Network Neutrality and Protocol Discrimination

In an ideal Internet all packets would be treated as equal by the Internet Service Providers (ISP) and backbone operators who transport them across cyberspace. Unfortunately, this is not always the case since many ISPs restrict or completely block Internet access to some services by discriminating against certain network protocols.

Several telecommunication companies, who are also offering Internet access, have for example been known to block the Voice-over-IP (VoIP) application Skype in their networks. The underlying reason for this discrimination has in most cases been because the telecommunication providers see Skype as a competitor to their own telephony services. Peer-to-peer (P2P) file sharing applications are also often blocked or bandwidth limited by ISPs.

The principle of network neutrality (also known as "internet openness") advocates that users should be able to send and receive data across the Internet without having the traffic discriminated based on content, application, protocol, source or destination. An ISP who is limiting the bandwidth of one or several P2P protocols is thereby violating the network neutrality principle. The legal requirements for ISPs to comply with the network neutrality principle varies between countries. However, from an ethical point of view it is pretty obvious that it should be the users, not the ISPs, who decide what protocols and applications can be used on the Internet. The network neutrality principle also protects the concept of an open Internet that allows for democratic communication.

P2P file sharing is a technology for efficient sharing of data between peers across the Internet. Just as with any other technology for transferring files, P2P file sharing can be used for sharing lawful as well as unlawful content. There is a great deal of lawful content, such as open-licensed software and digital media, that can be downloaded through P2P file sharing. Unfortunately, the amount of unlawful content available on P2P file sharing networks is significantly greater. Copyright violation, however, is not usually a concern for ISPs. The reason many ISPs block P2P traffic is because more than half of the traffic on the Internet is P2P traffic (according to the Ipoque Internet Study 2008/2009), and a small group of active P2P users can typically use up the majority of an ISPs available bandwidth.

Modern P2P file sharing applications such as Vuze, uTorrent and eMule have introduced protocol obfuscation techniques to avoid being fingerprinted by the port independent traffic classification methods. The popular VoIP application Skype applies obfuscation to all of its traffic, which makes the application difficult to identify through network monitoring.

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.