fiberman wrote:
Jay,
I changed all the phones to TCP preferred, and that seems to correct most of the issues. Looking at the Broadsoft VVX provisioning guide it seems Broadsoft recommends TCP Preferred for SIP which surprises me. Isn't UDP recommending for real time voice traffic?
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The real-time voice (RTP) is still UDP. SIP signaling is now TCP (if supported, hence "preferred"). The advanatages for SIP over TCP are that it handles fragmentation of large datagrams better and also has fewer issues traversing simple firewalls. The advantage for UDP is that it consumes less overhead. TCP solves some issues particularly when there are large SIP messages that must be fragmented. Of course your SBC and SIP PBX must support it. Both TCP and UDP are specified in the SIP RFC but the default these days is UDP.
Before I made this change I was noticing lots of SIP parse errors being reported on the Adtran, and the Polycom's were saying "please try again" on the screen.
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This is likely due to the multiple line appearances in the key system emulation. As of the last time I checked, Adtran's SIP proxy didn't support TCP although some other parts of the SIP stack do. So your phones are using the basic NAT firewall for SIP. The TA900 series are better at dealing with SIP UDP fragmentation than the 3120 but in corner cases with lots of shared-line appearances going to TCP seems to fix a lot of things.
Now that we are using TCP Preferred we will not be able to utilize Adtran VQM right? Also, should I turn off SIP Proxy if all phones are using TCP Preferred? What firewall settings should be put in place? Should SIP Services still be enabled?
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You can still use VQM, you'll need to select "All RTP" and not just "SIP RTP". This may cause a bump in CPU as there is more to inspect. If the box gets taxed, tweak VQM for less than 100% of calls. Nothing really to change in the firewall as long as you have NAT and Internet connection sharing configured. You're going from the inside out so it should just work. I would leave SIP enabled, it shouldn't hurt anything.
No, I can't seem to get them to drop the key system mentality. Have any advice on how to do so? Is call park/retrieve the solution? They are not willing to buy a 7100 or another PBX, so everything has to be done on the Broadsoft. I just hate to see these Advanced VVX 500's being used for a hosted line key system!
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The customer is always right, even when they're wrong they're still the customer. There are a few situations where a key system makes sense in terms of a warehouse or retail situation where hold-resume from different phones is common. The learning curve for call park is kind of steep for these environments. Shared call appearances and BLF generate a LOT of SIP. It's not just the registrations but the NOTIFY, SUBSCRIBE, and all of the messaging every time a call rings, is answered, or is put on or taken off of hold to change the lights on every single phone. This really doesn't scale well at all.
