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Chapter 16 - IP Protocol Addresses In this chapter, we’ll cover: TCP/IP addresses IP address hierarchy Properties of IP addresses Designing the format of IP Classes of addresses Dotted decimal notation UDM's IP addresses Internet address allocation Routers and IP addressing

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Chapter 16 - IP Protocol Addresses

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Chapter 16 - IP Protocol Addresses

  • In this chapter, we’ll cover:

    • TCP/IP addresses

    • IP address hierarchy

    • Properties of IP addresses

    • Designing the format of IP Classes of addresses

    • Dotted decimal notation

    • UDM's IP addresses

    • Internet address allocation

    • Routers and IP addressing


Motivation

  • Internet is a combination of individual networks, connected by Routers which can be envisioned as a single virtual network with uniform address format

  • Different technologies have different address formats; therefore, hardware addresses Can't be used

  • Every computer on network must have a unique IP address whose format must be independent of any particular hardware address format

  • Sending computer includes destination IP address in the frame which can be interpreted by any intermediate router

  • Routers examine destination IP address and forward packet to get it closer to destination


Communication Across the Internet


IP Address Hierarchy

Local Address (host-id)

Net work Address (net-id)

  • IP address consists of 32 bits

  • Each IP address is divided into a prefix and a suffix

  • Prefix identifies the network to which the computer is attached which is called net-id

  • Suffix identifies a computer within that network which is called host-id

  • Address format makes routing efficient


IP Address Hierarchy

Local Address (host-id)

Net work Address (net-id)

  • Every network in a TCP/IP internet is assigned a unique network number by:

    • Locally - Internet Service Providers (ISPs)

    • Globally - Internet Assigned Number Authority [NIC (Net. Inf. Center)]

  • Each computer on a specific network is assigned a host address (host-id) that is unique within that network by network manager

  • Host's IP address is the combination of the prefixnetwork number (net-id) and or suffixhost address (host-id)


  • Properties of IP Addresses

    • Every computer on the Internet should have a unique IP address to be able to send packets

    • IP address is the combination of network number prefix (net-id) and host address suffix (host-id)

      • Host-id, which assigned by network managers, may be reused on different networks

      • Network numbers (net-id) is unique and managed globally by a central authority, NIC

      • Address ranges are assigned in classes

    • NIC is running out of space!


    Designing the Format of IP Addresses

    • IP designers chose 32-bit addresses

    • Allocate some bits for prefix, some for suffix

    • Different technologies accommodate different network sizes

    • Different companies need different network sizes

      • Small prefix, large suffix: few networks, many hosts per network (Class A)

      • Large prefix, small suffix: many networks, few hosts per network (Class C)


    Classes of IP Addresses

    • Designers chose a compromise: multiple address formats that allow both large and small prefixes

    • Each format is called an address class

    • Class of an address is identified by its first four bits


    Classes of IP Addresses

    • Class A:

    • Class B:

    • Class C:

    • Class D:

    • Class E:

    bits 0 1 2 3 4 8 16 24 31

    0

    Network Address (net-id)

    Local Address (host-is)

    10

    Local Address

    Network Address

    110

    Local Address

    Network Address

    1110

    Multicast Address

    1111

    Reserved For Future Use


    IP Addresses

    • A range of IP addresses is assumed to be on a single “physical network” from the point of view of the Internet

      • Class A: 1-127.*.*.*

        • 27-1=127 networks

        • 224-1=16 Million hosts per network

      • Class B: 128-191.*.*

        • 214-1=16,065 networks

        • 216-1=65,025 hosts per network

      • Class C: 192-223.*.*.*

        • 221-1=2,015,775 networks

        • 28-1=255 hosts per network

        • Alholoun@UDMERCY.edu 198.109.25.23


    Classes of IP Addresses

    • Class A, B, and C are the primary classes which are used for computer addressing

    • Class D is used for multicast which is a limited form of broadcast where packets are delivered to all members of group

    • Routers manage delivery of single packet from source to all members of multicast group

    • Class E is reserved for future use


    Computing The Class of An Address

    First 4 BitsTable Index

    of Address (in decimal)Class

    00000A

    00011A

    00102A

    00113A

    01004A

    01015A

    01106A

    01117A

    10008B

    10019B

    101010B

    101111B

    110012C

    110113C

    111014D

    111115E


    Computing The Class of An Address

    • The class of an IP address can be computed from its address; therefore, it is called self identifying

    • The class can be extracted then calculated

      • If the combination starts with:

        • 0 bit class A

        • 10 bit class B

        • 110 bit class C

        • 111 bit class D

        • 1111 bit class E


    Dotted Decimal Notation

    32-bit Binary Number Equivalent Dotted Decimal

    10000001 00110100 00000110 0000000012 . 9 . 52 . 6 . 0

    11000000 00000101 00110000 00000011192 . 5 . 48 . 3

    00001010 00000010 00000000 0010010110 . 2 . 0 . 2 . 37

    10000000 00001010 00000010 00000011128 . 10 . 2 . 3

    10000000 10000000 11111111 00000000128 . 128 . 255 . 0

    • Class A, B and C all break between prefix and suffix on byte boundary

    • Dotted decimal notation is a convention for representing 32-bit internet addresses in decimal

    • Convert each 8 bits of address into decimal value; display separated by periods (``dots'')


    UDM's IP Addresses

    • UDM has 8 Class C networks: 198.109.25.xx,… 198.109.23.xx,...

