Polycom Audio Cuts

[Stewart]

I put in a good size install last month of about 40 Polycom phones and it seemed things were working well. Today users began complaining that this week (and maybe last week a little) that while they were on the phone audio would be perfect and then one side doesn't hear any audio for about 3 seconds. It may be the user on the phone or the outside called/calling party. I don't see any real rhyme or reason to it and want to be sure I've checked all my boxes before checking with the ISP (who also provides the SIP connection). I capture all audio and the one they had me check today showed the audio processed fine, but the outside party lost audio for a couple of seconds. To me it sounds like the trunk, but am not sure. They have a 10x10 fiber connection FYI.

Any help would be great. Thanks.

 

[Stewart]

Update:

Well, it seems it's not the trunks. I listened to another audio stream from a call and I hear the audio being received by the server and sent out to the phones just fine. If I watch the RTP timestamps as I hear the call through Wireshark, The audio is perfect from the trunk and out to the phone, but the stream back from the phone seems as if it's missing something. While the RTP timestamp is continuous, there is obviously some audio missing from the steam.

This is my only Polycom installation, all the others have been Aastras, and this is the only installation I'm experiencing this. Anyone experience this? It could be networking, but not sure where. The topology goes:
Server -> 8-port switch (holds the servers) -> 48 port gigabit poe switch -> phone
for all the phones.

 

[randy7376]

Are the switches managed? If so, I'd look at the statistics for the connection between the 8-port switch and 48-port PoE switch for any errors. If either switch has any kind of syslog, I'd check that, also. You might try putting the PBX server directly on the 48-port switch and see if your problem goes away or changes.

Last thought: Make sure you don't have a duplex mismatch between the switches.

 

[Stewart]

Thanks. I can't imagine it's a load issue on the switches since the Netgear has a 96Gb backplane, so maybe a duplex mismatch is something to check. The small switch, though, isn't managed.

You think there's any possibility of a configuration issue on the phones themselves? This is my only Polycom installation so I have nothing to compare it to and it's random. There are several hundred calls a day and this happens randomly maybe half a dozen times a day.

Other than this one issue (and some VERY funky setups to get remote phones working via cellular ISPs) the calls are practically perfect. I never really believed people who said that VOIP call quality could be better than POTS, but these are so I'd like to squash this bug quickly and furiously.

 

[randy7376]

SIP phones don't generate enough traffic, typically, to overload a modern-day switch. You want to look for signs that something may be preventing traffic from getting from point A to point B.

Simplify the connection as much as you can - that's why I suggested putting the PBX on the PoE switch. Take the 8-port out of the picture and see what changes.

Also, before you make the above change, you should be able to check the port on the PoE switch that is connected to the 8-port switch for any kind of errors. Look for FCS errors, alignment errors, runts, giants, etc. I have no experience with Netgear managed switches so I'm not sure what statistics they report. I've always used Cisco or HP ProCurve.

We have two Polycom Soundstation (a 4000 and 6000) that work great. One is in our corporate conference and the other is a remote to the corporate PBX for an office down the street. No problems nor complaints. The rest of our phones are all Aastra 6757is.

EDIT: Don't rule out a bad switch port, either!

 

[Stewart]

We'll try to get out there this morning and change things around. The switch was added because they need more than 48 ports to make it all work since we had to replace their RV082 with a custom PFsense box. I'll try just throwing their printers on it and change things around and see if that helps. Well, maybe I'll do that and change out the switch at the same time and attack from all the angles.

 

[atsak]

I have noticed this occasionally on Netgear switches, espeically unmanaged ones . . . rebooting the switches seemed to fix the problem. Netgear makes reliable equipment, but like the Dlink etc. they seem to have some weird stuff happening. HP have some new / cheaper 3com Procurve stuff that seems to be a bit better for this.

 

[Stewart]

Well, changed out the small switch and put the server directly on to the Netgear, and the problem got worse. I switched the cabling so that the system was on different ports and it went away.

There were no CRC errors on the ports, but once we pulled the equipment out of them, we noticed that the 2 ports the phone system and audiocodes were in were constantly changing from copper to fiber. It seems like what was happening was that when the media changed to the wrong type, all traffic stopped. Once it changed back, it's fixed.

Netgear has a firmware update that addresses this exact problem (released just a couple of weeks ago), but only if we're using a newer firmware version that what we're currently on. We need to schedule a time to update the firmware to address the issue and update it, but since the phones are all poe provided by this switch, it'll cause a company-wide reboot of the phones.

So that seems to have been the problem.

 

[Stewart]

The netgear switch is managed. It's the GS748TPS I believe. There isn't really a competitor to it. All 48 ports are gigabit and poe and all 48 ports can run poe at the same time. If you know of a direct competitor to it, I'd love to know.

