> Date: Fri, 1 Jun 2001 12:00:03 +0530 (IST) > From: "G.Sambasiva Rao" <gsraoat_private> > > I am beginner in this field and am from india. I would like to know > one thing regarding backup. Pl enlighten me. > > What is the necessity of ports to be open during backup? An analogy would be ISDN with its control channels (D-channel) and data channels (B-Channels). The user connects with one B-Channel using the D-Channel to provide info on the type of connection, speed, et al. The user transfers data. The ISDN modem decides that data is not flowing fast enough and signals the remote end (via the D-Channel) to open another B-Channel. This process repeats until one of two things happens: a) data is leaving the modem as fast as it is arriving; (The server has no more bandwidth.) or b) there are no more B-Channels available. (If you have an ISDN PRI connection, there can be LOTS of B-channels!) In the case of a) above, the machine doing the transferring is physically limited in speed. In the case of b) above, the transmission medium is limited. Backups work about the same. The machine doing the storage is the server while the machine doing the transfer is the client. The client signals the server that it has data to store. The server and client exchange 'signals' and open a data connection (one set of data ports). At this point, the server may signal the client to say that it can take data faster. They open another data connection. (Another set of ports). This process repeats until one of four things happens: a) The pipe cannot take any more data (get a faster LAN); b) The server cannot accept any more connections; c) The client cannot make any more connections; or d) The storage medium cannot take data any faster. In the case of b) or c) you might want to get a more robust OS or faster, bigger machines. In the case of d) you might consider either getting more tape drives (to handle the backup in parallel) or getting faster drives. Or both! Of course, getting faster involves more money. Sometimes, LOTS of money... You'd have to figure out if the time available for the backup is sufficient to complete the backup. If you have 12 hours and only 10 hours of data, why spend money to make things faster? Unless you are planning for the future and are expanding...? (Expanding, in this case, means either more machines (perhaps, more users) or more data to backup...) Since we were talking about backing up machines in the DMZ, each set of data connections is another set of ports to open through the firewall. The above is not exact, but I believe it is a fair representation. If not, someone will correct me... (I hope!) Hope this helps. Regards, Gregory Hicks _______________________________________________ firewall-wizards mailing list firewall-wizardsat_private http://www.nfr.com/mailman/listinfo/firewall-wizards
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