“Request /Reply Communication” Poornima Institute of Engineering & Technology, Jaipur Department of Computer Engineering A Presentation on Presented by,: Manish Bhardwaj Assistant Professor “Request /Reply Communication” Lecture No-17 Subject Code -8 CS3 Subject Name- Ds

OUTLINE Introduction to RPC RPC Operations Parameter Passing and Data Conversion Binding Compilation Exception and failures handlings Security RPC Exception and Failure Handling Exception Handling Failure Handling Secure RPC

Request /Reply Communication Service –oriented Request/ reply communication The Request/Reply (R/R) communications method is a very common technique for one application to request the services of another. It is used both by operating systems and applications NFS is implemented as a set of RPCs DCOM, CORBA, Java RMI, XML-RPC, etc., are all basically just RPC RPC is most widely used example.

What Is RPC

How it works The client makes a procedure call that sends a request to the server and waits. The thread is blocked from processing until either a reply is received, or it times out. When the request arrives, the server calls a dispatch routine that performs the requested service, and sends the reply to the client.

RPC Models [4] There are several variations on the standard RPC “synchronous request/response” model Each model provides greater flexibility, at the cost of less transparency Certain RPC toolkits support all the different models E.g. ONC RPC

RPC Models – Cont’d

Parameter Passing and Data Conversion Types of data which can be passed and representation of data in messages.

Binding Way to locate a server by client and how server registers it for services.

Compilation From where the stub procedures comes and how the linking is provided between client and servers.

RPC Exception and Failure Exception: in-band or out-band signaling Link failure: retransmission, sequence number and idempotent requests, Use of transaction id xid Server crash: – at least once: server raises an exception and client retries – at most once: server raises an exception and client gives up – maybe: server raises no exception and client retries Client crash: – orphan killed by client – orphan killed by server – orphan killed by expiration

Secure RPC Security is important RPC for two reason: RPC introduces vulnerability Acts as cornerstone of client /server computation. An Authentication protocol need to establish following rules for security: Mutual Exclusion Message Integrity, confidentiality and originality

Secure RPC Cs and Ss are 128-bit random numbers. • Cp = Cs mod M, and Sp = Ss mod M, where and M are known constants. SKcs = SCs p = (Ss)Cs = SsCs SKsc = CSs p = (Cs)Ss = CsSs

Sun’s Secure RPC