1. TCP/IP Protocol Suite Networks and Protocols Prepared by: TGK First Prepared on: Last Modified on: Quality checked by: Copyright 2009 Asia Pacific Institute of Information Technology

2. Networks and Protocols TCP/IP Protocol Suite Slide 2 of 27 Topic & Structure of the lesson Introduction to TCP/IP Address Resolution Protocol (ARP) Internet Control Message Protocol (ICMP) Internet Protocol (IP) User Datagram Protocol (UDP) Transmission Control Protocol (TCP)

3. Networks and Protocols TCP/IP Protocol Suite Slide 3 of 27 Learning Outcomes At the end of this module, YOU should be able to: Discuss the operations and implementations of different protocols under the TCP/IP suite. Discuss the benefits and considerations for choosing the appropriate TCP/IP protocol for use in a network.

4. Networks and Protocols TCP/IP Protocol Suite Slide 4 of 27 Key Terms you must be able to use If you have mastered this topic, you should be able to use the following terms correctly in your assignments and exams: Regenerate signals

5. Networks and Protocols TCP/IP Protocol Suite Slide 5 of 27 Main Teaching Points Repeater

6. Networks and Protocols TCP/IP Protocol Suite Slide 6 of 27 Introduction to TCP/IP Developed for the Advanced Projects Research Agency (ARPA) Designed to network a wide variety of computing platforms, allowing expensive resources to be shared across the USA Designed to be fault tolerant in case of nuclear or other war Originally heavily based on UNIX systems

7. Networks and Protocols TCP/IP Protocol Suite Slide 7 of 27 The purpose of TCP/IP Provides a common communication standard for network devices (e.g. mainframes, PCs, remote devices, telephones, etc.) Provides a framework for interconnection and interoperation regardless of platform or physical network medium Where is TCP/IP used? Basic applications: Telnet (23) : Remote terminal session Introduction to TCP/IP

8. Networks and Protocols TCP/IP Protocol Suite Slide 8 of 27 FTP (21/20) : File Transfer SMTP/POP (25/110) : Electronic mail NFS (uses RPC) : Network File System More advanced applications: HTTP (WWW port 80) A transport for just about everything TCP/IP overview The term TCP/IP is used generically to refer to anything and everything related to the specific network (IP) and transport (TCP) layer protocols: Introduction to TCP/IP

9. Networks and Protocols TCP/IP Protocol Suite Slide 9 of 27 TCP UDP IP ARP TELNET FTP Layered protocols Early communication software was one big program which did everything Introduction to TCP/IP

10. Networks and Protocols TCP/IP Protocol Suite Slide 10 of 27 Early communication software was one big program which did everything Difficult to modify and add new functionality The program was broken down into parts or layers, each layer with very specific functionality ISO 7 – layer model Introduction to TCP/IP

11. Networks and Protocols TCP/IP Protocol Suite TCP/IP stack TCP/IP in relation to the OSI 7 – layer model Data flow through stack Data from the application flows down through the layers Each layer ads its own header information Each layer multiplexes data from one or more higher places Introduction to TCP/IP

12. Networks and Protocols TCP/IP Protocol Suite Slide 12 of 27 Data from the network flows upward through the layer Each layer strips off the corresponding layer’s header information Each layer de-multiplexes information to one or more higher layers An Ethernet card recognises an Ethernet frame which has its own address in the destination address field The link layer passes the data to the correct network layer protocol based Introduction to TCP/IP

13. Networks and Protocols TCP/IP Protocol Suite Slide 13 of 27 The link layer passes the data to the correct network layer protocol based on the contents of the TYPE field The IP layer passes data up to the next layer based on the contents of the protocol field in the IP header The next layer passes data up to the specific application based on the contents of the Port field in the TCP/UDP header Introduction to TCP/IP

14. Networks and Protocols TCP/IP Protocol Suite Address Resolution Protocol (ARP) Addressing issues TCP/IP is designed for many different types of physical network: Ethernet Token Ring Leased lines Each has its own format for physical addressing To run successfully on all existing and future physical networks, IP addressing must be independent of the physical layer

