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Lecture 3

Lecture 3. Network Architecture. Host. Host. Application. Host. Channel. Application. Host. Host. Inter-Process Communication. Turn host-to-host connectivity into process-to-process communication. Fill gap between what applications expect and what the underlying technology provides.

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Lecture 3

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  1. Lecture 3 Network Architecture Datacom 1

  2. Host Host Application Host Channel Application Host Host Inter-Process Communication • Turn host-to-host connectivity into process-to-process communication. • Fill gap between what applications expect and what the underlying technology provides. Datacom 1

  3. Channel protocol, a simple example • Sender • Receives Data and destination from Application in Application’s format • Prepares and sends packets across the network with delivery guarantee—no guarantee about application data quality • Receives packets from network • Reciever • Sends and Receives Ack(nowledgements) • Sends Data to Application Datacom 1

  4. Channel Function: Sending Side • Creates packets from message-segmentation • Marks packets alternately with 0 or 1 • Attaches address of receiver • Sends next packet on (Ack)nowledgement • If 1 is sent and Ack is 0, resend • If 1 is sent and Ack is 1, send next • Etc. Datacom 1

  5. Channel Function: Receiving Side • Receive packets • Send Ack with 0 or 1 attached • Strip header • Reassemble message and send to application Datacom 1

  6. Layering • Use abstractions to hide complexity • Abstraction naturally lead to layering Datacom 1

  7. Layering • Alternative abstractions at each layer Application programs Request/reply Message stream channel channel Host-to-host connectivity Hardware Datacom 1

  8. Protocols • Building blocks of a network architecture • Provides communications service that higher level objects use to exchange messages • Each protocol object has two different interfaces • service interface: operations on this protocol • peer-to-peer interface: messages exchanged with peer • Term “protocol” is overloaded • Abstract object • specification of peer-to-peer interface • module that implements this interface-different implementations should be interoperable Datacom 1

  9. Interfaces Host1 Host2 Service High-level High-level interface object object Protocol Protocol Peer-to-peer interface Datacom 1

  10. Protocol Machinery • Protocol Graph • most peer-to-peer communication is indirect • peer-to-peer is direct only at hardware level Host 2 Host 1 Applicationemploys services of protocol stack RPP/HHP Asks Invokes Transmits Digital Digital Video Video File File library library application application application application application application RRP MSP RRP MSP HHP HHP

  11. Standards • Enternet Engineering Task Force (IETF) • International Standards Organization (ISO) +International Telecommunications Union (ITU) • Network Architecture-set of rules governing form and content of a protocol graph e.g. ISO or Internet Architecture Datacom 1

  12. Machinery (cont) • Multiplexing and Demultiplexing (demux key) • Encapsulation (header/body) Host 1 Host 2 Header is a message to a peer not a lower level protocol Application Application program program Data Data RRP RRP RRP Data RRP Data HHP HHP HHP RRP Data

  13. ISO or OSI ArchitectureOSI= Open Systems Interconnection End host End host Application Application Presentation Presentation Session Session Transport Transport Network Network Network Network Data link Data link Data link Data link Physical Physical Physical Physical One or more nodes within the network Datacom 1

  14. Typical OSI Services by Layer • Physical—transmission of raw bits • Data Link-transmission of frames—network adaptors and OS software implements this layer • Network- routing of packets • Transport-End host function- • Session-ties together transport streams-video+audio (obsolete) • Presentation-Data format etc. (obsolete) • Application layer-FTP, Video Conference etc. Datacom 1

  15. FTP HTTP NV TFTP UDP TCP IP … NET NET NET 2 1 n Internet Architecture • Defined by Internet Engineering Task Force (IETF) • Hourglass Design • Application vs Application Protocol (FTP, HTTP) Datacom 1

  16. Internet architecture-another view Datacom 1

  17. Internet architecture services by layer • Network • Ethernet—copper, network adapter, network device driver • Fiber Distributed Data Interface (FDDI) • IP-specifies interconnection of multiple networking technologies-creates single, unified network • Transport or end-to-end protocols • TCP reliable byte-stream channel • UDP Unreliable datagram delivery channel • Applications FTP, TFTP, SMATP, HTTP Datacom 1

  18. 3-features of Internet Architecture • Strict layering is abandoned • IP is the big idea—a single protocol for interconnecting networks and providing host-to-host connectivity • To become a standard requires a working implementation Datacom 1

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