It is interesting to know whether there is a way to conditionally mark *each* outgoing IP packet with a *different* DSCP/TOS marking?

Basically: If I have a TCP socket which is used by 2 different applications, each of which generates a particular kind of data; Is it possible to mark some flag using socket API's (or otherwise), which informs IP layer to perform DSCP marking based on the flag set?

Ex:
I write a program to do the following:
==> Open socket.
==> If data is from application A, set flag abc.
Or if data is from application B, set flag xyz.
==> Send.

And, when it reaches IP, it:
==> Marks DSCP field of the packet with 11 if flag abc is set;
==> Marks DSCP field of the packet with 22 if flag xyz is set.

Thanks for any pointers or suggestions.

Take a look at tc.

http://linux.die.net/man/8/tc

I do not know of a way to tag the traffic based on the socket but there should be some other way to identify the traffic based on ports, protocol, destination, etc.

Thanks Zmanea. But I was interested in knowing whether packets can be marked differently within a application which generates 2 types of data.
(In the example I wrote, I didn't actually mean 2 different applications (with different port numbers), but used it to imply two different types of data, sent on a single socket)

Thanks.

Hello Srikant,

Did you find any solution to your requirement.
Please share it, i am too stuck up @ the same point.

Thanks in anticipation
Regards, Sonika