Voice call drops for a few seconds

[andy4uk]

Hi all,

We have a client that is experiencing some issues with voice calls dropping for a few seconds.

Both Mitel controllers are MXe controllers with version 7.2

We have one system located in Newcastle and another system located in London, the sites have a 100mb leased line between the site and have QoS and Voice priority.

We can make calls no problem, but we seem to experience some calls being dropped for a few seconds - this is only when extensions calls from London to Newcastle and not from Newcastle to London.

I have checked the Voice Quality Statistics and cant see any packet loss.

Do any of you guys know what could possibly be causing this?

Thanks Andy

 

[Lundah]

Make sure the internal L2 switch on each controller is assigned an IP address and the IP is pingable. Changing the IP of the L2 switch will require a reboot of the controller.

 

[andy4uk]

Hi Lundah,

The L2 switch on each systems IP address can be pinged from each system, this is an un-usual problem.

The problem seems to be when Mitel IP phones are on a call between both sites, they can make and receive calls without any issues - its when they are on the call that there seems to be the voice dropping out (which will only happen for about a second, if that)

Its only noticed by the London users, and not the Newcastle users - also the only pattern seems to be it can happen or normally happens ever 5 minutes.

Regards

Andy

 

[RAMitel]

Sounds like a possible routing issue, when the users are talking to each other the media will be streaming from handset to handset do the phones have the correct gateway?

Also is there a router or firewall between sites that could be causing an issue?

 

[andy4uk]

Hi RAMitel,

Thank you for your reply!

I'll have the default gateways checked, would have though if there was an issue with the default gateway it wouldn't allow calls.

The link between the 2 sites is via an MPLS solution, I have been advised that there's no Firewall - but I would think that there's a router.

Andy

 

[RAMitel]

There will usually be a Cisco router at each end, have you checked the DSCP values as this is how the MPLS network will prioritize the voice traffic. (These are set in the DHCP Options).

Just out of interest are there VLANs at both sites and is it just the audio that drops for a few seconds whilst the call is still connected?

 

[Lundah]

I've seen cases where problems with the embedded L2 switch will do what you describe, so that's something to look into. Check the logs for anything mentioning "L2 subsystem", and make sure the RTC processor sees the L2 switch. You can do this by issuing the "ARPSHOW" Maintenance Command, and making sure you can see the IP of the L2 switch in the resulting output. But also check the IP path between controllers as well.

 

[andy4uk]

Thanks Lundah I have a check and will get back to you.

RAMitel yes there are vlan's configured at both ends, yes its just the audio - it drops for no more than a second, but can do this during the call a few times (but normally every 5 minutes or so)

 

[andy4uk]

Hi Lundah,

I have checked the ARPSHOW and can see the L2 switch IP address on both systems, there are no L2 Subsystem logs on either system either.

Within the LAN/WAN Configuration "IP Routing" I have added the Network address of the other Mitel system, no sure if the address is not in there if that would cause problems.

I'll also ask the client to speak to their MPLS provider to check the DSCP settings on the routers within their network.

Thank you

 

[Lundah]

Do you see anything in the logs on either end when you experience the dropped calls?

 

[andy4uk]

Hi Lundah,

Nothing seen on the logs, also with I have checked the Voice quality stats to see if there is any packet drops and I cant see anything.

 

[Billz66]

are there any devices connected to the phones ( PC's )

What kind of switches are used ate both sites

is the voice dropped in both directions ?

If I never did anything I'd never done before , I'd never do anything.....

 

[andy4uk]

Hi Billz66,

Not sure if there pc's connected to the rear of the handsets.

The voice is only dropped on the London IP Phones, and the switches are Cisco Meraki 48 port PoE switches.

When the voice is dropped it wont even be for a second, but its enough to notice - during a call they seem to think it happens every 5 minutes.

This issue seems to only be with calls between their 2 sites, external calls over the SIP trunks don't seem to be effected.

Andy

 

[Billz66]

spanning tree perhaps ?

if they have PC's connected getthem to try without them

we had a site where a network card in pc was broadcasting and causing issues as the broadcast transited the phone

we were chasing it for agees until we discovered that disconnecting the PC made all the issdue go away

new network driver fixed it i think ( or disabling IPV6)

If I never did anything I'd never done before , I'd never do anything.....