sundance-communications.com/forum Forums VOIP Phones & IP PBX VoIP & Cloud Phones, Hosted PBX, General IP Phones PBXMate

I am trying to assist a potential client with an echo issue on their Asterisk PBX. They have echo problems even for internal intercom calls. They have 3 buildings with 2 connected to the main by fiber with 100MbS transceievers. They have cheap Linksys GB switches throughout. I did some Wireshark analysis and their network seems pretty clean. I am looking into PBXMate as a posible sokution to the echo. Does anyone have any experience with it?

'Pretty Clean' doesn't cut it for VOIP. They are going to need better swithes. Also Asterisk echo cancelling can be dealt with thru hardware and software. Better make sure somebody hasn't tried to implement 1 method or the other. They don't get along very well without tweaking.

What makes me hesitant with this potential, heavy on the potential, client is that there is a very real chance of not fixing it to their satisfaction even after a significant outlay of money. Plus they only have one drop to every desk so they are running their data and voice together in the worst way. And I am not sure Schmooze will appreciate anything I do. I am thinking this is a perfect candidate for a Partner or Norstar.

So who carloaded them with the Asterisk and walked away? A silver-tongued-devil of a salesman, or their last/present IT guy who now realizes they are in over their head. The Asterisk is only as good as the network it's running on, the quality of the PRI/SIP trunks it's using, and the knowledge and experience of the Asterisk provider. JUST LIKE ANY OTHER PHONE SYSTEM, VOIP, TDM, or ANALOG!

If it were me, " Mr owner/customer, after evaluating your system, I recommend installing a completely separate network, with superior QOS switches, that are POE capable. If you cannot justify both, I would say that choosing between the 2 would be a crap-shoot. I am willing to do as you wish. However, I cannot, and will not, assume responsibility for the results if all of my recommendations are not implemented." (This is not going to be an easy thing to say, but, in the end, it's your reputation, and ass, that are on the line!

What makes me hesitant with this potential, heavy on the potential, client is that there is a very real chance of not fixing it to their satisfaction even after a significant outlay of money. Plus they only have one drop to every desk so they are running their data and voice together in the worst way. And I am not sure Schmooze will appreciate anything I do. I am thinking this is a perfect candidate for a Partner or Norstar.

Oh I know it, LH. This system is actually Asterisk based. It is a product called PBXAct and was sold by an independent vendor and included Schmooze tech support. That complicates things a lot because if I change things they could lose their support contract

You and I think alike here. What I have to do is to write up what they won't want to hear. I feel sorry for them as they spent about double what a brand new Partnr or MICS would have cost them complete with VM and all the trimmings. I *CAN* guarantee a perfect system with those products. No matter what I do with this system I can only hope for the best.

Its a prfect example of how VoIP is not always a good fit.

One more thing LH: is QoS really so important if you are running a completely seperate netwok for just VoIP? If you are not balancing and or prioritizing protocols like you would have to in a mixed environment does QoS become less of a consideration?

You are correct, unless they're using SIP trunks over the same WAN.

Well, what no one has touched on is the desk phones they are using. That is where I would look for Echo given what you have told me so far. But lets run through a few other things as well:

1) Is this system all IP? Or is there analog cross-connects, PRI's, POTS, etc involved anywhere?
2) Are there any audio artifacts, like chirping, skips, the "Max-Headrom" effect, etc?
3) What model desk phone is there? (look on the back if they've "rebranded" it)

True echo is usually only induced through analog methods, such as feedback and poor PSTN gateways. Since SIP is completely digital, hence lacking the ability to create "echo", I doubt it is coming from the switches the LAN rides over or the software. Problems with network conditions usually lead to chirps, skips, the "max headrom" effect, etc. That's the basis for my two questions.

So, assuming you are pure IP, and given what you have told me, I would venture to say it's the deskphone somehow. Either the handset design is generating feedback, or the phone is somehow generating side-talk.

The classic echo scenario would be caused by the PSTN to SIP gateway device. However, that doesn't really apply since you get the echo from phone to phone. That is pure digital, and the only method to induce echo is at the deskphone itself.

Hope that makes sense to you. One litmus test for this is to take a handset from another known good phone, and plug it into two IP Deskphones, and see if the echo goes away. If it does, then you found the culprit. The only other good test would be to take two known good IP Phones (Like a SNOM 300, Polycom IP320, etc), register it to their PBX, and see if echo persists. If it does at that point then you got me. SIP deskphone to SIP deskphone through Asterisk should generate NO echo, and sound about as clear as anything you've ever heard.

My money is still on crappy deskphones. I've seen this issue with Grandstreams before, and some of the knock-off chinese phones. Snom and Polycom never seem to have this particular issue.

As far as my opinion on QoS, it's good for controlling traffic spikes and occasional overload, I.E. your typical office LAN environment. It is not a solution to a network that is just simply overloaded. If the requirements are to push 100mb/s from file servers to workstations for video editors, no amount of QoS will fix this if the network is only 100mb/s. Smarter network topology and ultimately bandwidth is the way to go. If the problem is the lunch-rush to watch youtube videos, then QoS can help.

They have Aastra phones, models 6755i and 6731i. They have 30 to be exact. It is pure IP. They only have four analog trunks. Their call volume is actually quite low. Surprisingly low. They experience a lot of problems on internal calls. The reported issues were ear splitting volume on some calls, echo and dropped parked calls. There are three buildings. The major issue is internal calls from the remote buidlings to the main buidling. They are joined by multimode fiber with 10/100 transceivers into gigabit switches. Oddly they run gig into the phones which their PCs also plug into having only one drop per desk. So they have gigabit switches but fast ethernet phones throttling it all.

I dread the quote I will deliver - it's going to be expensive.