Routing Presentation

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

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

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

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

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

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.

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 -

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
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
1 4
2 4
3 3
4 4
6 4
Node 6 Directory
1 2
2 2
3 2
4 4
5 4

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.

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

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

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

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

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.

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.

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.

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.

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.

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

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.

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.

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

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.

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

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

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

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

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

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

Routing Presentation

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Routing Presentation