Comparison between-rpc-rmi-and-webservices-son-1228374226080667-8

ok

1. By
Jihed Othmani
Jing Wang
Karim Jouini
Mathieu Martin
1

2. Outline
The need
RPC (Remote Procedure Call)
Quick introduction
Samples
Advantages & disadvantages
Future?
RMI (Remote Method Invocation)
Quick introduction
Samples
Advantages & disadvantages
Future?
WebServices
Quick introduction
Samples
Advantages & disadvantages
Recap & Conclusion
2

3. The Need
More and more devices are connected, tempting us to
take advantage of their computational capabilities.
We would like to communicate, reuse code, share
services.
There are a lot of opportunities to leverage services
offered by others and to make your application publicly
available.
Provide a service without sharing code.
So : we need a standardization of protocols to ease
communication at the application layer.
That’s what we call middlewares.
3

4. 4

5. RPC – Quick Introduction
First system to address the need to communicate
across process’ and machines boundaries.
RPC was first described in 1976 by the RFC707.
Xerox used RPC in the popular software “courier”, 1981.
Paradigm:
The client process has to “know” the serving process
and instantiates the communication.
The client process calls a distant procedure and waits
for the response (or fail).
5

6. RPC – Samples
A “simple” server (part 1)
6

7. A “simple” server (part 2)
7

8. A “simple” client using our previous server
8

9. RPC – Advantages
Advantages :
Very simple logic and very low level, gives to the
programmer a lot of freedom to implement different
mechanisms on top of it.
Can be implemented by any language (including C !).
RPC exists since 1976, so its maturity and solidity are
undoubted.
9

10. RPC – Disadvantages
Using RPC can become very complex
The complexity is exposed as the number of procedures
Interaction with such a module requires using all these
interfaces in the right way and sequence.
A lot of code is needed for even simple applications.
RPC gives no answer to fundamental questions:
How to find peers ?
How to distribute the workload over multiple servers?
How failure and recovery should be handled?
How to send/receive complex data structures.
Security? Sasser, blaster, etc … Are RPC-vulnerability exploits
There are multiple different and incompatible RPC
protocols.
10

11. RPC – Future ?
RPC is way too complex to be used as middleware in
modern software.
RPC can be used as low level layer for more powerful
middleware layers, that would be able to provide us
with :
OOP
Load balancing
Failure detection/correction
Etc …
11

12. 12

13. RMI – Quick Introduction
The Java Remote Method Invocation API, or Java RMI,
is a Java application programming interface for
performing the object equivalent of Remote
Procedure Calls.
There are two common implementations of the API.
Java Remote Method Protocol (JRMP)
In order to support servers running in a non-JVM
context, a CORBA version was later developed.
Uses HTTP or IIOP as communication layer.
13

14. RMI – Samples
Here is a Server publishing a “Hello” Object
14

15. RMI – Samples
Here is client invoking the previous “Hello” Object
and calling “HelloFromServer()” On it !
15

16. RMI – Advantages & disadvantages
Advantages
Java, so portable and Oriented Object.
NAT-Firewall traversal capabilities.
Asynchronous possibilities with ARMI (Async’-RMI).
Easier to use and setup than CORBA.
RDMI enables dynamic invocation.
First attempt to address security.
Latest versions are CORBA-compatible (using IIOP).
Disadvantages
Java only…
16

17. RMI – Future ?
RMI still needs to find answers to:
How to implement real server-level security ?
How to perform load balancing ?
How to use RMI in other languages ?
17

18. 18

19. Web Services – Quick Introduction
A software system designed to support interoperable
machine-to-machine interaction over a network.
It refers to clients and servers that communicate over
the HTTP protocol used on the Web.
Web services range from such major services as
storage management down to much more limited
services such as the furnishing of a stock quote.
19

20. Web Services – Advantages
Universal Support.
Protocol not Platform.
Low Product Costs.
Evolutionary thanks to XML.
Business Oriented.
The standardized nature of the pieces that implement a Web service solves
many problems related to intersystem communication. For example:
The HTTP standard allows more systems to communicate with one another.
SOAP (built on XML) standardizes the messaging capability on different systems.
UDDI standardizes the publishing and finding of Web services.
WSDL standardizes the description of Web services, so providers and requesters
speak the same language.
Opportunities to take advantage of services offered by others and to make
your applications available to others as a Web service.
 Mashups (ex: Jogli.com)
20

21. Web Services – Disadvantages
No security standards: Web services are exposed to the public
using http-based protocols.
Adopting open security standards like SSL or XML-encryption
may be a solution.
Processing time and data traffic costs are significantly higher
Very verbose : Multiplication of the conveyed information mass.
But:
To buy a faster CPU is cheaper than employing a programmer and
systems administrator capable of handling RMI.
Performance differences less marked for more realistic applications
than for toys like “calculator”.
You can use cloud systems to easily scale.
No load balancing at the protocol level.
21

22. Web Services – Samples
Google's Web Service - access the Google search
engine.
Amazon's Web Service - access Amazon's product
information .
XMethods - collection of information about existing
Web services.
Getting the last stock quote.
22

23. 23

24. Recap
24
RPC RMI Web Services
Birth 1976 - 1981 ~ 1990 ~ 2000
Platform Library and OS-
dependant
Java Independent 
Transport OS-Dependent HTTP or IIOP HTTP(s)
Dev Cost Huge Reasonable Low
Security None Client-level Transport Level
Overhead None OOP + HTTP XML + HTTP
Dynamic invocationNone Yes, using RDMINatural
Versioning Huge problem Possible using
RDMI
Natural
Service lookup Impossible Java Naming and
Directory
UDDI

25. 25