04-network Layer-04 By Apcoms
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Link State Routing Protocol
CPS 422 Computer Networks
Link state routing involves five steps for a router: o Discover its neighbors and learn their network addresses o Measure the delay and cost to each of its neighbors o Construct a packet telling all it has just learnt o Send this packet to “all” other routers of the network o Compute the shortest path to every other router
NETWORK LAYER
Faisal Amjad CPS 422
Link State Routing Protocol
A Subnet B
C
2
4
3
A
1
5
D
6 8
E
7
F
Link state Packets for the Subnet
A Seq B 4 E 5
B Seq A 4 C 2 F 6
C Seq B 2 D 3 E 1
D Seq C 3 F 7
In this way the complete topology and all delays are experimentally measured and distributed to all other routers An algorithm to find the shortest path (e.g. Dijkstra’s Algorithm) can then be used to find the shortest path to every other router in the network Faisal Amjad CPS 422
E Seq A 5 C 1 F 8
F Seq B 6 D 7 E 8
Faisal Amjad CPS 422
Link State Routing Protocol The result of the algorithm can be installed in the routing tables and normal operation resumed Link state routing is widely used in actual networks OSPF is increasingly being used in the internet which uses link state routing Another variant called the Optimized Link State Routing (OLSR) protocol has been optimized for use within Mobile Ad hoc Networks (MANets). In OLSR the Flooding process is optimized by the use of Multi-Point Relays or MPRs Faisal Amjad CPS 422
Computing the new routes can be done as: A router accumulates the full set of link state packets It can then construct the entire subnet graph because every link is represented in the link state packets Every link is represented twice, once in each direction The two values can be different and may be averaged to get one value Dijkstra’s algorithm can now be used to calculate the shortest path to all possible destinations Faisal Amjad CPS 422
Reading Assignment State the effect of including or excluding “load” while measuring the line delay for link state routing State the differences between Distance vector routing and link state routing algorithm
Faisal Amjad CPS 422
1
CPS 422 Computer Networks
Link state routing involves five steps for a router: o Discover its neighbors and learn their network addresses o Measure the delay and cost to each of its neighbors o Construct a packet telling all it has just learnt o Send this packet to “all” other routers of the network o Compute the shortest path to every other router
NETWORK LAYER
Faisal Amjad CPS 422
Link State Routing Protocol
A Subnet B
C
2
4
3
A
1
5
D
6 8
E
7
F
Link state Packets for the Subnet
A Seq B 4 E 5
B Seq A 4 C 2 F 6
C Seq B 2 D 3 E 1
D Seq C 3 F 7
In this way the complete topology and all delays are experimentally measured and distributed to all other routers An algorithm to find the shortest path (e.g. Dijkstra’s Algorithm) can then be used to find the shortest path to every other router in the network Faisal Amjad CPS 422
E Seq A 5 C 1 F 8
F Seq B 6 D 7 E 8
Faisal Amjad CPS 422
Link State Routing Protocol The result of the algorithm can be installed in the routing tables and normal operation resumed Link state routing is widely used in actual networks OSPF is increasingly being used in the internet which uses link state routing Another variant called the Optimized Link State Routing (OLSR) protocol has been optimized for use within Mobile Ad hoc Networks (MANets). In OLSR the Flooding process is optimized by the use of Multi-Point Relays or MPRs Faisal Amjad CPS 422
Computing the new routes can be done as: A router accumulates the full set of link state packets It can then construct the entire subnet graph because every link is represented in the link state packets Every link is represented twice, once in each direction The two values can be different and may be averaged to get one value Dijkstra’s algorithm can now be used to calculate the shortest path to all possible destinations Faisal Amjad CPS 422
Reading Assignment State the effect of including or excluding “load” while measuring the line delay for link state routing State the differences between Distance vector routing and link state routing algorithm
Faisal Amjad CPS 422
1
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