跨变速网络的串行化延迟
我正在使用一个网络，其中入站线路是一条快速的 1 gig 线路，它到达边缘交换机，然后通过 T1 路由到一个单独的内部 1 gig 交换机，并具有 1 gig 线路输出。像这样的东西：
[外部]（1演出线）-> [边缘装置](T1线)-> [1演出开关]（1演出线路）-> 我正在处理的主要
是最大帧数据包，1500 字节 - 我了解 T1 线路的第一次序列化花费大约 12 毫秒，但是这种序列化延迟是否发生一次或两次？在第二个交换机（1 gig 设备）上，将数据包序列化到 1 gig 线路上，是否再次花费 12ms 左右，还是以仅约 10 秒左右的 1gig 速度完成？
I'm working with a network where there the inbound line is a fast, 1 gig line, which hits an edge switch and is then routed via a T1 to a separate internal 1 gig switch, with a 1 gig line output. Something like this:
[outside] (1 gig line) -> [edge device] (T1 line) -> [1 gig switch] (1 gig line) -> end
I'm working with mostly max frame packets, 1500 bytes -- I understand that the first serialization to the T1 line costs about 12 ms, but does this serialization delay occur once or twice? At the second switch, the 1 gig device, to serialize the packet onto the 1 gig line, does it cost on the order of 12ms again or is it done at the 1gig speed of only about 10ish us?
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与千兆以太网相比，当您的链路速度为 T1 时，绝大多数序列化延迟来自从千兆以太网到 T1 的序列化。请记住，您还从 T1 序列化到另一侧的 Gig，但延迟非常小，不值得考虑。
另请理解，您将经历光速（或电）通过电缆的延迟。在美国境内发送时，这通常会增加 50 毫秒或更长...具体取决于您的流量所采用的物理路径。
最后请注意，当您从千兆以太网速度转到 T1 时，数据包丢失略有增加是正常的...大多数路由器根本无法在不丢弃比“正常”更多的数据包的情况下非常优雅地处理这种速度转换。如果您可以选择增加 T1 端的出口数据包缓冲区（思科路由器当然有该选项），那么这是一个好主意。您的路由器供应商可能已经发布了针对此类情况的指南......
When you have a link at T1 speed compared to GigabitEthernet, the overwhelming majority of serialization delay comes from serializing from GigabitEthernet onto T1. Keep in mind that you also serialize from T1 to Gig on the other side, but the delay is so small it's not worth considering.
Also understand that you will exprience delay from the speed of light (or electricity) through the cabling. When sending across the US, this adds up to usually 50ms or more... depending on the physical path that your traffic takes.
Finally be aware that slightly increased packet loss is normal when you go from GigabitEthernet speeds to T1... most routers simply cannot handle that kind of speed transition very gracefully without dropping more packets than "normal". If you have the option of increasing your egress packet buffers on the T1 side (Cisco routers certainly have that option), it's is a good idea. Your router vendor might have published guidelines for these kind of situations...