Re: [Phys-L] phys-l instructions and archives

[John Denker <jsd@av8n.com>]

On 05/04/2013 09:15 AM, Carl Mungan wrote:

> I can access http://www.phys-l.org/ fine from home (with VPN
> turned off). But at work (or if I VPN into the Naval Academy), I can no
> longer access that page. It's not being blocked by USNA's filters; it
> simply cannot be found.

Three things that apply to everybody:

1a) Mail should be sent directly to phys-l@phys-l.org
 Sending mail to phys-l@www.phys-l.org (with a "www") is inelegant 
 and not recommended ... but it should work.

1b) Conversely, for web traffic, using the bare domain name phys-l.org is 
 expected to be /less/ reliable than going directly to www.phys-l.org.
 It requires a slightly hackish redirection of the HTTP traffic.

 Mnemonic: To reconcile (1a) with (1b), remember:  "www" means world 
 wide web.  It is for web traffic (i.e. HTTP).  Mail is something else.
 Mail is not HTTP.  Mail is not www.  Internet mail is older than HTTP
 by about 20 years.

2) The machine that hosts phys-l does not answer pings.  So if you're
 using ping or mtr to see whether the host is reachable, you will get
 false negative results.

 This may be fixable;  stand by for updates.

3) The machine that hosts the phys-l services does not have a fixed IP 
 address.  At present, we get around this using one level of indirection,
 as follows:

:; dig www.phys-l.org

www.phys-l.org.         81      IN      CNAME   phydocmarko.dyndns.org.
phydocmarko.dyndns.org. 60      IN      A       24.145.119.127

So one hypothesis is that somebody at USNA doesn't like dyndns.org (or
vice versa).

To figure out what's going on in a situation like this:

a) Please use the command-line interface to check what happens when you
 try to resolve the www.phys-l.org address.  On mac or linux use "dig" 
 or "host".  On windows I am told the corresponding command is "nslookup".

b) Please do the same for test.phys-l.org ... this should resolve to an
 IP address in one step, without indirection.  It is an A record not a
 CNAME record.

c) Please check what happens when you telnet directly to 24.145.119.127 
port 22, port 80, or port 443.