Turning a HTTP Proxy Server

1

• Turning a HTTP Proxy Server
• To
• WAP Gateway
• Hsing Mei Yi-Ming Wen
•  
• Web Computing Lab
• Computer Science and Information Engineering
  Department
• Fu Jen Catholic University
• http//weco.csie.fju.edu.tw
• mei_at_csie.fju.edu.tw

2
Outline

• Introduction
• Gateway Structure
• HTTP Proxy Operations vs. WAP Gateway Operations
• Implement Header Translation
• Convert HTTP Proxy to WAP Gateway
• Push Operation
• WAP Test-bed
• Conclusion and Future Work

3
Introduction

• Main tasks of WAP Gateway
• Content Compilation, Header Translation, Push
  Mechanism
• The Header Translation and Push Mechanism are two
  major concerns in this research
• On Header translation
• Our original HTTP proxy server is designed with
  coded HTTP header to enhance the internal
  operation speed
• Using a mapping table to replace the internal
  HTTP operation codes to WSP header codes
• On Push Mechanism
• Propose a possible push operation sequence to
  implement
• A WAP test-bed is under development

4
HTTP Proxy Operations

• User agent (i.e. client system) sends a request
  to the HTTP proxy, and asks for a particular
  resource (e.g. a page).

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HTTP Proxy Operations

• After receiving and interpreting the request,
  proxy checks if the resource had been cached in
  the disk. It's called a Hit when the resource is
  found and fresh enough, then proxy sends a
  response to user agent.

This effect of a cache is that the
request/response chain is shortened. Otherwise,
a Miss situation occurs, and the sequences
continue to next step.
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HTTP Proxy Operations

• Proxy rewrites all or part of the request, and
  forwards the reformatted message toward the
  origin server.

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HTTP Proxy Operations

• The web server receives the request, and replies
  a suitable response.

8
HTTP Proxy Operations

• After receiving the response sent by origin
  server, proxy would cache the message if it is a
  cacheable message.

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HTTP Proxy Operations

• At last, the response is replied to user agent.

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WAP Gateway Operations

• User agent (i.e. client system) sends a URL
  request to a WAP gateway (i.e. WSP request).

11
WAP Gateway Operations

• The WAP gateway decodes the request massage and
  translates the request line and request header
  (in binary-format) to HTTP format using a mapping
  table.

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WAP Gateway Operations

• The WAP gateway creates a connection to the web
  server and sends a HTTP request to it.

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WAP Gateway Operations

• The HTTP request is processed by the web server.
  If the URL refers to a static file, web server
  fetches the file to response with a HTTP reply
  header if the URL refers to a script
  application, web server starts the application.

4
14
WAP Gateway Operations

• The web server returns a HTTP reply message,
  which contains data or result from script
  application.

4
15
WAP Gateway Operations

• The WAP gateway encodes the received reply
  message, and translates HTTP well-known-formatted
  reply line and reply header to WSP binary-format
  using the mapping table.

4
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WAP Gateway Operations

• At last, the response is replied to user agent.

4
17
Http Proxy vs. WAP Gateway
Proxy
Gateway

• Difference

• Client side environment

• The protocol used between client and gateway

• The caching is an optional operation in the WAP
  Gateway

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Header Translation Implementation

• Threaded HTTP Proxy Controller

• Dispatch Module
• establish a socket connection, forward the
  request to record state and start request thread

• State Module
• binds the resources with the request

• Request Thread Module
• accomplishes all tasks starting from receiving
  client request, and up to responding reply message

• Request Decoding Module
• request line and request header decoding

• Proxy Connection Module
• connects to the web server , rewrites a HTTP
  request and sends to the Internet

• Reply Encoding Module
• response status line encoding and response header
  encoding

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Header Translation Example
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Convert Http Proxy to WAP Gateway

• A HTTP Proxy could to transfer to a WAP Gateway
  by adding some mechanisms

• On the client side, a header decoder and a header
  encoder for protocol translation are attached.

• On the server side, we add a content complier for
  content compacting.

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Push Operation Sequences

• A push operation in WAP occurs when a Push
  Initiator transmits content to a mobile client

• The Push Initiator is on the Internet, and the
  mobile client is in the WAP domain

Internet
WAP Domain

• The Push Proxy Gateway (PPG) is needed

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Push Operation Sequences

• A Push Initiator submits a push message to a PPG.
  The push message is a multipart type, which
  contains a

XML control entity and a content entity, and may
contain a RDF-format capabilities entity defined
in the user agent profile.
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Push Operation Sequences

• The PPG determines to accept or to reject the
  received push message. If the PAP push message
  element is

not valid with respect to its document type
definition (DTD), the PPG must rejects it.

• The PPG reports the acceptance/rejection result
  in the response which is an XML document.

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Push Operation Sequences

• The PPG parses control information of push
  message to determine where and how should
  deliver.

• A PI must identify client addresses for
  submitting.

• The PPG converts the protocols between the
  Internet and WAP domain.

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Push Operation Sequences

• If there is no error, the PPG must deliver either
  confirmed or unconfirmed push primitives.

• In a confirmed push, PPG sends a request to a
  Session Initiation Application (SIA) in order to
  create an active WSP session.

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Push Operation Sequences

• When a client receives a pushed message,
  Application Dispatcher (AD) parses the push
  message header to

• determine its destination application and to run
  it.

• If the Push delivery method is confirmed push,
  the client responses a primitive.

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Push Operation Sequences

• The PPG sends a Result Notification to inform the
  PI of the outcome of the push submission.

• The PI returns a response message to the Result
  Notification message.

• Listed push operation sequences are all required
  operations, It omits the optional operation
  part.

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WAP Test-bed

• Two major behavior in WAP Test-bed pull and push

• In pull condition, the Pull Event Generator
  simulates a great deal of clients and sends
  requests to gateway

• In push condition, the Push Event Driver starts
  scheduled push delivery with push messages
  according to subscriber list

• The Packet Filter classifies receiving packets
  and records the related information respectively

• According to the recorded information, the
  statistic analysis will be able to do

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Conclusion and Future Work

• Conclusion
• Quickly turning a HTTP Proxy Server to WAP
  Gateway by adding extra mechanisms is feasible
• A possible push operation sequence is proposed
• A WAP Test-bed to evaluate the WAP gateway

• Future Work
• Continue implementing the functionality of our
  WAP Push Gateway
• Complete the WAP Test-bed and investigate the
  gateway performance
• Support Jini services on the WAP Gateway
• Estimate the rationality of the proxy caching
  operation within WAP Gateway