I agree with this...from a customer perspective. I've seen ISPs block other traffic as well...even on "business" accounts, and break their customers networks. It's the Internet not a private network... I've never been a typical user though...maybe one of the "dozen" Mike refers to that runs a email server, web server, dns server, etc, etc, etc out of their house.
On Feb 26, 2016, at 9:31 AM, Keith Medcalf <kmedcalf@dessus.com> wrote:
ISP's should block nothing, to or from the customer, unless they make it clear *before* selling the service (and include it in the Terms and Conditions of Service Contract), that they are not selling an Internet connection but are selling a partially functional Internet connection (or a limited Internet Service), and specifying exactly what the built-in deficiencies are.
Deficiencies may include: port/protocol blockage toward the customer (destination blocks) port/protocol blockage toward the internet (source blocks) DNS diddling (filtering of responses, NXDOMAIN redirection/wildcards, etc) Traffic Shaping/Policing/Congestion policies, inbound and outbound
Some ISPs are good at this and provide opt-in/out methods for at least the first three on the list. Others not so much.
-----Original Message----- From: NANOG [mailto:nanog-bounces@nanog.org] On Behalf Of Maxwell Cole Sent: Friday, 26 February, 2016 07:19 To: Mikael Abrahamsson Cc: NANOG list Subject: Re: Thank you, Comcast.
I agree,
At the very least things like SNMP/NTP should be blocked. I mean how many people actually run a legit NTP server out of their home? Dozens? And the people who run SNMP devices with the default/common communities aren’t the ones using it.
If the argument is that you need a Business class account to run a mail server then I have no problem extending that to DNS servers also.
Cheers, Max
On Feb 26, 2016, at 8:55 AM, Mikael Abrahamsson <swmike@swm.pp.se> wrote:
On Fri, 26 Feb 2016, Nick Hilliard wrote:
Traffic from dns-spoofing attacks generally has src port = 53 and dst port = random. If you block packets with udp src port=53 towards customers, you will also block legitimate return traffic if the customers run their own DNS servers or use opendns / google dns / etc.
Sure, it's a very interesting discussion what ports should be blocked or not.
http://www.bitag.org/documents/Port-Blocking.pdf
This mentions on page 3.1, TCP(UDP)/25,135,139 and 445. They've been blocked for a very long time to fix some issues, even though there is legitimate use for these ports.
So if you're blocking these ports, it seems like a small step to block UDP/TCP/53 towards customers as well. I can't come up with an argument that makes sense to block TCP/25 and then not block port UDP/TCP/53 as well. If you're protecting the Internet from your customers misconfiguraiton by blocking port 25 and the MS ports, why not 53 as well?
This is a slippery slope of course, and judgement calls are not easy to make.
-- Mikael Abrahamsson email: swmike@swm.pp.se