Network Class 5

• Non-persistent HTTP

 

1. user enters URL (www.~)

2. HTTP client(browser) initiates TCP connection to HTTP server at www.~ on port 80

3. accept → HTTP client sends HTTP request message (containing URL)

4. HTTP server receives request message, forms response message

5. HTTP server closes TCP connection

6. HTTP client receives response message containing html file, displays html

7. Parsing html file, finds (10) referenced jpeg objects

8. repeated for each of (10) jpeg objects

 

 

• Non-persistent HTTP : response time

 

- RTT(Round Trip Time) : time for a small packet to travel from client to server and back

 

- HTTP response time: 2RTT + file transmission time

 

 

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• non-persistent HTTP issues:

     - requires 2 RTTs per object

     - browsers often open parallel TCP connections to fetch referenced objects

     - OS overhead for each TCP connection

 

• persistent HTTP:

     - server leaves connection open after sending response

     - subsequent HTTP messages between same client/server sent over open connection

     - client sends requests as soon as it encounters a referenced object

     - as little as one RTT for all the referenced objects