lec-8 - What's next. Network Applications Web and HTTP 19...

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19 Aug 2008  BITS C481 (Computer Networks) 1 What’s next… Network Applications Web and HTTP
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19 Aug 2008  BITS C481 (Computer Networks) 2 HTTP connections Nonpersistent HTTP At most one object is sent over a TCP connection. HTTP/1.0 uses nonpersistent HTTP Persistent HTTP Multiple objects can be sent over single TCP connection between client and server. HTTP/1.1 uses persistent connections in default mode
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19 Aug 2008  BITS C481 (Computer Networks) 3 Non-Persistent HTTP: Response time Definition of RTT: Time to send a small packet to travel from client to server and back. Response time: One RTT to initiate TCP connection One RTT for HTTP request and first few bytes of HTTP response to return File transmission time Total = 2RTT + transmit time time to transmit file initiate TCP connection RTT request file RTT file received time time
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19 Aug 2008  BITS C481 (Computer Networks) 4 Persistent HTTP Nonpersistent HTTP issues: Requires 2 RTTs per object OS overhead for each TCP connection Browsers often open parallel TCP connections to fetch referenced objects Persistent HTTP Server leaves connection open after sending response Subsequent HTTP messages between same client/server sent over open connection Persistent without pipelining: Client issues new request only when previous response has been received One RTT for each referenced object Persistent with pipelining: Default in HTTP/1.1 Client sends requests as soon as it encounters a referenced object As little as one RTT for all the referenced objects
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 BITS C481 (Computer Networks) 5 HTTP request message Two types of HTTP messages: request , response HTTP request message: ASCII (human-readable format) GET /somedir/page.html HTTP/1.1 Host: www.someschool.edu User-agent: Mozilla/4.0 Connection: close Accept-language:fr (extra carriage return, line feed) request line
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lec-8 - What's next. Network Applications Web and HTTP 19...

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