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-- 1
Sub Topic : IP Addressing Concepts
Teaching Aids : Diagrams, Animations
-- 2
Recap
In the previous class, you have learnt about
• Leased line, DSL and Cable MODEM
-- 3
Objectives
On completion of this period, you will be able to know about
• What is an IP Address?
• What is network prefix and host number?
• What is Internet address?
• What is sub-netting and no sub-netting?
-- 4
What is an IP Address?
• Internet identifier including information about how to reach a network location (via the Internet routing system)
• IPv4: 32-bit number. Written in Dotted Decimal Notation 205.150.58.7.– 4 billion different host addresses
• IPv6: 128-bit number. Written in Hex Decimal Notation2001:0503:0C27:0000:0000:0000:0000:0000
– 16 billion network addresses
-- 5
IP Addresses
Application dataTCP HeaderEthernet Header Ethernet Trailer
Ethernet frame
IP Header
version(4 bits)
headerlength
Type of Service/TOS(8 bits)
Total Length (in bytes)(16 bits)
Identification (16 bits)flags
(3 bits)Fragment Offset (13 bits)
Source IP address (32 bits)
Destination IP address (32 bits)
TTL Time-to-Live(8 bits)
Protocol(8 bits)
Header Checksum (16 bits)
32 bits
Fig .1
-- 6
Network Prefix and Host Number
•The network prefix identifies a network and the host number identifies a specific host (actually, interface on the network)
•How do we know how long the network prefix is?
–Before 1993: The network prefix is implicitly defined (see class-based addressing)
–After 1993: The network prefix is indicated by a net mask
network prefixnetwork prefix host numberhost number
-- 7
• IP addresses are written in a so-called dotted
decimal notation• Each byte is identified by a decimal number in the
range [0..255]:10000000 10001111 10001001 10010000
Dotted Decimal Notation
1st Byte
= 128
3rd Byte
= 137
4th Byte
= 144
128.143.137.144
2nd Byte
= 143
Fig.2
-- 8
IP Address
• Every interface have a unique Internet address (IP address)
• Consist of 2 parts – network id and host id
• 32-bit address
• 5 Classes
–A – 0.0.0.0 to 127.255.255.255 (224 nodes)
–B – 128.0.0.0 to 191.255.255.255 (216 nodes)
–C – 192.0.0.0 to 223.255.255.255 (28 nodes)
–D – 224.0.0.0 to 239.255.255.255
–E – 240.0.0.0 to 247.255.255.255
-- 9
IP Address contd….
• When Internet addresses were standardized (early 1980s), the Internet address space was divided up into classes• Class A: Network prefix is 8 bits long• Class B: Network prefix is 16 bits long• Class C: Network prefix is 24 bits long
• Each IP address contained a key which identifies the class• Class A: IP address starts with “0”• Class B: IP address starts with “10”• Class C: IP address starts with “110”
-- 10
IP address contd…
Class C network id host11 0
Network Prefix24 bits
Host Number8 bits
bit # 0 1 23 242 313
Class B 1 network id host
bit # 0 1 15 162
Network Prefix16 bits
Host Number16 bits
031
Class A 0Network Prefix
8 bits
bit # 0 1 7 8
Host Number24 bits
31
-- 11
IP Address contd…
Class D multicast group id11 1bit # 0 1 2 313
04
Class E (reserved for future use)11 1bit # 0 1 2 313
14
05
Fig .4
-- 12
Special IP Address
•All 0’s is reserved to refer to a network number
•All 1’s is reserved to refer to a broadcast address
-- 13
Sub-netting
• Class A and B has too many nodes
• Network is divided to sub-network
• Improve network performance
• Indicate by subnet mask
-- 14
No Sub-netting
• All hosts think that the other hosts are on the same network
128.143.70.0/16
128.143.137.32/16subnetmask: 255.255.0.0
128.143.71.21/16subnetmask: 255.255.0.0
128.143.137.144/16subnetmask: 255.255.0.0
128.143.71.201/16subnetmask: 255.255.0.0
Fig .5
-- 15
128.143.0.0/16
128.143.137.32/24subnetmask: 255.255.255.0
128.143.71.21/24subnetmask: 255.255.255.0
128.143.137.144/24subnetmask: 255.255.255.0
128.143.71.201/24subnetmask: 255.255.255.0
128.143.137.0/24Subnet
128.143.71.0/24Subnet
With Sub-netting
• Hosts with same extended network prefix belong to the same network
Fig .6
-- 16
Summary
In this class, you have learnt about
• At the network layer, a global identification system that
uniquely identifies every host and router is necessary for
delivery of packet from host –to-host
• An IP v4 address is 32 bit long and uniquely and
universally define a host or router on the Internet
-- 17
Summary contd……
• In classfull adressing,the portion of IP address that
identifies the network is called netid
• In classfull adressing,the portion of IP address that
identifies the host or router on the network is called
the hostid
-- 18
Summary contd..
• An IP address defines a device’s connection to a network
• There are five classes in IPv4 addresses
• Classes A, B and C differ in the no. of host allowed per network
• Class D is for multicasting and class E is reserved
-- 19
(a) 32
(b) 48
(c) 24
(d) None of the above
Quiz
1. IP version 4 is of ______ bits
-- 20
(a) 5
(b) 4
(c) 6
(d) None of the above
Quiz
2. In IP addressing there are ___ classes
21
Frequently Asked Questions
1. Discuss the concepts of IP addressing
2. Describe the classes of IP version 4 addressing
3. Write a short note on default gate ways