Technical measures (part III): Protocol and port blocking

This week Future of Copyright will devote specific attention to technical measures against piracy that can be employed by ISPs. Today we discuss the pros and cons of  protocol and port blocking.

In addition to blocking specific addresses, it is also possible to block certain transfer protocols and corresponding ports. Modern routers in ISP networks can distinguish between various kinds of IP traffic, such as BitTorrent, Skype, eDonkey, KaZaA or Napster. Subsequently, ISPs can choose to block access on the basis of traffic type. The simplest way to do this is by closing off the port used by the protocol, but many modern downloading tools and protocols now have ways of circumventing this measure. Often they make use of standard ports (which cannot be blocked as they are also used for essential services such as e-mail and surfing the web) or change ports at regular intervals.

Even though most ISPs are reluctant to block protocols and ports, several of them do use the aforementioned measures to protect their own networks or business models: ISPs that do not support Internet phone services usually block the Voice over Internet Protocol. Most ISPs are not very keen to block protocols and ports, however, as it clashes with the principles of net neutrality. According to these principles, all Internet traffic is deemed equal; there should be no data discrimination. In addition, blocking ports is often not in the ISP's best interests as many consumers are primarily interested in downloading. However, the dramatic increase in P2P (BitTorrent) traffic forces many providers to impose certain limits, as P2P increases data traffic costs and interferes with the quality of other services such as VoIP, video streaming, e-mail and surfing the web.