All things related to multicast

["Timothy P Shortall" <>]

I ran into two issues that may be relevant to the discussion.  One, although
many of my switches supported igmp snooping, some of the switches didn't.
With those switches the multicast traffic reverted back to broadcast and the
performance, as one would expect, dropped substantially.  After configuring
cgmp on the layer 3 interfaces performance improved.  The other issue
involved RealNetworks back-channel multicast streaming.  We had a few layer2
firewalls between the servers and the clients, and when the clients
attempted to obtain streams the traffic returning from the server appeared
as new streams and were blocked and the streams would rollback to HTTP, TCP,
or UDP streams.  The data ports and multicast addresses in the RTSP packets
were not read.  After opening a few ports and a few multicast addresses all
worked as expected.

In short check the igmp/cgmp issue, and the firewall issue.  Hope it helps.

Regards,
 
Timothy P. Shortall
University of Maryland
Networking & Telecommunications Services
301.405.2994

-----Original Message-----
From: David Farmer 
[mailto:]
 
Sent: Thursday, September 01, 2005 3:38 PM
To: Prashant Chopra; 

Cc: 

Subject: RE: Multicast QoS

Do you have reason to believe the packet loss is due to congestion?  
Like the interfaces are really busy, or you have queues building on 
your routers, etc...   If not then QOS might not be an issue, it may be 
more fundamental problem.

By leaf nodes you mean client subnets off a router?  What are you 
using for a router, and what code level?  I assume you are doing PIM 
Sparse Mode, etc...  Don't forget about something as simple as duplex 
mis-match, it can cause all kinds of weird problems, and TCP can 
mask it well.



On 1 Sep 2005 Prashant Chopra wrote:

> Colleagues,
> 
> Problem Statement 
> We have 6 multicast streams running at 1.6 Mbps. Clients connected to
> the leaf nodes are receiving really bad signal - very bad that there
> are more lost packets than received packets. Unicast works okay -
> transport is TCP not UDP. With Multicast, at a single hop from the
> server, clients receive everything just fine - no packet loss. This
> indicates that server is sending all the packets. But at the leaf
> nodes, things fall apart.
> 
> Question to Everybody
> > Do any of you have any experience of best practices with ToS
> > settings on
> the streaming server (Microsoft) and/or QoS settings on the networking
> side(Cisco)?
> 
> Our Troubleshooting Path
> We are doing some troubleshooting by trying out RTSPU to find out if
> there is a generic UDP issue instead of a Multicast UDP issue. This
> won't help much in resolving the issue, but might help isolate the
> scope of the problem.
> 
> Regards,
> Prashant Chopra
> Chief Architect
> CampusEAI Consortium
> 1940 East 6th Street, 11th Floor
> Cleveland, OH 44114
> Tel:  216.589.9626
> Mobile: 216.402.4505 
> Fax:  216.589.9639 
> Conference Line: 319.643.7750  Pin: 117423#
> www.campuseai.org 
> 
> 
> -----Original Message-----
> From: Alan Crosswell 
> [mailto:]
>  
> Sent: Wednesday, August 31, 2005 7:18 PM
> To: Prashant Chopra
> Subject: Re: Multicast QoS
> 
> Nope.  You could send your question to 
> 
> though /a
> 
> Prashant Chopra wrote:
> > Alan,
> > 
> >  
> > 
> > I was wondering if you are familiar with anyone that is
> > knowledgeable about Multicast QoS.
> > 
> >  
> > 
> > Regards,
> > 
> > Prashant Chopra
> > 
> > //Chief Architect//
> > 
> > **CampusEAI Consortium**
> > 
> > 1940 East 6th Street, 11th Floor
> > 
> > Cleveland, OH 44114
> > 
> > Tel:  216.589.9626
> > 
> > Mobile: 216.402.4505
> > Fax:  216.589.9639
> > Conference Line: 319.643.7750  Pin: 117423#
> > www.campuseai.org <http://www.campuseai.org/>
> > 
> >  
> > <mailto:>
> > 
> >  
> > 
> 
> 



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