Re: CSMA

From: Pascal Bourguignon (spam_at_mouse-potato.com)
Date: 09/24/05 

Date: Sat, 24 Sep 2005 23:33:56 +0200

"rishi.shah@patni.com" <rishi.shah@patni.com> writes:

> I am implementing a project in c++/unix in which I need to simulate a
> CSMA MAC layer.
> The project is a simulation of peer to peer network where is each peer
> is a process on some unix machine. Though each client has a separate
> TCP communication line, I have to assume that they have a common line
> and each of the process has to follow the CSMA mechanism while
> transmitting that is if there is a collision while transmitting then
> both the processes have to revert back and transmit after some random
> interval of time. I have to assume that the entire network is runnning
> on a 9.6kbps line. Each peer notifies every other client if it sends a
> packet on the common line.
> I am struggling as to how to design such a network where I have to
> detect a collision since there is no delay in the unix socket
> communication. One idea could be to send the packet to a recipient,
> wait for x msec and then send a signal to the recipeint to go ahead. If
> the sender receives a packet from some other source during the xmsec
> wait time then it will not send the signal and the recipient will
> discard the packet.
> Are there any better ideas to solve this problem?

You need to have a line object and some packet objects, and the line
objects will be given packet objects at times and will compute when
there's a colision.

If your simulation runs on a distributed network, you have to maintain
a common clock to avoid some remote node sending packets in the past. 

-- 
"I have challenged the entire quality assurance team to a Bat-Leth
contest.  They will not concern us again."

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