1. 2001 Copyright SCUT DT&P Labs 1 The Principle of TCP/IP Part 1

2. 2001 Copyright SCUT DT&P Labs 2 1. History of TCP/IP 1969: ARPANET went into operation four packet-switched nodes at three different sites connected together via 56 kbit/s circuits using the Network Control Protocol (NCP) funded by the U.S. Department of Defence 1974: TCP/IP designed by Vinton G. Cerf and Robert E. Kahn 1979: IP version 4 documented

3. 2001 Copyright SCUT DT&P Labs 3 1. History of TCP/IP (Contd) 1979: the Internet Control and Configuration Board (ICCB) formed 1979: BSD Unix with TCP/IP supplied to Universities 1980: ARPA started converting machines to TCP/IP 1983: mandate that all computers connected to ARPANET use TCP/IP 1983 ARPANET split into two separate networks, ARPANET for further research MILNET for the military

4. 2001 Copyright SCUT DT&P Labs 4 1985: the ARPANET was heavily used and congested 1986: NSFNET developed to replace ARPANET universities and research organisations connected to regional networks regional networks connected to a main backbone six nationally funded super-computer centres connected to backbone The original links were 56 kbit/s. 1988: Links upgraded to T1 (1.544 Mbit/s) The NSFNET T1 backbone connected a total of 13 sites 1991: NSF decided to move the backbone to a private company 1993: New Internet backbone, ANSNET, with T3 (45 Mbit/s) links 1. History of TCP/IP (Contd)

5. 2001 Copyright SCUT DT&P Labs 5 1993 NSF Solicitations 1993 NSF Solicitations four separate projects for which proposals were invited: Create a set of Network Access Points (NAPs) Implement a Route Arbiter Provide a very high-speed Backbone Network Service (vBNS) Transition existing “regional” networks 1. History of TCP/IP (Contd)

6. 2001 Copyright SCUT DT&P Labs 6 2. Today's Internet Distributed architecture operated by commercial Network Service Providers (NSPs) Connected together at Network Access Points (NAPs) high-speed switch to which a number of routers can be connected for the purpose of traffic exchange allows Internet traffic from the customers of one provider to reach the customers of another provider. ISPs provide Internet services to end customers Connection point between a customer and an ISP is called a point of presence (POP) ISP networks exchange information with each other by connecting to NSPs that are connected to NAPs, or by connecting directly to NAPs

7. 2001 Copyright SCUT DT&P Labs 7 3. Internet Architecture Board (IAB) Organisation The IAB organisation The IAB Board IESG Research groupsWorking groups IRTFIETF

8. 2001 Copyright SCUT DT&P Labs 8 4. Active IETF (Internet Engineering Task Force) Working Groups Applications Internet Operations and Management Routing Security Transport User services General

9. 2001 Copyright SCUT DT&P Labs 9 5. Active IRTF (Internet Research Task Force) Research Groups End-to-End Information Infrastructure Architecture Internet Resource Discovery Network Management Reliable Multicast Routing Secure Multicast Services Management

10. 2001 Copyright SCUT DT&P Labs 10 6. Internet Assigned Number Authority (IANA) IANA RIPE Reseaux IP Europeen APNIC Asia Pacific Network Information Centre ARIN American Registry for Internet Numbers

11. 2001 Copyright SCUT DT&P Labs 11 Draft Paper RFC Spec Proposed Standard Review by IETF and IESG not to exceed two years IESG recommends promotion to proposed standard. RFC publishes as RFC. Otherwise it is sent back to the IETF work group. Implementation and test for a minimum of 6 months Draft Standard Evaluation of implementation for a minimum of 4 months 7. RFC Standards Track Process

12. 2001 Copyright SCUT DT&P Labs 12 IESG - Internet Engineering Steering Group The Internet Engineering Steering Group forms part of the IETF (Internet Engineering Task Force) and is comprised of the IETF Chairman and the Area Managers of each of the associated working groups.

