今天上课的时候还听见可爱的胖胖老师说，很多文章只告诉你一项技术的优点，但讲到缺点的文章就会少很多了。那么，现在就接着翻译来数落下DSDV的缺点吧！
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The main purpose of DSDV is to address the looping problem of the conventional distance vector routing protocol and to make the distance vector routing more suitable for ad hoc networks routing. However, DSDV arises route fluctuation
because of its criteria of route updates. At the same time, DSDV does not solve the common problem of all distance vector routing protocols, the unidirectional links problem.
DSDV的主要目的是消除传统的DV路由协议中出现的循环问题，从而使DV更适合应用于ad hoc网络中的路由问题。然而，因为它的路径更新的准则使DSDV增加了路径波动。同时，DSDV没能解决所有DV路由协议中一个常见的问题：单向链接问题。
阻尼振动 Damping Fluctuation
Fluctuation is a general problem arising in DSDV by the following criteria of route updates:
• Routes are always preferred if the sequence numbers are newer, routes with older sequence numbers are discarded.
• A route with a sequence number equal to that of an existing route is preferred if it has a better metric, and the existing route is discarded or stored as less preferable.
因为路径更新标准，波动问题是DSDV中一个常见的问题：
- 具有更新的序列号码的路径总是更被接受，而有老的序列号的路径将被舍弃。
- 一个具有与已存在的路径相同序列号码的路径，如果它有很小的metric值，那么已存在的路径将被舍弃或被存储为less preferable。
The broadcasts of routing information by mobile nodes are asynchronous events, though some regularity is expected. In the case of many mobile nodes independently transmitting update messages and having markedly different transmission
intervals, it may turn out that a particular mobile node receives new update packets in a way that causes this mobile node to consistently change route back and forth between different next hops, even though no network topology change has taken place. This
fluctuation happens because of the above two route selection criteria. Conceivably, a mobile node can always receive two routes with equal sequence numbers or with a newer sequence number one after the other via different neighbors to the same destination,
but the mobile node always gets the route with the worse metric first. This situation leads to the fluctuation with a continuing burst of new update packets. This can happen when there are many mobile nodes, all transmitting their updates irregularly. Alternatively,
if the mobile nodes are acting independently and with and with markedly differently transmission intervals, the situation can occur with fewer mobile nodes.
先出去下。。。一会补全！