1. Internet Protocol
Routing
Prepared by:
Mahmoud Hikmet Haval Sliman Zhakaw Hashm
Supervisor :
Omer Sheerko

2. Overview
• What's Router?
• What does a router do?
• What's Routing & How do packets get from A to B in the
Internet?
• Routing Table.
• Connectionless Forwarding
• ISP Routing Tasks
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3. What's Router?
• A router consists of a computer networking device that
determines the next network point to which a data packet has
to be forwarded on its way to its destination
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4. What does a router do?
• find path
• forward packet
• find alternate path
• forward packet
• repeat until powered off
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5. What's Routing Protocol?
• Routing Protocol decide on routes to be taken data and transmit
• How do packets get from A to B in the Internet?
A B
Internet
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6. Routing Protocols
• Distribute the knowledge of the current topology
state of the network to all routers
• This knowledge is used by each router to
generate a forwarding table, which contains the
local switching decision for each known
destination address
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7. Routing Protocols
• correct operation of the routing state of a
network is essential for the management
of a quality network service
• accuracy of the routing information
• dynamic adjustment of the routing
information
• matching aggregate traffic flow to network
capacity
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8. The routing table
One routing table is needed for each router
The routing table consists of at least three information
fields:-
the Network ID : i.e. the destination network id
Cost: i.e. the cost or metric of the path through which
the packet is to be sent
Next Hop: The next hop, or gateway, is the address of
the next station to which the packet is to be sent on the
way to its final destination
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9. The routing table
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10. Connectionless Forwarding
• Each router (switch) makes a LOCAL decision to forward the
packet towards B
A B
R1 R4
R2
R3
R6
R7
R5
R8
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11. Connectionless Forwarding
• This is termed destination-based connectionless forwarding
• How does each router know the correct local forwarding
decision for any possible destination address?
• Through knowledge of the topology state of the network
• This knowledge is maintained by a routing protocol
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12. Exterior routing
ISP Routing Tasks
Interior routing
Customer routing
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13. Interior Routing
•discovers the topology of a network
through the operation of a distributed
routing protocol
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14. Cont…
• describe the current network topology.
• Routing protocols function through either
• distributed computing model (distance
vector)
• parallel computing model (link state)
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15. Routing Protocols
• Distance Vector Routing Protocols
• RIP is the main laible to choice the best way to
transmit data from A to B
• Each node sends its routing table (dest,
distance) to all neighbors every 30 seconds
• Lowest distances are updated with the
neighbor as next hop
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16. Routing Protocols
• Link State Routing Protocols
• Each router re-computes the routing
table in parallel using the common link
state database
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17. A
20
10
4
10
40
5
6
10
15
10
5
B
5
5
45
R1 R4
R2
R3
R6
R7
R5
R8
Path Selection
Minimum time to transmit data from A to B is 39 units 17

18. A
20
10
4
10
40
5
6
15
10
5
B
5
5
45
R1 R4
R2
R3
R6
R7
R5
R8
Dynamic Path Adjustment
If R5 – R7 breaks, minimum cost path from A to B is
Now 51 units
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19. Thank you
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