[Freeswitch-users] Problem with rtp streams and stair-stepped (or ramped) increased lag

William King william.king at quentustech.com
Wed Jun 26 03:48:34 MSD 2013


Nathan,

I had a chance to diagnose the issue live on a system today. While I'm
not yet sure we are hitting the same issue, I'm now confident the
problem I'm hitting is not FS related, but looks to be kernel related. I
was able to get multiple calls up all with large 5+ second delays.
Restarting the calls did nothing to clear the problem. Restarting
Freeswitch repeatedly also had no effect. Upon restarting the box, the
problem was gone.

Also in my diagnostics I've found that it isn't all UDP packets that are
effected. I now have a switch mirroring the port and a pcap running
locally on the machine. I'll see tomorrow if it's just a matter of an
inbound or outbound network stack buffer(or network stack priority) issue.

William King
Senior Engineer
Quentus Technologies, INC
1037 NE 65th St Suite 273
Seattle, WA 98115
Main:   (877) 211-9337
Office: (206) 388-4772
Cell:   (253) 686-5518
william.king at quentustech.com

On 06/25/2013 05:13 AM, Nathan Neulinger wrote:
> I guess the big question is this:
> 
> 	Is it _supposed_ to recover?
> 
>  From Tony's notes, it's sounding like it's very critically dependent on the timer in the switch, which very well be the 
> current cause of my issues.
> 
> What I probably need to do is have a pair of phones automatically calling each other, and just leaving them up - just to 
> generate a continuous independent background stream. That'll tell me if any glitches are specific to a particular 
> channel, or if they are common across multiple calls - which I'd expect if the timer was swinging.
> 
> I don't know where my latency is being introduced unfortunately...
> 
> -- Nathan
> 
> On 06/25/2013 01:59 AM, Avi Marcus wrote:
>> It sounds like I saw  this on a home internet connection to a public server when the connection had varying latency.
>> Once the call jittered, it never recovered.
>> My stop-gap was to add a small jitter buffer <http://wiki.freeswitch.org/wiki/Jitterbuffer>, e.g. <action
>> application="jitterbuffer" data="100:200:20"/> to the user dialplan.
>> This /seemed /to make FS handle rewriting the timestamps for drift rather than relying on the Linksys ATA to do that.
>>
>> Probably the wrong solution, but all I had time/understanding for.
>> -Avi
>>
>>
>> On Tue, Jun 25, 2013 at 4:42 AM, Nathan Neulinger <nneul at mst.edu <mailto:nneul at mst.edu>> wrote:
>>
>>
>>
>>     On 06/24/2013 08:24 PM, Anthony Minessale wrote:
>>      > fsctl debug_level 10
>>      > Also make sure ve host has high res timing.
>>
>>     Turned up logging, will wait for next occurrence.
>>
>>     Not sure on the latter - it's a vmware ESXi 5.1 box running FC 17 x86_64 as the guest.
>>
>>     /dev/rtc /dev/rtc0 exist
>>     posix and soft timers are loaded in fs
>>
>>     I've got a bunch of unused Dell 1950's on hand, so could use a few of those machines if needed to get vmware out of the
>>     picture.
>>
>>     -- Nathan
>>
>>     ------------------------------------------------------------
>>     Nathan Neulinger nneul at mst.edu <mailto:nneul at mst.edu>
>>     Missouri S&T Information Technology (573) 612-1412 <tel:%28573%29%20612-1412>
>>     System Administrator - Architect
>>
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> 



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