EE534 Communication and Computer Network Simulation OSPF: Open Shortest Path First A Routing Protocol Based on the Link-State Algorithm Name: Duong Le Due: 3/27/2012
I. Objective: The objective of this lab is to configure and analyze the performance of the Open Shortest Path First (OSPF) routing protocol. II. Over view: In Lab 6 we discussed RIP, which is the canonical example of a routing protocol built on the distancevector algorithm. Each node constructs a vector containing the distances (costs) to all other nodes and distributes that vector to its immediate neighbors. Link-state routing is the second major class of intradomain routing protocol. The basic idea behind link-state protocols is very simple: Every node knows how to reach its directly connected neighbors, and if we make sure that the totality of this knowledge is disseminated to every node, then every node will have enough knowledge of the network to build a complete map of the network. Once a given node has a complete map for the topology of the network, it is able to decide the best route to each destination. Calculating those routes is based on a well-known algorithm from graph theory—Dijkstra’s shortest-path algorithm. OSPF introduces another layer of hierarchy into routing by allowing a domain to be partitioned into areas. This means that a router within a domain does not necessarily need to know how to reach every network within that domain—it may be sufficient for it to know how to get to the right area. Thus, there is a reduction in the amount of information that must be transmitted to and stored in each node. In addition, OSPF allows multiple routes to the same destination to be assigned the same cost and will cause traffic to be distributed evenly over those routers. In this lab, you will set up a network that utilizes OSPF as its routing protocol. You will analyze the routing tables generated in the routers and will observe how the resulting routes are affected by assigning areas and enabling load balancing.
III. Implementation: 1. 2. 3. 4. 5. 6.
Create a New Project Create and configure the Network Configure the simulation Duplicate and configure the Scenario to get Areas Scenario and Balanced Scenario Run the Simulation View and compare the Results
IV. Results:
Figure 1: The route for the traffic demand between RouterA and RouterC in No_Areas Scenario
Figure 2: The route for the traffic demand between RouterB and RouterH in No_Areas scenario
Figure 3: The route for the traffic demand between RouterA and RouterC in Areas scenario
Figure 4: The route for the traffic demand between RouterB and RouterH in Balanced scenario
V. Exercises: 1. Compare Areas and No_Areas: Figure 1 and figure 3 show the route for the traffic demand between RouterA and RouterC in No_Areas scenario and Areas scenario. As shown in these figure, these route are different. In No_Areas scenario, that route in figure1 is selected because the cost of the path from RouterA to RouterC is smallest. In Areas scenario, the routers first look for destination in their area itself even if there is other alternative which is better. Because RouterA, RouterB and RouterC are in the same area, therefor a direct route from Router A to Router C is selected even though its cost (20) is more than the one in the No_Areas scenario. The OSPF hierarchy capability makes the topology of an area hidden from the rest of the network. Therefore, each router in an area only knows the complete topology inside its area. Compare Balanced and No_Areas: Figure 2 and figure 4 show the route for the traffic demand between RouterB and RouterH in No_Areas scenario and Balanced scenario. In Balanced scenario, from Router B to Router H there are two least cost paths (40) as seen in figure4. OSPF allow distributing the traffic over multiple paths that have equal cost to the destination, hence the load is shared by both the routes. That was not the case with the No_Areas scenario because that feature (load balancing) did not enable.
2. a/ No_Areas scenario: Routing table of RouterA.
Figure 5: Routing table of RouterA in No_Areas scenario
The addresses in the “Dest. Address” column above are the addresses of the networks not individual. For example, the address 192.0.11.0 represents the network connecting RouterA with RouterB (Use the information in OSPF-No_Areas-ip_addresses file – in generic data). The values in the “Metric” column represent the total cost of the routes from RouterA to the farthest router in the destination networks. For example the route from RouterA to network 192.0.7.0(network connecting RouterE with RouterG) costs 15 because it from RouterA then go to RouterD (address 192.0.2.1) as “Next Hop” and reach RouterG at the end, the route is A-D-E-G, the total cost is 5+5+5=15
b/ Areas scenario: Routing table of RouterA.
