Description
Objectives
1. To develop link state (LS) routing algorithm
Network topology and data
A network topology is defined by a set of nodes N and a set of edges E, formally defined as:
• N = set of nodes (routers)
• E = set of edges (links between connecting nodes)
It is assumed that the following information will be available for a network.
– Router ID, which is its index into the tables below, is given at the command line.
– Number of nodes, N, in the topology will be given by the command line.
– Table with costs C, NxN, will be obtained from file1 (name given at the command line).
– Table with machines, names, IP addresses, and port numbers, Nx3, will be obtained from file2 (name
given at the command line).
Your main data will be:
– Neighbor cost table – contains the cost from every node to every node, initially obtained from file1.
– Least cost array – obtained with the link state algorithm.
LS routing protocol
Each router iteratively runs LS to find its forwarding table to every other node in the network (i.e. the shortest path
tree) using Dijkstra algorithm. The pseudo code as described in the class textbook, is given as follows:
Data:
define N, E, C, and “empty” Nprime arrays
set source node to u
Define D(v) cost of path from source u to dest v
Define p(v) predecessor node along path from u to v
Initialization:
Nprime ← u
for each node v in N:
If v adjacent to u
D(v) ← C(u,j)
p(v) ← u
else
D(v) ← INFINITY
D(u) ← 0 // Distance from source to source
Loop:
while all nodes not in Nprime:
node ← node in N with min D(node) // node with the least distance neighbor will be selected first
remove node from N and add to Nprime
update D(v) for all v adjacent to node and not in Nprime
D(v) ← min (D(v), D(node)+C(node, v)(
p(v) ← v (if D(v) is minimum, or node if D(node)+c(node, v) is minimum
Repeat
LS Code at each router
You may build your code with 3 threads, each with the following task:
– Thread 1 loops forever. It receives messages from other nodes and updates the neighbor cost table.
When receiving a new cost c from x to neighbor y, it should update the cost in both costs: x to y and y to
x.
– Thread 2 reads a new change from the keyboard every 10 seconds, updates the neighbor cost table, and
sends messages to the other nodes using UDP. It finishes 30 seconds after executing 2 changes. You
may execute this part in the main thread.
COEN 146 – Lab assignment 7 2/2
– Thread 3 loops forever. It sleeps for a random number of seconds (10-20), run the algorithm to update the
least costs. After the algorithm executes it outputs the current least costs.
Make sure to use a mutex lock to synchronize the access to the neighbor cost table.
The messages between the routers will have 3 integers:
<Routers’ ID>
The input for Thread 2, will have two integers:
The table with costs will look like this if N = 3:
<0,0> <0,1> <0,2>
<1,0> <1,1> <1,2>
<2,0> <2,1> <2,2>
where <i,j> represents the cost between node i and node j. If <i,j> is equal to infinite (defined as 10,000), nodes i
and j are not neighbors.
The table with machines will look like this, if N = 3.
Requirements to complete the lab
Demonstrate to the TA LS routing for a network of your choice and upload source code to Camino.
Be sure to retain copies of your source code. You will want these for study purposes and to resolve any grading
questions (should they arise)
Please start each program with a descriptive block that includes minimally the following information:
/*
* Name:
* Date:
* Title: Lab7 – ….
* Description: This program …
*/
