Internetworking Technologies & Services (II)

1. Internetworking Technologies & Services (II) • Introduction to TCP/IP • Models • Packet formats • Addressing • Routing • IPv6 • TCP/IP Troubleshooting • TCP/IP Management • Applications and Services

2. TCP/IP Evolution • Set of protocols developed by the U.S. Defense Department's Advanced Research Projects Agency (DARPA) during the early 1970s. • De facto Standard. • Well suited for LAN’s and WAN’s • Birth of the Internet: National and International Connectivity

3. TCP/IP Evolution • Standards maintained by Internet Activities Board (IAB) through the Internet Engineering Task Force (IETF) • Standards maintained on line in Request for Comments documents (RFC) (e.g. IP is defined in RFC791 and TCP in RFC 793)

4. TCP/IP Model • TCP/IP Protocol Suite, ARPANET (DARPA) Application Transport (TCP,UDP) Internet (IP) Network Access Physical

5. OSI to TCP/IP Models • 7-layer OSI and TCP/IP Protocol Architectures Application Application Presentation Session Transport (TCP,UDP) Transport Internet (IP) Network Network Access Data Link Physical Physical

6. TCP/IP Network Architecture

7. IP - Internet Protocol • The Internet Protocol (IP) is a packet-based protocol used to exchange data over computer networks. IP handles addressing, fragmentation, reassembly, and protocol multiplexing. • It is the foundation on which all other IP protocols, collectively referred to as the IP Protocol suite, are built (TCP, UDP, ICMP, ARP, etc.). • IP is a network-layer protocol that contains addressing and control information that allows data packets to be routed.

8. IP - Internet Protocol • IP is responsible for moving packet of data from node to node. IP forwards each packet based on a four byte destination address (the IP number). The Internet authorities assign ranges of numbers to different organizations. The organizations assign groups of their numbers to departments. IP operates on gateway machines that move data from department to organization to region and then around the world.

9. TCP - Transmission Control Protocol • The Transmission Control Protocol (TCP) is built upon the IP layer. TCP is a connection-oriented protocol that specifies the format of data and acknowledgments used in the transfer of data. TCP also specifies the procedures that the computers use to ensure that the data arrives correctly. • TCP allows multiple applications on a system to communicate concurrently because it handles all multiplexing of the incoming traffic among the application programs.

10. TCP - Transmission Control Protocol • TCP is responsible for verifying the correct delivery of data from client to server. Data can be lost in the intermediate network. TCP adds support to detect errors or lost data and to trigger retransmission until the data is correctly and completely received. • Sockets is a name given to the package of subroutines that provide access to TCP/IP on most systems.

11. UDP - User Datagram Protocol • The User Datagram Protocol (UDP) is used when reliability mechanisms in TCP are not needed. UDP is a connection-less-oriented protocol.

12. IP Packet Format

13. IP Packet Format • Version: • Indicates the version of IP currently used. • IP header length (IHL): • Indicates the datagram header length in 32-bit words. • Type-of-service: • Specifies how a particular upper-layer protocol would like the current datagram to be handled. Datagrams can be assigned various levels of importance through this field. • Total length: • Specifies the length of the entire IP packet, including data and header, in bytes.

14. IP Packet Format • Identification: • Contains an integer that identifies the current datagram. This field is used to help piece together datagram fragments. • Flags: • A 3-bit field of which the low-order 2 bits control fragmentation. One bit specifies whether the packet can be fragmented; the second bit specifies whether the packet is the last fragment in a series of fragmented packets.

15. IP Packet Format • Time-to-live: • Maintains a counter that gradually decrements down to zero, at which point the datagram is discarded. This keeps packets from looping endlessly. • Protocol: • Indicates which upper-layer protocol receives incoming packets after IP processing is complete. • Header checksum: • Helps ensure IP header integrity. • Source address: • Specifies the sending node.

16. IP Packet Format • Destination address: • Specifies the receiving node. • Options: • Allows IP to support various options, such as security. • Data: • Contains upper-layer information.

17. IP Network Addressing • IP address is 32 bits in length, divided into either two or three parts: • First part designates the network address • Second part (if present) designates the subnet address • Third part designates the host address • Conceptual Interpretation of IP Addresses • [Internet Part:Local Part] - Original • [Internet Part:Physical Network:Host] - With subnets

18. IP Network Addresses • IP addressing supports five different network classes: • Class A: Mainly used with a few very large networks. Provide only 7 bits for the network address field. • Class B: 14 bits for the network address field, 16 bits for the host address field. Offers a good compromise between network and host address space • Class C: Allocate 22 bits for the network address field, provide only 8 bits for the host field. The number of host may be a limiting factor • Class D: Reserved for multicast groups, the 4 highest-order bits are set to 1, 1, 1, and 0. • Class E: Reserved for future use, the four highest-order bits are all set to 1.

