Universal Identifier UNIVERSAL IDENTIFIER Universal network = globally accepted method for identifying each computer. Host identifier = host is identify by three things names = what an object is ! address = address identifier (where the host is !) router = it tells how to get at host (by IP address)

Name – Identifies what an entity is – Often textual (e.g., ASCII) Address – Identifies where an entity is located – Often binary – Sometimes called locator Route – Identifies how to get to the object

Original Classful Addressing Scheme TCP/IP designers selects the scheme for each host’s IP address. This IP address is of 32 bit. The 32 bit Internet address is assigned to each host. This IP address is used to communication with all other host in to the network. This 32 bit internet address is unique and known as universal identifier. Prefix of any IP address is identifies the network. IP address = netid (network identifier) + hostid (host identifier)

IP Address Division Address divided into two parts – Prefix (network ID) identifies network to which host attaches – Suffix (host ID) identifies host on that network

Division Of Internet Address Into Prefix And Suffix How should division be made? – Large prefix, small suffix means many possible networks, but each is limited in size – Large suffix, small prefix means each network can be large, but there can only be a few networks – Known as classful addressing.

Desirable Properties Of An Internet Addressing Scheme Compact (as small as possible) Universal (big enough) Works with all network hardware Supports efficient decision making – Test whether a destination can be reached directly – Decide which router to use for indirect delivery – Choose next router along a path to the destination

Description Classful Addressing These are self identifying address,.(means no boundary between prefix and suffix) Class is identify by first three high order bits. Class A: - more than 2 16 hosts connected bits – netid, 24 bits – hostid Class B: - used for intermediate size networks. hosts between 2 8 to bits – netid, 16 bits – hostid Class C: - used for network having 2 8 hosts. 21 bits – netid, 8 bits - hostid

Address specify network connections Multi-homed hosts: - Conventional computer which has two or more physical network connections known as multi- homed hosts. IP address encode both network and host Encoding is used to make effective and efficient forwarding of packet.

Network and Directed Broadcast Addresses -Hostid is 0 is never assigned to any host. -Hostid 0 is always reserved to refer to the network. Directed Broadcast Address: - -Refers to all the hosts on the network. -Hostid having all 1 s is reserved for directed broadcast. -When any packet sent to the computer whose hostid is all 1 s, than single copy of the packet is transferred to the network from the source machine. Directed broadcast address has valid netid and hostid having all 1

-Subnet and classless extensions Subnet addressing allows us to split one IP network address into smaller multiple physical networks known as sub networks. -IP Multicast Addresses: - Any packet deliver to single computer known as unicast delivery. Any packet deliver to all computers known as multicast address Class D addresses are reserved for multicasting.

Weaknesses in Internet Addressing If any computer moves from one network to another network than its IP address must change. The PC cannot assigned a permanent IP address because the IP address is for the network to which it connects. Once the prefix is chosen than total number of computer attached to the network are fixed. So when the number of computer grows into the network than prefix is selected again and all the computers are numbered again

Dotted Decimal Notation Internet addresses are decimal integer separated by decimal points

Classful Address Ranges CLASSLowest AddressHighest Address A B C D E

Summary of Special Address Conventions 1.all 0’s – Startup source address 2.All 1’s - Limited broadcast (local net) 3. Directed broadcast for net 4. Loopback (it is never appear on the network) netAll 1s / All 0s 127Anything often 1

Description Internet Assigned Number Authority has control over the IP numbers After 1998, Internet Corporation For Assigned Names and Numbers has handled the IP numbers Central authority only assigns the network portion of IP address.

Reserved Address Prefixes How IP address are assigned to private intranet. (internet doesn’t connect with the global Internet) There are chances for conflicts between private internet address and Global Internet address. So, to avoid conflicts between private internet address and global Internet address, IETF reserved several addresses. Eg: Assigned to IBM corporation, Assigned to AT&T, such address might be used in private network.

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