One of the most widely used routing protocols in IP networks is the Routing Information Protocol（RIP）。 RIP is the canonical example of a routing protocol built on the（ ）algorithm.Routing protocols in internetworks differ slightly from the idealized graph model.In an internetwork, the goal of the routers to forward packets to various （ ）.Routers running RIP send their advertisement about cost every （ ） seconds.A router also sends an update message whenever an update from another router causes it to change its routing table.It is possible to use a range of different metrics or costs for the links in a routing protocol.RIP takes the simplest approach, with all link costs being equal （ ）。 Thus it always tries to find the minimum hop route.Valid distances are 1 through （请作答此空）。This also limits RIP to running on fairly small networks.
A.6
B.10
C.15
D.16