A VOIP question

[ericgeater]

This is less about security, so my apologies.  We use PRIs at my employer.  If I'm on a telephone call with someone using a VOIP system, sometimes there seems to be a lag between the moment a word is spoken, and the moment that word's signal arrives at the other party.

This occasionally causes a dead-air gap to occur at the end of a sentence. The side effect is a compulsion for one or both parties to fill this gap, which means the parties will briefly speak over one another. This can be frustrating if it's a long-duration call.

Is anyone else familiar with this symptom? I think the term is called "latency", but there are lots of terms that I might misunderstand. I need to know what to call it, because I'm a little concerned that one of our phone-replacement proposals is a SIP trunk system on a best-effort Comcast Business line.

thanks!

eric

[rslade]

> ericgeater (Newcomer III) posted a new topic in Tech Talk on 08-16-2019 04:36 PM

>   If
> I'm on a telephone call with someone using a VOIP system, sometimes there seems
> to be a lag between the moment a word is spoken, and the moment that word's
> signal arrives at the other party.
[...]
>   Is anyone else
> familiar with this symptom? I think the term is called "latency", but there are
> lots of terms that I might misunderstand. I need to know what to call it,
> because I'm a little concerned that one of our phone-replacement proposals is a
> SIP trunk system on a best-effort Comcast Business line.

Yes. You used to see it a lot on long distance calling where satellite links were
used. (You still see it on "live" news broadcasts where they are talking to someone
in the field, again, usually when they are using satellite links.) It is probably
generally referred to as latency, although latency more commonly refers to a
fixed delay, and with VoIP it is probably going to be variable, and then you get
into jitter as well.

And, yes, in any voice system these days you should be detailing the SLA on
maximum latency. "Best effort" isn't always good enough ...

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[Shannon]

@ericgeater, what you're experiencing might be latency, but as @rslade said, if the delay isn't constant, jitter could also be affecting the quality of the call.

First rule out issues on your own network / systems; after that, if the delays occur only when communicating with external parties, you can assume that it's related to the ISP or the other party's network / systems.

Check this article for tips on improving VoIP quality, do some online research if your organization plans to procure new systems, have the vendor properly address your concerns & last but not least, ensure that there's an SLA.

[K-Med]

Lots of people don't configure QOS to prioritize voice traffic and this can be the result. Our VoIP system does not have any of this latency at work, but we've also adjusted all the networking gear to prioritize voice traffic over all other traffic.

[rslade]

> K-Med (Newcomer II) posted a new reply in Tech Talk on 08-23-2019 05:48 PM in

> Lots of people don't configure QOS to prioritize voice traffic and this can be
> the result. Our VoIP system does not have any of this latency at work, but we've
> also adjusted all the networking gear to prioritize voice traffic over all other
> traffic.

Also depends upon what you are using at the network layer, and how much
mangement (as you point out) that you commit to it. If you (and possibly also
your provider) use ATM the results can be very solid.

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