1. Content Network Navigation Sanjoy Sanyal:www.itforintelligentfolks.blogspot.com

4. Try This! Go to the Command Line and type >ns lookup www.yahoo.com And typical response will be Server: Address: …… Name: Address: Your Server details Host details The Hosts file still exists!. It is used to allow users to specify an IP address to use for a hostname without checking DNS You can find it here: indowsystem32rivers tc Sanjoy Sanyal:www.itforintelligentfolks.blogspot.com

6. DNS Components Source : Wikipedia Sanjoy Sanyal:www.itforintelligentfolks.blogspot.com

11. DNS Request Resolution Home Client Local ISP Root Name Server gTLD Name Server 1 2 3 4 5 6 7 8 Home Client resolver is configured to communicate with local name server at ISP. Home Client sends recursive request for IP address Local name server at ISP sends iterative request to root name server. Root name server responds with gTLD Name Server Local name server sends iterative request to gTLD name server The gTLD name server provides the authoritative name server for the requested domain The local name sever sends iterative request to authoritative name sever The server responds with authoritative answer The local DNS responds back to client and caches the reply 1 3 4 5 2 6 7 8 Sanjoy Sanyal:www.itforintelligentfolks.blogspot.com

13. Switching Connecting to Endpoints The key issue in switching is to ask which web server to connect to? The objective is to balance the load between servers In this section we will discuss several ways to achieve load balancing Sanjoy Sanyal:www.itforintelligentfolks.blogspot.com

15. Web Switches: Layer 4 switching Internet HTTP Server RTSP Server FTP Server Web Swith Name Server Client The Web switch is assigned an IP address – actual , registered and routable. Traffic does not stop at the Web Switch – connected thru to the real web Server Web switch can be configured to examine TCP Port numbers in making switching decisions (hence Layer 4 switching) The Web switch is called the VIP (Virtual IP address). Clients only see the VIP Port 80 traffic Port 554 traffic Port 20,21 traffic Sanjoy Sanyal:www.itforintelligentfolks.blogspot.com

20. Network Address Translation S IP=X D IP = SW Client X Switch SW Association SIP X SW DIP SW A SIP SW A DIP X SW S IP=SW D IP = A S IP=A D IP = SW Server A Annotation S = Source D = Destination Connecting individual clients to real servers behind a Web switch requires switch to perform NAT Switch does not terminate the protocol. It adjusts the header parameters Similar translation is required for port numbers The header checksums will also have to be adjusted Additional translations are needed to handle FTP and ICMP messages Number of associations can be large! Sanjoy Sanyal:www.itforintelligentfolks.blogspot.com

23. Layer 7 Switching: 3 steps Server Web Switch Client GET Step 1: Accept client connection and receive GET request GET Step 2: Choose server, make a connection and send GET request Client Step 3: Splice connections together (after translating TCP packet sequence and acknowledgement numbers) Sanjoy Sanyal:www.itforintelligentfolks.blogspot.com

25. Steering Client Requests Once the destination has been selected (which is what we have learnt so far) several techniques can direct client requests to the destination Sanjoy Sanyal:www.itforintelligentfolks.blogspot.com

28. Understanding GSLB Internet Web Swith and Authoritative DNS Local DNS server Client The Client’s DNS resolver requests IP address from its local DNS server – belonging to ISP The request makes its way thru the DNS system till it reaches an authoritative server name for the domain The network is configured such that the only authoritative server names are GSLB-enabled switches The response is the service node that is likely to give the best performance since the GSLB switch is aware of the health of all service nodes Performance Information Exchange Web Swith and Authoritative DNS Sanjoy Sanyal:www.itforintelligentfolks.blogspot.com

30. Understanding HTML rewriting LA Server East Coast Client West Coast Client NY Server Main Server … http://ny.rewrite.net/.../logo.jpg http://ny.rewrite.net/.../text. html http://ny.rewrite.net/.../figure.jpg … http://la.rewrite.net/.../logo.jpg http://la.rewrite.net/.../text. html http://la.rewrite.net/.../figure.jpg Sanjoy Sanyal:www.itforintelligentfolks.blogspot.com