networking-11

networking-11 - Introduction to Networking Internet:...

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Unformatted text preview: Introduction to Networking Internet: Example • Click -> get page • Specifies- protocol (http)- location (www.cnn.com) Internet: Locating Resource • www.cnn.com – name of a computer – Implicitly also a file • Map name to IP address – DNS host local com cnn.com? cnn.com? a.b.c.d a.b.c.d Internet: Connection • Http sets up a connection (tcp) – between the host and cnn.com to transfer the page • The connection transfers page as a byte stream – without errors: flow control + error control Host www.cnn.com Connect O K G et page Page; close Internet: End-to-end • Byte stream flows end to end across many links/switches: – routing (+ addressing) • That stream is regulated and controlled by both ends: – retransmission of erroneous or missing bytes; flow control HOST CNN.COM end-to-end pacing and error control routing Internet: Packets • The network transports bytes grouped into packets • Packets are “self-contained”; routers handle them 1 by 1 • The end hosts worry about errors and pacing – Destination sends ACKs; Source checks losses C HOST: B CNN.COM: A A | B | # , CRC | bytes B: to C Internet: Bits • Equipment in each node sends packets as string of bits • That equipment is not aware of the meaning of the bits • Frames (packetizing) vs. streams 01011...011...110 Transmitter Physical Medium Receiver 01011...011...110 Optical Copper Wireless Internet: Points to remember • Separation of tasks – send bits on a link: transmitter/receiver [clock, modulation,…] – send packet on each hop [framing, error detection,…] – send packet end to end [addressing, routing] – pace transmissions [detect congestion] – retransmit erroneous or missing packets [acks, timeout] – find destination address from name [DNS] • Scalability – routers don’t know full path – names and addresses are hierarchical Internet : Challenges • Addressing ? • Routing ? • Reliable transmission ? • Interoperability ? • Resource management ? • Quality of service ? Concepts at heart of the Internet • Protocol • Layered Architecture • Packet Switching • Distributed Control • Open System Protocol • Two communicating entities must agree on: – Expected order and meaning of messages they exchange – The action to perform on sending/receiving a message • Asking the time Layered Architectures • Human beings can handle lots of complexity in their protocol processing. – Ambiguously defined protocols – Many protocols all at once • How computers manage complex protocol processing? – Specify well defined protocols to enact. – Decompose complicated jobs into layers; • each has a well defined task Layered Architectures • Break-up design problem into smaller problems – More manageable • Modular design: easy to extend/modify....
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This note was uploaded on 02/19/2008 for the course CS 4410 taught by Professor Vollset during the Fall '07 term at Cornell.

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networking-11 - Introduction to Networking Internet:...

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