Sonicwall TZ-105 QoS for Voip

Slaanesh

I was wondering if someone might give some help please.

We are moving from Eircom ISDN/analogue lines to a voip solution from Welltel.
We have the welltel system which is 5 phones and a small PBX unit which communicates with their SIP servers. It's a neat little system and does all we need it to do. Out numbers are being ported today from Eircom but I'm having problems with VOIP traffic dropping when the internet connection is congested.

We have Image 6Mbit up/down. It's generally a good service and has been solid for years. It has however been a bit crap the last month (Ballycoolin). I've been ringing complaining and they say there is some local interference that the engineers are trying to isolate. Sometimes you get 5mbit, sometimes only 1. However this should really be enough for the Voip calls so I just need to prioritise the traffic on the Sonicwall.

Here's the current config:

I have set the ingress/egress on the WAN interface to be the max speed 6000Kbp/s.



Next I have set the access rules for the SIP server to be Bandwidth Managed on the High priority



Finally the different priorities:



If I do a speed test whilst on a call, depending on the direction of data at the time. The recipient will either not here me or be all broken up. Or I will not hear them etc.

What am I doing wrong? Help please!

Cheers.

witnessmenow

It's a long time since I didnt anything with SIP, so what I am telling you could be wrong!

When I was previously setting up bandwidth management device (not a sonic wall) I needed to set the max WAN speed to the minimum that your speed could be.

Think about this scenario: you told your device you have 6Mb available, but there is only 2mb actually available

You have 30% of your bandwidth reserved for SIP, which is 2Mb. (Side note: Depending on the codec of your phone that only allows ~ 2 external calls, g711 is 100KBps per call )

Lets say you are using the max bandwidth reserved for calls.

Then you run a speed test, your sonicwall thinks it has 4Mb to give to your speed test, so it says it will limit anything over 4Mb to that queue, but it will happily allow it have full access to 2Mb, which is all you have!

Does that make sense?

In the above scenario if you set the sonicwall that its wan was 2Mb and gave SIP 90% of the bandwidth your calls should be unaffected by the speed test, because the sonic wall would allow it to have 200Kb

The issue with this is the times that you do have 6Mb available, the sonic wall will only allow 2Mb

Tbh the internet really isn't good enough for VOIP if it hits 1Mb a second at any times, that is a max of 3 calls on a compressed codec, and thats if the internet is not being used for anything else.

Slaanesh

Thanks for the explanation. I was wondering how that worked.

The Voip codeic nowhere near a hog as that. It's 10KB/sec up and down per connection. So even with all 4 lines going, that's only .4 Mbit/sec each way.

We've escalated the issue with the provider and it's actually gotten the worse it's ever been 16% packet loss on my ping tests. I would imagine (pardon the pun) that they are doing some tests.

I don't think it's going to work either way with that much packet loss. If I can get a connection that gives a steady constant up and down then I might be able to try what you said by limiting it to the minimum rate and then giving the SIP traffic the required percentage of that to handle at least 2-3 calls when the line is being maxed. rare that more than 2 are on the phone at the same time.

Looks like we could be getting a DSL line just for the Voip. That's an extra €60 a month just for that, shouldn't be needed.

Mr. G

How are Imagine giving you broadband?

If it isn't through a phone line, you might be able to get up to 24Mb. You can get your provider to set a profile so that your upload is 2Mb rather than 1.1Mb. Your download would be less however. This might help solve your problem.

Generally speaking, allow 100Kbps per concurrent call on G711 codec.

Slaanesh

Hi,

Imagine are providing us a fixed wireless product which is supposed to be 6Mbit up/down. However it's highly erratic at the moment and I'm currently experiencing 16% packet loss at times which of course is unusable in a voip situation.

witnessmenow

Ya as you know any packet loss is pretty much not acceptable for VoIP. How are the pings? Anything over 100ms will be noticeable

General rule of thumb is:

With G711, as Mt G says, its ~100Kbps
With G729 which not all phones systems support it would be ~33Kbps
There wasn't anything that used less when I was in the game

I believe SIP has silence suppression built in for long pauses so it would be possible to have multiple active calls not using multiples of what I listed above (as in 10 G729 calls might not be using 330Kbps at anyone time), but you need to allow for multiples.

Mr. G

Slaanesh wrote: »

Hi,

Imagine are providing us a fixed wireless product which is supposed to be 6Mbit up/down. However it's highly erratic at the moment and I'm currently experiencing 16% packet loss at times which of course is unusable in a voip situation.

Have you tried looking into ADSL? It is generally cheaper and you would not have any packet loss. That is pretty horrific.

You can also get pings lowered. Shop around is my advice. Imagine have levied a €4 + VAT charge which comes into effect next month. It was hidden at the bottom of an email with your monthly bill. We're with Imagine for broadband but I'm thinking of moving away since we have until the end of the month to move without penalty.

They're usually good to deal with and I've never had any speed or broadband difficulties, bar the 24 hour incident during the storms

Nate--IRL--

Are you sure the Rule you've set is actually catching the traffic you want to manage? Observe if there is actually traffic being caught by the rule, by mousing over the icon beside the edit icon in the firewall rules.

Also I've had a lot of problems with packet loss with the 5.9 firmware, but rolling back to 5.8 can be problematic.

Nate