Mitel Forums - The Unofficial Source
Mitel Forums => Mitel Software Applications => Topic started by: griam01 on October 18, 2017, 12:48:40 PM
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I haven been troubleshooting an issue for a while now that a customer is giving us examples of jitter in some calls. We have been running tcpdump on the MBG and reviewing the captures. I even teleworkered a phone to their system and did a test call and the audio was fine, but when I look at the capture it shows 5% packets out of sequence and with wrong time stamp on all legs of the captures (Internally on the MBG from one port to the other, as well as the interface to and from the SIP SBC). I did a similar test on another customer that is setup identically (all of our system are cloud based pbx's in the same Datacenter with the same SIP trunks) and that tcpdump shows clean, virtually nothing out of sequence or wrong time stamp. Any ideas what to look for that would cause the packets out of sequence or wrong timestamp especially internally on the IP for the MBG from one port to another? Thanks in advance for your time.
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I have the same issue at a site.
Did you get any further with this?
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This probably doesn't answer your question directly but is perhaps food for thought if you didn't know or think of this already:
firstly out of order or sequence is to be expected as UDP is inherently unreliable. The reason why you may not experience audio issues even if you see out of order packets is due to the jitter buffers to correct these issues, up to a point obviously.
as a test, you could try multiple captures at multiple points for the same call and compare. perhaps run a trace on the mbg and on the phone for the same call.
Also look at the direction of the packets, for instance on the internal leg of MBG, packets travelling toward the internal side should be in order since the jitter buffer would have sorted them out as they came in on the dirty interface. packets travelling northbound could be out of order/sequence since they were not yet subjected to the jitter buffer. audio issue may be one way or two way since there are two distinctly different stream. the fact that they belong to the same call does not mean the network treats both streams equally.
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Thanks for the advise. We have tried captures at the MBG on both the phone side and the SIP trunk side as well as captures on the ISP network. The only captures that we have not received yet are on the phone side specifically on the customer's network. These are 6940 phones and apparently Mitel said that voice quality stats in the MCD are not accurate. The customer has not reported any other issues and we have not made any changes, so not sure what is going on.
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Thanks for the advise. We have tried captures at the MBG on both the phone side and the SIP trunk side as well as captures on the ISP network. The only captures that we have not received yet are on the phone side specifically on the customer's network. These are 6940 phones and apparently Mitel said that voice quality stats in the MCD are not accurate. The customer has not reported any other issues and we have not made any changes, so not sure what is going on.
Has the customer actually complained about something?
Sent from my E5823 using Tapatalk
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Yes, they claim they get choppy audio. I hear a little bit of jitter in part of the call, but not horrible at all, just a bit of choppy during a sentence. When they provide these examples, it is usually a 10+ minute call and they are complaining of one sentence.
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Yes, they claim they get choppy audio. I hear a little bit of jitter in part of the call, but not horrible at all, just a bit of choppy during a sentence. When they provide these examples, it is usually a 10+ minute call and they are complaining of one sentence.
Ok. Best is to compare the RTP from different parts of the network if possible, for the same call and look at the RTP packet order for each trace. This should give you an idea of what is causing the latency and ultimately jitter
Sent from my E5823 using Tapatalk
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What type of switch(es) are they using? I have seen good switches make up for a lot of networking sins or make a good network even better.
Not for me of course since I always program everything perfect from endpoint to server :-X
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I will have to wait for the customer to provide us with the captures at the end unit.
I believe they are Cisco switches, but they are not managed by us, but rather the customer. We manage the router and have confirmed the configuration is good from the site.
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Yeah usually if they pay for Cisco goods they have some good people managing them. I found an early 2000's 3M switch in a closet once and replacing it was once of the best decisions I ever made.