Figure 6: Routing table of RouterA in Areas scenario
The addresses in the “Dest. Address” column above are the addresses of the networks not individual. For example, the address 192.0.11.0 represents the network connecting RouterA with RouterB (Use the information in OSPF-Areas-ip_addresses file – in generic data). The values in the “Metric” column represent the total cost of the routes from RouterA to the farthest router in the destination networks. The difference from this scenario and No_Areas scenario is the chosen routes for some destinations and hence the assigned metrics to these routes. It is because RouterA first checks if the receive router is in its own area, if yes then it sends to that router within that area, even though there was a better alternative. For example, the path from RouterA to network 192.0.9.0 (network connecting RouterB with RouterC) has a cost of 40 because it uses either RouterC (192.0.10.1) or RouterB (192.0.11.1) as next hop, and reach RouterB or RouterC at the end, the route is A-B-C or A-C-B with the cost is 20+20 = 40
c/ Balanced scenario: Routing table of RouterA.
Figure 7:Figure 6: Routing table of RouterA in Balanced scenario
The routing tables for Router A in the balanced scenario and No_Areas scenario are same. The reason being, both select the least cost paths, but the difference is that in balanced scenario a router can send packets to other routers through more than one path if those paths have same cost. This is done to balance the load. Hence the metric values for all the entries are calculated in the same way as that for the No_Areas scenario.
3. The following table show the link state database of RouterA LSA Type: Router Links, Link State ID: 192.0.19.1, Adv Router ID: 192.0.19.1 Sequence Number: 47, LSA Age: 3 LSA Timestamp: 22.916 Link Type: Stub Network, Link ID: 192.0.19.1, Link Data: 255.255.255.0, Link Cost: 0, Link Type: Point-To-Point, Link ID: 192.0.18.1, Link Data: 192.0.11.2, Link Cost: 20, Link Type: Stub Network, Link ID: 192.0.11.0, Link Data: 255.255.255.0, Link Cost: 20, Link Type: Point-To-Point, Link ID: 192.0.17.1, Link Data: 192.0.10.2, Link Cost: 20, Link Type: Stub Network, Link ID: 192.0.10.0, Link Data: 255.255.255.0, Link Cost: 20, Link Type: Point-To-Point, Link ID: 192.0.16.1, Link Data: 192.0.2.2, Link Cost: 5, Link Type: Stub Network, Link ID: 192.0.2.0, Link Data: 255.255.255.0, Link Cost: 5, LSA Type: Router Links, Link State ID: 192.0.18.1, Adv Router ID: 192.0.18.1 Sequence Number: 46, LSA Age: 3 LSA Timestamp: 22.916 Link Type: Stub Network, Link ID: 192.0.18.1, Link Data: 255.255.255.0, Link Cost: 0, Link Type: Point-To-Point, Link ID: 192.0.19.1, Link Data: 192.0.11.1, Link Cost: 20, Link Type: Stub Network, Link ID: 192.0.11.0, Link Data: 255.255.255.0, Link Cost: 20, Link Type: Point-To-Point, Link ID: 192.0.17.1, Link Data: 192.0.9.2, Link Cost: 20, Link Type: Stub Network, Link ID: 192.0.9.0, Link Data: 255.255.255.0, Link Cost: 20, LSA Type: Router Links, Link State ID: 192.0.16.1, Adv Router ID: 192.0.16.1 Sequence Number: 51, LSA Age: 4 LSA Timestamp: 24.546 Link Type: Stub Network, Link ID: 192.0.16.1, Link Data: 255.255.255.0, Link Cost: 0, Link Type: Point-To-Point, Link ID: 192.0.14.1, Link Data: 192.0.3.2, Link Cost: 5, Link Type: Stub Network, Link ID: 192.0.3.0, Link Data: 255.255.255.0, Link Cost: 5, Link Type: Point-To-Point, Link ID: 192.0.19.1, Link Data: 192.0.2.1, Link Cost: 5, Link Type: Stub Network, Link ID: 192.0.2.0, Link Data: 255.255.255.0, Link Cost: 5, Link Type: Point-To-Point, Link ID: 192.0.15.1, Link Data: 192.0.1.2, Link Cost: 5, Link Type: Stub Network, Link ID: 192.0.1.0, Link Data: 255.255.255.0, Link Cost: 5, LSA Type: Router