ISP port blocking practice

Patrick W. Gilmore patrick at
Sat Oct 24 00:12:22 UTC 2009

The original intent of Net Neutrality laws had nothing to do with  
blocking or not on random ports.  It had to do with giving an unfair  
advantage to the provider in question to sell competing services.   
Much like anti-trust legislation doesn't stop a company from cornering  
a market, just stops them from using that Market Power to create  
artificial advantages in other market segments to the detriment of the  

Putting this into a hypothetical example: If your access to iTunes,  
NetFlix, Amazon, etc. is filtered / rate limited / whatever, but you  
can order On-Demand from the company who owns the same piece of <fiber| 
copper> which delivers the Internet, especially if that is the only  
broadband connection you can buy because of monopoly / duopoly  
protection, then this is deemed "unfair".  Anti-net-neutrality people  
spin this into "but suppose I want to charge extra for premium access  
to YouTube?"  A != B, their argument does not address the underlying  
point of the rule.  Do not be fooled by such spin.

Back to the original question, no provider is blocking port 25 to  
force you to buy their mail services - they usually give it out for  
free with a connection!  Add in the "reasonable network management /  
preventing abuse / best common practices" argument, which are backed  
up with 3rd party documents, and I don't think anyone rational would  
call this a violation of Network Neutrality.

The problem is, not everyone is rational, and no law is written  
perfectly.  Some spammer _will_ file a lawsuit claiming their spam is  
CAN-SPAM compliant, therefore legal, and the provider cannot block  
them.  This will use legal resource, and may even result in un- 
blocking while a judge who knows what the box on his secretary's desk  
where his "e-mail" (huh?) gets printed is found.  And that could take  
a while.

Would that life were perfect.  But it is not, so we muddle through as  
best we can.  And I think we can do better than allowing a gov't  
sponsored monopoly use that monopoly to decide what things we can and  
cannot do based on what will raise their profit margin.

One other personal comment: I believe if you paid for a resource, you  
should be allowed to dictate its use, even to your customers (as long  
as it is clear when they paid what the rules are).  That said, there  
are no cable or DSL providers in the US who "paid" 100% for their  
resources, no matter what the executives at these companies think.   
This is not opinion, this is fact.

OTOH: Companies who set up WiMAX or satellite or other technologies  
which do not depend on gov't grants, tax relief, right-of-way,  
monopoly protection, etc. should be allowed to do as they please.   
Yes, this includes filtering iTunes so you buy their movie streaming  
service.  Of course, I have no idea if such a company exists, but it  
certainly is not impossible to set one up.  I just don't know if it  
can make any money against companies that are funded by, granted  
exclusive rights by, or are helped in other ways by the gov't.  I fear  
the answer is "no way in hell".

All of this is IMHO, of course.


On Oct 23, 2009, at 7:33 PM, James R. Cutler wrote:

> No, blocking a port does not restrict a customers use of the network  
> any more than one way streets restrict access to downtown stores. It  
> just forces certain traffic directions in a bicycle/motorcycle/car/ 
> van/truck neutral manner. Carry anything you want.  Others laws  
> restrict incendiary content.
> On Oct 23, 2009, at 6:15 PM, Dan White wrote:
>> On 23/10/09 17:58 -0400, James R. Cutler wrote:
>>> Blocking the well known port 25 does not block sending of mail. Or  
>>> the
>>> message content.
>> It does block incoming SMTP traffic on that well known port.
>>> I think the relevant neutrality principle is that traffic is not  
>>> blocked
>>> by content.
>> My personal definition doesn't quite gel with that. You're deciding  
>> for the
>> customer how they can use their connection, before you have any  
>> evidence of
>> nefarious activity.
>> Would you consider restricting a customer's outgoing port 25  
>> traffic to a
>> specific mail server a step over the net neutrality line?
>> -- 
>> Dan White
> James R. Cutler
> james.cutler at

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