Venkat Hallale wrote: > I am measuring the diffrent kinds of traffic like FTP traffic , WWW > traffic , Mail Traffic etc. at my gateway. The method which I have chosen > is , each of these services runs under different standard ports like 20 > ,21 for FTP , 80 for WWW etc. using the Linux IPCHAIN utility. I am > getting the values correctly, i.e. it is giving some exact values when I > tranfers a file or access any WWW server. > > Now my problem is , when a ftp or www clients gets connected to the ftp > or WWW server , it send a request to that particular port, and that > server will assign a different port not that particular port. At my > gateway I am listening to that particular port not the server assigned > ports and I am getting the exact values. Now the question is how this has > been happening. I am listing at that pericular ports, and servers will > assining different ports, How this mapping is done internally ? please > direct me some good URLs. For HTTP and non-passive FTP, the server end of the connection will use the reserved port (20 for FTP transfers), so these connections are easily identified. Passive FTP transfers use an ephemeral port at each end, so you cannot identify these connections. -- Glynn Clements <glynn@sensei.co.uk> - : send the line "unsubscribe linux-net" in the body of a message to majordomo@vger.rutgers.edu
