This PPt explains about router and routing

1. Concepts of Router and Routing
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2. Router
• A device that connects two or more computer networks
together is called as a Router
• It allows two or more different computer networks to
send data to each other
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3. Router Contd….
Fig.1
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4. Router Contd….
Fig.2
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5. Router Contd….
Fig.3
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6. Router Contd….
• A router is a computer whose software and hardware
are designed to perform the tasks of routing and
forwarding information (sending the information
to the destination).
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7. Router Contd….
Routers generally contain
• A specialized operating system
• RAM
• NVRAM
• Flash memory and
• one or more processors
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8. Router Contd….
• Routers operate in two different planes
• Control Plane: The router learns the outgoing interface
that is most appropriate for forwarding specific packets to
specific destinations
• Forwarding Plane: The router is responsible for the actual
process of sending a packet received on a logical interface
to an outbound logical interface
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9. Control Plane Activities
• Routers periodically disseminate topology information to all
the other routers with the help of control packets (e.g.
:HELLO, TC packets)
• Topology information contains the information about the one
hop and two hop neighbors to each of the router, link cost
etc
• Link cost can be defined in several terms: a time estimate, a
distance estimate, congestion estimate, bandwidth estimate
etc. for the communication link between router and its one
hop neighbor
• After learning the topology information, every router
computes shortest route from itself to every other router in
the Internet
• The computed shortest routes are stored in a route cache in
the form of routing table
• Routing table gives the nest hop router to which packet has
to be forwarded to send it in the shortest path for each
destination IP address ( network part of IP address) 9

10. Forward Plane Activities
• The Packet which arrive at Router’s interface is first
buffered (stored)
• The Router examines the packet’s header and the picks
the destination IP address to where the packet has to
reach
• It looks into the routing table to know the next hop router
to which the packet has to be forwarded in order to send it
in the shortest path
• Then Router forwards the packet to the corresponding
next Router address via one of its ports
• The same process is carried out at each Router along the
shortest path till the destination router is reached
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11. Types of Routers
Various types of routers
• Edge Router
• Border Router
• Core router
• Enterprise Router
• Access Router
• Distribution Router
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12. Symbol for Router
Fig.4
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13. 13
Router Connecting Various Subnets
TOKEN RI
NG
Fig.5
NETWORK
A BUS N
Y
Z
ROUTER
ETHERNE
X
T
NETWORK
C

14. Router Concepts
• Router must have three interfaces and three Network
Interface Cards (NICs) to interact with the networks A, B and
C at the junctions X and Y and Z as shown in figure 5
• In Internet, there are number of networks that communicate
with each other. Therefore, there would be as many routers
as networks
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15. Routing
• Routing is the process of selecting paths in a network to
send data or physical traffic
• Routing is performed for many kinds of networks,
including the telephone network , the Internet, and
transport networks
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16. Router Contd….
• Routing directs forwarding, the passing of logically
addressed packets from their source towards their
ultimate destination through intermediary nodes
• Nodes are hardware devices called routers, bridges,
gateways, firewalls, or switches
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17. Router Contd….
• Ordinary computers with multiple network cards can also
forward packets and perform routing, though they are not
specialized hardware and may suffer from limited
performance
• The routing process usually directs forwarding on the
basis of routing tables which maintain a record of the
routes to various network destinations
• Thus constructing routing tables, which are held in the
routers' memory, becomes very important for efficient
routing
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18. Router Contd….
• Therefore, Routing is the process of sending the data in
the form of packets called datagrams from the source to
the destination computers through many networks
• Routing algorithms take the decisions about routing
process and factors affecting them are as follows
• Least cost routing
• Distributed routing
• Packet life time
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19. ROUTING AND ROUTERS
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20. Summary
In this class, you have learnt about
• Router and routing concepts
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21. Quiz
1. A Router is connected to five networks.
Then number of NICs required by the
router is
a) 2
b) 3
c) 5
d) 7
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22. Frequently Asked Questions
1. Differentiate between Router and Routing?
2. List the various types of routers
3. Write short notes on routing
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