Advanced Topics in Operating Systems

Fall 1997

BGU Math & Computer Science Department

Protocol (PRELIMINARY!)

Protocol for client-server communication will consist of the following levels:

Socket Level Protocol

At this level, the protocol for socket connection is determined. We suggest reliable stream-oriented sockets. Thus, server does a listen, and then accept on its socket (this creates a new scoket descriptor). Upon connection, get message, perform operations, and respond via new socket descriptor. After sending returned result, either disconnect or leave socket around, depending on type. All servers must support at least the former type.

Message Level Protocol

Since we suggest single request connection at the socket level, each message will contain a return socket address to connect to, and an NFS request. The message should also include a host name and process ID, and a time stamp. A socket address will be reserved for future use, and contain -1 in the type field if not used. Types and structure defined by the include file comm_protocol.h.

NFS Level Protocol

These will follow the structure as in /usr/include/nfs include files. Message from client to server will consist of a procedure number, followed by the relevant argument structure, and response is a response structure, where applicable, as follows (first struct is paramenters, second is returned structure):

Errata and Addendum

We found that uid and gid are not transmitted. To add this, put them in the above order at the end of the message body (as sent by client). In this way, servers and clients that do not have the feature can work with no changes.