Broadcast Containment

[dskalish19004]

Good Afternoon. currently we are using Cisco 2950 switches on a Comcast Metro ENS network to several sites. Our one site is configred for a 100mb service. where the others are at 20mb 

we arent certain if it a problem or a symptom. Comcast reports we are exceeding a broadcast containment of 512kb/s  at the 100mb site. clearly the bitrates of some of our audio streamvia various VLANs might exceed this in a cumulative nature. i thought this 512kb/s to be rather low for a fiber network. this threshold is set in their Ciena 3930 switch. 

We will be upgrading to the Cisco 2960s soon  

I cant say with any certainty that a loop is occuring somewhere either  The digital audio transport devices are either Bi directional or uni directional . no multicasting at this time  

We are experiencing packet loss when this threshold is exceeded  

Any feedback is much appreciated  

- Dave

[Joseph W. Doherty]

Disclaimer

The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

Liability Disclaimer

In no event shall Author be liable for any damages wha2tsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.

Posting

So, Comcast is saying you have the full 100 Mbps, or 20 Mbps, per site, but broadcasts are capped at 512 Kbps?  If so, that's a rather curios limitation.  You might ask Comcast, why.

Also, unclear why your other traffic would be affected.  Generally, most forms of traffic, including, to my knowledge, audio and video, don't use broadcast packets.

However, that said, an ENS setup is a great configuration for one site with higher bandwidth, e.g. 100 Mbps to 10 Mbps, to overrun another, or for an aggregate of multiple sites' traffic to overrun another.

Did you purchase and use the different classes of services that Comcast offers?  If so, are you sure you're not over running whatever class (hopefully premium class) caps used by audio and video?

[dskalish19004]

Hi Joseph. thanks for your kind reply. The ENS setup can be a very good solution as i have laid out. i wonder if comcast deployed this without really taking a closer look to the type of traffic we are generating. We are learning alot. Its a service they want to expand to the broadcasters. but i'll be hesitant to recommend anything until we meet head to head. I believe a better managed switch approach will help. we are going to work with their Level 3 support people to monitor broadcast containment while we shed some load. there still is no indication one way or the other that a loop is occuring. i was advised by one expert not to use storm control. now i am not so sure about that. i will leave an update once i get more feedback. We removed one device ( a Harris Intraplex) that is working in one direction that appears to be causing the ports to flood. the theory being that device should be changed to a bi-directional use, rather than to push digital audio in only one direction. 

we do have two tiers. premium and standard. the devices had been working fine in the standard region fine up until recently. we may change the QOS to the premium region   the large capacity site is 70/30 standard/premium. this site is the location of the problem.