In debates over Internet neutrality, “port blocking” may not be getting the headlines these days, but it was once a more common practice among Internet service providers (ISPs) and is still in use today. A new report from the Broadband Internet Technical Advisory Group (BITAG) , of which CDT is a member, makes a strong recommendation against the practice of port blocking unless no other reasonable alternatives exist. The report discusses alternatives to port blocking for ISPs to consider and other steps to minimize its impact when deployed.
From CDT’s perspective, the report and its recommendations make a significant contribution to the debate about Internet neutrality. Port blocking by its nature discriminates among Internet traffic and often is used to thwart specific applications. Minimizing its use and establishing safeguards for when it does get used therefore help to keep the Internet more neutral and open.
Port Blocking Defined
Internet applications, such as email and web browsing, make use of multiple kinds of address information on the network, including IP addresses and port information, to send data between computers on the Internet. IP addresses and port numbers are analogous to street addresses and apartment numbers – a letter can reach a particular apartment building based solely on street address (the IP address), but an apartment number (the port) is needed for the letter to reach an individual unit in the building.
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