Simulated network-layer routing via the distributed Bellman-Ford algorithm, aka distance vector routing with poison reverse.

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Basics

Add a node to an existing network or, if this is the first node, create a new network.

python bfclient.py <listening-port> <timeout> <ip-address1 port1 distance1> <ip-address2 port2 distance2> ...

Nodes listen on localhost:listening-port. timeout is how frequently a node broadcasts its distance vector to its neighbors. Edges to other nodes in the network are defined through the ip-address port distance argument triples.

Timeouts should be within 3x each other, e.g. 1 second and 2.9 seconds. If, say, one node's timeout is 3x greater than a neighbor's timeout, then, as defined in code, the link will be closed. Because one node still believes the edge is active, the edge will be reactivated a moment later. This will continue to happen over and over. For this reason it is important to set the timeouts of connected nodes to within 3x each other.

Examples

• Start a 2-node network with 1 edge. Run this on separate machines or terminal windows.

  python bfclient.py 20000 4 localhost 20001 25.0

  python bfclient.py 20001 4 192.168.56.1 20000 25.0
  

  In this example, localhost is 192.168.56.1, ie. if running on the same machine, for convenience you can use localhost instead of inputing the IP. The first command will add node listening on localhost:20000 with a timeout of 4 and one edge. The second command adds a node to the network listening on localhost:20001 with the same timeout and edge.

• You can also build up links gradually instead of defining the entire network from the beginning. In this example we setup a 4-node network.

  python bfclient.py 20000 4
  

  python bfclient.py 20001 4 localhost 20000 25
  

  python bfclient.py 20002 4 localhost 20000 5.6 localhost 20001 3.14
  

  python bfclient.py 20003 4 192.168.56.1 20001 32.0 localhost 20000 5
  

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User Input

Available commands while client is active:

• neighbors output a node's neighbors
• showrt output routing table
• linkdown <neighbor-ip> <port> take down an network edge
• linkup <neighbor-ip> <port> restore a link that was previously taken down using linkdown
• linkchange <neighbor-ip> <port> <link-cost> change an edge's cost
• close remove node from network. simulates a node failure.