Transcript IP Address
IP Addressing
Background
• There are 3 types of networks.
• Individual computer, computer
network(homogeneous network),non
homogeneous network.
• A message pertaining to a non-homogeneous
network is
•
SIO
Service
information octet
OPC
DPC
label
CIC
Actual Message
Identifying a node
• A node has to be identified so that in the label we can
input from which node a message has to be
transferred ,to the recipient node.
• These information will be given in OPC(Originating
point code) and DPC(Destination .. ….)
• CIC stands for (Circuit identification code),
the route the message travels from the origination to
the termination.
In order to understand this we will first examine how a
telephone network operates.
Sri Lanka Telephone Networks
.A
Fixed Lines
SLT
Suntel
Lanka Bell
There are 3 operators
There are 5 operators
Mobile
Dialog
Mobitel
Hutch
Tigo
Airtel
How to identify the network?
• In a fixed network
Area code
2,3
5
5
7 digits
SLT
Lanka bell
Suntel
• SLT digit 2 indicates for wire lines
Digit 3 indicates CDMA(wireless lines)
All the other operators suntel and lankabell will have
4 and 5 to identify their network.
In a fixed telephone Network
• Identifying the network will be from the network number ,
this number is available after the area code (Area Code+
Network Number) for fixed operators.
• For eg: Ratnapura area code is 45 , Ratnapura SLT numbers
starting with 45 2 or 3, Lankabell no’s 45 5
• How many telephones can SLT provide to Ratnapura area?
• How many telephones the Lanka Bell can provide in
Ratnapura area?
• Area code of Sri Lanka is given in the attached annexure
• How many telephones each operator can provide in Sri
Lanka”?
• How many mobile telephones and how many fixed
telephones in a given geographical area?
Area codes of
Sri Lanka
Sri Lankan numbering plan
• ,
Area code
Fixed Line
Network number
Individual customer
identification
Mobile
How to identify the operator in the
mobile network?
• No Area code
9 digits
• How many telephones could be provided by
dialog for the whole of Sri Lanka?
• Answer: 10 million subscribers.
Sub-Network
• Local Area Network or PBX(Private Branch
Exchanges)
• Suppose there are 800 telephones in your
university.
• Do you want to have direct lines?
• Within the campus , do you want to dial full
number of a given telephone?
Sub Network Numbering
• Sabaragamuwa campus can be provided with 3 digits to identify each
telephone in the campus.(Assume 1000 telephones in the campus)
• Hence the least significant 3 digits of the numbering plan has to be privately
used by the campus .
• Let’s analyze that the campus has decided to select SLT as the network
operator.
• The campus should have the national numbering ,045 2 XXX YYY .
• The SLT operator will allocate XXX from their numbering resources, for eg:
We assume 200
• Then the campus authority is having the freedom to allocate 1000 numbers
for a particular location, i.e YYY digits
• Hence the telephone number of the campus for external uses will be 045 2
200 YYY, where as with in the campus , it can be only YYY
The concept of sub numbering(Local Area
If any extension dials more
Network)
than 3 digits implies an
• .
(Direct outward dialing)
outbound call from the
university network, this will be
analyzed by the campus PAPX
and call be routed accordingly
000
001
SLT
Network
University
Of
Sabaragamuwa
002
Local
Numbers
999
045 2 200 999
(Direct inward dialing)
The concept of sub numbering(Wide Area
Network)
• Assume 4 universities such as sabaragamuwa, Ruhuna,
peradeniya and colombo to be provided with 10,000
extensions with the following breakdown
• Peradeniya-4000, Colombo- 3000, Sabaragamuwa-2000, Ruhuna-1000
• Assume that the entire network is interconnected as 1 network so that 1
area code could be allocated .
• Assume 90 as the area code which will be provided by the government.
• Assume SLT as the network operator, then the network operator code will
be 2.
• Since there are 10,000 extensions in the numbering plan , the least
significant 4 digits are allocated for extension numbers.
• The Wide area internal numbering plan can be as follows:
Wide area network internal numbering.
