Hi,

Am Monday 02 February 2004 23:48 schrieb Balaji Bapulal Thoguluva:

I am writing a software to parse SIP messages. I have couple of questions that I would like to clarified.

maybe your questions are better placed at the SIP mailing lists.

1. How to recognise if a packet is a SIP or a non-SIP packet?. SIP uses

TCP, UDP as underlying transport.

How to recognise that a request is a HTTP request or not? Parse it! If you can parse it, it is a valid request of that protocol. If you fail it is probably not a valid request (or your parser is faulty).

2. How to know the direction of the SIP message if it is from SIP proxy or

from SIP client?. I ask this question because in most of the SIP messages, the header fields are copied from previous messages and so the from, To header fileds doesn't always signify he direction

If you dont know if the IP/host is a proxy or a UA i dont know a safe way to determine if the type/class of the device.

3. Can Call-ID be used to find the number of distinct phone call taken

place between different SIP UA's?.

No. The content of the Call-ID depends on the UA implementation and e.g. can be randomly.

4. What is the significance of dialog-ID? and how can it be used?

AFAIK it's the internal identifier of an UA for one dialog state. This can be equal to the To or From tag, but can also be something completely different.

Regards Nils