1.Network Basics

2. What is a computer network? a collection of computing nodes and links connecting the nodes why we need it? to transfer data to others 2 3. What is the Internet? originally means Inter-network a network of networks now means a network using IP (Internet Protocol) for inter-networking equivalent to IP networks deployed in the whole world3 4. What is a network protocol? a pre-defined rule for data transfer examples: IP, TCP, UDP, HTTP, RTP why do we need it?4 5. What we learn in this class architecture of the current networks basic operations of network protocols how they are implemented several well-known network applications 5 6. Network Layering the current network protocols are implemented based on layering concept currently, there are five layers: physical, data-link, network, transport and application why ?6 7. Physical LayerNICNetwork Interface CardEthernet CardLAN cardComputer A Computer BDataWire Physical Layer 7 8. Physical Layer Twisted pair Coaxial Cable Fiber Optics RF 8 9. Physical Media physical link: Twisted Pair (TP) transmitted data bit two insulated copper propagates acrosswires link Category 3: guided media:traditional phone signals propagate in wires, 10 Mbps solid media: copper, ethernet fiber Category 5 TP:100Mbps ethernet unguided media: signals propagate freelye.eg., radio 9 10. Physical Media: coax, fiberFiber optic cable: Coaxial cable: glass fiber carrying light wire (signal carrier) withinpulses a wire (shield) high-speed operation: baseband: single channel 100Mbps Ethernet on cable high-speed point-to- broadband: multiple point transmission (e.g., channel on cable 5 Gps) bidirectional low error rate common use in 10Mbs Ethernet 10 11. Physical media: radio signal carried inRadio link types: electromagnetic microwave spectrum e.g. up to 45 Mbps channels no physical wire LAN (e.g., waveLAN) 2Mbps, 11Mbps bidirectional wide-area (e.g., cellular) propagation e.g. CDPD, 10s Kbps environment effects: satellite reflection up to 50Mbps channel (or obstruction bymultiple smaller channels)objects 270 msec end-end delay interference 11 12. Hardware Building Blocks General purpose computers such as PC, workstation, Laptop and PDA connected to aCPUnetwork. Either end-hosts orNetwork Cache(T network) o intermediate nodes adaptor(switch or router)I/O bus Memory 12 13. Hardware Building Blocks -Links Implemented on a variety of different physical media, including twisted pair, coaxial cable, optical fiber and space. Used to propagate signals. 13 14. Wireless Links Global links PCS, GSM Wireless LAN IEEE 802.11a, b, g Piconet Bluetooth (upto 1 Mbps) 14 15. Data Link LayerComputer A Computer BComputer CData Data link layer MAC Data Data link layer15 16. Data Link Layer Unique ID Medium Access Control (MAC) CSMA/CD (Carrier Sense Multiple Access/Collision Detection) CSMA/CA (Collision Avoidance) Token Ring TDMA (Time Division Multiple Access)16 17. Network Layer RouterIP Data link layer 17 18. Network Layer Routing RIP Routing Information Protocol OSPF Open Shortest Path First18 19. IP Packet Format 0 4 816 1931Version HLen TOSLengthIdent FlagsOffsetTTL Protocol ChecksumSourceAddr DestinationAddrOptions (variable)Pad(variable)Data19 20. Transport Layer Computer AComputer B netscapenetscape telnet ftptelnet ftpDate DateTCPTCP Date TCP DateTCPIP IP TCP Date IP TCP DateIP Data link layer MAC IPTCP DateMAC IPTCP DateData link layer 20 21. Transport Layer End-to-end delivery Transmission Control Protocol (TCP) Flow control Advertised Window Error control Checksum Reliable delivery Loss detection and retransmission User Datagram Protocol (UDP)21 22. Typical Limitations of the Network Drop messages Reorder messages Deliver duplicate copies of a given message Limit messages to some finite size Deliver messages after an arbitrarily long delay22 23. UDP (User Datagram Protocol) Extending the host-to-host deliver service of the underlying network into a process-to-process communication service. Port number Well-known port number Port mapper Checksum pseudoheader Used for delay-sensitive applications23 24. UDP Header Format 0 16 31SrcPortDstPort ChecksumLengthData 24 25. TCP Segment 041016 2431Source Port Destination PortSequence NumberAcknowledgement NumberHeaderUAP R S FReserved R C S S Y I Window Size LengthGKH T NN ChecksumUrgent Pointer OptionsPadding Data25 26. Internet Protocol Graph FTP HTTPNV TFTPTCPUDP IPNET1NET2 NETn26 27. Alternative View of theInternet ArchitectureApplicationTCP UDPIP Network27