WAP-WML (2)

WAP-WML (2) - System Design Patterns 1 Model 1 architecture...

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1 System Design Patterns
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2 Model 1 architecture
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3 Model 2 architecture – MVC Design Pattern
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4 Various clients for an Enterprise Application
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5 The Wireless Web
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6 HTTP and HTML Why they are not suitable for the wireless web? WAP i-Mode Agenda
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7 HTTP and HTML
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8 The World Wide Web Application-Layer Protocol: HyperText Transfer Protocol (HTTP) Two versions http/1.0, http/1.1 Currently, http1.1 is used by most implementations Language HyperText Markup Language (HTML)
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9 HTTP Transaction An HTTP transaction consists of an HTTP request issued by a client, and an HTTP response sent from a server. All HTTP transactions are stateless. server maintains no information about past client requests Client Server request response
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10 Example: HTTP messages Request to Server, port 80 Request to Server, port 80 GET / HTTP/1.0 Response from Server Response from Server HTTP/1.1 200 OK Date: Tue, 12 Nov 2002 06:33:50 GMT Server: Apache/1.3.20 (Unix) Last-Modified: Fri, 05 Oct 2001 06:10:55 GMT Content-Length: 195 Content-Type: text/html Connection: close <HTML> <HEAD><TITLE> ABC Company’s Homepage </TITLE></HEAD> <BODY><IMG SRC=“abc.gif”> <IMG SRC=“www.cityu.hk/abc_company.jpg”> </BODY> </HTML> HTTP messages are in ASCII HTTP messages are in ASCII (a human-readable format) (a human-readable format)
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11 TCP Transport Service HTTP uses TCP: 1. client initiates TCP connection to server, port 80 2. server accepts TCP connection from client 3. http messages exchanged between browser (http client) and Web server (http server) 4. TCP connection closed
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12 Problems with HTTP Protocol headers are unnecessarily Protocol headers are unnecessarily large large Headers are readable for humans and in ASCII. Protocol headers are sometimes Protocol headers are sometimes redundant redundant Many information fields are transferred over and over again with each request
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13 Problems with HTTP Uncompressed content transfer Uncompressed content transfer Unless the applications compress content (e.g. GIF and JPEG images). Using TCP Using TCP huge overhead per request (3-way- handshake) slow-start problem
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TCP Connection Setup Overhead Host A Host A (Client) (Client) Host B Host B (Server) (Server) TCP SYN TCP SYN/ACK TCP ACK HTTP Request HTTP Response Connection Connection Setup Setup Data Data Transmission Transmission Time    Event t Host A sends a TCP SYN chronize packet to Host B t+1 Host B receives A's SYN t+2 Host B sends it's own SYN chronize t+3 Host A receives B's SYN t+4 Host A sends ACK nowledge ACK . TCP connection is established. The 3 way handshake The 3 way handshake
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WAP-WML (2) - System Design Patterns 1 Model 1 architecture...

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