atcomsystems.ca/forum Forums TDM Business Telephone Systems Toshiba Telephones & Systems StrataNet / VOIP Call Quality Issue

Here's the brief on my setup again--it's a School District. I've got 9 systems (8 CIX670s and 1 CIX100). They're all connected to one another using StrataNet with MIPU cards over our Fiber WAN.

We're experiencing jitter/skipping/etc during calls between one site and any other site. 8 sites are working fine, but 1 of them (a CIX670 with two MIPU24 cards) is experiencing the issue.

The site that is experiencing the issue is our High School/Career and Technology Center campus. Our setup is quite strange and might actually be the cause of the issue, but I'd like all of your professional opinions on the matter. We have a main cabinet with processor and several digital line cards in it at the Career and Technology Center. Then we have an expansion cabinet connected via fiber at the High School. In this expansion cabinet we have 2 MIPU 24 port cards connected to our network. There are approximately 4 (brand new) 3com gigabit switches in between the MIPU cards IP connections and the processor's IP connection. We had to place the MIPU cards in the expansion cabinet because of a limitation of space in the main cabinet.

To clarify a bit, the call quality issues aren't between phones IN the system, but between phones on this system and phones on any of our other StrataNet connected systems. The Fiber WAN connection is identical between sites, expect that this site has this odd arrangement.

This site is our highest bandwidth user, but never comes even close to the gigabit capacity we have there. We've VLANed off the voice data and as far as we know QoS is enabled on all the switches. We've even tried to get the skipping/jitter to occur by saturating the connection both up and down to almost it's max without recreating the jitter. We had the saturation going for minutes before even hearing the jitter (this was after hours). I think there might be spikes occurring that might cause the issue but shouldn't QoS take care of most of this? Is there something further we can try? Is it the split cabinet MIPU/processor setup that might be causing this?... so many potential areas... It's not even a HUGE amount of jitter, just at certain points in the day.

Thanks in advance.

Nice one...
CG, I don't think Vlan info gets passed across routers by default. What routers are you using?
Seems you have the bandwidth but no priority.
Diffserve may be the answer. I think that may be more of a router protocol.
Take a laptop to the affected site. Make it's IP address and subnet etc the same as the phones. Run Pingplotter and target the MIPU card. You will see the hops and the issues/problems.
It may be that the gateway of the phone system is not what you think it should be as well.
Sounds like a router programming issue.

Dave

@Dave: It is a great setup we have at that campus. For switching/routing we use 3com 5500G and 4500G Layer 3 Switches. We trunk between the switches so the VLAN reaches across both buildings from cabinet to cabinet. They can ping one another, can reach the gateway, and can reach the "main" system across the WAN where they make calls out and can reach any other system to communicate. Everything is operating well, it just skips a bit during conversations with off-campus phones/outside numbers.

I forgot to mention, these are DKT phones, not IPT phones.

Hmmm... OK.
I would still highly recommend taking a laptop, setting it up on the voice subnet, downloading Pingplotter, and targeting the Mipu card from the affected site.
I did this on a very similar site that had more than enough bandwidth to spare that had similar problems to yours.
In less than 15 mins I noticed a spike of delay every 60 secs or so between 2 of the sites. The spike was well over 300ms which caused havoc with the VOIP.
Bandwidth aside, you have to consider delay, jitter, and of course the dreaded packet loss.

Dave

You recommend to go to the site having the choppiness and then using Pingplotter to target the MIPU of that system or another system across the WAN? We've attempted pinging the MIPU of the affected site from across the WAN and haven't noticed loss of the pings already. Is this pingplotter similar to this?

Did you ever figure out what was causing the spikes or how to avoid them in your situation?

Go to either site and use Pingplotter to target the "other" MIPU, not the one on the site you are at.
Pingplotter will show you delay/jitter/packet loss and also show you all the hops inbetween.
The problem we had was that the provider was bonding 2 T-1's together and one of their routers (hop) was having a fit with that. We never lost a packet but the delay screwed things up.
https://www.pingplotter.com/download.html
Download the 30 day trial pro version and set it up to ping the other side every 1 second, sit back and relax, make phone calls and see which hop is the problem.

Dave

Here's the update--long in coming.

We've done some ping/transfer/loss tests as suggested and noticed weird behavior in general. We switched to G.729 compression, upped the jitter buffer and intervals between the systems, and tried switching MIPU cards. Things don't skip any longer, as far as we can tell, for now. It's only been a day since it stopped, but we'll see. There is a difference in voice quality, although it's just "different". hard to tell exactly. just seems that people's voices have a slightly different tone. Oh well, for now it's 99% good so problem solved as far as I'm concerned!

Thank you Canuckvoip for your help and advice!

Cool/interesting...
Only guessing but I bet the change in jitter buffer settings was the help/fix.
G.729 is great if you have no packet loss. If you do have packet loss, G.729 makes things worse because you are cramming more info/words into the same sized packets so you end up losing more syllables/words.
You may be wanting to leave well enough alone but I'd be curious if going back to G.711 with no other changes gives you your quality back while keeping the skipping at bay...
BTW, glad I could help. What weird things did you see?

Dave

We're having our dealer come in and move the IP cards to the main cabinet (not expansion cabinet) soon. It should eliminate the weird routing we've got going on there. At least that's the hope. Trying the "keep it simple stupid" approach.