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Addressing in TCP/IP

Addressing in TCP/IP. LESSON 6 (September 22, 1995) Daniel Z. Tabor Jr. New Jersey Institute of Technology. A Need for Identification Internet Address Classification Network and Host ID Ranges Addresses Specify Network Connections Network and Broadcast Addresses Multicast Addresses.

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Addressing in TCP/IP

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  1. Addressing in TCP/IP LESSON 6 (September 22, 1995) Daniel Z. Tabor Jr. New Jersey Institute of Technology

  2. A Need for Identification Internet Address Classification Network and Host ID Ranges Addresses Specify Network Connections Network and Broadcast Addresses Multicast Addresses Weaknesses in IP Addresses Common Representation of Addresses Loopback Addresses Obtaining an IP Address Contacting the NIC Network Byte Ordering Mapping Names to IP Addresses Outline:Addressing in TCP/IP

  3. A Need for Identification: • There is a need to establish: • A globally accepted method of identifying computers. • To provide a universal communication service.

  4. A Need for Identification: • TCP/IP universal host identifiers - are standard compact binary addresses used for efficient computation in routing and identification. • Scheme is analogous to physical network addressing where: • Each host on the internet is assigned an integer address (IP address) of 32-bits. • That address is represented in “dotted-decimal” notation.

  5. A Need for Identification: • Each address is a conceptual pair of (netid, hostid) • netid: identifies a network • hostid: identifies a host on that network.

  6. Internet Address Classification: • IP Addresses(version 4) • Five classes (A,B,C,D,E) • They are distinguished by their first 5 bits. • Addresses are 32-bits. • Later versions of the Internet Protocol may have more classes and use a different number of bits to represent an address. • IPv6 (proposed) uses 64-bits.

  7. Internet Address Classification: • Class E - (11110) - Reserved for future use. • Class D - (1110) - Multicast addressing. • Currently being used with applications that use selective broadcasting in communication: • Video-conferencing. • MBONE • Audio-conferencing.

  8. Internet Address Classification: • The three highest-order bits are used to determine the three Primary Classes: • Class A - (0) - used for a handful of networks which have more than 65,536 (216) hosts attached to each. • Netid = 7 bits • Hostid = 24 bits • Ex. (10.0.0.1) - ARPANET

  9. Internet Address Classification: • Class B - (10) - used for intermediate size networks that have between 256 (28) and 65,536 (216) hosts attached to each. • Netid = 14 bits • Hostid = 16 bits • Ex. (128.235.251.11) - Hertz.njit.edu

  10. Internet Address Classification: • Class C - (110) smallest configuration for hosts. Allows for less than 256 (28) hosts attached to each. • Netid = 21 bits • Hostid = 8 bits • Ex. (195.213.49.3) - Local area networks • Addresses are designed to allow extraction of either id quickly which makes gateway routing more efficient.

  11. 0 1 2 3 4 8 16 24 31 Class A netid hostid 0 Class B netid hostid 1 0 Class C netid hostid 1 1 0 Class D multicast address 1 1 1 0 Class E reserved for future use 1 1 1 1 0 IPv4 Address Types:

  12. Address Network Range Host Range Class A 0.0.0.0 - 127.0.0.0 0.0.0 - 255.255.255 Class B 128.0.0.0 - 191.255.0.0 0.0 - 255.255 Class C 192.0.0.0 - 223.255.255.0 0 - 255 Class D 224.0.0.0 - 239.255.255.255 N/A Network and Host IDRanges:

  13. Addresses Specify Network Connections: • Gateways connect two or more physical networks. Each connection requires its own IP address. • Conventional computers that have two or more physical connections are called multi-homed hosts and require multiple IP addresses. • IP addresses specify both a network and a host on that network (not an individual machine, but its connection to the network).

  14. Network and BroadcastAddresses: • Hostid = 0 (128.235.0.0) : names/addresses the network as a whole. (Ex. NJIT network) • Hostid = All 1’s (128.235.255.255) : directed broadcast address which refers to every host on that network. (Ex. Hertz.njit.edu) • Netid & Hostid = All 1’s (255.255.255.255) : limited broadcast address provides broadcast address independent of assigned Netid.

  15. Network and BroadcastAddresses: • Directed broadcast addresses require knowledge of the network address, limited broadcast addresses do not. • Limited broadcast addresses provide a broadcast address for local networks, independent of the assigned Netid.

  16. Network and BroadcastAddresses: Notations • 1’s => ‘All’ • 0’s => ‘This’ • Netid = 0 => ‘This network’

  17. Multicast Addresses: • Multicast addresses - provide multi-point delivery of packets. • Also known as selective broadcasting, multicast addressing is a subset of normal broadcasting. • Multicast addresses can be hardware or software addresses. • See Lesson 17 (Multicast IP and the MBONE) for further information.

  18. Weaknesses in IP Addresses: • If a host moves to a different network, it must change it’s IP address. • If the number of hosts grows more than 255 (Class C): • The addressing scheme must be changed to a Class B. • Extremely time consuming administration changes must also be made to enable the address change.

  19. Weaknesses in IP Addresses: • Routing: • Multiple IP addresses for a single host may be routed entirely different from each other. • The route chosen depends upon the address chosen (in some cases). • Knowing only one IP address for a single host may sometimes NOT be enough.

