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VOIP calls being dropped

Posted on 2016-09-21
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Last Modified: 2016-11-16
Hi

I have around 10 voip phones which have been working without fault but about 4 weeks ago, they started dropping calls and sometimes when people pickup the call, there is no one there. Also, the indicators on the phones which indicate people are available/on the phone are not updating in a timely manner. The voip provider is blaming this on a change in our network but there has been no changes to our knowledge. Ive been running wireshark for the past 24 hrs in an effort to find out what could be causing this but I have no idea what I need to look for in the wireshark logs.

Any suggestions on how best to tackle this type of issue?

Thanks
SycamoreIT
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by:Felicia King
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Where is the SIP service coming from? Is there an on-premise phone system that is on the same PoE switch with the VOIP phones or what is the setup? If the calls are dropping and the phones are not getting timely information, it sounds like latency or unreliable connection.
But you don't specify where the phone services is actually coming from.

Are these all phones that direct connect out to an internet provider for hosted phone service or is there a phone system on premise and if it is on premise, where is it in relation to the phones?
The best option is a dedicated PoE switch with just the phones and phone system on it.
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by:SycamoreIT
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The phones are connected to a Poe switch which is then connected to our firewall. The phone switch is off site at the providers so hosted.

Is there any tools I can use to detect the drops?
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Felicia King earned 250 total points (awarded by participants)
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Yes, your firewall should have all the capabilities needed in order to allow you to see and track all the traffic associated with the subnet that the phones are on. The phones should all be on their own subnet and then all that traffic on that subnet should be QoS prioritized with a WAN policy in the Firewall. QoS marking of 5 or 6 should work well.
If you have the phones mixed in with the PCs and other stuff on the same subnet, that is very inadvisable because how else are you supposed to QoS the traffic?
I suppose you could QoS mark and prioritize the traffic to the destination which is the offsite provider.
You would set a unique policy for that and then guarantee a minimum bandwidth set to that policy.
Probably 300 kbps all the time would be a floor of a guarantee to all traffic destined for the offsite phone switch provider.
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by:SycamoreIT
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The phones and PC's are mixed and always have been. I could setup up QoS on the Firewall (Fortinet) and see if that makes a difference but thats another challenge in itself. Its odd that it was working and for whatever reason, it is no no longer working.

I will have to arrange a site visit to see what is plugged into the PoE and whats plugged into the normal network. I was hoping to carry out the fix remotely without having to visit site since its 200+ miles away.
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by:Felicia King
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I don't know about Fortinet. I am a WatchGuard security architect. I can tell you that it would take me less than 5 minutes in a Firebox to setup a policy for traffic prioritization to that offsite provider destination. If you are a Fortigate expert, should be about the same amount of time for setup and testing.
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by:masnrock
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Do the phones have a dedicated internet connection, or is it shared with the company network? Assuming the shared scenario, I'd be looking at QoS as Felicia has mentioned, but I would also be wondering about the quality of the internet connection itself. If there are latency problems, that's going to be a challenge. If the ISP is having problems, that's going to be a challenge, If the SIP provider (or their backend carrier) is having issues, that's going to be a challenge. There are a lot of pieces that need to be picked apart in order to figure this all out.

I would start with checking to see that the internet connection and firewall are working properly, and then check the QoS.
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by:SycamoreIT
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I have a BT Infinity Connection which terminates in my office space. Ive moved the phones over to this connection and they work fine. Ive done this by adding the BT Router to the existing network and just change the default gateway address on the phones to point to the BT router rather than the Virgin/Office complex internet connection. This works without issue. Its when the traffic is routed over the internal network which belongs to the office provider we get the problems. We are now currently setting up wireshark captures to see what is happening to our voip traffic when its routed over the virgin/building network. Tricky situation since no on wants to take responsibility for the issue and Im the only one who gives a dam!

Lets see what next weeks wireshark logs turn up.
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by:masnrock
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So the Virgin connection belongs to the office complex? They may have some interesting rules in place that would make things far more difficult to troubleshoot. Sometimes the best solution is just to have a connection that you have 100% control over.
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