mishkin@apollo.HP.COM (Nathaniel Mishkin) (06/28/90)
In article <jwright.646370800@quonset>, jwright@cfht.hawaii.edu (Jim Wright) writes: |> nick@bischeops.UUCP (Nick Bender) writes: |> >As for the efficiency side - you have one more call using RPC than NCS: |> > |> > RPC: user -> portmap -> user -> server -> user |> > NCS: user -> LLB -> server -> user |> > |> >Of course the GLB may make an even larger difference, but is this a case |> >of micro-optimization? |> |> This is a question, not a statement of fact. Is my understanding correct? |> |> For RPC, your first "->" must be directed to a specific machine which |> you know will be running your server. All the portmap does is say how |> to actually connect to the server on that machine. |> |> For NCS, the first "->" is routed (without client program intervention) |> to the location broker, which then sends your request to the machine |> which can process the call. Thus you are not required to have a priori |> knowledge of where the server resides. I think there's probably some bit of confusion here. (It's a little hard to tell since I never got a copy of the innermost article above.) The "LB" consists of two pieces: The Global Location Broker (GLB) and the Local Location Broker (LLB). An LLB runs on every machine and does the forwarding job (i.e., transparently forwards a request sent to the MACHINE to the appropriate server PROCESS on the machine). We believe that the facts that this scheme results in only one real network message exchange and that it's all transparent to the application are important. The GLB is a place a client can look to find the address of a particular machine. Clients make an RPC to the GLB and then use the results to make a call to another machine. While these two steps can be pretty much concealed (via NIDL's auto-binding mechanism), from the point of view of the wire, two message exchanges occur, as opposed to the one that occurs when using (just) the LLB (i.e., because you know the machine you want to talk to a priori). -- Nat Mishkin Cooperative Object Computing Operation Hewlett-Packard Company mishkin@apollo.hp.com
mishkin@apollo.HP.COM (Nathaniel Mishkin) (07/06/90)
For those interested in seeing yet more discussion on RPC, please cast your gaze to comp.protocols.misc. I'm posting my replies there now. -- Nat Mishkin Cooperative Object Computing Operation Hewlett-Packard Company mishkin@apollo.hp.com