15. Networks and Protocols TCP/IP Protocol Suite Slide 15 of 27 You have no control over the address assigned to your network interface The manufacturer encodes the address onto the interface (i.e. physical address) If the card fails and is replaced, the machine’s physical address changes Addressing problems: Machines send data to each other using the physical address We want to send data to another computer’s IP address Address Resolution Protocol (ARP)

16. Networks and Protocols TCP/IP Protocol Suite Slide 16 of 27 Address Resolution Protocol (ARP) The ARP protocol is used to do this Example of ARP process: machine A wants to send data to machine B whose IP address is aaa.bb.ccc.ddd sends a broadcast packet, with 0806 in the type field Who has IP address aaa.bbb.ccc.ddd? machine B recognises its own IP address and responds, ‘Hello, that’s me! Here is my hardware address’

17. Networks and Protocols TCP/IP Protocol Suite Slide 17 of 27 machine A now has B’s physical address The IP frame can now be coded into a properly addressed Ethernet frame Address Resolution Protocol (ARP)

18. Networks and Protocols TCP/IP Protocol Suite Slide 18 of 27 The answer is held in a cache so that the next time A has data for B, it can simply look in the cache for its physical address Frequently used addresses stay in the cache Others time-out so as not to waste memory space Address Resolution Protocol (ARP)

19. Networks and Protocols TCP/IP Protocol Suite Slide 19 of 27 Internet Control Message Protocol (ICMP) IP provides best-effort delivery Delivery problems can be ignored; datagrams can be “thrown away” ICMP provides error-reporting mechanism Error detection Internet layer can detect a variety of errors: Checksum (header) Time-To-Live (TTL) expired No route to destination network Can’t deliver to destination host (e.g no ARP reply)

20. Networks and Protocols TCP/IP Protocol Suite Internet layer discards datagrams with problems Error reporting Some errors can be reported Router sends message back to source in datagram Message contains information about problem Encapsulation in IP datagram Types of messages ICMP defines error and informational messages Internet Control Message Protocol (ICMP)

21. Networks and Protocols TCP/IP Protocol Suite Slide 21 of 27 Internet Control Message Protocol (ICMP) Error messages: Source quench Time exceeded Destination unreachable Redirect Fragmentation required Informational messages: Echo request/reply Address mask request/reply Router discovery

22. Networks and Protocols TCP/IP Protocol Suite Slide 22 of 27 Message Transport ICMP encapsulated in IP ICMP messages sent in response to incoming datagrams with problems ICMP message not sent for ICMP message Internet Control Message Protocol (ICMP)

23. Networks and Protocols TCP/IP Protocol Suite Slide 23 of 27 ICMP and Reachability An Internet host A, is reachable from another host B, if datagrams can be delivered from A to B ping program tests reachability – sends datagram from B to A that A echoes back to B Use ICMP echo request and echo reply messages Internet layer includes code to reply to incoming ICMP echo request messages Internet Control Message Protocol (ICMP)

24. Networks and Protocols TCP/IP Protocol Suite Slide 24 of 27 Internet Control Message Protocol (ICMP) Ping sample output (Windows)

25. Networks and Protocols TCP/IP Protocol Suite Slide 25 of 27 Internet Protocol (IP) IP module is central to Internet technology Routes IP packets between intermediate systems Fragmentation and re-assembly Unreliable datagram service IP address: 32 bit value Usually written as four octets in dotted decimal notation Consists of two parts: network number and host number Three classes of IP address: class A, B, and C Twenty + RFCs specifying IP

26. Networks and Protocols TCP/IP Protocol Suite Slide 26 of 27 Internet Protocol (IP)

27. Networks and Protocols TCP/IP Protocol Suite Slide 27 of 27 Internet Protocol (IP) Ver – format of IP header (e.g. 4 or 6) IHL – IP header length in 32 bit words TOS – Type of Service Total length – bytes in the datagram Identification – IP packet ID number Flags – may/don’t/last/more fragment(s) Fragment Offset – for fragment reassembly TTL – packet time to live (hops) Protocol – protocol to give data to

28. Networks and Protocols TCP/IP Protocol Suite Slide 28 of 27 Header Checksum – checksum on header only Source Address – IP address of packet originator Destination Address – IP address of destination IP Address Classes Internet Protocol (IP)

