Inefficient communications protocols: Although it was designed for reliability and congestion-avoidance, TCP carries significant overhead and can have suboptimal performance for links with high latency or packet loss, both of which are common across the wide-area Internet. Middle mile congestion exacerbates the problem, as packet loss triggers TCP retransmissions, further slowing down communications. Additionally, for interactive applications, the multiple round trips required for HTTP requests can quickly add up, affecting application performance Most web browser also limit the number of parallel connections they make fora given host name, further limiting performance overlong distances for sites that consist of many objects. TCP also becomes a serious performance bottleneck for video and other large files. Because it requires receiver acknowledgements for every window of data packets sent, throughput (when using standard TCP) is inversely related to network latency or round trip time (RTT). Thus, the distance between server and end user can become the overriding bottleneck in download speeds and video viewing quality. Table 1 illustrates the stark results of this effect. True HD quality streams, for example, are not possible if the server is not relatively close by.