13. 2001 Copyright SCUT DT&P Labs 13 8. Internet Protocol Suite and OSI Reference Model DATA LINK PHYSICAL NETWORK TRANSPORT SESSION APPLICATION PRESENTATION NETWORK INTERFACE (LAN - ETH, TR, FDDI) (WAN - Serial lines, FR, ATM) INTERNET (IP, ARP, RARP) TRANSPORT (TCP or UDP) APPLICATION (FTP, TELNET, SNMP, DNS) ICMP, IGMP

14. 2001 Copyright SCUT DT&P Labs 14 9. TCP/IP Protocol Stack Based on Data Flow OSPFEGPTCPUDPICMPIGMP IPRARPARP RIPBGP Ethernet, Token Ring, PPP, and so on Telnet, FTP, TFTP,HTTP,SNMP,SMTP, and so on Port Number Protocol Number Type code Application Layer Data Link Layer Internet Layer Transport Layer

15. 2001 Copyright SCUT DT&P Labs 15 Internet Protocol (IP)

16. 2001 Copyright SCUT DT&P Labs 16 1. Internet Protocol (IP) Provides logical 32-bit network addresses Routes data packets Connectionless protocol No session is established “Best effort” delivery Reliability is responsibility of higher-layer protocols and applications Fragments and reassembles packets

17. 2001 Copyright SCUT DT&P Labs 17 2. IP Packet Structure Source Address Version Type of Service Total LengthIHL IdentificationFragment Offset ProtocolTime to LiveHeader Checksum Destination address PaddingOptions (variable) 32 bits (4 Bytes) IP header is normally 20 bytes long Flags DATA (variable)

18. 2001 Copyright SCUT DT&P Labs 18 DTRUNUSEDPRECEDENCE D = Delay T = Throughput R = Reliability 2.1 Type of Service (TOS) 3 1 11 2 2. IP Packet Structure

19. 2001 Copyright SCUT DT&P Labs 19 Version: the field keeps track of which version of the protocol the datagram belong to. IHL: it is provided to tell how long the header is, in 32-bit words. Type of service: the field allows the host to tell the subnet what kinds of service it wants. Identification: it is needed to allow the destination host to determine which datagram a newly arrived fragment belong to. DF: it stands for Don’t Fragment. MF: it stands for More Fragment. Fragment offset: the field tells where in the current datagram the fragment belongs. 2. IP Packet Structure

20. 2001 Copyright SCUT DT&P Labs 20 Host A Network Interface IP Fires & Forgets Reliability & Sequencing IP Routes If Possible Router Host B Network Interface IP Delivers as Received Reliability & Sequencing PACKET Fragmented Packet 1. Internet Protocol (IP)

21. 2001 Copyright SCUT DT&P Labs 21 2. IP Packet Structure Time to live: the field is a counter used to limit packet lifetimes. Protocol: the field tells which transport process to give it to. TCP is one possibility, but so are UDP and some others. Header checksum: it verifies the header only. Source address & Destination address: they indicate the network number and host number (IP addresses). Options: they may include Security, Strict source routing, Loose source routing, Record route, Timestamp and so on.

22. 2001 Copyright SCUT DT&P Labs 22 2.2 Fragmentation Router 1 Router 2 MTU =1500 IP HeaderOriginal IP Packet data area IP Hdr 1 Data 1 IP Hdr 2 Data 2 IP Hdr 3 Data 3 MTU = 4500 bytes FDDI ETHERNET bytes 2. IP Packet Structure

23. 2001 Copyright SCUT DT&P Labs 23 3. Traditional IP Address Classes CLASS A CLASS B CLASS C 0 1 0 1 1 0 NET ID HOST ID

24. 2001 Copyright SCUT DT&P Labs 24 3. Traditional IP Address Classes 1 1 10 Group Identification Class D Used for multicast group usage - first 4 high-order bits are 1110 1st Octet between 224 and 239 Class E Reserved for future use - first 5 high-order bits are 11110

25. 2001 Copyright SCUT DT&P Labs 25 4. Addressing Guidelines Network ID cannot be 127 127 is reserved for loop-back function Network ID and host ID cannot be 255 (all bits set to 1) 255 is a broadcast address Network ID and host ID cannot be 0 (all bits set to 0) O means “ this network only ” Host ID must be unique to the network

26. 2001 Copyright SCUT DT&P Labs 26 5. Private IP Address Space 10.0.0.0 - 10.255.255.255 1 “ Class A ” network 172.16.0.0 - 172.31.255.255 16 “ Class B ” networks 192.168.0.0 - 192.168.255.255 256 “ Class C ” networks

27. 2001 Copyright SCUT DT&P Labs 27 A network (class A, B or C) is allowed to be split into several parts for internal use but still act like a single network to the outside world. These parts are called subnet. Subnet mask is employed to distinguish different subnet. Example: one of the ways to subnet a class B network 1 0 Host 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 NetworkSubnet IP address Subnet mask 6. Subnet

