The following text is copyright 1999 by Network World, permission is hearby given for reproduction, as long as attribution is given and this notice is included.
Blocking for cause
by Scott Bradner
When I get Internet service I want full Internet service but that is not what one gets from some Internet service providers (ISPs). Some ISPs block or control their user's ability to use some protocols. This has been a bone of contention for us Internet purists for quite a while. But in some cases it might just be a reasonable thing to do.
One of the things that made the Internet what it is today is the freedom that Internet users have to experimentation. In the Internet most applications are run on the user's own computers. If you and I want to create a new application and run it over the Internet we can just do that. We do not need permission of the ISPs or a government agency or a phone company. Any blocking of data flows by ISPs limits this freedom.
But some ISPs insist on blocking some types of data. One type of thing that many cable TV-based ISPs block is the set of protocols which are used in Microsoft Windows for their "Net Neighborhood" feature. This makes a lot of sense because if this traffic is not blocked you can peer at your neighbor's computer. (As a mac user this does not effect me one way or another.)
A particularly galling type of blockage is where an ISP limits the ability for the user to send email. In this case the ISP sets up a filter that only lets the user send email to the ISP's email server. This is frequently done in the name of preventing spam (unsolicited bulk email). The ISP programs their mail server to refuse to forward email that is being sent to thousands of destinations or limits the amount of mail that the individual user can send in a day. This will limit the ability of a user to use that ISP to distribute their spam.
This sounds like a socially responsible thing to do but it can be a real danger. All of the user's mail has to go through a server that the user does not control and which records who they send mail to. In addition, a dishonest ISP employee has a very easy place to eavesdrop on the mail if they wanted to.
AT&T WorldNet seems to have a better idea. They do install this type of restriction on new accounts but the restriction can be removed after the account has been around for a while. The normal way that these spam artistes work is to use a free testing account, often with a false name and credit card info, to send a batch of spam then never user the account again, AT&T's model can stop this practice. In addition, the extra time gives the account billing information to check out so if spam is sent at a later date AT&T has a real person to talk to. This restriction is one I can live with.
disclaimer: Most things are not restricted at Harvard, ego for example, but the above is my support for some.