MBG/Teleworker problems on T1

[vlevalois]

We have a MAS 2.1 installed in server-gateway mode connected to a 3MB pipe on one end and on the other, we have a T1 connected to a router and into a LAN with approx 5 Teleworker phones, each with a PC connected to it.

Problem is this. One conversation with no internet activity, ok. As soon as a computer (any) starts downloading anything (could be a simple web page), we experience some jitter, but after a minute or so, the Teleworker side gets massive dropouts, to the point that it is unusable. The other side, whether from a C.O. or an IP phone directly connected to the ICP, still hears them perfectly.

This is a T1 circuit, which should be able to handle this, so it can't be a bandwidth issue.

Can anyone point to anything else to look at?

Thanks!

 

[vlevalois]

BTW this is MBG 5.2.21 and MCD 4.2.

 

[Supernova99]

Is your T1 link synchronous?
I.e. is it 2mb upstream and downstream.
Most links provide a lower upstream than down and I suspect this is why you are having drop outs.
Each voice call requires 100k both up and downstream depending on who is talking so if your upstream rate limit is say 256k then you can only have 2 calls at any one time as the 3rd call will not have sufficient bandwidth.
Using the internet simultaneaously will also affect the bandwidth available.
There is an option for the MBG and the 3300 of compression which will reduce the call to around 30k in each direction. So if you are stuck with a limited T1 upstream rate then this could be an option.

Share what you know - Learn what you don't

 

[vlevalois]

The T1 is 1.5Mbps both ways, just a standard T1. We also tried compression (with licenses) and the results were not any better, just poorer voice quality. We've implemented this on plenty of DSL's and cable modems without any issues. First time on a T1, which was always considered the holy grail for low latency connections, especially when both locations (MBG and TW phones) are using the same carrier.

The phones should be throttling the data of the PC connected to the phone. Is there intelligence in the MBG to know if a different PC from the same remote WAN connection is using up bandwidth even though the phone it is connected to is not on a call? Example, Phone/PC A, B and C. Phone A is on a call, PC B is watching YouTube videos. What's preventing PC B from chewing up downstream? My guess is nothing.

 

[kwbMitel]

The phones should be throttling the data of the PC connected to the phone

ummm no. The phone does not do anything to the PC data. The only measure possible is the Phone can introduce VLAN tagging and prioritization on its own packets and thru prioritization gain an advantage over the PC data. Without VLAN tagging, the phone and PC compete equally for bandwidth.

By what means have you proven that this is not a bandwidth issue? It sure sounds like one to me.

**********************************************
What's most important is that you realise ... There is no spoon.

 

[LoopyLou]

agree. Its bandwidth issue. Do you priority set on your layer 2? Do you priority at layer 3?

The single biggest problem with communications is the illusion that it has taken place.

 

[vlevalois]

My understanding was the the phones in TW mode have a "large adaptive jitter buffer" and will accommodate poor poor quality connections... I know that's the company line, but it was my understanding that when the PC is plugged into the phone there's bandwidth throttling going on, could be wrong.

We're not prioritizing traffic with VLANs at this stage but that seems like the next step to take.

Just can't believe that a couple of phones on a T1 would have this much trouble, still doesn't make sense.

 

[vlevalois]

Update, also checked that we tested the connection with only 2 phones plugged into the switch (POE Dell). The report is that we got deterioration of the call even in that scenario with 2 calls going on at the same time...

 

[LoopyLou]

The phones do have a jitter buffer to deal with the fact that in most cases TW calls have to cross the internet if used in a home office.

I would initiate either: priority on your network or try establishing compression for the teleworker phones.

The single biggest problem with communications is the illusion that it has taken place.

 

[vlevalois]

We've tried compression, it makes the problem worse and the voice quality in general degrades faster. The question I have about VLAN'ing the phones and prioritizing voice, is how is that going to prevent downstream congestion from the internet down to the router, etc.?

 

[kwbMitel]

A thought occured to me today. Have you checked the link speeds from the phone to the switch?

Sometimes the auto-negotiate fails and you end up with a half duplex connection (which would be bad)

**********************************************
What's most important is that you realise ... There is no spoon.

 

[vlevalois]

Have not checked that in the switch. Need to apply a static IP to the switch and go in, etc. Would be a good idea, thanks for the tip!

 

[LoopyLou]

kwbMitel has a good suggestion ( as usual ). The phone will try to auto negotiate speed and duplex. If it fails it could be defaulting to the lowest. Check if the layer 2 is reporting error logs on the ports and if need be you could go static with speed and duplex.

The single biggest problem with communications is the illusion that it has taken place.