Dropped Calls

I am trying to solve a problem that is starting to get annoying for both us and our customers.

We can be sure than 20% of calls daily we deal with get dropped right in the middle of conversations, causing either us calling the customer back or them trying to get us back and finding they are dealing with a new customer support person.

We have elmeg 290 phones, however regardless of location across the county, and via different forms of connectivity, this problems remains.

I would like to know things we can check before throwing this at voipfone technical support. I can rule out the ISP side of it :wink:
Aquiss Broadband - The perfect partner to Voipfone (With London Network Peering) :P

Dropped calls could be caused a million and one things but the most common of these are as follows

Connectivity issues such as dropped packets or latency

Carrier issues - we would need details of problem numbers so that we can raise any faults with the relevant carriers

Phone, adaptor, firmware or codec issues

Local network issues normally cured by using qos

If you're using elmegs you can send us a sip trace from the phone that is experiencing the dropped calls and this can help to diagnose any problems.

Voipfone Customer Services

iNet Telecoms Ltd (Voipfone)
Sovereign House
227 Marsh Wall
E14 9SD
United Kingdom

Registered number: 05168033
Vat Registration Number 858850966

Telephone: 020 7043 5555
Fax: 020 7043 5556

Web: http://www.voipfone.co.uk
Blog: http://www.voipfoneblog.co.uk
Forum: http://www.voipfoneuserforum.co.uk
Twitter: http://www.twitter.com/voipfone

When we get dropped calls, it's almost always due to some kind of network service interruption between us and Voipfone.

Usually, it's accompanied by various other funnies: the odd "Forbidden" message when dialling (but then a redial goes straight through); dropped calls on transfer; poor audio quality (or, as one of my users puts it, "It's gone all daleky again!").

9 times out of 10 I've been able to attribute this to our ISP (BT, soon to be relegated to the dustbin thank goodness!). Once it was Voipfone themselves (and Lee got it fixed in 15 minutes from the time I notified him!).

To diagnose the source of the problem, I'd suggest running "MTR" at one of your problem locations. When you get a dropped call, I'm sure you'll see some associated packet loss somewhere in the route to Voipfone.

It doesn't take much packet loss to cause the problem - particularly if you have several calls active from one location at the same time.

The only other suggestion I've got is to look at what other traffic you're running over the same connection. If you're running over a standard ADSL or ADSLMax pipe, take care with usage of your upstream bandwidth in particular. A QoS-capable router should help with this, or, do as we did - have a completely separate ADSL (in fact, soon to be SDSL) connection for VoIP.


I have recently had a couple of dropped calls, but both have been when I've dialled a UK mobile phone number - is this a general voip issue?

Rather irritating considering the amount of business people who use mobiles these days!


Your Virtual Assistant Service
Staffordshire, England

We call a lot of mobiles, without any major problems.

Do remember that not every call-drop is Voipfone's fault - or that of their providers or your ISP. Sometimes it's down to the other end's telephone service provider.

With mobiles, there's also the issue of coverage. In some cases, dropped mobile calls might simply be down to signal strength issues.

I have experienced dropped calls on just one of our extensions today. It's bizarre it happened before and would usually only affect one line at a time out of 20 ish extensions. Trace route is looking alright. Just thought I'd mention it incase anyone was experiencing similar problems.

Tracing route to sip.voipfone.co.uk []
over a maximum of 30 hops:

1 <1 ms <1 ms <1 ms home.gateway []
2 17 ms 18 ms 16 ms l1.ar21.gs1.dsl.pipex.net []
3 16 ms 15 ms 16 ms ge-0-1-1-0.cr02.gs1.dsl.pipex.net []

4 15 ms 16 ms 15 ms pc9.cr05.tn5.bb.pipex.net []
5 17 ms 15 ms 16 ms ge-1-5-0-cr0.thn.datahop.it []
6 17 ms 15 ms 16 ms voipfone-gw.sov.datahop.it []
7 17 ms 15 ms 15 ms

Trace complete.

T :?

I've been speaking to the Voipfone technical folks about this at length, as we've had the problem in spades.

There seems to be two sets of "no audio" or "one-way audio" problems:
- affecting inbound PSTN to VoIP calls
- affecting VoIP to VoIP calls where one or both end is a Snom or Elmeg

They're confident they've found the bug causing the first one, and the fix should be implemented overnight tonight.

They may have also found the bug causing the second one. If so, that will also be implemented tonight.

We believe that these bugs have now been squashed and you should no longer experience the odd dropped or silent call.

It seems that one of the service upgrades we performed at the weekend caused some clients - mainly snom and elmegs - to go slightly mad. The problem was identified today and a fix implemented this evening.

Should you continue to experience this problem, or any other problem, please email support with as much information as possible. (We need the time and number called or calling and, if possible, a SIP trace to pin it down fully).

We apologise for any inconvenience and thank you for your patience.

Any users who did not experience the above problems, I guess you were lucky ;-)


Lee Rose (Technical Director)

Hi Lee,

I hate being the one who breaks the news, but we are loosing calls all over the shop still :(

Call basically goes silent, and then we end up talking to ourselves (ok we do that anyway, but i rather go mad as well :lol: )

All elmeg 290 phones here.
Aquiss Broadband - The perfect partner to Voipfone (With London Network Peering) :P

You said the call *goes* silent ... does that mean that all's well to begin with?

The problem that Lee's team have just fixed was related to no or one-way audio on pickup - ie from the moment the call is connected.

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