BackgroundThe goal of Universal Service is such that all

computers on all physically different networks can communicate.

Physical addresses allow communication between computers on one network.

IP AddressesThe IP address provides virtual addressing.

The address is software controlled, whereas the address for the network card is hardware based.

The IP addressing scheme is quite complex, and there have been many revisions to the IP scheme.

IP Addresses (cont.)IP addressing allows integration amongst the

pc`s in heterogeneous(irregular series) networks.

To send a packet, the destination address is the IP address of the computer, not the hardware address! This allows for communication across networks.

IP Addresses (cont.)32 bits binary in length (IPv4)128 bit hexadecimal in length (IPv6)Addresses are divided into a prefix and suffixThe suffix is the host addressThe prefix is the network number

IP ClassesPeople commonly throw around terms like

“Class C”, but it should really be termed “Class C address” or “Class C address space.”

Class A: 16777216 hosts!Class B: 65536Class C: 256

IP Class Scheme

IP Class SchemeFrom the previous figure, we see that the 32-bit

address is split into 4 octets.IP addresses are self identifying.If the first 4 bits of the first octet are

0xxx: Class A address10xx: Class B address110x: Class C address1110: Class D address (Multicast)1111: Class E address

Dotted DecimalIP addresses are generally read in dotted

decimal format. 0.0.0.0 through 255.255.255.255

Much better than reading: 10000001 00110100 00000110 00000000

Dotted Decimal with ClassesClass A:

1 prefix octet (128 networks)3 suffix octets (16777216 hosts)

Class B: 2 prefix octets (16384 networks)2 suffix octets (65536 hosts)

Class C:3 prefix octets (2097152 networks)1 suffix octet (256 hosts)

Address Space

Address Delegation (cont.)RFC 1597 – Private networks

10.0.0.0 – 10.255.255.255 (Full Class A)172.16.0.0 – 172.31.255.255 (16 Class B’s)192.168.0.0 – 192.168.255.255 (Full Class C)

Special Addresses (cont.)Limited Broadcast Address

All 1’s in the entire address.Limited broadcast address is restricted to the

local subnet.255.255.255.255

Special Addresses (cont.)Loopback addresses

Loopbacks are used for testing. An IP looback is application-level testing.

Any information sent to the loopback address is never passed to the network segment. It is handled internally in the TCP/IP stack.

127.x.x.x

Special Addresses (cont.)This computer’s address

If a computer doesn’t know what it’s own address is, but needs to communicate to another machine, it designates the address of 0.0.0.0 for itself.

Applications include DHCP, BOOTP