19. IP Network Address Representation • Binary Notation: • 1000 0000.0000 1010. 0000 0010.0001 1110 • Hexadecimal Notation: • 80.0A.02.1E • Dotted Decimal Notation: • 128.10.2.30

20. IP Network Addresses • Class A: [0:netid:hostid] • Class B: [10:netid:hostid] • Class C: [110:netid:hostid] • Class D: [1110:Multicast] • Class E: [11110:Reserved]

21. IP Primary Network Addresses

22. IP Primary Network Addresses • Class A: 0 through 127; e.g. 10.2.0.37 • netid = 10. and hostids = 10.0.0.0 to 10.255.255.255 • Note: 127.0.0.0 network addresses are reserved for loopback addressing • 24-bits available; 16,777,216 possible hostid IP addresses • Class B: 128 through 191; e.g. 129.24.24.119 • netid = 129.24. and hostids = 129.24.0.0 to 129.24.255.255 • 16-bits available; 65,536 possible hostid IP addresses • Class C: 192 through 223; e.g. 198.6.7.3 • netid = 198.6.7. and hostids = 198.6.7.0 to 198.6.7.255 • 8-bits available; 256 possible hostid IP addresses

23. IP Primary Network Addresses • Class D: 224 through 239 • Multicast • Class E: 240 through 255 • Reserved for future use

24. IP Network Addresses • Addresses specify network connections • IP addresses do not specify a host but a connection to a network • Network and broadcast addresses • IP address with all bits of HOSTID field set to 0 is reserved to refer to the network • IP address with all bits of HOSTID field set to 1 is a broadcast address (hardware/software supported) • Limited Broadcast • Local network broadcast address is 32 1’s (i.e. 255.255.255.255) • Provides broadcast capability to local network independent of IP

25. IP Network Addresses • Subnet addressing and multicast • Designed to conserve network addresses • Multipoint delivery • Loopback Address • Not all possible addresses have been assigned to classes • Class A address 127.0.0.0 is reserved for loopback • Use in testing TCP/IP and for inter-process communications on the local machine • Packets with network address should never appear on any network

26. IP Network Addresses • IP address limitations • address refers to network connection not host • IP address authority • All IP addresses are assigned by a central authority • IANA: Internet Assigned Number Authority has ultimate control • INTERNIC: Internet Network Information Center assigns addresses • Network Byte Order • Internet standard for byte order specifies integers be sent most significant byte first • Big Endian style; lowest memory address holds the high order byte of the integer

27. IP Network Address Mapping • Logical: IP addresses define Layer 3 (Network Layer) logical addresses • Physical: Layer 2 (Data Link Layer) physical addresses is a function of IP addresses • Address Resolution (Mapping): Translation from logical address (IP address) to an equivalent physical hardware address ( Ethernet address) ; required for information exchange between host-to-host and host-to-router located on the same physical network

28. Address Resolution Techniques • Table lookup (e.g. WANs) • Closed-form computation (e.g. Configurable networks) • Message exchange (e.g. LAN with static addressing)

29. ARP - Address Resolution Protocol • TCP/IP can use any type of address resolution techniques, dependent on underlying hardware • ARP allows a host or a router to find the physical address of a host or a router connected to the same physical network, given the target IP address

30. RARP - Reverse Address Resolution Protocol • RARP allows a host or a router to obtain its IP address or another host or router IP address • Normally used at boot time requiring a RARP server

31. ICMP - Internet Control Message Protocol • Error reporting protocol • Echo and reply messages to test node reachability across an internet. Redirects messages to simulate efficient routing • Time exceeded messages to inform sources that a datagram has exceeded its allocated time to exist within the internet • Used by routers to determine addresses of directly attached routers and to discover the subnet mask currently used by an internet

32. IP Subnets and Network Masks • Subnets provide extra flexibility to network administrators by subdividing IP networks into smaller subnetworks • IP subnets define two or more physical networks that share a common netid field (portion of 32-bit address that is assigned by the NIC) • Subnetting allows routers to hide complexity of multiple LANs from the rest of the Internet and Enterprise WANs (e.g. if IP address = 129.24.8.1 then Network = 129.24., Subnet = 8. to 15., Host = 1)

33. IP Subnets and Network Masks • Subnet masks are used to specify the number of bits used to define a subnet • Subnet masks use the same format and representation techniques as IP addresses (e.g. 255.255.255.0) • Subnet masks have 1’s in the netid and subnet fields, and 0’s in the hostid field • Class B Subnetting example: • Before Subnetting: [10:netid:hostid]; • After Subnetting: [10:netid:subnet:hostid];

34. Subnet Mask Construction • Assign a value of 1 to all the bits in the netid field (i.e. first 8/16/24 bits of Class A/B/C networks) • Assign a value of 1 to each bit in the subnet field • Assign a value of 0 to each bit in the hostid field • Convert to dotted decimal or hexadecimal notation

35. Subnet Mask Construction • Class B Address Info • 129.24.0.0 to 129.24.255.255 • netid = 129.24. • hostid = 16 bits (i.e. 65,536 potential IP addresses) • Subnet Mask Assumptions: • netid bits = 16 • potential hostid bits = 16 • If we divide the address space into 32 subnets we will have 2048 hostids or IP addresses per subnet

