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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 l.jpg
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 l.jpg

  • 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

Ip address hierarchy l.jpg
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 hierarchy5 l.jpg
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 l.jpg
    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 l.jpg
    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 l.jpg
    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 addresses9 l.jpg
    Classes of IP Addresses

    • Class A:

    • Class B:

    • Class C:

    • Class D:

    • Class E:

    bits 0 1 2 3 4 8 16 24 31


    Network Address (net-id)

    Local Address (host-is)


    Local Address

    Network Address


    Local Address

    Network Address


    Multicast Address


    Reserved For Future Use

    Ip addresses l.jpg
    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.*.*.*

    Classes of ip addresses11 l.jpg
    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 l.jpg
    Computing The Class of An Address

    First 4 Bits Table Index

    of Address (in decimal) Class

    0000 0 A

    0001 1 A

    0010 2 A

    0011 3 A

    0100 4 A

    0101 5 A

    0110 6 A

    0111 7 A

    1000 8 B

    1001 9 B

    1010 10 B

    1011 11 B

    1100 12 C

    1101 13 C

    1110 14 D

    1111 15 E

    Computing the class of an address13 l.jpg
    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 l.jpg
    Dotted Decimal Notation

    32-bit Binary Number Equivalent Dotted Decimal

    10000001 00110100 00000110 00000000 12 . 9 . 52 . 6 . 0

    11000000 00000101 00110000 00000011 192 . 5 . 48 . 3

    00001010 00000010 00000000 00100101 10 . 2 . 0 . 2 . 37

    10000000 00001010 00000010 00000011 128 . 10 . 2 . 3

    10000000 10000000 11111111 00000000 128 . 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 l.jpg
    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:

      • [email protected]

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

    Address classes l.jpg
    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:

    CLASS Range of Values

    A 0 through 127

    B 128 through 191

    C 192 through 223

    D 224 through 239

    E 240 through 255

    Networks and hosts in each class l.jpg
    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 in Max Number Bits in Max Number of

    Class Prefix of Networks Suffix Hosts per Network

    A 7 128 24 16777216

    B 14 16384 16 65536

    C 21 2087152 8 256

    Internet address allocation l.jpg
    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 l.jpg

    • 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

    Example20 l.jpg

    prefix 128.211


    prefix 192.5.48

    prefix 128.10

    prefix 10

    Berkeley broadcast address l.jpg
    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 l.jpg
    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 addressing24 l.jpg
    Routers and IP Addressing



    Token Ring


    Multi homed hosts l.jpg
    Multi-Homed Hosts



    • 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 l.jpg

    • 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 l.jpg
    Subnet Addressing


    Local Address

    Network Address


    Network Address



    • 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 addressing28 l.jpg
    Subnet Addressing





    Horrible example of ip addressing l.jpg
    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

    Summary l.jpg

    • 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