1. “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

2. 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

3. 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.

4. What Is RPC

5. 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.

6. 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

7. RPC Models – Cont’d

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

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

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

11. 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

12. 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

13. 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

14. Sun’s Secure RPC