29. Networks and Protocols TCP/IP Protocol Suite Slide 29 of 27 Internet Protocol (IP)

30. Networks and Protocols TCP/IP Protocol Suite Slide 30 of 27 Internet Protocol (IP)

31. Networks and Protocols TCP/IP Protocol Suite Slide 31 of 27 Internet Protocol (IP) Subnet Mask You have no control over the network address Assigned by e.g. RIPE, RIR, etc. Subnet mask allows you to assign part of the host field of the address to be network number Allows your network to be divided into interior networks; externally only one network address is sufficient to access your site Keeps size of external routing tables to a minimum

32. Networks and Protocols TCP/IP Protocol Suite Slide 32 of 27 Internet Protocol (IP) The effect of the Netmask

33. Networks and Protocols TCP/IP Protocol Suite Slide 33 of 27 Internet Protocol (IP) As the number of subnets increases, the number of hosts possible on each subnet decreases The node number of a host on a given subnet is added to the subnet address to give the complete IP number for the node E.g. With a subnet mask of 255.255.255.128 and a network number of 193.77.140.128, Host 1 on this network would have the IP number – 193.77.140.129

34. Networks and Protocols TCP/IP Protocol Suite Slide 34 of 27 Best-effort Delivery IP is designed to work over all types of network hardware, which may malfunction So IP datagrams may get lost, may be duplicated, may be delayed, may be delivered out of order, or may be delivered in a corrupt state We need higher layers of protocol software to deal with these errors Internet Protocol (IP)

35. Networks and Protocols TCP/IP Protocol Suite Slide 35 of 27 User Datagram Protocol (UDP) Connectionless unreliable datagram delivery service Adds only port number for multiplexing and delivery to application and checksum If checksum fails on receipt, packet is simply discarded If application can’t accept data, packet is discarded] Low overhead: only 8 bytes of header added Used for broadcasts NFS DNS

36. Networks and Protocols TCP/IP Protocol Suite Slide 36 of 27 UDP datagram: Source port – sending process (reply to this port) Destination port – receiving process Length – length of UDP header + data Checksum – pseudo header + UDP header + data User Datagram Protocol (UDP)

37. Networks and Protocols TCP/IP Protocol Suite Slide 37 of 27 Transmission Control Protocol (TCP) The transport layer has no concept of routing does not know about any intermediate nodes Reliable delivery TCP works on top of IP TCP is connection-oriented. It corrects lost, corrupted, out-of-order and delayed packets Guaranteed delivery service Positive acknowledgement with timeout and re- transmission

38. Networks and Protocols TCP/IP Protocol Suite Slide 38 of 27 Sliding window protocol Full-duplex connection Used for: Telnet FTP SMTP There are Twenty RFCs describing TCP How TCP ensures reliability Every message has a sequence number. The receiver can tell if a message is missing or out of order Transmission Control Protocol (TCP)

39. Networks and Protocols TCP/IP Protocol Suite Slide 39 of 27 Corrupted messages are detected by means of checksums TCP acknowledges all correctly received messages (sends ACK to the sender) TCP header: Transmission Control Protocol (TCP)

40. Networks and Protocols TCP/IP Protocol Suite Slide 40 of 27 Transmission Control Protocol (TCP) Initial sequence numbers are chosen randomly and sent to the other side when the connection is set up Source port – the sending process Destination port – the receiving process Sequence number – sequence number of first byte of data in the segment Acknowledgement number Valid if ACK bit is set Gives sequence number of next data expected to be received

41. Networks and Protocols TCP/IP Protocol Suite Slide 41 of 27 Data offset (or HLEN) – number of 32-bit words in TCP header Flags (or Code Bits) Window – number of bytes sender will accept Checksum – pseudo header + TCP header + data Urgent – points to byte in segment that follows urgent data

42. Networks and Protocols TCP/IP Protocol Suite Slide 42 of 27 Quick Review Question

43. Networks and Protocols TCP/IP Protocol Suite Slide 43 of 27 Follow Up Assignment

44. Networks and Protocols TCP/IP Protocol Suite Slide 44 of 27 Summary of Main Teaching Points

45. Networks and Protocols TCP/IP Protocol Suite Slide 45 of 27 Q & A Question and Answer Session

46. Networks and Protocols TCP/IP Protocol Suite Slide 46 of 27 Topic and Structure of next session Next Session