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To obtain optimal Geode performance, the network needs to exhibit the following characteristics.

低延时

The term latency refers to any of several kinds of delays typically incurred in the processing of network data. These delays include:

延时问题涉及到在跨网络处理数据过程中的各种类型的延时. 这些延时包括:

• 广播延时 – 这与网络传播距离有关, 数据跨网络到达目的地,  和信号通过的中介地. 延时范围从本地网络(LAN)的纳秒到微秒延时, 到卫星通信系统的0.25秒延时.
• 传输延时 – 这些延时是发送所有数据包的比特流到链接网络层所需要的时间, 这是一个包长度和链接层速率的问题. 例如, 为了传输一个10 Mb 文件跨 1 Mbps 链接层将需要10秒中, 而跨 100 Mbps 链接层只需要 0.1 秒.
• 处理延时 – 这个延时是处理包头, 检查比特级错误, 确定包的发送目的地的所花时间. 在高速路由环境处理延时基本是最小的. 然而, 对于网络处理复杂加密或深度包检测, 处理延时还是比较大的. 另外, 处理 NAT 的路由器也有高于正常处理的延时, 因为这些路由器都需要检查, 和修改输入和输出包.
• 队列延时 – 这些延时都是路由队列所消耗的时间. 网络设计的实际情况是一些队列延时将出现. 有效的队列管理技术是关键的, 可以保障高优先级的流量体验
• Propagation delays – these are the result of the distance that must be covered in order for data moving across the network to reach its destination and the medium through which the signal travels. This can range from a few nanoseconds or microseconds in local area networks (LANs) up to about 0.25 seconds in geostationary-satellite communications systems.
• Transmission delays – these delays are the result of the time required to push all the packet’s bits into the link, which is a function of the packet’s length and the data rate of the link. For example, to transmit a 10 Mb file over a 1 Mbps link would require 10 seconds while the same transmission over a 100 Mbps link would take only 0.1 seconds.
• Processing delays – these delays are the result of the time it takes to process the packet header, check for bit-level errors and determine the packet’s destination. Processing delays in high-speed routers are often minimal. However, for networks performing complex encryption or Deep Packet Inspection (DPI), processing delays can be quite large. In addition, routers performing Network Address Translation (NAT) also have higher than normal processing delays because those routers need to examine and modify both incoming and outgoing packets.
• Queuing delays – these delays are the result of time spent by packets in routing queues. The practical reality of network design is that some queuing delays will occur. Effective queue management techniques are critical to ensuring that the high-priority traffic experiences smaller delays while lower priority packets see longer delays.

最佳实践

It should be noted that latency, not bandwidth, is the most common performance bottleneck for network dependent systems like websites. Therefore, one of the key design goals in architecting a Geode solution is to minimize network latency. Best practices for achieving this goal include:

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