Transcript universal identifier

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 216 hosts connected. - 65536.
7 bits – netid, 24 bits – hostid
Class B: - used for intermediate size networks.
hosts between 28 to 216
14 bits – netid, 16 bits – hostid
Class C: - used for network having 28 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 multihomed 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 1s is reserved for directed broadcast.
-When any packet sent to the computer whose hostid is all 1s,
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
10000000 00001010 00000010 00011110
128.10.0.30
Classful Address Ranges
CLASS
Lowest Address
Highest Address
A
B
C
D
E
1.0.0.0
128.1.0.0
192.0.1.0
224.0.0.0
240.0.0.0
127.0.0.0
191.255.0.0
223.255.255.0
239.255.255.255
255.255.255.254
Summary of Special Address Conventions
1. all 0’s – Startup source address
2. All 1’s - Limited broadcast (local net)
3.
net
All 1s / All 0s
Directed broadcast for net
4.
127
Anything often 1
Loopback (it is never appear on the network)
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: - 9.0.0.0 Assigned to IBM corporation,
12.0.0.0
Assigned to AT&T, such address might be used
in private network.
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