EE122 Discussion 10192011 DNS Mapping between names eg wwwcnncom and addresses eg 15716625518 Hierarchy of DNS servers Root servers Toplevel domain TLD servers Authoritative DNS servers ID: 1045641
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1. DNS, Web, TCP Sequence NumbersEE122 Discussion10/19/2011
2. DNSMapping between names (e.g., www.cnn.com) and addresses (e.g., 157.166.255.18)Hierarchy of DNS serversRoot serversTop-level domain (TLD) serversAuthoritative DNS serversDefault Name Server
3. HTTPRequest-response protocolBased on a global naming system…which uses the DNS for resolutionHTTP runs on top of TCP
4. TCP Sequence NumbersInitial sequence number for the connection is not zeroSequence number refers to the first byte in the TCP packet payload
5. Example (from class)Packet arrives:Seq: 2323Ack: 4001W=3000[no payload]Appropriate response?Seq: 4001, payload: 4001-8000Seq: 2001, payload: 2001-5000Seq: 4001, payload: 4001-5000Seq: 5001, payload: 5001-6001Seq: 8001, payload: 8001-9000