[SIPForum-discussion] sip prack

[gurudatt balaji]

Hi

PRACK is Provisional ACK

Provisional responses (typically 18x) without using PRACK are not reliable.

So if the 18x is carrying SDP information then if the 18x didn't get through
then early media (which could contain an important announcement) would fail.

PRACK makes sure that the 18x is reliable. The 18x gets sent and then the
sender waits for a PRACK request. If, after a while the PRACK isn't
received, the 18x is retransmitted. The retransmissions of the 18x message
try to make sure that the early media succeeds.

And ACK is final acknowledgement

You can read RFC3261

Reg
Balaji

On Thu, Dec 30, 2010 at 8:58 PM, karthik <karthik8989 at rediffmail.com> wrote:

> Hi ALL,
>
> Please help me understand this....
>
> 1.What is prack?
>
> 2.why is prack used?
>
> 3.What are the reasons for using prack?
>
> 4.What is the difference between prack , ack and 200 OK?
>
> Thanks,
> Karthik
>
>
>
>
> <http://sigads.rediff.com/RealMedia/ads/click_nx.ads/www.rediffmail.com/signatureline.htm@Middle?>
> _______________________________________________
> This is the SIP Forum discussion mailing list
> TO UNSUBSCRIBE, or edit your delivery options, please visit
> http://sipforum.org/mailman/listinfo/discussion
> Post to the list at discussion at sipforum.org
>
>


-- 
Reg
Balaji
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://sipforum.org/pipermail/discussion/attachments/20101231/78c2a468/attachment-0002.html>