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 ___25___ algorithm. Routing protocols in intemetworks differ slightly from the idealized graph model. In an internetwork, the goal of the routers to forward packets to various ___26___.
Routers running RIP send their advertisement about cost every ___27___ 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 ___28___. Thus it always tries to fend the minimum hop route. Valid distances are 1 through ___29___. This also limits RIP to running on fairly small networks.
28（）
A.1
B.15
C.16
D.length of the link
的斜面上放一木板
，重为
，板上放一重为
的木箱
，斜面上有一固定的挡板，先用平行于斜面的绳子把木箱与挡板拉紧，然后在木板上施加一平行斜面方向的拉力
，使木板从木箱下匀速抽出，此时，绳子的拉力
. 设木板与斜面间的动摩擦因数
，求拉力