 

[Linetux]

And now you know why I use HP PoE switches

 

[Linetux]

Why pay for or bother running GbE to the phones?

I use HP 2610-48-PWR in those scenarios.

Desktop ports get 1G ports on non-PoE switches. Phone networks are separated (physically and logically).

 

[RonRussell]

We've seen similar issues with 3Com, Linksys & Adtran switches. And they were always related to storm / broadcast control features not functioning correctly. Lesson learned is to become educated on the type of equipment chosen and be sure to get updates done prior to turn-ups. We always do extensive testing prior to implementing any type of new stuff that we haven't used before. But even then we sometimes miss something.

 

[Stewart]

Is that switch capable of providing PoE to all ports simultaneously? With a maximum power rating of 96W it seems not. The client already had the full GbE network and these Polycom 670s were selected because they had GbE switches built in allowing them to run on the same physical network without any slowdown. This switch has been in place much longer than the phones.

I don't mind switching over to the ProCurve line of switches. We looked for a higher line of switches to replace the Netgears but the closest we and our vendors could find was a Cisco which was great, if we only want to PoE 24 of the 48 ports. It's an extra $8K to power the other 24. We couldn't find a suitable ProCurve, but I'll look into this model.

I'm not concerned with phone traffic on the local network. It's got plenty of throughput to handle it without a problem. In fact, the audio quality is practically perfect. We run the outside audio over a separate fiber line separating the Voice from the data. The only issue we've had is the flapping on these 2 ports.

With all the installs we've done, I've yet to find an instance where any traffic load on the LAN has affected call quality, it's always WAN traffic. It's definately best practice as I can see it theoretically, and I'm sure there are instances it matters, but I just haven't had an issue. I can push as much as I can up and down from the pc to the server through the phone to saturate the phone and I never notice.

 

[Stewart]

In other words, you just never know. Of all the systems we've put in, this is the first time a switch has caused an issue. We usually use Netgear switches, but have used Intellinet's in a couple installs. This is the first problem we've had related to that.

What line of switches have you settled on?

 

[RonRussell]

After 3Com bit the dust (via HP purchase) we started selling and installing Adtran. We like them for many of the same reasons that we used to like 3com. Pricing is good and there are no hidden costs. Warranty is lifetime just like 3Com used to be. Performance is good as long as you understand how to configure the network. Training is excellent with most online and no or low cost. Support is superb - provided from Adtran's headquarters in Huntsville, AL.

 

[dswartz]

I have an 8-port procurve and have been very happy.

 

[Linetux]

The 2610-48-PWR is a 10/100 PoE switch with 2 GbE uplink ports. Fully managed, lifetime warranty, etc. Of all the devices I have to manage, I think their CLI is the best. Web interface isn't bad. But definitely a step above the 3Com (which I used to use religiously). The 2610-48 can provide up to 8.4W to all 48 ports (which is all I've ever needed). The 24-port version of the same switch can provide 15W to all 24 ports. I can usually pick them up for around $1900.

If you get into GbE, it's a different story. For 24 ports, you can pick a E2520G-24-PoE ($1400) or you can get a E2910-48G-PoE ($4500). The price quickly escalates when you're dealing with GbE and PoE. Sometimes, but not always, it's just cheaper to run a separate cable/setup for the phones vs. buying Gb for the phones. But I understand why you're doing it now. It's also worth considering two switches and trunking them together - it'd be a lot cheaper (and provide all 15W of power to all ports if you need that). But 6amps of power is a lot of power for a switch to draw... make sure you have the right power backup stuff supporting all that!

If you really want to go nutz, the 3500yl is there for you. It can even act as a firewall if you'd like (not that I suggest you try doing so, but it can). You can find them for around $5K... but that's something I put at the core of busy networks, not at the edge serving up phones and PC's

 

[Stewart]

Then I'm back where I started. Nothing really competes with this Netgear I'm finding. What everyone else offers is quite a bit more money. And in the size of the companies I work with, it just isn't feasible. Maybe the cost is justified, but since it's just a matter of PoE, I wonder if it's really just about nailing larger companies. Generally switching capacity and throughput are more than adequate on all the models for this usage model.

 

[Stewart]

Does Adtran even make a 48-port gigabit switch w/ full PoE? I can't seem to find it.

 

[luckman212]

Stewart-
did you ever resolve this issue?
I'm curious b/c I have netgear PoE switches at home w/ my 2 Polycom's and I have noticed the EXACT same issue (audio drops out for 3-4 seconds, usually very near the beginning of a call) and then picks back up again. I also have a fiber 25m/25m connection.

setup is:
polycom ip335<->gs108pe<->gs108e<->router(pfSense)<->VerizonONT

btw this is polycom UC fw v3.3.1