Remote Office Phone Latency Issues

I have been trying to troubleshoot issues at our remote office where the phones latency seems to be running high leading to intermittent quality issues during phone calls. I’ve tried everything from replacing the infrastructure (switches, cables) to testing on another FreePBX box, to going through Site-to-Site VPN, and over the public IP. Here are the relevant details:

PBX Firmware: 3.211.63-9
Asterisk (Ver.
SIPStation for trunks (Averages 80ms)

T1 at Main Office dedicated to phone/server traffic (SIP, RTP)
T1 at Branch Office dedicated to phone traffic (SIP, RTP)
Sonicwall NSA 220 at each branch with Site-to-Site VPN

30 Phones (24 at Main Branch, 6 at Remote)
Remote Office Phones are:
(4) Polycom 501
(1) Polycom 601
(1) Polycom Soundstation behind a Linksys PAP2T

Running a ping or traceroute from one office to the other is almost always between 20-30ms. Very rare packet loss after replacing infrastructure.

Main Branch Phone Latency averages 20-40ms, Phone quality is perfect and without issue.
Remote Branch Phone Latency averages 85-125ms, Phone calls experience brief drops of audio, muffled sounds, general jitter issues.

Something very interesting though, the Polycom Soundstation that sits behind the Linksys PAP2T runs right at about 42ms latency on average and works fine. No issues whatsoever with it.

As mentioned above, connecting over the Site-to-Site VPN shows absolutely no improvement over going across the public IP.

This issue has been the bane of my existence for the last few months now and I cannot express how grateful I would be for help in resolving it. Look forward to hearing your ideas! Thank you.


EDIT: Forgot to add, phones are all using G.711
Have considered trying G.729 but felt like something else was at play here besides the codecs.

subtle bump! :stuck_out_tongue:

Just an update: the quality issues can only be heard on our end. Outside callers do not hear any issues and the quality sounds perfect to them. Scouring the net now because I feel like I’ve seen the cause of this issue somewhere out there.

If anyone has any thoughts feel free to chime in, otherwise this thread is just a lonely journal entry :stuck_out_tongue:

Any update on this issue? It sounds basically exactly like what’s happening with my system. One of our “branches” is located about 100 yards from our main office but isn’t hooked into our local network because it was cheaper just to have the ISP do another drop in. But all of the phones are somewhere in the 2-3s range on latency, making them drop in and out. Other branches, ones hundreds of miles away, are running 50s latencies. I’ve been guessing its the router but no telling.

It ended up being a combination of things that helped resolve it. I’ll warn you right now the majority of the issues originated in the router/firewall. Our company uses Sonicwall firewalls, which although they are easy to use, are not actually very friendly with SIP and PBX systems. Lots of little issues and quirks that you have to work out with the NAT and access rules.

Other causes were the older model Polycoms which don’t play well with that particular firewall, had to adjust their codecs to G.729 and purchase the necessary licenses for that. Now all my branch office phones are running on G.729 and that helped significantly.

Also, several of the branch office Polycoms were replaced with Yealinks which have not had any issues whatsoever. They just work. No quality issues so far.

I’m having trouble remembering but I know there were a few other significant changes I had to make to get things just right. What I mentioned above though would be a good starting point. Once again, if there’s anything I’ve learned working with Asterisk, it’s that the majority of issues have to do with the router/firewall.

If I remember what the other things that I did are, I’ll post it back up here.

Thanks for the response. That basically confirms my hypothesis which was that it’s the router and perhaps a bit of bandwidth overutilization. We’re using Edgewater devices on a couple branches and what I’ve learned is that even though they’re specifically made with VoIP in mind, they tend to cause significant trouble unless they’re configured perfectly. The Polycom’s as well seem to be a significant source of trouble for me. They’re incredibly finicky when it comes to their firmware and application.

When I first started this project to transition our phone system, one of the first paragraphs of a book I purchased said something along the lines of “VoIP is extremely difficult.” Understatement.