CMPE 541 TERM PROJECT PRESENTATION Remote Procedure Call for Distributed Processing

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CMPE 541TERM PROJECT PRESENTATION Remote
Procedure Call for Distributed Processing
EASTERN MEDITERRANEAN UNIVERSITYDEPARTMENT OF
COMPUTER ENGINEERING

• MERYEM ERBILEK

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OUTLINE

• Introduction
• Remote Procedure Call (RPC)
• Features of RPC
• User Package
• Design Issues of RPC
• How RPC works?
• Possible failures of RPC
• Conclusion
• References

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INTRODUCTION

• Remote Procedure Calling mechanisms integrate
• Client/Server arrangement with conventional
• procedural programming languages.
• ?In that case clients communicates with servers
  by
• calling procedures.

Client
Server
Request
Reply
Figure1 Client/Server Model
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Remote Procedue Call

• clients can only access to resources (in server)
  only by calling procedures which are supplied by
  services
• In RPC these services are modules with an
  interface that exports procedures to operate
  resources.
• ( ex authentication service?validity of
  names passwords )
• is modelled on the local procedure call but
  actually called procedure is executed in
  different remote process.

Caller
Called
Request
NETWORK
Reply
Figure2 RPC
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Features of RPC

• Remote procedure has I/O parameters
• Input parameters client ? server
• values of arguments(in request msg) copied into
  variables
• and passed as parameters to procedure (in the
  server).
• Output parameters server ? client
• They are used to replace variables in the client.
  
• Caller computer cant access to variables in
  called computer

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User Package

• is a library of conventional procedures that can
  be used in application programs.

Relationship between a client program,user
package andsoftware below RPC interface.
User Package Interface
?
RPC Interface
Figure3 Levels in client software
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User Package

• Why to support application program with user
  package
• RPC interface is not the most convenient for
  client programs because
• There are differences between local and remote
  procedures
• Service should be defined at a level appropriate
  for the widest possible use
• There are some tasks such as location of suitable
  server that must be performed by client

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User Package

• Advantages of user package
• The application progragrammer dont need to work
  in an interface definition language.
• Improve the performance and reduce the complexity
  of remote service (because some of the
  functionality of service can be put in user
  package).

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Design Issues of RPC

• Interface definition specifies characteristics
  of procedures which are provided by server but
  visible to clients.
• Exception handling is needed for reporting
  failures to clients (caller).
• Transparency is up to designers of interface
  languages.
• Transparent case client calls procedures in
  normal way
• Non-Transparent case client uses special
  notation for calling remote procedures.

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How RPC works?

• Binding is necessary when client and server
  starts first.
• Stub Procedure deals with marshaling and
  unmarshaling
• Communication Module deals with communication of
  client and server.

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Local Call ----------- Local Return
Marshalling Parameters ----------------- Unmarshal
ling Results
Send Req. --------- Receive Reply
CLIENT COMP.
NETWORK
Return ---------- Execute procedure
Marshalling Results --------------- Unmarshalling
Parameters
Send Reply --------- Receive Req.
SERVER COMP.
Figure4 RPCs flow of activity
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Possible failures of RPC

• 1. Request to server may lost
• 2. Server may crashes after receiving request
• 3. Reply to client may lost.
• 4. Client may crashes after sending request.

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CONCLUSION

• RPC is an attractive technique
• to the application programmer it is similar to an
  ordinary procedure call
• RPC is general technique for interprocess
  communication
• Today RPC is the core of many distributed
  systems
• used from object oriented Corba systems and
  reliability issues are more evident than in past.
• reliability issues are more evident than in past

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REFERENCES

• 1 Coulouris, G., Dollimore, J., Kindberg, T.,
  Distributrd Systems Concepts and Designs, 1994.
• 2 Y.Liu , D.B.Hoang,1996.OSI remote procedure
  call Standardization issues, design and
  implementation.Computer communications
  20,Elsevier B.V.
• 3 Sullivan, M. ,Anderson, D.,1989.Marinette a
  System for Parallel Distributed Programming Using
  a Master/Slave Model.IEEE.
• 4 Software Engineering Enstitute, Remote
  Procedure Call,
• Available at http//www.sei.cmu.edu/str/desc
  riptions/rpc.html
• 5 A. D. Marshall, Remote Procedure Call,
  Available at http//www.cs.cf.ac.uk/Dave/C/node33
  .htmlSECTION003300000000000000000