DNS, Web, TCP Sequence Numbers EE122 Discussion 10/19/2011.

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DNS, Web, TCP Sequence Numbers EE122 Discussion 10/19/2011

DNS Mapping between names (e.g., and addresses (e.g., ) Hierarchy of DNS servers – Root servers – Top-level domain (TLD) servers – Authoritative DNS servers – Default Name Server

HTTP Request-response protocol Based on a global naming system – …which uses the DNS for resolution HTTP runs on top of TCP

TCP Sequence Numbers Initial sequence number for the connection is not zero Sequence number refers to the first byte in the TCP packet payload

Example (from class) Packet arrives: –S–Seq: 2323 –A–Ack: 4001 –W–W=3000 –[–[no payload] Appropriate response? Seq: 4001, payload: Seq: 2001, payload: Seq: 4001, payload: Seq: 5001, payload: Seq: 8001, payload: