The document provides a comprehensive overview of routing in networking, detailing various routing algorithms including fixed routing, flooding, adaptive routing, and their corresponding properties and design parameters. Key algorithms like Dijkstra's are discussed, alongside their advantages and challenges, emphasizing the importance of network information and performance criteria. Additionally, it covers techniques such as multicast routing, distance vector routing, and link state routing, exploring their functionalities and applications.

1. Routing
12-NTU-1065 Mohsin Shoukat
12-NTU-1083 Shahmeer Ali

2. Table of Contents
• Routing
• Desirable properties of routing
• Design parameter of routing algorithms
• Fixed Routing
– Dijkstra Algorithm
• Flooding Routing
• Adaptive/Dynamic Routing
– Distance Vector Routing
– Link state Routing
• Multicast Routing

3. Router
• A routers networking hardware device which send and receive
data packets to other networks.

4. Routing
• The routing is to chose the best cost effective
path, which is selected by routing algorithm

5. Desirable Properties of Routing
 Correctness and simplicity
 Robustness
 Stability
 Fairness and Optimality
 Efficiency

6. Design Parameter of Routing Algorithms
Performance criteria :Number of hops , Cost , Delay, Throughput
Decision time : Datagram , Virtual circuit
Decision plane :EACH NODE (Distributed), Central Node (Centralized) , Originated
Node (Source).
Network Information source: None , Adjacent node , Nodes Along Route , All
Nodes.
Network information updating time: continuous, periodic , major load change ,
topology change.

7. Fixed Routing
A route is selected for each source-destination pair of nodes in network.
The routes are fixed they only may change if there is change in topology in
network.
Fixed Routing :Example
• SUCH a big routing directory is created in network control center.
• This has a big drawbacks. If this NC center fail everything fail, so it is not very
reliable.
From
Node
To Node
1 2 3 4 5 6
1 - 2 3 2 2 2
2 1 - 1 6 6 6
3 1 1 - 4 5 1
4 6 6 3 - 5 6
5 4 4 3 4 - 4
6 2 2 2 4 4 -

8. Fixed Routing
As directory is packet receive and send it to its next node.
Question is how these directory created?
Node 1 Directory
Destinatio
n
Next Node
2 2
3 3
4 2
5 2
6 2
Node 2 Directory
Destination Next Node
1 1
3 1
4 6
5 6
6 6
Node 3 Directory
Destination Next Node
1 1
2 1
4 4
5 5
6 1
Node 4 Directory
Destinatio
n
Next Node
1 6
2 6
3 3
5 5
6 6
Node 5 Directory
Destination Next Node
1 4
2 4
3 3
4 4
6 4
Node 6 Directory
Destination Next Node
1 2
2 2
3 2
4 4
5 4

9. Dijkstra algorithm
It find the least cost paths from given node to all other nodes .
It work on static condition when topology and cost fix.
• These are basic steps:
• -initialization; M= {s} , Dn =dSN for n!=s
• -find neighboring nodes not in M has least-cost path from s
include in M.
• -update the least cost path.

10. Dijkstra Algorithm
Iteration M C(2) path C(3) path C(4) path C(5) path C(6) path
1 (1) 2, 1-2 2, 1-3 ------- ------- -------
2 (1,2) 2, 1-2 2, 1-3 6,1-2-4 ------- 3, 1-2-6
3 (1,2,3) 2, 1-2 2, 1-3 5,1-2-6-4 7, 1-2-6-4-5 3, 1-2-6

11. Dijkstra Algorithm
Iteration M C(2) path C(3) path C(4) path C(5) path C(6) path
4 (1,2,3,6) 2, 1-2 2, 1-3 5, 1-2-6-4 7, 1-2-6-4-5 3, 1-2-6
5 (1,2,3,4,6) 2,1-2 2, 1-3 5, 1-2-6-4 7, 1-2-6-4-5 3, 1-2-6
6 (1,2,3,4,5,6) 2, 1-2 2, 1-3 5, 1-2-6-4 7,1-2-6-4-5 3,1-2-6

12. Fixed routing
Advantages:
• Simple, cost given, least cost path given you can use it simple.
• Works well for stable load network.
• Same for virtual-circuit or datagram.
Problems:
• Lack of flexibility, if network condition change it fail
• Does not react to failure network, or congestion condition

13. Flooding Routing
• Require no network any information whatsoever
• Every incoming packet is send to all node except from which it come.

