[asterisk-users] tcpdum

[Jeff LaCoursiere]

I'll assume that you suspect that asterisk is adding latency that you 
would like to tune.  There is no simple variable that will affect latency 
as far as I know, but certainly one thing to look at is codec translation. 
Make sure your inbound and outbound paths are using the same codec, or 
latency will be added for sure.

You can use tcpdump to measure the latency and the effect of anything you 
do to attempt tuning in a rough way - each packet has a timestamp at the 
beginning measured in ten thousandths (I think?) of a second.  You should 
be able to see the RTP packet arrive and then leave again... just subtract 
the timestamps for your added latency.

Cheers,

j

On Mon, 15 Dec 2008, michel freiha wrote:

> Dear Sir,
>
> What I'm interested to is to know how much time the rtp packets takes from
> the time it access the asterisk server,to when it'll leave
> Is this function or variable exist anywhere?
>
> Regards
> On Mon, Dec 15, 2008 at 10:55 PM, Jeff LaCoursiere <jeff at jeff.net> wrote:
>
>>
>> No.  TTL in the header is about hop traversal.  Each IP router that
>> forwards the packet will reduce this number in the live packet until it
>> reaches zero, when it will be dropped.  I believe this is to eliminate
>> route loops creating packet storms.
>>
>> FWIW this is how traceroute works - it sends out packets with continually
>> increasing TTLs and the router that drops the packet will send back a
>> notification, so you can "trace" each hop...
>>
>> What is it you are trying to do or measure?
>>
>> j
>>
>> On Mon, 15 Dec 2008, michel freiha wrote:
>>
>>> Dear Sir,
>>>
>>> There is no relation between TTL and the latency on asterisk server?
>>>
>>> Regards
>>>
>>> On Mon, Dec 15, 2008 at 10:39 PM, Jeff LaCoursiere <jeff at jeff.net>
>> wrote:
>>>
>>>>
>>>> TTL is part of the UDP header (Time To Live).  It isn't really about the
>>>> voice at all.
>>>>
>>>> Length 345 is the number of bytes in the packet.
>>>>
>>>> j
>>>>
>>>> On Mon, 15 Dec 2008, michel freiha wrote:
>>>>
>>>>> *Dear All,
>>>>> I run the below tcp dump on my asterisk server
>>>>>
>>>>> tcpdump -i eth0 -n -s0 -v udp port 5060
>>>>>
>>>>> I got the following result
>>>>>
>>>>> 20:29:48.596867 IP (tos 0x10, ttl  64, id 0, offset 0, flags [DF],
>> proto
>>>> 17,
>>>>> length: 373) SIP_PROXY_IP.5060 > Asterisk_IP.5060: UDP, length 345
>>>>>
>>>>> What i need to know please what TTL means specifically and what is the
>>>> best
>>>>> value og TTL and what is the lengh vale mean
>>>>>
>>>>> Regards*
>>>>>
>>>>
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>>
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>