Re: [foxboro] network storm

  • From: "Hicks, Gaylon F" <gfhicks@xxxxxxx>
  • To: <foxboro@xxxxxxxxxxxxx>
  • Date: Mon, 9 Feb 2009 12:44:08 -0500

Thanks Mike.  I think I have officially reached the limits of my
knowledge.  

But, having never let not knowing stop me from speaking (or typing),
I'll throw this out.  We had the COMEX Multicast Suppession limits on
our network set up 64Kb/sec, and it worked fine, and was pretty much
impervious to a COMEX multicast storm (the silver bullet for I/A
processors).  We upped that to 128 Kb/sec while troubleshooting a
problem that ultimately ended up being a bad ZCP, but based on the
network sniffing we did on our system, 64kb/sec is more than enough
bandwidth for COMEX Multicast for our application.  Your mileage may
vary.

To the best of my knowledge (see "limits" above), the COMEX multicast is
only used when initially opening displays on a workstation, and when
ZCPs/FCMs boot up (not sure about that one).  Otherwise, the COMEX
multicast traffic is really, really, really, low.  But, as Mike stated
below, if the normal COMEX multicast traffic doesn't get through, you
are going to have some issues, primarily with workstations.

Ain't switches fun?

Thanks,
Gaylon



-----Original Message-----
From: foxboro-bounce@xxxxxxxxxxxxx [mailto:foxboro-bounce@xxxxxxxxxxxxx]
On Behalf Of Davis, Mike A
Sent: Monday, February 09, 2009 7:55 AM
To: foxboro@xxxxxxxxxxxxx
Subject: Re: [foxboro] network storm

In response to Gaylon, let me muddy the water a little more. 

"multicast rate limiting policies.  Although it works fine, it doesn't
(or didn't) fall under the umbrella of officially tested
configurations."

Or normal refer to Comix Multicast Suppression (CMS), CMS is based on
internal policy commands of the switch and the multicast MAC addresses
used. The policy commands allows the switch to rate limit the traffic on
ingress ports, only the DFE-Gold and DFE-Platinum switches can support
this function.

Due to the importance of the multicast protocol within the network,
blanket multicast rate suppression is neither recommended nor practical.
However, the Comix Multicast protocol used primarily between the I/A
workstation and Control Processors can be rate limited without a direct
impact on the MESH Network, but this rate limiting must not impede the
performance of I/A communications between the end devices, because of
this concern, the minimum setting is 1Mbps. Since the CMS is based on
internal policy commands of the switch and the multicast MAC addresses
used, only the DFE-Gold and DEF-Platinum switches can support this
function. 

Monitoring of this function when traffic exceeds the rate limit can only
be performed on the DFE-Platinum series switches via the syslog or trap
servers.

This function has been officially tested however when the deployment of
LDP occurred the configurator software tool had limitation on it ability
to deploy both CMS and LDP this has since been corrected and will be
available on the next release rev 3.1.2
 
Thank You
Mike Davis

 
 
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