28. 2001 Copyright SCUT DT&P Labs 28 6.1 Subnet Mask Blocks out a portion of the IP address to distinguish the Network ID from the host ID Specifies whether the destination ’ s host IP address is located on a local network or on a remote network. The source ’ s IP address is ANDed with its subnet mask. The destination ’ s IP address is ANDed with the same subnet mask. If the result of both ANDing operations match, the destination is local to the source, that is, it is on the same subnet. 6. Subnet

29. 2001 Copyright SCUT DT&P Labs 29 6.2 Subnet Mask Example For example 160.30.20.10 is on the same subnet as 160.30.20.100 if the mask is 255.255.255.0 Note: 1 AND 1 = 1. Other combinations = 0. IP Address10100000 00011110 00010100 00001010 Subnet Mask11111111 11111111 11111111 00000000 10100000 00011110 00010100 00000000Result 160.30.20.10 255.255.255.0 160.30.20.0 IP Address10100000 00011110 11001000 01100100 Subnet Mask11111111 11111111 11111111 00000000 10100000 00011110 00010100 00000000Result 160.30.20.100 255.255.255.0 160.30.20.0 6. Subnet

30. 2001 Copyright SCUT DT&P Labs 30 6.3 Subnetting INTERNET PRIVATE NETWORK 160.30.0.0/24 160.30.1.0/24 160.30.2.0/24 ……………. 160.30.254.0/24 160.30.255.0/24 Routing Advertisement 160.30.0.0/16 Before subnetting: 1 network with approx.. 65 thousand hosts After subnetting: 256 networks with 254 hosts per subnet 6. Subnet

31. 2001 Copyright SCUT DT&P Labs 31 Example 1: network with customized mask Allocated IP address space 160.30.0.0/16 8 bits available for subnets and 8 bits available for host 0255 0000 1111 No. of Subnets xxxx 1010 00000001 1110 0000 160.30.0.x xxxx 1010 00000001 1110 1111 160.30.255.x 3 octet mask 255.255.255.0 Maximum of 256 subnets (2 8 ) NetworkHost 6. Subnet

32. 2001 Copyright SCUT DT&P Labs 32 Example 1: network with customised mask (continued) Allocated IP address space 160.30.0.0/16 8 bits available for subnets and 8 bits available for host 0255 0000 1111 No. of hosts 0000 0001 1010 00000001 1110xxxx 160.30.x.1 1111 1110 1010 00000001 1110xxxx 160.30.x.254 3 octet mask 255.255.255.0 Maximum of 254 hosts (2 8 - 2) NetworkHost 6. Subnet

33. 2001 Copyright SCUT DT&P Labs 33 Subnetting Example 2 200.200.200.0255.255.255.0 Network Address Subnet Mask Allocated IP address space 200.200.200.0/24 200.200.200.64 200.200.200.0 62 hosts per network Note: Subnet mask for each subnet = 255.255.255.192 200.200.200.192 200.200.200.128 6. Subnet

34. 2001 Copyright SCUT DT&P Labs 34 Example 3: Network with Variable Length Subnet Masks (VLSM) Allocated IP address space 200.200.200.0/24 want 2 subnets with 50 hosts and 8 subnets with 10 hosts? 200.200.200.0 200.200.200.0 /26 (max of 62 hosts) 200.200.200.64 /26 (max of 62 hosts) 200.200.200.192 /28 (max. of 14 hosts) 200.200.200.208 /28 200.200.200.224 /28 200.200.200.240 /28 200.200.200.128 /28 (max. of 14 hosts) 200.200.200.144 /28 200.200.200.160 /28 200.200.200.176 /28 Note: Subnet masks /26 = 255.255.255.192 /28 = 255.255.255.240 6. Subnet

35. 2001 Copyright SCUT DT&P Labs 35 Example 4: Network with VLSM 160.40.140.0 255.255.252.0 160.40.156.0 255.255.255.0 160.40.152.0 255.255.252.0 160.40.157.12 255.255.255.252 160.40.157.4 255.255.255.252 LAN 1 LAN 3 LAN 2 160.40.144.0 255.255.252.0 160.40.148.0 255.255.252.0 Site A Site C Site B 160.40.156.1 160.40.140.1 160.40.152.1 160.40.157.5 160.40.157.6 160.40.157.13 160.40.157.14 160.40.148.1 160.40.144.1 6. Subnet