      • All hosts at UDM have 198.109.2x.xx prefix:

      • Alholoun@UDMERCY.edu 198.109.25.23

      • Suffix bytes are used to determine local networks and computers through subnetting


    Address Classes

    • While dotted decimal makes separating network address from host address easier, determining class is not so obvious

    • Look at first dotted decimal number, and use this table:

    CLASSRange of Values

    A 0 through 127

    B128 through 191

    C192 through 223

    D224 through 239

    E240 through 255


    Networks and Hosts in Each Class

    • Classing scheme does not yield equal number of networks in each class

    • Class A:

      • First bit must be 0

      • 7 remaining bits identify Class A net

      • 27-1= 127 possible class A nets

    Address Bits inMax Number Bits inMax Number of

    Class Prefixof Networks SuffixHosts per Network

    A71282416777216

    B14163841665536

    C2120871528256


    Internet Address Allocation

    • Addresses in the Internet are not used efficiently

    • UDM uses 200-300 out of possible (8*28)

    • Large organizations may not be able to get as many addresses in the Internet as they need

    • Example: UPS needs addresses for millions of computers

    • Solution - set up private internet and allocate addresses from entire 32-bit address space


    Example

    • Select address class for each network depending on expected number of hosts

    • Assign network numbers from appropriate classes

    • Assign host suffixes to form internet addresses for all hosts


    Example

    128.211.6.115

    128.211.28.4

    prefix 128.211

    router

    192.5.48.3

    128.10.0.1

    prefix 192.5.48

    prefix 128.10

    10.0.0.49

    192.5.48.85

    prefix 10

    128.10.0.2

    10.0.0.37


    Special IP Addresses


    Berkeley Broadcast Address

    • Berkeley UNIX, which distributed by Berkeley Software Distribution, in common use

    • Berkeley broadcast uses all 0s for broadcast instead of all 1s for host suffix

    • This non-standard implementation spread with BSD UNIX

    • Many networks are designed to accept both standard & Berkeley broadcast forms


    Routers and IP Addressing

    • IP address identifies a connection between a computer & a network, not a computer

    • Router has a connection to multiple physical networks; therefore, routers have multiple IP addresses


    Routers and IP Addressing

    Ethernet 131.108.0.0

    131.108.99.5

    223.240.129.2

    WAN

    78.0.0.0

    223.240.129.17

    78.0.0.17

    Token Ring

    223.240.129.0

    router


    Multi-Homed Hosts

    R2

    R1

    • Hosts can also be connected to multiple networks to increase reliability and performance ( 2 or more)

    • Each interface has an address

    • Multi-homed hosts have multiple addresses


    Subnetting

    • Used to squeeze more “network” numbers out of a given address space so you can assign IP addresses more rationally

    • Saves space in routing tables

    • Subnetting implements a second-level net/host hierarchy based on geography.

    • Results in a network topology of clusters of local networks interconnected be wide-area networks

    • outside the subnetted network , the subnet structure in invisible

    • Within the subetted network, routers must make routing decisions based on the full subnet address(network number plus subnet number)


    Subnet Addressing

    110

    Local Address

    Network Address

    110

    Network Address

    net-id

    Node-id

    • The local address can be further divided into local net-id and host-id on that net

    • For Class C, 8 bits 2+6 bits which allows:

      • 22=4 local nets; i.e. 4 nets share the same class

      • 26=64 hosts on each local net

    • Other Examples: 8 bits : 3+5 bits (23=8 nets & 25=32 hosts)


    Subnet Addressing

    Internet

    198.109.25.0.1……. 198.109.25.0.63

    R

    198.109.25.1.1……. 198.109.25.1.63

    Netid 198.109.25.1

    Netid 198.109.25.0


    Horrible Example of IP addressing

    • You can see that in a network like this you will have to have a routing table entry for every single host you’ve got


    Subnetting Example


    Summary

    • Virtual network needs uniform addressing scheme which is independent of hardware

    • IP address is a 32-bit address; each interface gets a unique IP address

    • IP address is composed of a network address and a host address

    • Network addresses are divided into three primary classes: A, B, and C

    • Dotted decimal notation is a standard format for Internet addresses:

    • Routers have multiple addresses - one for each interface


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