ADTRAN 1200263L1-1.2A Manual do Utilizador descarregar pdf (Página 9)

61200263L1-1.2A ATLAS Router User Manual 2-1

Chapter 2 Technology Overview

IP ROUTING

Internet Protocol (IP) routing is performed at layer 3 of the Open System Intercon-

nection (OSI) model. (Refer to the Frame Relay User Manual for a description of the

OSI model.) The routing process determines the optimal path for data packets to

travel and then moves the data packets along that path. Routers exchange infor-

mation about paths or routes that reach additional LAN segments. This exchange

of routing information allows a router to build a detailed knowledge of the net-

work topology. Criteria for selecting the best path can include such items as dis-

tance, number of hops (servers or routers), and cost of the transportation media.

ATLAS supports Routing Information Protocol (RIP), a protocol based on hops.

Each route has a set number of hops (routers or servers) that it must travel

through to reach a final destination. If a new route to a host address that has a

fewer number of hops is learned, it becomes the preferred route. When a new

route is learned, the router increments the hop count by one and immediately

broadcasts the new route over the other interfaces. To prevent routing loops, RIP

defines a hop count of 16 as an infinite or unreachable route.

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ADTRAN 1200263L1-1.2A Manual do Utilizador Página 9