WAP-WML

WAP-WML - System Design Patterns 1 Model 1 architecture...

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1 System Design Patterns
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Manisha Akolkar Model 1 architecture
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Manisha Akolkar Model 2 architecture – MVC Design Pattern
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Manisha Akolkar Various clients for an Enterprise Application
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5 The Wireless Web
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Manisha Akolkar 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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Manisha Akolkar 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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Manisha Akolkar 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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Manisha Akolkar Example: HTTP messages Request to Server, port 80 Request to Server, port 80 GET / HTTP/1.0 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)
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Manisha Akolkar 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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Manisha Akolkar 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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Manisha Akolkar 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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Manisha Akolkar 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 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 t+5 Host B receives ACK . TCP connection is established. The 3 way handshake The 3 way handshake
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Manisha Akolkar TCP Sync packet contents Source address Destination address Packet size Packet format Content type to be sent across by the next packet
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Manisha Akolkar TCP slow start problem TCP slow start is an algorithm Avoids "congestion collapse" in a network (network flooding ) First transmission should be a single packet.
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WAP-WML - System Design Patterns 1 Model 1 architecture...

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