Links, Link State ID: 192.0.14.1, Adv Router ID: 192.0.14.1 Sequence Number: 50, LSA Age: 6 LSA Timestamp: 24.546 Link Type: Stub Network, Link ID: 192.0.14.1, Link Data: 255.255.255.0, Link Cost: 0, Link Type: Point-To-Point, Link ID: 192.0.12.1, Link Data: 192.0.5.2, Link Cost: 10, Link Type: Stub Network, Link ID: 192.0.5.0, Link Data: 255.255.255.0, Link Cost: 10, Link Type: Point-To-Point, Link ID: 192.0.13.1, Link Data: 192.0.4.2, Link Cost: 10, Link Type: Stub Network, Link ID: 192.0.4.0, Link Data: 255.255.255.0, Link Cost: 10, Link Type: Point-To-Point, Link ID: 192.0.16.1, Link Data: 192.0.3.1, Link Cost: 5, Link Type: Stub Network, Link ID: 192.0.3.0, Link Data: 255.255.255.0, Link Cost: 5, LSA Type: Router Links, Link State ID: 192.0.12.1, Adv Router ID: 192.0.12.1 Sequence Number: 52, LSA Age: 7 LSA Timestamp: 24.931 Link Type: Stub Network, Link ID: 192.0.12.1, Link Data: 255.255.255.0, Link Cost: 0, Link Type: Point-To-Point, Link ID: 192.0.13.1, Link Data: 192.0.6.1, Link Cost: 10, Link Type: Stub Network, Link ID: 192.0.6.0, Link Data: 255.255.255.0, Link Cost: 10, Link Type: Point-To-Point, Link ID: 192.0.14.1, Link Data: 192.0.5.1, Link Cost: 10, Link Type: Stub Network, Link ID: 192.0.5.0, Link Data: 255.255.255.0, Link Cost: 10, LSA Type: Router Links, Link State ID: 192.0.13.1, Adv Router ID: 192.0.13.1 Sequence Number: 53, LSA Age: 5 LSA Timestamp: 24.931 Link Type: Stub Network, Link ID: 192.0.13.1, Link Data: 255.255.255.0, Link Cost: 0, Link Type: Point-To-Point, Link ID: 192.0.15.1, Link Data: 192.0.7.1, Link Cost: 5, Link Type: Stub Network, Link ID: 192.0.7.0, Link Data: 255.255.255.0, Link Cost: 5, Link Type: Point-To-Point, Link ID: 192.0.12.1, Link Data: 192.0.6.2, Link Cost: 10, Link Type: Stub Network, Link ID: 192.0.6.0, Link Data: 255.255.255.0, Link Cost: 10, Link Type: Point-To-Point, Link ID: 192.0.14.1, Link Data: 192.0.4.1, Link Cost: 10, Link Type: Stub Network, Link ID: 192.0.4.0, Link Data: 255.255.255.0, Link Cost: 10, LSA Type: Router Links, Link State ID: 192.0.17.1, Adv Router ID: 192.0.17.1 Sequence Number: 49, LSA Age: 15 LSA Timestamp: 29.546 Link Type: Stub Network, Link ID: 192.0.17.1, Link Data: 255.255.255.0, Link Cost: 0, Link Type: Point-To-Point, Link ID: 192.0.19.1, Link Data: 192.0.10.1, Link Cost: 20, Link Type: Stub Network, Link ID: 192.0.10.0, Link Data: 255.255.255.0, Link Cost: 20, Link Type: Point-To-Point, Link ID: 192.0.18.1, Link Data: 192.0.9.1, Link Cost: 20, Link Type: Stub Network, Link ID: 192.0.9.0, Link Data: 255.255.255.0, Link Cost: 20, Link Type: Point-To-Point, Link ID: 192.0.15.1, Link Data: 192.0.8.2, Link Cost: 5, Link Type: Stub Network, Link ID: 192.0.8.0, Link Data: 255.255.255.0, Link Cost: 5, LSA Type: Router Links, Link State ID: 192.0.15.1, Adv Router ID: 192.0.15.1 Sequence Number: 48, LSA Age: 13 LSA Timestamp: 29.546 Link Type: Stub Network, Link ID: 192.0.15.1, Link Data: 255.255.255.0, Link Cost: 0, Link Type: Point-To-Point, Link ID: 192.0.17.1, Link Data: 192.0.8.1, Link Cost: 5, Link Type: Stub Network, Link ID: 192.0.8.0, Link Data: 255.255.255.0, Link Cost: 5, Link Type: Point-To-Point, Link ID: 192.0.13.1, Link Data: 192.0.7.2, Link Cost: 5, Link Type: Stub Network, Link ID: 192.0.7.0, Link Data: 255.255.255.0, Link Cost: 5, Link Type: Point-To-Point, Link ID: 192.0.16.1, Link Data: 192.0.1.1, Link Cost: 5, Link Type: Stub Network, Link ID: 192.0.1.0, Link Data: 255.255.255.0, Link Cost: 5,
Using the _OSPF-NO_Areas-ip_addresses file to determine the IP address of each router.
From these informations, I have the map for the topology of the network:
Destination B C D E F G H
Next Hop B D D D D D D Routing table of Router A
Metric 20 15 5 10 10 15 20
