3120 - SIP Proxy Transparent - Breaks BLF (UDP fragmentation)

[Anonymous]

Hey everyone,

We are testing a NetVanta 3120 with transparent SIP proxy.  Polycom phones behind it, pointed directly to our SBCs.

I noticed that when the Polycom phones are set up for Busy Lamp Fields _and_ UDP signaling, the system fails to process fragmented SIP UDP packets.  If I disable transparent proxy, the Polycom receives BLF correctly.

I can also change the Polycom to use TCPpreferred - this works by simply by-passing the ALG (which is in errata for the release notes).  The goal is to have Voice Quality Monitoring working, with Polycom phones using BLF.

If I go TCP, then VQM stops reporting stats

If I go UDP, then BLF fails, but VQM works

The NV3120 is currently running R10.4.0.E (we've tested several older releases as well).

If we put the Polycom phones behind a TA900 system, the BLF works as UDP with VQM.

The code we use is simply:

  no ip firewall alg sip

  ip access-list extended sip-acl

  ip sip

  ip sip udp 5060

  ip sip tcp 5060

  ip sip proxy

  ip sip proxy transparent

  ip rtp quality-monitoring sip

Has anyone seen this issue before? 

In debug mode (debug sip strack level error) we see the following errors:

23:52:56.942 SIP.STACK ERROR  TRANSPORT    TransportUdpEventCallback - sock 42: The UDP buffer is not big enough.

23:52:57.993 SIP.STACK ERROR  TRANSPORT    TransportUdpEventCallback - sock 42: The UDP buffer is not big enough.

23:52:59.917 SIP.STACK ERROR  TRANSPORT    TransportUdpEventCallback - sock 42: The UDP buffer is not big enough.

23:53:03.917 SIP.STACK ERROR  TRANSPORT    TransportUdpEventCallback - sock 42: The UDP buffer is not big enough.

[Anonymous · Accepted solution]

jessiebryan - Thank you for posting your question on the forum. Unfortunately, the SIP proxy on the NetVanta 3120 does not support packets larger than 4K bytes and is unable to support more than 4 BLFs (Busy Lamp Fields). This is the reason you are seeing the SIP Stack error when you use SIP UDP signaling. There are AOS products available that are have an enlarged SIP proxy buffer size. If you would like to find out which products support this, I suggest contacting Adtran Application Engineers. You can reach them in the following way:

- Sending an email to applications.engineer@adtran.com

- Calling 888-423-8726

- Opening a webticket using the following link: https://www.adtran.com/openacase

Please do not hesitate to let us know if you have any questions.

Thanks,

Noor

[Anonymous]

-

I went ahead and flagged this post as “Assumed Answered.”  If any of the responses on this thread assisted you, please mark them as either Correct or Helpful answers with the applicable buttons.  This will make them visible and help other members of the community find solutions more easily.  If you still need assistance, I would be more than happy to continue working with you on this - just let me know in a reply.

Noor

[Anonymous]

I went ahead and flagged the "Correct Answer" on this post to make it more visible and help other members of the community find solutions more easily. If you don't feel like the answer I marked was correct, feel free to come back to this post and unmark it and select another in its place with the applicable buttons.  If you still need assistance, we would be more than happy to continue working with you on this - just let us know in a reply.

Thanks,

Noor

[Anonymous]

Noor,

Can you post which products do support this large buffer size? What is the 4 BLF limit? Is that 4 contacts, four phones, or what?

[Anonymous]

fiberman - In general, a BLF (busy lamp field) refers to a line which shows the status of other user phones, voicemail boxes, etc., that are connected to the same PBX.

As far as which products support the larger buffer size, it might be easier to list which products are limited to the 4K buffer:

- NetVanta 3120

- NetVanta 3130

- NetVanta 3200 series

- NetVanta 3300 series

At the time of this post, all other AOS products that support the SIP proxy should support a larger SIP buffer.

Thanks,

Noor

[jayh]

Noor, do you know if this is a hardware/ASIC limitation or is it possible that a future AOS will allow a larger buffer on these devices?

[Anonymous]

- It is due to a hardware limitation so the sip proxy buffer will not be increased for those platforms.

Thanks,

Noor