In the 2016 National WAN Report Survey, respondents were asked to indicate the factors that had the greatest impact on their WAN. Considering that unlike the regional network, the WAN has some performance limiting features, such as packet loss and high latency, so it is not surprising that two of the top five factors expressed by respondents are related to performance. As we are experiencing a fundamental shift from traditional WAN to SD-WAN, it is now an important time to understand how SD-WAN solutions can improve network performance.d bandwidth
Typical WANs operate at megabit speeds due to the way service providers charge for corporate WAN links such as MPLS, while typical LANs operate at gigabit speeds. One advantage of SD-WAN is that it allows network organizations to narrow this gap by making full use of relatively inexpensive Internet bandwidth. There is no doubt that in some cases, increasing bandwidth can improve performance. However, if any, the relationship between performance improvement and increased bandwidth is rarely linear. To understand this, please refer to an example where a large file is sent from the WAN link from Boston to San Francisco. If the bandwidth of the WAN link is doubled, the time required to send the file may be reduced, but it is unlikely to be reduced by half. This kind of thing is caused by many reasons. One reason is the TCP window size, which is the amount of data that can be sent before the sending device stops waiting for an acknowledgment from the receiving device. Sticking to file transfers, it is likely that file transfers will not take full advantage of the increased bandwidth due to the size of the TCP window, and may only see negligible improvements in performance.
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