All things related to multicast

[Bruce Curtis <>]

  Some switches have a feature that can limit broadcast and/or  
multicast traffic.

  We once had a similar problem with some older Nortel 450 switches,  
once we set them to not limit multicast packets/traffic things  
returned to normal.





  The fifth post on this page (4th reply) is from a nearby  
University.  They saw a similar problem, if I recall correctly when  
they talked to our PC support folks here our folks saw the same  
problem and decided it must be a Zen bug.

http://forums.novell.com/novell-product-support-forums/zenworks/desktop-management/zw-desktop-management-7x/zdm7-imaging-netware-windows-servers/224413-slow-multicast-fast-unicast.html


  Here are some other examples of other folks seeing the same problem.




http://forums.novell.com/novell-product-support-forums/zenworks/desktop-management/zw-desktop-management-7x/zdm7-imaging-netware-windows-servers/299487-slow-multicast.html



http://forums.novell.com/novell-product-support-forums/zenworks/desktop-management/zw-desktop-management-7x/zdm7-imaging-netware-windows-servers/302334-slow-multicast-again.html

http://forums.novell.com/novell-product-support-forums/zenworks/desktop-management/zw-desktop-management-7x/zdm7-imaging-netware-windows-servers/325499-very-slow-multicast.html


http://forums.novell.com/novell-product-support-forums/zenworks/desktop-management/zw-desktop-management-7x/zdm7-imaging-netware-windows-servers/224567-slow-multicast-sessions.html


http://forums.novell.com/novell-product-support-forums/zenworks/desktop-management/zw-desktop-management-7x/zdm7-imaging-netware-windows-servers/224554-slow-multicast.html



http://forums.novell.com/novell-product-support-forums/zenworks/desktop-management/zw-desktop-management-7x/zdm7-imaging-netware-windows-servers/224413-slow-multicast-fast-unicast.html




On May 8, 2008, at 12:48 PM, 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
> To: wg-multicast
> 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


---
Bruce Curtis                         

Certified NetAnalyst II                701-231-8527
North Dakota State University