[169472] in North American Network Operators' Group
Re: Filter NTP traffic by packet size?
daemon@ATHENA.MIT.EDU (Keegan Holley)
Thu Feb 27 20:43:15 2014
From: Keegan Holley <no.spam@comcast.net>
In-Reply-To: <CADE4tYXj30DeXS2-Jr1m87JGTB=xTbYVZTje-RvtWoB903jcPA@mail.gmail.com>
Date: Thu, 27 Feb 2014 20:42:44 -0500
To: Brandon Galbraith <brandon.galbraith@gmail.com>
Cc: "nanog@nanog.org" <nanog@nanog.org>
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
On Feb 26, 2014, at 12:44 PM, Brandon Galbraith =
<brandon.galbraith@gmail.com> wrote:
> On Wed, Feb 26, 2014 at 6:56 AM, Keegan Holley <no.spam@comcast.net> =
wrote:
> > More politely stated, it=92s not the responsibility of the operator =
to decide what belongs on the network and what doesn=92t. Users can run =
any services that=92s not illegal or even reuse ports for other =
applications. That being said commonly exploited ports (TCP 25 for =
example) are often blocked. This is usually done to block or protect an =
application though not to single out a particular port number.
>=20
> Don't most residential ISPs already block port 25 outbound? =
http://www.postcastserver.com/help/Port_25_Blocking.aspx
>=20
> Blocking chargen at the edge doesn't seem to be outside of the realm =
of possibilities.
As I said, SMTP is blocked because it=92s the default port for a =
commonly run and often misconfigured application. Blocking the chargen =
port is definitely reasonable, but it=92s not a popular application. =
Most people use the port as an clever non-default port for some other =
service like ssh.
