Routing Flashcards
What is star topology?
This is when each node is connected to a single router. Different routers are connected together
What is mesh topology?
This is when all nodes are connected to all other nodes
What is a Graph (when talking about a network)?
This is a diagram of the network with all the links and routers. Each link has a weighting based on its bandwidth or another parameters depending on what the graph is showing. [IMAGE 6]
How is a path between two nodes chosen?
The path with the minimum weight for each hop is chosen
What is distance vector routing?
Router just knows which neighbouring router has the best link (with smallest weight) and so will send a packet that way hoping that this is overall the best route.
What is link state routing?
Router knows the entire network topology and so will find the most optimal path overall
What does each node on a network that uses vector routing know?
It knows which node to send a packet to for every destination and it knows the weight of that route. [IMAGE 7]
How does each node on a network that uses vector routing know which node to send data to?
Each node broadcasts its routing table and this allows the neighbouring nodes to update theirs accordingly. Eventually all nodes will be updated with a up to date routing table.
What happens when a new node is added to the network?
Neighbouring nodes update their tables with the new node. Then the new tables will be propagated across a network until all nodes have information for the new node. [IMAGE 8]
What can occur if a link is broken like in the example below? [IMAGE 9]
The node C updates its table to show that the weight to get to D is ∞.
Then 2 things can happen
- C updates the nodes around it to show that the link is broken and so all other tables will know not send data that way
- B updates C so that C sends data destined for D to B. Then C updates B. Then B updates C. Each time this repeats and the weight to get to D increases until it is infinite. [IMAGE 10]
What happens if a node is added 2 nodes in a network?
The new node broadcasts its routing table and the network updates acordingly
What does DSDV routing stand for?
DSDV = Destination Sequence Distance Vector routing.
What is dynamic source routing (DSR)?
When a node wants to send a packet to another node but does not know the route it floods the network with route requests (RREQ). Eventually the shortest route is found and the data is returned to the transmitting node.
What is the process for route discovery for DSR?
- Transmitting node floods network with RREQ packets
- RREQ packets are duplicated and sent to neighbouring nodes until the first one reaches the destination node.
- When the first RREQ packet reaches the destination, a RREP packet is sent back the way that the RREQ packet came to the transmitting node [IMAGE 11]
- The transmitting node then sends the data the way that the RREP node arrived
