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CSCE 201 - Farkas 1 CSCE 201 CSCE 201 Computer Networks Computer Networks

CSCE 201 - Farkas1 CSCE 201 Computer Networks. CSCE 201 - Farkas2 Reading Assignment Required: – Security Awareness: Chapter 3 Recommended: – Internet

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Text of CSCE 201 - Farkas1 CSCE 201 Computer Networks. CSCE 201 - Farkas2 Reading Assignment Required: –...

  • CSCE 201 - Farkas*

    CSCE 201 Computer Networks

    CSCE 201 - Farkas

  • CSCE 201 - Farkas*Reading AssignmentRequired:Security Awareness: Chapter 3Recommended:Internet Society (ISOC) homepage, http://www.isoc.org Computer Network, http://en.wikipedia.org/wiki/Computer_network Easttom: Chapter 2

    CSCE 201 - Farkas

  • CSCE 201 - Farkas*Before InternetIsolated, local packet-switching networks only nodes on the same network could communicateEach network is autonomous:

    different services different interfaces different protocols

    CSCE 201 - Farkas

  • CSCE 201 - Farkas*Before Internet (cont)ARPANET: sponsored by Defense Advanced Research Projects Agency (DARPA): 1969: interconnected 4 hosts 1970: host-to-host protocol: Network Control Protocol (NCP) 1972: first application: e-mailUniv. of California at LA (UCLA)Stanford Research Institute (SRI)Univ. of California at Santa Barbara (UCSB)Univ. of Utah

    CSCE 201 - Farkas

  • CSCE 201 - Farkas*InternetConnect Existing Networks:ARPANET, Packet Radio, and Packet SatelliteNCP not sufficient Develop new protocol 1970s: Transmission Control Protocol (Kahn and Vinton) Based on packet switching technologyGood for file transfer and remote terminal access Divide TCP into 2 protocolsInternet Protocol (IP): addressing and forwarding of packetsTransmission Control Protocol (TCP): sophisticated services, e.g. flow control, recovery1980: TCP/IP adopted as a DoD standard1983: ARPANET protocol officially changed from NCP to TCP/IP1985: Existing Internet technology 1995: U.S. Federal Networking Council (FNC) define the term Internet

    CSCE 201 - Farkas

  • CSCE 201 - Farkas*Goals (Clark88)Connect existing networksSurvivabilitySupport multiple types of servicesMust accommodate a variety of networksAllow distributed managementAllow host attachment with a low level of effortBe cost effectiveAllow resource accountability

    CSCE 201 - Farkas

  • CSCE 201 - Farkas*Internet ChallengeInterconnected networks differ (protocols, interfaces, services, etc.)Solutions:Reengineer and develop one global packet switching network standard: not economically feasibleHave every host implement the protocols of any network it wants to communicate with: too complex, very high engineering costAdd an extra layer: internetworking layerHosts: one higher-level protocolNetwork connecting use the same protocolInterface between the new protocol and network

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  • CSCE 201 - Farkas*LayeringOrganize a network system into logically distinct entitiesthe service provided by one layer is based only on the service provided by the lower level entity

    CSCE 201 - Farkas

  • CSCE 201 - Farkas*Without LayeringEach application has to be implemented for every network technology!SMTP FTPHTTPCoaxial cableFiberopticApplicationTransmissionMedia

    CSCE 201 - Farkas

  • CSCE 201 - Farkas*With LayeringIntermediate layer provides a unique abstraction for various network technologiesSMTP FTPCoaxial cableFiberopticApplicationTransmissionMediaIntermediate layer

    CSCE 201 - Farkas

  • CSCE 201 - Farkas*LayeringAdvantagesModularity protocols easier to manage and maintainAbstract functionality lower layers can be changed without affecting the upper layersReuse upper layers can reuse the functionality provided by lower layers DisadvantagesInformation hiding inefficient implementations

    CSCE 201 - Farkas

  • CSCE 201 - Farkas*TCP/IP Networking ModelTCP/IP has a different layered modelNetwork Access LayerPhysical ConnectionLAN ConnectionInternetwork Layer (IP)WAN ConnectivityUnreliable Datagram ServiceTransport Layer (TCP)Error CorrectionReliable ConnectionApplication Layer

    CSCE 201 - Farkas

  • CSCE 201 - Farkas*Network Access LayerResponsible for physical connectionShapeSizeVoltagesResponsible for rules of how to put bits on the wireThese are the building blocks for the networkThe goal of the physical layer is to move information across one hop

    CSCE 201 - Farkas

  • CSCE 201 - Farkas*Internet LayerTransports data from one end-user system to another end-user systems by hopping across as many physical connections as necessaryProvides a mechanism to connect many LANs together effectivelyConnectionless and unreliable datagram protocolProtocols:Internet ProtocolRouting ProtocolSupporting Protocol

    CSCE 201 - Farkas

  • CSCE 201 - Farkas*IP HeaderCommentsHLen header length only in 32-bit words (5
  • CSCE 201 - Farkas*IP AddressesIP provides logical address space and a corresponding addressing schemaIP address is a globally unique or private number associated with a host network interfaceEvery system which will send packets directly out across the Internet must have a unique IP addressIP addresses are based on where station is connectedIP addresses are controlled by a single organization - address ranges are assignedThey are running out of space!

    CSCE 201 - Farkas

  • CSCE 201 - Farkas*Routing Protocols Enable routing decisions to be made Manage and periodically update routing tables, stored at each router Autonomous collection of routers:Under single administrationUse same routing protocol: Interior Gateway Protocol (IGP)Use Exterior Gateway Protocol (EGP) to communicate other systems Router : which way to send the packet closer. (Keep routing table small and allow to handle unlimited number of systems.) Protocol types: ReachabilityDistance vector

    CSCE 201 - Farkas

  • CSCE 201 - Farkas*Supporting ProtocolsHandle specific tasksAddress Resolution Protocol (ARP)Reverse Address Resolution Protocol (RARP)Internet Control Message Protocol (ICMP)Internet Group Management Protocol (IGMP)

    CSCE 201 - Farkas

  • CSCE 201 - Farkas*The Domain Name SystemEach system connected to the Internet also has one or more logical addresses.Unlike IP addresses, the domain address have no routing information - they are organized based on administrative unitsThere are no limitations on the mapping from domain addresses to IP addresses

    CSCE 201 - Farkas

  • CSCE 201 - Farkas*Domain Name ResolutionDomain Name Resolution: looking up a logical name and finding a physical IP address There is a hierarchy of domain name serversEach client system uses one domain name server which in turn queries up and down the hierarchy to find the addressIf your server does not know the address, it goes up the hierarchy possibly to the top and works its way back down

    CSCE 201 - Farkas

  • CSCE 201 - Farkas*Transport Layer (TCP)Present a reliable end-to-end pipe to the applicationData either arrives in the proper order or the connection is closedKeeps buffers in the sending and destination system to keep data which has arrived out of order or to retransmit if necessaryProvides individual connections between applications

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  • CSCE 201 - Farkas*TCP Connection EstablishmentThree-way handshakeGoal: agree on a set of parameters: the start sequence number for each side Client (initiator)Server

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  • CSCE 201 - Farkas*Application LayerUses the reliable TCP connections to accomplish useful work over the networkclient-server applicationsstandard applicationstelnet (port 23)mail (port 25)finger (port 79)ftp (port 21)Each application uses a port and a protocolEach port can have many connections

    CSCE 201 - Farkas