sent:	Sunday, February 16, 1997 4:46 PM
>To:	Peter Berger
>Cc:	[email-masked]
>Subject:	Re: packet loss between mbone2.UU.Net & SanFrancisco.mci.net 
>
>Peter Berger writes:
>> At NANOG, at least one Large Provider Who Shall Remain Nameless
>> indicated in conversation that they had tried using native multicast
>> on Cisco IOS (I believe version 11.2, though I wouldn't swear to it)
>> and encountered performance degradation in (unicast) packet forwarding
>> sufficient to convince them to immediately revert to tunneling.
>
>Gee, I'd like to hear from people who do NOT work for Cisco (sorry
>guys), who are using Cisco's version of mrouting (PIM?), AND who are
>getting a tunnel to the MBONE through a UNIX mrouted daemon. If any of
>these people exist, that's a datapoint. Their collective opinions are
>another. I'd sure like to see both these points.
>
>> That's all I meant.  And I am -certainly- not implying that there is
>> any other router vendor that I am aware of that does native multicast
>> better. 
>
>Er...Is there another vendor who even does native multicast?
>------
>Dave Hayes - Altadena CA, USA - [email-masked] 
>Freedom Knight of Usenet - http://www.jetcafe.org/~dave/usenet
>
>    "They that can give up essential liberty to obtain a little temporary 
>    safety deserve neither liberty nor safety."        -Benjamin Franklin

---

From: Paul Gray <[email-masked]>
Date: Mon, 17 Feb 1997 14:38:31 -0500

Hi,

What is "Ascend IGMP proxy support"? Does this just forward IGMP
multicast messages to a multicast router for processing? Any details
would be appreciated.

Thanks,
Paul