-uses algorithm and metrics to build and maintain a routing information
Topology and metrics
- category of algorithm
- distance vector or link state or hybrid of different methods to perform path selection more efficiently
- When the routing database contains more than one route
- a metric is calculated to determine which path will be selected for use in the IP routing table.
- The path with the lowest cost metric is preferred.
- The type of algorithm determines which factors are used to calculate the metric.
- Distance vector protocols use the number of hops to the destination as the metric.
- The route with the fewest hops is the least-cost path and will be selected for use.
- Convergence
- it is the process whereby routers running dynamic routing algorithms agree on the network topology
- A sinkhole means that a packet is discarded without notification to the source; a loop causes the packet to be forwarded around the network until its TTL expires.
- A network where all the routers share the same topology is described as steady state.
Autonomous Systems (AS)
- A network under the administrative control of a single owner is referred to as an autonomous system (AS).
- Interior Gateway Protocol (IGP) is one that identifies routes within as AS.
- An Exterior Gateway Protocol (EGP) is one that can advertise routes between autonomous systems.
- An EGP includes a field to communicate the network’s autonomous system ID and allows network owners to determine whether they can use paths through another organization’s network.