COMPUTER NETWORKS CS610 Lecture-25 Hammad Khalid Khan

Review Lecture 24  Addresses for Virtual Internet  The IP addressing Scheme  The IP Address Hierarchy  Original Classes of IP Addresses

Computing The Class Of An Address  Whenever it handles a packet, IP software needs to separate the destination address into a prefix and suffix.  Classful IP addresses are self-identifying because the class of an address can be computed from the address itself.

Computing The Class Of An Address

Dotted Decimal Notation  Dotted decimal notation is a syntactic form, the IP software uses to express 32-bit binary values when interacting with humans.  Dotted decimal represent each octet in decimal and uses a dot to separate octets.

Dotted Decimal Notation

Classes And Dotted Decimal Notation  In class A the last three octets correspond to a host suffix.  In Class B the last two octets are the host octets.  Class C only has one octet to represent the host.

Classes And Dotted Decimal Notation  The range of decimal values found in the first octet of each address class.

Division Of The Address Space  The IP class scheme does not divide the 32-bit address space into equal size class and the classes do not contain the same number of networks.

Division Of The Address Space  A prefix of n bits allows unique network numbers, while a suffix of n bits allows host numbers to be assigned on a given network.

Division Of The Address Space

Authority For Addresses  Throughout the internet, each network prefix is unique.  Networks obtain their network numbers from their Internet Service Provider (ISP).  The Internet service providers coordinate with The Internet Assigned Number Authority to obtain their network numbers.

Classful Addressing Example  Here we have a private TCP/IP network which consists of four physical networks.  The first step is to assign IP addresses. – Usually assigned class C addressed.  Network administrator computes the ultimate size of each physical network and assigns a prefix.

Classful Addressing Example Class B Class A Class B Class C

Summary  Computing the Class of an IP Address  Dotted Decimal Notation  Classes & Dotted Decimal Notation  Division of the Address Space  Authority For Address  A Classful Addressing Example