1. Modeling Internet Topology Kenneth L. Calvert Matthew B. Doar Ellen W. Zegura Presented by Kiran Komaravolu

2. Why do we need to model the Internet Topology Large networks abstracting the real Internet are rarely available to work with. Simulations Simulation tools need a model of the internet to work with. Analysis of new protocols. It is easier to develop new protocols and test them on a simulation testbed rather than on the real Internet.

3. Building blocks of the Internet. Transit Domains Wide Area Networks E.g.., MCI’s backbone network. Stub Domains Campus networks, Corporate networks. Wont route other stub domain traffic. LANs Eg., Research labs in the CSE department.

4. What the user provides. T: Total number of transit domains. NT: Average number of nodes per transit domain. S: Avg number of stub domains per transit domain. NS: Avg number of nodes per stub domain. L: Avg number of LANs attached to a stub node. NL: Avg Number of nodes per LAN # Routing nodes = T*NT(1+S*NS) # Host nodes = T*NT*S*NS*L*NL

5. What the user provides. ET: Avg number of edges between transit nodes of same domain. ETT: Avg number of edges between transit nodes of different domains. ES: Avg number of nodes between stub nodes. E ST : Avg number of nodes between a stub domain and its transit domain. ELS: Avg number of nodes from a LAN to a stub node.

6. Generation process. 1. Create the transit domains and connect them while satisfying E TT. 2. For each transit domain create the transit nodes and interconnect them. Each transit domain has on average NT nodes. 3. Select end points in transit domains. 4. Locations for the stub domains are chosen. Each stub domain on average has N S nodes. Edges are generated within each stub domain as to satisfy Es requirement. 5. Each stub domain is connected to one or more transit domains. 6. Locations for the LANs are chosen. For each LAN on average NL nodes are inserted. 7. Each LAN is connected to a stub node by an edge from the centre router to the stub node.

8. Implementation details. Transit-Stub model. Supports only two level hierarchy. Generates connected sub-graphs according to given specifications. Extra nodes (Nodes available after satisfying connectivity) are added randomly. Edges are given weights, used while determining routing policies.

9. Implementation details. Tiers WAN, MAN, LAN hierarchies are supported. Number of WANs = 1 Produces connected sub-graphs by joining all nodes in one domain using a minumum span tree. Gateways are shown as two inter-connected nodes (a LAN node and a MAN node)

10. Single layer Tiers N/W 3 layer Tiers N/W

11. Questions ?