•
•
•
•
•
•
•
•
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Peradeniya 0YYY , 1YYY, 2YYY,3YYY (4000 extensions)
Colombo 4YYY,5YYY,6YYY(3000 extensions)
Sabaragamuwa 7YYY,8YYY(2000 extensions)
Ruhuna 9YYY(1000 extensions )
Any srilankan dialing this Wide area network will dial 10
digits.They are as follows:
090 2 XX YYYY , XX can be any 2 digits which will be allocated by
SLT, assume it as 00
Then the wide area network numbering will be
090 2 00 Y1 Y2 Y3 Y4 , where Y1 denotes the University ,
Y1=0,1,2,3 represents ‘Peradeniya’ … etc
Wide Area Network working
• .
(Direct outward dialing)
000
Sabaragamuwa
001
002
SLT
Network
Ruhuna
Colombo
Peradeniya
9999
090 2 00 9999
(Direct inward dialing)
Telephone network in the world
• Inorder to complete the analysis on telephone numbering
let’s try 2 understand about how the world telephones
operates.
• CCITT has decided 15 digits as the total length
• How many telephones in the world you can have?
• 1 peta telelphones(10 10)
Country
code
……..
15 digits
Numbering of computer networks.
• Similar to the telephones a computers to communicate through the
internet the packets transmitted may pass through several LANs and
WANs before reaching the destination computer
•
For this level of communication we need a global addressing scheme
•
Today the term IP address is used to mean a logical address in the
network layer of the TCP/IP protocol suite.
•
IPv4 was standardised by Internet Engineering Task Force (IETF) in 1981
• Every machine on internet has a unique identifying number which is
known as IP Address. An example of an IP address is shown below
• 216.27.61.137
Basics of IP address
•
•
•
•
•
•
•
Any computer element connected to a computer network such as internet will
be identified by 32 bits(We learned analogy in the telephone network this as
15 digits)
The number of computers that could be connected to the internet is : 2 to the
power 32)
In order to save the addresses unlike telephones the IP addresses will be
provided to customers as dynamic(means only when the computer is
connected to the network , a temporary IP address will be provided by the
service provider.) or static (similar to telephone network , one permanent IP
address will be allocated) The ADSL line will provide static IP addresses while
ILL will provide dynamic IP addresses.
IP address is normally shown in dot decimal format :
32 bits consists of 4 bytes and each byte will be converted to denary
What we have studied up to now is IPv4(version 4 , still using)
In future IPv6 will be used and where 128 bits are there instead of 32 bits , so
that much more computers can be provided with fixed (static) IP address.
The relationship between ‘dot’,’hexa
and IP addresses
The characteristics of IP Address
• World Wide Web(WWW) doesn’t differentiate countrywise,unlike
telephone networks.
• Each terminal will be defined by 32 bits , as an IP address.
• The IP address has been structured according to the networks
and the number of computers in that network that is going to be
operated .
• Hence the IP address can be segregated into network and the
host .
• There are two types of addressing method in IP. Classful and
Classless
• At the inception of IP, Classful addressing was used. However later
moved towards Classless addressing.
• In classful addressing consist of 5 types. They are Class A, Class B,
Class C, Class D, Class E
Dot decimal IP Address
8 Bits
Class A
0
10
.
8 Bits
Hosts
14 Bits
Network
Class C
8 Bits
7 Bits
Network
Class B
8 Bits
Hosts
110
Network
Class D
1110
Class E
0
Hosts
Summary of Classful addressing
Summary of Classful addressing
contd…
• Disadvantage of classful addressing is each class is divided
into a fixed number of blocks consisting of fixed number of
addresses.
• A large part of the available addresses are wasted. Hence this
method is becoming obsolete.
• To somewhat overcome the wastage of addresses subnetting
was introduced during classful addressing era
Introduction to Subnet
• The two level hierarchy (network and host numbers) were
initially thought to be sufficient, but by 1984, it became clear
that a third hierarchical level was needed and so the “subnet”
was added to the hierarchy at that time
• Large block of class A and B is divided into several groups
and each group is assigned to smaller networks (called
subnets)
• A subnet was added into the HOST
Shown in the diagram.
Why?
Introduction to Subnet contd…
• Because we can control the number of hosts we want to
allocate if we have another function.
