疑难问题汇集

问题一：

hold-queue和fair-queue 这俩命令有什么用处
关于hold-queue有:
Each interface has a hold-queue limit. This limit is the number of data packets that the interface can store in its hold queue before rejecting new packets. When the interface empties one or more packets from the hold queue, it can accept new packets again.
这么看好象hold-queue只是把更多的包先存下来,而尽量少地discard,不过又听同事说好象不是
另外,fair-queue好象是动态地预留一些queue给一些特定的class,是吗
这俩种queue和一般的input-queue有什么关系吗?
因为我看加这命令的端口上input-queue并不满啊


答： hold-queue就是队列中能容纳的数据包的上限.

fair-queue是一种公平队列机制(WFQ).
WFQ 是一种对网络中所有流量提供公平的带宽分配的动态调度方式.WFQ根据权重,优先级来鉴别流量,把它加入到某个队列里,并决定队列之间的带宽分配.WFQ 采用基于流是算法,该算法把交互式的流量同时调度到队列的最前端来减少响应时间,并公平的分配剩余的带宽.当拥塞信息产生的时候,高带宽的数据流的信息将 被丢弃;而低带宽的数据流的信息仍然被加到队列中.

WFQ对每个队列的带宽分配的方式,由权重来决定,而权重又取决于IP优先级.公式为:
队列的带宽分配百分比=(该队列IP优先级+1)/(所有队列的IP优先级+1)

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WiFi Protected Access, Pre-Shared Key

WPA is a more powerful security technology for Wi-Fi networks than WEP. It provides strong data protection by using encryption as well as strong access controls and user authentication. WPA utilizes 128-bit encryption keys and dynamic session keys to ensure your wireless network's privacy and enterprise security.

There are two basic forms of WPA:
• WPA Enterprise (requires a Radius server)
• WPA Personal (also known as WPA-PSK)

Either can use TKIP or AES for encryption. Not all WPA hardware supports AES.

WPA-PSK is basically an authentication mechanism in which users provide some form of credentials to verify that they should be allowed access to a network. This requires a single password entered into each WLAN node (Access Points, Wireless Routers, client adapters, bridges). As long as the passwords match, a client will be granted access to a WLAN.

Encryption mechanisms used for WPA and WPA-PSK are the same. The only difference between the two is in WPA-PSK, authentication is reduced to a simple common password, instead of user-specific credentials.

The Pre-Shared Key (PSK) mode of WPA is considered vulnerable to the same risks as any other shared password system - dictionary attacks for example. Another issue may be key management difficulties such as removing a user once access has been granted where the key is shared among multiple users, not likely in a home environment.

还有 WPA TKIP or AES?这个网页的讨论，看看

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