Greetings, On Fri, 26 Feb 2016, Keith Medcalf 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.
I wholeheartedly agree! When purchasing an "Internet connection", we expect that to be full access to the Internet. Granted, *some* parts of the Internet are up/down or never available, but the *protocols* should *ALL* be available. Customers regularly use various VPN protocols from GRE, SIT, and IPIP, monitoring protocols such as SNMP, as well as RTP and SIP (where we spend the bulk of our time troubleshooting). Customers EXPECT their packets to be passed unhampered. Otherwise, all the provider is giving them is acces to email and to surf for porn. That provider would simply be offering an "entertainment" connection to the public Internet, not full Internet access. However, if a 'provider' wishes to block ANYTHING, then they need to inform the customer IN WRITING exactly what will be blocked so that customer doesn't waste their time and money with said (limited) service and vote with their wallet by buying *real* Internet service, elsewhere. --- Jay Nugent Nugent Telecommunications consulting Ypsilanti, Michigan
-----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
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