All things related to multicast

[jf <>]

Another thing to check is to make sure your multicast traffic is staying 
in the same transmit queues.  If you are policing and remarking DSCP, 
you will want to make sure all traffic toward that multicast address 
receives the same color.

Ying Zhang wrote:
> Thanks for all the replies. To answer all the questions, in case it's 
> helpful for other people.
>  
> In the test lab, we have three clients and one server on a Nortel 
> ERS5510 switch with all gig-uplinks. Unicast take 30 minutes and 
> multicast takes 75 minutes. In the real environment with 30 clients, 
> unicast takes 38 minutes while multicast take 3 hours 5 minutes. We found:
>  
> - there is no speed mismatch;
> - no difference with/without IGMP ;
> - very limited configuration on Novell server and client concerning 
> mcast, like bandwidth cap, buffer size, request missed packet etc.;
> - in the imaging process, 74 bytes control packets really slow things 
> down. sniff program can't interpret it and no document found on this. We 
> think it's the application causing the slowness.
>
>     ----- Original Message -----
>     *From:* Ying Zhang 
> <mailto:>
>     *To:* wg-multicast 
> <mailto:>
>     *Sent:* Tuesday, May 06, 2008 10:17 AM
>     *Subject:* Lab imaging using multicast
>
>     Hello all,
>      
>     In our university, we using Novell ZENworks preboot services to
>     image thousands of lab computers. We found if use unicast to do
>     imaging, it takes about 30 minutes for each client, while using
>     multicast takes hours to image a lab with 20+ machines. And the time
>     increases proportionally with the number of machines. What is
>     strange about this is it takes a lot longer to do multicast, no
>     matter how many clients are being imaged.
>      
>     The server and clients are on the same VLAN. So no multicast routing
>     is involved. IGMP is enabled on the switch. It uses group address
>     231.164.242.170. Just wondering if any other universities have
>     similar experience and what could be done on the network side to
>     improve the performance. Any help is appreciated.
>      
>     Ying
>     UNB