NETWORK LAYER
IP Addressing
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ANNOUNCEMENT: Rescheduled NO PRACTICAL SESSIONS ON
TUESDAY 22, November 2010 Rescheduled sessions: MONDAY:
November 21, 2010, NW202 PRAC GROUP 1: 13.00 – 14.00 --- PRAC GROUP 2: 15.00 – 16.00 PRAC GROUP 3: 16.00 – 17.00 PRAC GROUP 4: 17.00 – 18.00
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Review - Local Area Networks
So far, we have only discussed local area networks (LAN), Underlying physical medium is shared. Data sent to a LAN goes to ALL of the
computers on that LAN. The size of LANs is limited.
An electrical signal can only travel a limited distance.
LAN size can be extended by using Repeaters
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Review - Wide Area Network (WAN)
Network that covers large geographic area
A Wide Area Network (WAN) is made up from interconnected LANs
Network devices such as Switches or Routers can be used to join LANs together to form a WAN Any examples? Internet…
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802.3 LAN
Cat5 UTP
WAN
ISP
Router
TCP/IP Protocol Stack
Two computers, anywhere in the world can communicate, even when not directly connected.
TCP/IP - a suite of protocols, is the reference model that provides specifications for the Internet IP protocol operates at
Layer 3 or Internet/ Network layer
TCP works at Layer 4
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TCP
IP
Protocol
Network Layer
Network layer is responsible for moving data through a set of networks (Figure 1).
Router (R) helps to connect different networks together A, B, C, D are different
networks (Figure 1) IP protocol operates at
Network Layer IP protocol uses IP
Address to identify a PC uniquely in the Internet.
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R
R
R - Router
R R
R
RR
Figure 1
Figure 1
Network Addressing: Analogy with telephone numbers
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Network addresses are similar to Phone numbers Area Code / Phone Number 831 – 479-5783
Network address helps to identify path (route) through network cloud from start to destination. Each network (red ring in the
figure 2) has an address 1.0 as 1 is the common
number between 1.1, 1.2, 1.3 Each host (PC) within the
network has an address (blue ring), e.g., 1.3
Router
Figure 2
Figure 1
Why two Addresses for computer on network?
Both Layer 2 (Ethernet) and Layer 3 (IP) Addresses are needed:
Layer 2 / MAC address Physically burned into the
NIC Doesn’t change The device’s real identity
Layer 3 / Protocol address Configurable
Can be changed The device’s “mailing”
address Needs to change when
device is moved connected to a network
having different network address
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Review: What is the MAC and IP Address on my computer?
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Flat versus Hierarchical10
Layer 2 - Flat addressing schemes Next available Social Security Number MAC addresses
Layer 3 - Hierarchical addressing schemes Phone numbers ZIP codes IP addresses
IP Addresses11
Older Technology - Classful IP Addressing Defines IP address as belonging to one
of the available five classes: Class A Class BClass C Class DClass E
Current technology - Classless IP Addressing
IP Address12
IP Addresses are 32 bits.
Divide into four 8 bit sections (octets).
Convert from binary to decimal.
Classful IP Addressing13
Five different classes of IP addresses A, B, C, D, E
Class A, B and C are primary classes Used for assigning IP addresses
Class D, E used for special purposes Class D for multicast
E.g., Videoconferencing Class E addresses are reserved for
experimentation
IP Address Classes14
Network ID Host ID
Network ID Host ID
8 16
Class A
32
Class B 10
Class C110
Multicast AddressesClass D1110
Reserved for experimentsClass E
1111
248
Look at the first group of numbers in the dotted decimal notation
Class Range A 0-127 B 128-191 C 192-223 D 224-239 E 240-255
Which Class has the largest Host ID and how many bits long?
Which class has the largest Network ID and how many bits long?
Subnet mask - NetID /HostID boundary
Every machine on the network must know which part of the host address will be used as netid and hostid. Subnet mask identifies
the boundary between netid and hostid
Which class has more hosts?
Which class supports more networks?
Default subnet masks are Class A : 255.0.0.0 Class B : 255.255.0.0 Class C : 255.255.255.0
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Network Host Host Host
Network Network Host Host
Network Network Network Host
1st octet 2nd octet 3rd octet 4th octet
Class A
Class B
Class C
Find Network/Host ID from IP Address
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Logical ‘AND’ IP address and subnet mask to get Net-ID. E.g. IP address is 192.24.134.23, Find Network ID
using default subnet mask of 255.255.255.0 for class C Find the binary representation of IP address and
subnet mask Logical ‘AND’ with subnet mask
11000000.00011000.10000110.00010111 IP Address 11111111.11111111.11111111.00000000 Subnet mask for
Class C 11000000.00011000.10001010.00000000 Network ID
Convert binary to decimal value Network ID: 192.24.134.0
AND
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Hierarchy in IP addressing
• IP addresses are hierarchical.• Conceptually each IP address is a pair
• Divided into a prefix and a suffix– Prefix (net-id) identifies network to which
computers are attached.– Suffix (host-id) identifies computers within
that network.
RD-CSY1017-07/08
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Loopback address 127.0.0.0
Network address IP address with all host bits set to 0
Example: 172.16.0.0, subnet mask:255.255.0.0 Broadcast address
IP address with all host bits set to 1 Example: 172.16.255.255, subnet
mask:255.255.0.0
Special IP Addresses
RD-CSY1017-07/08 19
Private IP Addresses
Private IP Addresses cannot exist on the public Internet.
Name Address Translation (NAT) used to give data packets a “legitimate” IP source address.
Class B: 172.16.0.0 to 172.31.0.0
(In the 3rd Octet, the 128, 64, and 32 bit are off. The 16 bit is on.)
Class C: 192.168.0.0 to 192.168.255.0
(256 separate Class C Addresses)
Class A: 10.0.0.0(Favored by large enterprises because of its flexibility)
Grouping Devices into Networks and Hierarchical Addressing
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Divide a large network into subnetworks Geographical area Functionality
Departments Admin, HR…
IP addressing example21
223.1.1.1
223.1.1.2
223.1.1.3
223.1.1.4 223.1.2.9
223.1.2.2
223.1.2.1
What is the class of IP address in the figure?
Which network device is connecting the two networks?
Subnet Masks – Your Turn!22
Underline the network portion of each address:
Network Address Subnet Mask
172.0.0.0 255.0.0.0
172.16.0.0 255.255.0.0
192.168.1.0 255.255.255.0
192.168.0.0 255.255.0.0
192.168.0.0 255.255.255.0
10.1.1.0 /24
10.2.0.0 /16
10.0.0.0 /16
What is the other portion of the address?
Subnet Masks – Your Turn!23
Underline the network portion of each address:
Network Address Subnet Mask
172.0.0.0 255.0.0.0
172.16.0.0 255.255.0.0
192.168.1.0 255.255.255.0
192.168.0.0 255.255.0.0
192.168.0.0 255.255.255.0
10.1.1.0 /24
10.2.0.0 /16
10.0.0.0 /16
What is the other portion of the address? Host Addresses