(Illustration by Gaich Muramatsu)
On Sun, 24 Jan 1999, SOM Bandyopadhyay wrote: > I have this question for CODA ... > > 1. Is there a callback mechanism from CODA server to client? Yes, just like in AFS, it's like oplocks in SMB protocol, but the cached data is persistent. > > 2. If so, does it happen when clients are not connected to servers? In > that case, do CODA servers initiate TCP connections to CODA clients? First of all, we use UDP not TCP. Our RPC2 package has a concept of connections, that are supposedly more light weight than TCP. All these connections are multiplexed over a single UDP socket. For file transfers we use a "side effect" called SFTP, which uses one other socket. The servers and clients drop all callback and connection information when the connection disappears. When the client reconnects, it needs to revalidate it's cache, for which it uses a fast, multilevel cache validation scheme. > > 3. If 2 is true...then I have list of problems and concerns including Oh dear... > > a) how do u handle DHCP address change? Probably this works just fine. I don't think that the IP of the client is every stored across disconnection, as you see above. When that client comes back, with a different IP, the server just sees a new client, but that is fine. Admittedly, this may not quite work correctly at the moment, but the what I am trying to say is that I don't see a design problem. > b) firewalls limiting incoming connections.. This is a sore point. We need to modify the UDP connection setup so that the client also sets up the "reverse" connection for the callbacks (where the server is on the client and the client is on the Coda server.). > c) limitations of Win95/98 ( may be NT workstations) to > handle large number of incoming connections... This is no problem, since we use a single UDP socket on the server (well, in fact we use two) for all clients. - Peter - > > etc.... > > > thanks, som. > >Received on 1999-01-25 09:11:33