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Chapter 2

Chapter 2. Internet Protocol. DoD Model. Four layers: Process/Application layer Host-to-Host layer Internet layer Network Access layer. The DoD and OSI Models. The TCP/IP Protocol Suite. Process/Application Layer Protocols. Telnet – terminal emulation File Transfer Protocol (FTP)

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Chapter 2

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  1. Chapter 2 Internet Protocol

  2. DoD Model • Four layers: • Process/Application layer • Host-to-Host layer • Internet layer • Network Access layer

  3. The DoD and OSI Models

  4. The TCP/IP Protocol Suite

  5. Process/Application Layer Protocols • Telnet – terminal emulation • File Transfer Protocol (FTP) • Trivial File Transfer Protocol (TFTP) – not as flexible as FTP • Network File System (NFS) - UNIX and NT can access each other’s files • Line Printer Daemon (LPD)

  6. Process/Application Layer Protocols • X Window – GUI for client/server • Simple Network Management Protocol (SNMP) – gathers network info from devices • Domain Name Service (DNS) – resolves addresses • Dynamic Host Configuration Protocol (DHCP) – assigns addresses

  7. Host-to Host Layer Protocols • Shields applications from complexities of network • Protocols • Transmission Control Protocol (TCP) • User Datagram Protocol (UDP)

  8. TCP Segment Format

  9. UDP Segment

  10. TCP Sequenced Reliable Connection-oriented Acknowledgements Virtual circuit Lots of overhead UDP Unsequenced Unreliable Connectionless Low overhead Can handle routine network traffic (SNMP) with ease Key Concepts

  11. Port Numbers • Used by TCP and UDP to communicate with upper layers • Port Numbers: • < 1024: “Well-known port numbers” • Defined in RFC 1700; linked to specific applications or protocols • > 1024: Dynamically assigned • Used by upper layers to communicate between hosts, keep various connections separate • Created by source host

  12. Port Numbers for TCP & UDP

  13. Internet Layer Protocols • Used to route and provide standard interface for upper layers • Internet Protocol (IP) • Internet Control Message Protocol (ICMP) • Address Resolution Protocol (ARP) • Reverse Address Resolution Protocol (RARP)

  14. IP • Looks at packet addresses • Looks at routing table • Chooses path to send packet • What network is the destination on? (IP, software, or logical address) • What is the ID on the network? (hardware, MAC address) • Receives segments, makes datagrams/packets

  15. IP Header

  16. The Protocol Field in IP Header

  17. ICMP • Internet Control Message Protocol • Handles many management functions • Destination unreachable • Buffer full • Hops • Ping • Traceroute

  18. Local ARP Broadcast

  19. RARP Broadcast

  20. Hierarchical IP Addressing Scheme • IP addresses = 32 bits • Divided into 4 sections or octets or bytes • Each byte containing 8 bits • Left to right is general to specific • Depicting IP addresses: • Dotted decimal: 172.16.30.56 • Binary: 10101100.00010000.00011110.00111000 • Hexadecimal: 82 39 1E 38

  21. IP Addressing • Terminology • Bit: one digit: 1 or 0 • Byte: 7 or 8 digits • Octet: Always 8 bits (base-8 addressing) • Network Address: Used to send packets to a remote network • Broadcast Address: Sends information to all nodes on a network • All networks and nodes: 255.255.255.255 • All nodes on 172.16 network: 172.16.255.255 • All subnets & hosts on 10 network: 10.255.255.255

  22. Summary of the Three Classes of Networks

  23. Class A Addresses • Structure • Network.node.node.node • Class A Valid Host IDs • 10.0.0.0 All host bits off • 10.255.255.255 All host bits on • Valid hosts = 10.0.0.1 - 10.255.255.254 • 0’s & 255s are valid hosts but hosts bits cannot all be off or on at the same time! • 224-2 = 222

  24. Class B Addresses • Structure • Network.Network.node.node • Class B Valid Host IDs • 172.16.0.0 All host bits off • 172.16.255.255 All host bits on • Valid hosts = 172.16.0.1 - 172.16.255.254 • 0’s & 255s are valid hosts but hosts bits cannot all be off or on at the same time! • 216-2 = 214

  25. Class C Addresses • Structure • Network.Network.Network.node • Class C Valid Host IDs • 192.168.100.0 All host bits off • 192.168.100.255 All host bits on • Valid hosts = 192.168.100.1 - 192.168.100.254 • 0’s & 255s are valid hosts but hosts bits cannot all be off or on at the same time! • 28-2 = 26

  26. Private IP Addresses • Use private addresses within a company • Translate private to real addresses for Internet use • 10.x.x.x • 172.16.x.x to 172.31.x.x • 192.168.x.x

  27. Broadcasts • Layer 2 broadcast to all LAN nodes • All 1s (binary) or Fs (hex) • Layer 3 broadcast to all network nodes • All host bits turned on • Unicast to one particular host • Multicast to several nodes

  28. NAT • Network address translation • Converts private to public IP addresses • Static NAT for one-to-one mapping of these addresses • Dynamic NAT uses a pool of public IP addresses • Overloading many private addresses to one public address (port address translation)

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