Transcript IP Address - Department of Computing & Immersive Technologies

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NETWORK LAYER
IP Addressing
ANNOUNCEMENT: Rescheduled
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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

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)
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
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…
802.3
LAN
WAN
Cat5 UTP
ISP
Router
TCP/IP Protocol Stack
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
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
Protocol
TCP
IP
Network Layer
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Network layer is responsible for
moving data through a set of
networks (Figure 1).
R
R
Router (R) helps to connect
different networks together
 A, B, C, D are different
networks (Figure 1)
R
R
R
R
Figure 1
IP protocol operates at Network
Layer
R
IP protocol uses IP Address to
identify a PC uniquely in the
Internet.
Figure 1
R - Router
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


Figure 1
1.0 as 1 is the common number
between 1.1, 1.2, 1.3
Router
Each host (PC) within the network has
an address (blue ring), e.g., 1.3
Figure 2
Why two Addresses for computer on network?
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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
Review: What is the MAC and IP Address on my
computer?
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Flat versus Hierarchical
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
Layer 2 - Flat addressing schemes
 Next
available
 Social Security Number
 MAC addresses

Layer 3 - Hierarchical addressing schemes
 Phone
numbers
 ZIP codes
 IP addresses
IP Addresses
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
Older Technology - Classful IP Addressing
 Defines IP address as belonging to one of the
available five classes:
 Class A
 Class B
 Class C
 Class D
 Class E
 Current technology - Classless IP Addressing
IP Address
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IP Addresses are 32 bits.
Divide into four 8 bit sections (octets).
Convert from binary to decimal.
Classful IP Addressing
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
Five different classes of IP addresses
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
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 Classes
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 Look at the first group of
numbers in the dotted decimal
Network ID
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notation
Class A Network ID
 Class
Range
 A
0-127
Class B 10
 B
128-191
 C
192-223
Class C 110
 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?
Class D
Class E
Host ID
16
24
32
Host ID
1110
Multicast Addresses
1111
Reserved for experiments
Subnet mask - NetID /HostID boundary
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
Every machine on the network
must know which part of the host
address will be used as netid
and hostid.
Class A
 Subnet mask identifies the
boundary between netid and Class B
hostid
 Which class has more hosts? Class C
 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
1st octet
2nd octet
3rd octet
4th octet
Network
Host
Host
Host
Network
Network
Host
Host
Network
Network
Network
Host
Find Network/Host ID from IP Address
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
Logical ‘AND’ IP address and subnet mask to get Net-ID.
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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

AND


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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
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Network ID: 192.24.134.0
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.
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Special IP Addresses
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
Loopback address
 127.0.0.0
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Network address
 IP
address with all host bits set to 0
 Example:
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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
RD-CSY1017-07/08
Private IP Addresses
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
Private IP Addresses cannot exist on the public Internet.
Name Address Translation (NAT) used to give data packets
a “legitimate” IP source address.
Class A: 10.0.0.0
(Favored by large enterprises because of its flexibility)
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)
RD-CSY1017-07/08
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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 example
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What is the class of IP address in the figure?
Which network device is connecting the two networks?
223.1.1.1
223.1.1.2
223.1.2.1
223.1.1.4
223.1.2.9
223.1.2.2
223.1.1.3
Subnet Masks – Your Turn!
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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
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What is the other portion of the address?
Subnet Masks – Your Turn!
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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
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What is the other portion of the address?
 Host Addresses