Jitter

[o.rodriguezmartin]

Hi

Anyone can tell me what positive and negative jitter means.

IPM give as information about maximum,minumun, etc for both positive and negative jitter.

I dont understand very well this concepts.

For example, when we talk about VoIP traffic it is said jitter must not to exceed 30 mseg.

When saying this, what are they talking about? Positive, negative,...

Thanks for your help

Octavio

[minie]

I hope following url can be helpful to you. In a nutshell, jitter is the variation between current packet delay and last packet delay. If current delay is 20ms and last one was 18ms, then you got positive 2ms in jitter. If current is 16ms, then you got negative 2ms.

http://www.cisco.com/en/US/tech/tk869/tk769/technologies_white_paper09186a00801b1a1e.shtml#definedelayjitterpacketloss

[o.rodriguezmartin]

Hi

Looking at the document it seems positive jitter to be when time different between two arriving packets it higher than time different between two sending packets. And the opposite for negative jitter.

In this way if I want to know, for example, maximum jitter in a time interval I´ll have to look for the maximum positive or negative jitter in that interval.

If we say jitter must be least than 20 msec it means positive or negative jitter must be least than 20 msec.

Thanks

Octavio

[Martin Ermel]

just informational:

the definition of jitter you have is identical to the the definiton of jitter minie wrote.

"For 2 packets, packet #1 (P1) and packet#2 (P2),

the Jitter between P1 and P2 is

(R2 - S2) - (R1 - S1) == (R2 - R1) - (S2 - S1),

where S1 is the sending time for P1 on the source; R1 is the receiving time for P1 on the target; S2 is the sending time for P2; and R2 is the receiving time for P2.

Note that the clocks on the two devices do not need to be sycronized."

look at this document (Fig 26):

http://www.cisco.com/en/US/partner/products/sw/iosswrel/ps1831/products_configuration_guide_chapter09186a00800ca63e.html

[o.rodriguezmartin]

Hi

I´d only like to confirm the following:

Maximun jitter, for example, in a time interval is the maximum jitter gotten in that interval. No matter if it is positive or negative jitter ?

In other words, is it useful to know if we are getting positive or negative jitter ? Why?

Thanks

Octavio