36. Subnet Mask Construction • xxxx xxxx.xxxx xxxx.xxxx xxxx.xxxx xxxx (32-bits) • 1111 1111.1111 1111.xxxx xxxx.xxxx xxxx (Step 1) • 1111 1111.1111 1111.1111 1xxx.xxxx xxxx (Step 2) • 1111 1111.1111 1111.1111 1000.0000 0000 (Step 3) • 255.255.248.0 (Step 4) • Hexadecimal representation = FF FF F8 00

37. Subnet Mask Construction • Sample Subnet hostid assignment • 129.24.8.0 (Reserved: not used) • 129.24.8.1 • 129.24.8.2 • . . . . . . . . . • 129.24.8.255 • 129.24.9.0 • 129.24.9.1 • 129.24.9.2 • . . . . . . . . . • 129.24.15.255 (Reserved: Subnet directed broadcast address)

38. Subnet Mask Construction • Subnet Ranges (32 subnets/30 useable) • 129.24.0.0 to 129.24.7.255 (Reserved: not used) • 129.24.8.0 to 129.24.15.255 • 129.24.16.0 to 129.24.23.255 • 129.24.24.0 to 129.24.31.255 • 129.24.32.0 to 129.24.39.255 • . . . . . . . . . . . . . . • 129.24.232.0 to 129.24.239.255 • 129.24.240.0 to 129.24.247.255 • 129.24.248.0 to 129.24.255.255 (Reserved: not used)

39. Subnet Mask Construction • Samples of other Subnet Masks for Class B network: • 255.255.255.192: 1,024 subnets with 64 hostids per subnet • 255.255.255.224: 2,048 subnets with 32 hostids per subnet • 255.255.255.240: 4,096 subnets with 16 hostids per subnet • 255.255.255.248: 8,192 subnets with 8 hostids per subnet • 255.255.255.252: 16,384 subnets with 4 hostids per subnet • Samples of other Subnet Masks for Class C network: • 255.255.255.192: 4 subnets with 64 hostids per subnet • 255.255.255.224: 6 subnets with 32 hostids per subnet • 255.255.255.240: 16 subnets with 16 hostids per subnet • 255.255.255.248: 32 subnets with 8 hostids per subnet • 255.255.255.252: 64 subnets with 4 hostids per subnet

40. IP Routing Definitions and Terminology • Routers are Layer 3 (Network Layer) devices • Traditionally routers were called gateways • Routers are used for information exchange within a group of networks under the same administrative authority and control (Autonomous Systems) • Routing can be both dynamic and static • Routing involves the determination of routing paths and the transport of information groups (packets) through an internetwork

41. IP Routing Definitions and Terminology • Path determination may be based on a variety of metrics (values resulting from algorithmic computations on a particular variable,for example, network delay) or metric combinations.

42. IP Routing Protocols/OSI Model

43. Routing Algorithms Design Goals • Correctness • Simplicity/Low Overhead • Robustness/Stability • Rapid Convergence • Flexibility

44. Routing Algorithm Types • Static or Dynamic • Distributed or Centralized • Single-Path or Multi-Path • Flat or Hierarchical • Host-Intelligent or Router-Intelligent • Intra-Domain or Inter-Domain • Link State or Distance Vector

45. RIP - Routing Information Protocol • RIP is a distance vector, intra-domain routing protocol originally designed for PUP (Xerox PARC Universal Protocol, 1980) and used in XNS • RIP became associated with both UNIX and TCP/IP in 1982 when the Berkeley Standard Distribution (BSD) implementation of UNIX began shipping with a RIP implementation referred to as routed • RIP is formally defined in RFC 1058

46. RIP Routing Table

47. RIP Packet Format

48. RIP Packet Fields Description • Command: • Indicates that the packet is a request or a response. The request command requests the responding system to send all or part of its routing table. Destinations for which a response is requested are listed later in the packet. The response command represents a reply to a request or, more frequently, an unsolicited regular routing update. In the response packet, a responding system includes all or part of its routing table. Regular routing update messages include the entire routing table. • Version number: • Specifies the RIP version being implemented. With the potential for many RIP implementations in the Internet, this field can be used to signal different, potentially incompatible, implementations.

49. RIP Packet Fields Description • Address family identifier: • Follows a 16-bit field of all zeros and specifies the particular address family being used. On the Internet, this address family is typically IP (value = 2), but other network types may also be represented • Address: • Follows another 16-bit field of zeros. In Internet RIP implementations, this field typically contains an IP address • Metric: • Follows two more 32-bit fields of zeros and specifies the hop count. The hop count indicates how many internetwork hops (routers) must be traversed before the destination can be reached

50. OSPF - Open Shortest Path First • OSPF is a relatively recent intra-domain, link state, hierarchical routing protocol developed for IP networks by the Internet Engineering Task Force (IETF) • OSPF was derived from an early version of OSI's IS-IS routing protocol