In this project, you will implement a link state routing system. Each node in the network will be connected to one or more other nodes. Using hello packets and bounded flooding, you will implement a system to inform all of the nodes in the network of the current network topology. Each node will also build a routing table that minimizes the number of hops to all other nodes in the network.

This project will be the first introduction to several key ideas that will be used later in the semester. It will also combine what you have learned (and probably most of the code) from projects one and two.

A key building block for this project will be the timer thread. By using the timer thread, you will be able to cause events to happen in your system at specific times in the future (for example sending hello packets at a fixed interval of time).

The implementation for the timer thread will be via the queue abstraction you built for project two. When a thread wishes to schedule an event in the future, it enqueue’s a request to the timer thread. When the requested time interval has elapsed, the timer thread enqueues a message indicating that the time interval has finished.

The interface for a thread that wishes to use the timer thread is:

Note: Alarm Ids should be globally unique and will likely be allocated in the context of the application thread making the request. If this is the case, don’t forget to use synchronization (e.g. mutex’s) around the update of the alarm ids.

In this project you will need to exchange messages between different threads in your system. In order to allow a single thread to respond to a variety of different message types such as a timer event or the arrival of a data packet, you will need to define a common message format to pass via the queues. Each message should start with an integer field that indicates the type of the message (e.g. TIMER_REQ, TIMER_ACK, TIMER_EXPIRE, etc.). In addition, each message can contain a variety of parameters that are specific to that message (e.g. when the alarm should expire). You should define a C struct (note: if using C++, this should still be a struct not a class) that includes a field for the message type, and a union for any message specific fields that are required.

Each "node" in your network is a UNIX process that will receive data on a specific port from its neighbors, and send data to its neighbors on their designated ports. A node is a multi-threaded program that needs to be able to respond to packets it receives from neighbors, compute routing tables, and send information about its neighbors to other hosts. Nodes only terminate when they are killed.

The format of the network configuration file is shown below. You should use ports from your assigned ports for each node. The number after the links statement are the node numbers that are directly connected to that node.

Node fe90::0001 (tracy, 5000) links fe90::0002

Node fe90::0002 (tracy, 5001) links fe90::0003 fe90::0004

Node fe90::0003 (tracy, 5002) links fe90::0002 fe90::0004

Node fe90::0004 (tracy, 5003) links fe90::0002 fe90::0003

Every HELLO_INTERVAL mili-seconds, a node sends a hello packet to all of its neighbors. When a host receives a HELLO packet, it records the link as operational. If no HELLO packet has been received from a neighboring host in the past DEAD_INTERVAL mili-seconds, it assumes the link (or host) has failed. Every TOPOLOGY_INTERVAL mili-seconds, a host sends it current list of active neighbors to all other nodes in the network (via a flooding message). Every ROUTE_UPDATE_INTERVAL mili-seconds, a host re-computes its routing tables based on its current knowledge of the network topology.

The routing tables should be computed using a variation of Dikstra’s algorithm. When a new routing table is built, it should be printed to the screen. Also, when new topology information (not currently available to that node) is received, it should also be printed. Each node will have a routing table entry for every other node in the network, and information about the first hop to that node (i.e. the node number of the first hop).

The parameters for network operation are read from a configuration file at the start of the node operation. For this project the required parameters (and their default values) are:

The parameters in the file are represented one per line. Each line is a variable name, a space, and then an integer value for the parameter value. A line that starts with # is a comment line, and it should be ignored.

This project will have a variety of threads that perform specific functions. I would suggest having three threads (in addition to the initial thread). One thread should manage timer events, the second thread should receive packets from the network and en-queue them to the appropriate handler thread. The third thread would be responsible for building routing tables. It might make sense to split the routing thread into two separate threads, one for maintaining topology information, and the other for building the routing tables.

Each message you send over the wire (between hosts) should be an IPv6 packet. The format of an IPv6 packet is:

In addition, you will need to generate packets in specific formats. During the rest of the semester, you will need to be able to generate ICMP, POSPF, and PTCP packets. In particular for this project, you will need to generate POSPF (Pseudo Open Shortest Path First) packets, the routing protocol for CMSC417. You will design the specific format for these packets to meet your needs. The protocol types and their value for the nextHeader field of the IPv6 packet are:

You should submit a tar file that contains the source code for your implementation of the queue abstraction. Like the earlier programs, you should submit a tar file. The tar file should include a Makefile that compiles your code.

You should also submit a script file for each of the nodes using the configuration files supplied.