• That is, if we want more hosts there will be less subnet bits
and if we want less hosts we can have more subnets.
• In that way, Hosts wont be wasted neither used less!
Optimizing IP addressing
Examples
Subnet Example 1
Let’s find the corresponding Network, Subnet and Host for a given IP address
and a subnet Mask.
IP Address : 10.27.32.100
Subnet Mask : 0xFFFF0000
Step 1
Turn both of them into Binary format
IP address : 0000 1010 0001 1011 0010 0000 0110 0100
Subnet Mask : 1111 1111 1111 1111 0000 0000 0000 0000
Step 2
Identify which class is IP address. Since it starts from 0, The class is A.
Class A : 7 bit Net , 24 bits Host
Step 3
AND both Subnet and IP address together
IP Add : 0000 1010 0001 1011 0010 0000 0110 0100
Sub Net : 1111 1111 1111 1111 0000 0000 0000 0000
Result : 0000 1010 0001 1011 0000 0000 0000 0000
Step 4
Observe the result. The last bits which are 0’s represent number of Host.
In this example, Number of 0’s (in the end of result ) are 16 bits.
So the corresponding binary of the 0’s in results are taken in the IP address.
Which would come to 0010 0000 0110 0100 = 32.100
So the HOST is 32.100
Step 5
IP Add : 0000 1010 0001 1011 0010 0000 0110 0100
Sub Net : 1111 1111 1111 1111 0000 0000 0000 0000
Result : 0000 1010 0001 1011 0000 0000 0000 0000
We know that number of host bits in this example are 16 bits.
This is Class A address and they have 24 bits for Host + Subnet
So the Subnet bits are 24 – 16 = 8 bits
Imagine you have no 0’s in the end of the result (It is for the HOST not for subnet!)
That would leave the result as 0000 1010 0001 1011
Take 8 bits from the least significant bit which would give 0001 1011 = 27
So the SUBNET is 27.
Step 6
The rest is simple!
Result : 0000 1010 0001 1011 0000 0000 0000 0000
Ignore the bits allocated for Host and Subnet in the result.
That would leave 0000 1010 = 10
So the Network is 10
Result
IP Address : 10.27.32.100 : 0000 1010 0001 1011 0010 0000 0110 0100
Subnet Mask : 0xFFFF0000 : 1111 1111 1111 1111 0000 0000 0000 0000
Network : 10
Host : 32.100
Subnet : 27
Now, few examples for you
1. IP Address : 136.27.33.100
Subnet Mask : 0xFFFFFE00
2. IP Address : 136.27.34.141
Subnet Mask : 0xFFFFFE00
3. IP Address : 193.27.32.197
Subnet Mask : 0xFFFFFFC0
Answers
1.
Answers
2.
Answers
3.
Classless Addressing
• To overcome address depletion classless addressing was
designed
• In this scheme there are no classes but the addresses are still
granted in blocks
• Restrictions:
– The addresses in a block must be contiguous, one after another.
– No. of addresses in a block must be a power of 2 (1,2,4,8,…).
– The first address must be evenly divisible by the number of
addresses.
• Example
A block of 4 addresses is granted to a small office.
First 205.16.37.32
Last 205.16.37.35
• We see that the addresses are contiguous. The number of addresses is a
power of 2 (4= 22), an the first address is divisible by 4. The first address,
when converted to a decimal number is 3,440,387,360, which when
divided by 4 results is 860,096,840
Classless Addressing contd..
• Mask…….
Example
A block of addresses is granted to a small organisation. We know that one
address is 205.16.37.39/28.Find the first address, last address and the
number of addresses assigned to the organisation.
Solution
Binary representation is
11001101 00010000 00100101 00100111.
we set 32-28 rightmost bits to 0
11001101 00010000 00100101 00100000
Hence the first address is
205.16.37.32
Last address
Set 32-n rightmost bits in binary
to 1s
Hence the last address is
11001101 00010000 00100101 00101111
205.16.37.47
Number of addresses
The value of n is 28. Hence the no. of addresses is 232-28 = 16
NOTE: The first address in a block is used as the network address to represent
the organisation to the rest of the world and is not assigned to any device.