Very strange jitter and packet loss on wlan

aod8 · #1 (**permalink**) 05-02-2006, 10:55 AM

Hi,

I am conducting voice qos tests on my VoIP network (sip and rtp enabled). I am doing this by examining the rtcp reports sent between clients.I calculate the jitter by getting the "interarrical jitter field" which is in rtp timestamp unit from the rtcp report and dividing by the sampling rate of the codec to get the jitter in ms. I am using an application called wan killer to stress the network with traffic

My problem is this: When I carry out the above tests over the fixed network, I get valid values and everything works out ok. However if i conduct a test between two clients on the same wireless lan, I get odd jitter results. It appears that the jitter repeats itself.

e.g.

27ms
27ms
69ms
69ms
12ms
12ms

Everything is always repeated. Also with the packetloss, I am examining certain fields and they are also repeated.

This ONLY happens on the wireless network. Can anyone explain this or think of a possible reason?....I am at my wits end trying to figure this out.

Many thanks in advance,
Aisling.

John_in_NC · #2 (**permalink**) 04-29-2007, 11:40 PM

I have no clue on how to do QOS via wirelss, I would however suggest that you reduce your MTU's on Voice Traffic

ibartolic · #3 (**permalink**) 06-13-2007, 10:20 AM

Few tips on VoIP over WLAN you could find on:
Wireless IP Telephony - VoWLAN

baby.kris · #4 (**permalink**) 12-27-2007, 08:45 AM

What handhelds are used in this test? Are you getting jitter buffering issue when a call is made between wireless and wired or between WLAN phones? Are u getting noise when call is establised?? Does it use SIP or H.323?? wht ver of H.323 and SIP?? if u have ACLs in ur WLAN router..try adding rules to prioritze the Voice traffic by subnet or by protocol. Also wht server are u using for the test???