# ShortestPathSwitching
##Author
Anthony Feudale
acf003@colostate.edu
## How Far I Got
I was able to successfully complete the assignment in full. Fulfilling
Part 1 Procedural,
Option 2 Static Routing with Shortest Path Implementation
Part 4 Dynamic Changes to the Topology
## Changes Made
The principle changes made were:
1. The creation of an uninitialized HashMap shortestPaths variable in init().
2. The creation of a method dijkstraPaths() which calculates the shortest paths for all the switches in a given
topology and whose return value is the HashMap for shortestPaths. Based on code found at Github for Dijkstra's.
https://github.com/vnatesh/SDN-Controller/blob/b762e3476a6cc85b72b5d083096b2c17023f6ac6/ShortestPathSwitching.java#L130
Hashmap looks like this logically:
{switch1 : {switch1 : null, switch2 : switch1, ...},
switch2 : {switch1: switch2, switch2 : null, ...}, ...}
2. The creation of a method removeAllFlowTableRules() which removes all the existing rules for the flow table.
3. The creation of a method setAllFlowTableRulesForAllHosts() which sets all the flow tables rules for each all
hosts using the shortest path calculated and saved in shortestPaths.
4. The creation of a method logData() which just pretty prints a bunch of useful logging.
5. The 4 new methods are called in each of the 6 methods with TODO's except init() and start().
Essentially, anytime a change is made to our topology in anyway I just recalculate the shortest paths, nuke the
flow rules, and put the new flow rules in. I also print output at each step to see how things look inside.
6. There are also some helper methods for the four main methods, as well as another method
setAllFlowTableRulesForAllHostsLinear() that I used to figure out how to set Flow rules in a super simple
linear topology. I don't use it in the final setup but I left it in there to illustrate the evolution of
the program.
Works with all the topologies I've tried fully pinging all and recalculating if a link or switch is removed.