36. 2001 Copyright SCUT DT&P Labs 36 7. Classless Inter Domain Routing (CIDR) Route Aggregation Route Aggregation

37. 2001 Copyright SCUT DT&P Labs 37 Variable Length Subnets from 1 to 16 CIDR prefix-length Subnet Mask # Individual Addresses # Classful Networks 32 B 64 B 128 B 1 A or 256 Bs 2 A 4 A 2 M 4 M 8 M 16 M 32 M 64 M 255.224.0.0 255.192.0.0 255.128.0.0 255.0.0.0 254.0.0.0 252.0.0.0 /11 /10 /9 /8 /7 /6 /4 /5 240.0.0.0 248.0.0.0 16 A 8 A128 M 256 M 64 A 32 A 128 A 1024 M 512 M 2048 M 192.0.0.0 224.0.0.0 128.0.0.0 /2 /3 /1 /16255.255.0.01 B or 256 Cs65,534 4 B 2 B 8 B 262,142 131,070 524,286 255.252.0.0 255.254.0.0 255.248.0.0 /14 /15 /13 16 B1 M255.240.0.0/12 7. Classless InterDomain Routing (CIDR) Route Aggregation

38. 2001 Copyright SCUT DT&P Labs 38 Variable Length Subnets from 17 to 32 CIDR prefix-length Subnet Mask # Individual Addresses # Classful Networks 1/8 C 1/4 C 1/2 C 1 C 2 Cs 4 Cs 8 Cs 16 Cs 32 Cs 64 Cs 30 62 126 254 510 1,022 2,046 4,094 8,190 16,382 255.255.255.224 255.255.255.192 255.255.255.128 255.255.255.0 255.255.254.0 255.255.252.0 255.255.248.0 255.255.240.0 255.255.224.0 255.255.192.0 /27 /26 /25 /24 /23 /22 /21 /20 /19 /18 /17255.255.128.0128 Cs32,766 1/16 C14255.255.255.240/28 1/32 C6255.255.255.248/29 1/64 C2255.255.255.252/30 7. Classless InterDomain Routing (CIDR) Route Aggregation

39. 2001 Copyright SCUT DT&P Labs 39 7. Classless InterDomain Routing (CIDR) Route Aggregation ISP The INTERNET 200.25.16.0/20 200.25.16.0/24 200.25.17.0/24 200.25.18.0/24 200.25.19.0/24 200.25.20.0/24 200.25.21.0/24 200.25.22.0/24 200.25.23.0/24 200.25.24.0/24 200.25.25.0/24 200.25.26.0/24 200.25.27.0/24 200.25.28.0/24 200.25.29.0/24 200.25.30.0/24 200.25.31.0/24 200.25.16.0/21 200.25.24.0/22 200.25.28.0/23 200.25.30.0/23 200.25.0.0/16 Company A Company B Company CCompany D

40. 2001 Copyright SCUT DT&P Labs 40 Subnet ID Tables No. of bits in mask Subnet Mask 255.255.255.248 255.255.255.252 255.255.255.240 255.255.255.224 255.255.255.192 255.255.255.128 255.255.255.0 255.255.254.0 255.255.252.0 255.255.248.0 255.255.240.0 255.255.224.0 255.255.192.0 29 30 28 27 26 25 24 23 22 21 20 19 18 16 17 255.255.0.0 255.255.128.0 Subnet IDs 0 0,16,32,48,64,80,96,112,128,144,160,176,192,208,224,240 0,8,16,24,32,40,48,56,64…………….,216,224,232,240,248 0,4,8,12,16,20,24,28,32,…………….236,240,244,248,252 0,2,4,6,8,10,12,14,16,18,…………….246,248,250,252,254 0,1,2,3,4,5,6,7,8,9,10,11,…………….251,252,253,254,255 0, 128 0, 64, 128, 192 0,32,64,96,128,160,192,224 3rd Octet 4th Octet 0, 128 0, 64, 128, 192 0,32,64,96,128,160,192,224 0,16,32,48,64,80,96,112,128,144,160,176,192,208,224,240 0,8,16,24,32,40,48,56,64…………….,216,224,232,240,248 0,4,8,12,16,20,24,28,32,…………….236,240,244,248,252 7. Classless InterDomain Routing (CIDR) Route Aggregation

41. 2001 Copyright SCUT DT&P Labs 41 The end of part 1