As noted initially, the Internet would be a better place had it treated all packets equal, but as long as ISPs want to play hardball by discriminating against certain protocols, the need for protocol obfuscation will remain. Unfortunately, such obfuscation of measurable protocol properties inhibits the ability for researchers to measure trends and usage of various protocols and applications on the Internet. There are, however, situations when it could be argued that ISPs should be allowed to perform traffic shaping. One such situation is the case where different classes of traffic require different types of network performance. VoIP traffic, for example, requires low latency transmissions with minimal jitter but does not require very much bandwidth. Transfers of large files across the Internet, on the other hand, require high bandwidths but are generally very resilient against both jitter and latency.

An ISP with the knowledge of what protocols are being used in each session could use that information to apply Quality of Service (QoS) to cater the different needs of the various protocols and applications. In reality, however, such QoS assignments would typically result in the VoIP traffic receiving a higher priority than the file transfer. This would imply that it is beneficial for a VoIP protocol to be identifiable, but not for a file transfer protocol. As a result, it's likely that designers of protocols for large file transfers might attempt to mimic protocols with better QoS prioritizations in order to fool ISPs' traffic classification attempts. Hence, don't be surprised if applications that gain on mimicing other protocols or hiding through obfuscation actually start applying these techniques. This is one of the reasons I believe that using protocol identification in order to discriminate against certain protocols is futile.

Erik Hjelmvik is an independent network security researcher and open source developer. He also works as a software development consultant, specializing in embedded systems. In the past, Erik served as an R&D engineer at one of Europe!s largest electric utility companies, where he worked with IT security for SCADA and process control systems.

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