MCU4500 series and Polycom HDX bandwidth interop

[Bob Fitzgerald]

Hello!

A customer brought this to my attention and I haven't been able to determine a good reason for it yet.  First, here are the parameters;

- MCU4515 running 4.4(3.49)

- Polycom HDX (a 7000 and an 8000) running 3.03

- MCU and endpoints registered to a gatekeeper, no bandwidth restrictions (they say)

- calls made at 1.2M

- MCU calls endpoints, H323

When the HDX endpoints connect, the incoming bandwidth to the MCU is half of the outgoing bandwidth to the HDX.  I can find no setting on the MCU that has any effect on this.  Default bandwidth settings on the MCU (inbound and outbound) are set higher than the actual call rate.

I have tried testing with a MCU4510 running 4.4(3.49) and two Cisco endpoints (EX90 and C90), endpoints registered to a VCS and the MCU unregistered.  The call rate stays even, inbound and outbound. 

Is there any unpublished MCU interop data that has some mention of this issue?  The customer says this was not an issue when the MCU was at 4.2(1.50).

Thanks!

[Paulo Souza]

Hi Bob,

I think this tip can help you:

http://www.cisco.com/en/US/docs/telepresence/infrastructure/articles/mcu_low_frame_rate_high_resolution_endpoint_kb_152.shtml

Regards

Paulo Souza

Please rate replies and mark question as "answered" if applicable.

[Bob Fitzgerald]

Hi Paulo,

Thanks for the reply.  I don't this this is quite the same.  In this instance, there are only the two endpoints (the HDX7000 and the HDX8000) in the conference, viewing each other in full screen.  There shouldn't be any flow control to reduce the call rate becasue a full screen image is needed from each endpoint.  Also, I think that page needs a little updating, since the setting it references is by default enabled when the Media Ports on the MCU are set to HD, which they are in this case.

Thanks!

[Paulo Souza]

Hi Bob,

Well, this is the only parameter I can point related to incoming bandwidth from Polycom HDX endpoints, this prevents the MCU from reducing incoming bandwidths. I guess you could try to disable this parameter anyhow, you have nothing to lose  =)

I also performed a search to see if there is any bug or known limitation, but I didn't find anything.

Regards

Paulo Souza

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[Patrick Pettit]

HI Bob.  If you disable content on MCU, do you see the TX and RX the same here?

Just Curious....

VR

P2

[Bob Fitzgerald]

Hey there Patrick,

I'll have them try it and let you know.

Thanks!

[Patrick Pettit · Accepted solution]

Thanks Bob.  The reason why this is occurring now is because MCU had some previous issues in honoring bit rates etc.  This was fixed in MCU 4.4 under CSCuh81255.  

When HDX calls, it always Opens LC for ExtendedVideoCapability at the onset of any call.  This leaves MCU to split the BW in halve for main and content when the system wants to send content.  Since HDX already opened content channel towards MCU, MCU must reserve the amount of BW for content when the HDX decides to send and to not exceed 1.25 meg in your case. 

Hopefully this makes sense to ya...

Let me know if it doesn't. 

VR

P2

[Bob Fitzgerald]

Well, I understand what you're saying, but whether or not that kind of behavior makes sense..... 

Haven't heard back from customer yet, but I give you a heads up when I do.

Thanks!

[Patrick Pettit]

Hi Bob. Im pretty sure if he removes content, it will be even. The reason we halve this is because we have to allocate BW for content as well. Since Polycom likes to open duo channel early to make it ready, MCU has to be ready to allocate it and go. This bug referenced here, the MCU didnt honor the default BW, and it caused problems with some customers.

For most of our endpoints, we dont open duo until its requested to do so from the endpoint. Once endpoint opens or requests to send content, MCU will flow main channel to half to allow other half for duo. Once our systems stop duo, we close channels, and MCU re-flows main video back to the bit rate requested.

Hope this clears things up a bit.

VR
P2

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[Bob Fitzgerald]

Hi Patrick,

Sorry, I did understand the first time, I was just goofing a little.  I did hear back from the customer any they said that yes indeed, disabling Content allowed full bandwidth in both directions. 

Thanks!