Summary of Networking and Internet-working Devices

     SUMMARY

• Internet-working devices connect networks to create an internet.
• Networking and Internet-working devices are divided into four categories : Repeaters, Bridges , Routers, and Gateways.
• A repeaters is a device that operates in the physical layer of the OSI model. Its purpose is regeneration of the signal.
• Bridges operate in the physical and data link layers of the OSI model. They have access to station addresses and can forward or filter a packet in a network.
• Routers operate in the physical, Data link, and Network Layers of the OSI model, They decide the path a packet should take.
• Gateways operate in all seven layers of the OSI model. They convert one protocol to another and can therefore connect two dissimilar networks.
• There are two methods to calculate the shortest path between two routers : Distance vector routing and link state routing.
• In distance vector routing, each Router periodically shares its own knowledge about the network with its immediate neighbour Routers.
• In distance vector routing, each Router has a table with information about Networks (ID, Cost, and the Router to access the particular Network).
• In link state routing each Router creates its own link state packet (LSP). Every other Router receives this LSP through the flooding process. All Routers therefore have the same information, this is complied into the link state database.From this common database, each router finds its own shortest paths to the other Routers by using the Dijkstra algorithm.
• A cost is assigned to a packet when it leaves the Router in link state routing.
• In link state routing, Every Router has its own unique routing table.

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