nanog mailing list archives

Re: ISP port blocking practice


From: Dan White <dwhite () olp net>
Date: Fri, 23 Oct 2009 21:35:31 -0500

On 23/10/09 17:43 -0500, Justin Shore wrote:
It does block incoming SMTP traffic on that well known port.

Then the customer should have bought a class of service that permits servers.

That justification is a slippery slope. At what point do you draw the line
on what constitutes business use? Is running a web server business use? A
mail server? What about a server which participates in a peer to peer
network? VPN?

I certainly think you're within your right as a network operator to
determine what is business use. I don't happen to feel that running a
protocol server in and of itself meets that definition.

Would you consider restricting a customer's outgoing port 25 traffic to a
specific mail server a step over the net neutrality line?

I do this all the time. For example I don't let my customers send or receive mail (or any traffic for that matter) from prefixes originating from AS32311 (Colorado spammer Scott Richter). Now if I was blocking mail to dnc.org, gop.com, greenpeace.org, etc or restricting Vonage to .05% of my bandwidth then yeah that would violate net neutrality principles. The difference is one stifles speech and is anti-competitive. The other mitigates a network security and stability risk.

I think I worded my question a bit wrong. I meant to hypothetically propose
a common scenario: You only allow your customers to connect to your SMTP
server, and if they attempt to connect to *any* other SMTP server, they are
blocked or redirected to your SMTP server.

--
Dan White


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