14. Flooding Routing
Advantages:
• Reliable.
• All routes are tried, so at least one packet goes to shortest route.
• All nodes direct or indirectly visited.
Problems:
• Generate large number copies are generate which make congestion.
• Suitable if use damping mechanism so that larges number of packets are not
make.
Technique To Use
• Hop-Count: a hop counter is contain in header of packet and it decrease each
one time when pass through the node and discard when it reach to zero.
• Sequence Number: Keep track of packets which are responsible for flooding
using a sequence number .Avoid sending them out second time.

15. Flooding
Utilities Of Flooding:
 Flooding is robustness: in case of war or load or topology change under such
case this is very useful
 May be used in virtual circuit like when packet reach to D from least cost path
it send acknowledgment and it save.
 Flooding always uses shortest path since it explore every possible path to D.
 Some time to messages all nodes so it’s good. To upgrade info this helpful
 Rather its disadvantages it’s also have imp utilities.

16. Selective Flooding
• A variation which is slightly more practical is Selective Flooding.
• The router don’t send packets to in all direction but in the direction to the
destination. Give weightage to check whether it is going to D or moving away
to D.

17. Random Routing
• This has the simplicity and robustness of flooding with far
less traffic load.
• A node only selective one outgoing path for retransmission of incoming packet.

18. Random Routing
 Don’t need the info of the network like how many packets are in Queue
bandwidth etc.
 Round Robin fashion in which you chose random and choose a link and next
time you choose other link etc.

19. Random Routing
 A refinement is to assign a Probability to each outgoing link and to select the
link based on that probability
 So here the Data Rate is used as network information use higher data rate
path so packet shall be deliver to the destination but it also has a limitation like
it don’t select cost effective path

20. Adaptive routing
 Adaptive routing use networking information for it’s routing
 Routing decision change as condition on the network change.
 Two principal that affecting routing decision.
– Failure: when a node, link fail it can’t longer use as a route.
– Congestion: when a particular area of the network congested it is desirable
to move the route packets around the congestion area.
So adaptive routing changes dynamically with the networking condition.

21. Adapting Routing
• For Adaptive Routing, there must be exchange network information among
the nodes.
• Number Of Hops (simplest one but the not use i.e. for particular ‘S’ TO ‘D’ how
many hops packets use)
• Time Delay in msec (for a particular S to D , queue length is know we can call
the time delay)
• Total Packets : Total number of packets queued in network.

22. Adapting Routing
 More Information Exchange, Better Routing, More Overhead
 More Frequent, Better Routing, More Overhead
So there is trade off.

23. Adaptive Routing
Problems
• Routing is done dynamically changing condition so it put Burdon on
switching nodes.
• More processing power required for Routing Decisions
• It may react too quickly to change network state, thus produces
Congestion.

24. Adaptive Routing
Advantages
• Improve performance
• Can aid in congestion control
• Widely used

25. Distance Vector Routing
• Key characteristic:
Knowledge about Entire Network.
Routing only to Neighbor.
Information sharing at Regular Interval.
Network ID Cost Next Router

26. Link State Routing
• Basic steps:
• Identify the neighboring nodes.
• Measure the delay or cost to each of its neighbor.
• Form a packet contain all the information.
• Send the packets to all other nodes (flooding)
• Compute the shortest path to every other node (Dijkstra algorithm)
• Here in link state information gather is only from its neighboring nodes rather entire
network like distance routing.
• So the basic idea is it gather information to its neighboring node and route to all like
flooding.
• And information sharing gather is done after regular interval.
Advertise ID NetworkID
(destination)
Cost Next Router

27. Link State Routing
Problems
 Information is gather at regular interval
 More complex
 It’s make some kind of database.
 Computational power and memory
 Expensive

28. Multicast Routing
• Sending information from S to D. but in some case we have to
send some message to a group of peoples.
• Uses for Broadcasting
 Technique
-Find The Spanning Tree
-Flooding

29. Review
• Routing
• Desirable properties of routing
• Design parameter of routing algorithms
• Fixed Routing
• Dijkstra Algorithm
• Flooding routing
• Adaptive/dynamic routing
• Adaptive Routing
• Distance vector routing
• Link state routing
• Multicast routing