  20. Weaknesses in IP Addresses: • Availability: • The number of available IP addresses is rapidly reducing, forcing temporary extensions of the IP addressing scheme, until a more scaleable scheme can be put in place. • If a stable replacement for the current IP addressing scheme is not in place within 5-10 years, all IP addresses will be completely exhausted. (IPv6)

  21. Common Representationof Addresses: • Dotted Decimal Notation - a common way of representing an IP address by using four decimal integers separated by decimal points to ease in reading. • Each integer represents the value of the binary numbers contained within that octet of the address. • Example: 10000000 00001010 00000010 00011110 = 128.10.2.30

  22. Loopback Addresses: • Class A address 127.0.0.0 • Reserved for loopback on any local machine to test the communication system and for inter-process communication (IPC) on that machine. • Network 127 addresses should never appear on any network, be routed or propagated beyond the network interface card (NIC). • Commonly used as local IP addresses when configuring PCs for pseudo-SLIP connectivity.

  23. all 0s This host all 0s host Host on this net all 1s Limited broadcast (local net) net all 1s Directed broadcast for net 127 anything (often 1) Loopback Summary of Addresses:

  24. Obtaining an IP Address: • Network Information Center (NIC) is the central authority which ensures that all Internet addresses are unique. It does so by managing the approval and assignment of all IP network addresses. • When requesting an IP address, you should choose a type which fits the current and anticipated future sizes of your company.

  25. Obtaining an IP Address: • Sample size networks and appropriate address classes: • Local Area Networks: Class C • Campus-wide Networks: Class B • Large Companies: Class B • International Networks: Class A

  26. Image source: Internetworking with TCP/IP vol I (1995 Prentice Hall, Douglas Comer)

  27. Obtaining an IP Address: • Applying for IP addresses is only needed if your network is going to be connected to the Internet on a permanent basis. • Currently there is a long waiting list for companies and organizations to obtain IP addresses. • The NIC may soon charge for IP addresses because of the increased demand and lack of available addresses.

  28. Obtaining an IP Address: • When should an organization apply for an IP address? • Any organization that connects to the Internet has no option, they must obtain a registered number. • If an organization communicates with it’s subsidiaries using the Internet, it too must request a registered number.

  29. Obtaining an IP Address: • Advantages and Disadvantages of Registering: • Advantage: • Ensuring that your address and naming conventions are protected (njit.edu). • Disadvantage: • When you connect to the Internet, your use of a registered address is recorded in the Assigned Numbers RFC along with a contact names of administrators and policy personnel..

  30. Obtaining an IP Address: • Choosing a network number without official registration: • Avoid Class A addresses. • Do not copy examples given in a configuration handbook or textbook. • Avoid well-known addresses that are published. • Use high-end Class B or C addresses at random.

  31. Contacting the NetworkInformation Center: • Contacting the NIC: • Snail Mail: Government Systems Inc, Attn: Network Information Center 14200 Park Meadow Drive Suite 200 Chantilly, VA 22021

  32. Contacting the NetworkInformation Center (continued): • Voice: • 1-703-802-4535 • 1-800-365-DNIC • Fax: • 1-703-802-8376 • E-Mail: • NIC@NIC.DDN.MIL

  33. Network Byte Ordering: • Little Endian - lowest memory address contains low-order byte of integer. • Big Endian - lowest memory address holds the high-order byte of the integer. • Direct copying may change the value of data from machine to machine. • TCP/IP protocols define Network Standard Byte Order - most signification byte first (Big Endian)

  34. Mapping Names toIP Addresses: • Most users do not directly use IP addresses when using network services, they use Domain Names which map to IP addresses. • When connecting to a server at NJIT, you use the domain name (hertz.njit.edu) and not it’s IP address (128.235.251.11). • Domain names are not IP addresses, but mapped to them for readability by the Domain Naming System (Lesson 13).

  35. ETHERNET 128.10.0.0 128.10.2.3 128.10.2.8 128.10.2.26 MERLIN (multi-homed host) GUENEVERE (Ethernet host) LANCELOT (Ethernet host) 192.5.48.3 GLATISANT (router) TALIESYN (router) TOKEN RING 192.5.48.0 192.4.48.7 192.5.48.6 10.0.0.37 To ARPANET 128.10.2.70 192.5.48.1 ARTHUR (token ring host) Image source: Internetworking with TCP/IP vol I (1995 Prentice Hall, Douglas Comer)

  36. QuestionsAddressing in TCP/IP • What range of addressesshould never appear on a network? • If billions of different IP addresses can be created from 32-bits, why is there a shortage? • If we can identify computers using hardware addresses, why use IP addresses? • What are the differences between the IP addressing scheme and the U.S. telephone numbering scheme? • Why have a network standard byte order?

  37. Reference MaterialsAddressing in TCP/IP • IP Address to Latitude/Longitude -(http://cello.cs.uiuc.edu/cgi-bin/slamm/ip2ll/) • Network Information Center (NIC) - (http://ds.internic.net/) • DNS Resources Directory - (http://www.dns.net/dnsrd/) • Internetworking w/ TCP/IP Vol I, Douglas Comer. • Internet Standards - RFCs (ftp://nic.merit.edu/documents/std/)

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