This has been niggling me for some time now:

My NetBSD/i386 1.3.1 machine talks to the outside world via PPP
through a modem to a Linux machine.  The Linux machine has a dial-out
line of it's own, which connects it to an ISP.  Got that?

Now, over the last few months there have been a few minor changes to
this arrangement: a different Linux machine on a different dial-in
number; change back to the original setup, etc..  Each time, I have a
poke about under /etc and fiddle a few things until I get some sort of 
connectivity to the rest of the world.  Currently, I am happy with the 
connection to the Linux box.

My problem is: I am experiencing intermittent (?) problems with
connections beyond the Linux box!  Specifically, I can happily browse
away [1] to /some/ sites, but other sites don't seem to deliver any
data!  Also, occasionally, when confronted with the following series
of status messages from Netscape:

  Connect: Contacting host: a.b.c...
  Connect: Host a.b.c. contacted.  Waiting for reply... 

I can actually abort the connection (i.e. hit <ESC>), then attempt it
again, with the result that connection comes up and data starts
flowing!

Summary:

1. some web sites (read HTTP server machines) are accessible immediately;

2. some web sites seem to require a second connection before they are
   accessible, and

3. some web sites don't seem to be accessible at all!

Further:

- 'ping' gets sensible responses from the sites of case 3 (!).

Here is the output from 'tcpdump -i ppp0' on my machine, when
attempting to reach www.xfree86.org (my machine is obelix; the Linux
box is echidna):
 
15:06:49.568608 obelix.premium.com.au.1109 > echidna.premium.com.au.domain: 1+ A? www.xfree86.org. (33)
15:06:50.711168 echidna.premium.com.au.domain > obelix.premium.com.au.1109: 1* 1/4/4 (206)
15:06:52.728658 obelix.premium.com.au.1334 > public.XFree86.Org.www: S 1953605145:1953605145(0) win 16384 <mss 1460,nop,wscale 0,nop,nop,timestamp 39684 0>
15:06:53.356337 public.XFree86.Org.www > obelix.premium.com.au.1334: S 2128045057:2128045057(0) ack 1953605146 win 17520 <mss 1460> (DF)
15:06:53.356451 obelix.premium.com.au.1334 > public.XFree86.Org.www: . ack 1 win 17520
15:06:53.539763 obelix.premium.com.au.1110 > echidna.premium.com.au.domain: 47802+ (45)
15:06:53.580745 obelix.premium.com.au.1334 > public.XFree86.Org.www: P 1:259(258) ack 1 win 17520
15:06:54.890118 obelix.premium.com.au.1334 > public.XFree86.Org.www: P 1:259(258) ack 1 win 17520
15:06:55.088131 echidna.premium.com.au.domain > obelix.premium.com.au.1110: 47802* 1/4/4 (267)
15:06:57.890141 obelix.premium.com.au.1334 > public.XFree86.Org.www: P 1:259(258) ack 1 win 17520
15:06:58.565251 public.XFree86.Org.www > obelix.premium.com.au.1334: . ack 259 win 17520 (DF)

...then nothing else!  Hit <ESC>, however, then try the URL again, and
voila!  I have the page for www.xfree86.org on my screen!

Trying www.xemacs.org, however is a different kettle of fish:

15:16:59.722036 public.XFree86.Org.www > obelix.premium.com.au.1334: R 2921:2921(0) ack 260 win 17520 (DF)
15:17:08.659664 obelix.premium.com.au.1340 > public.XFree86.Org.www: F 307:307(0) ack 32912 win 17520
15:17:08.665632 obelix.premium.com.au.1112 > echidna.premium.com.au.domain: 1+ A? www.xemacs.org. (32)
15:17:08.891221 echidna.premium.com.au.domain > obelix.premium.com.au.1112: 1 1/3/3 (188)
15:17:08.897055 obelix.premium.com.au.1347 > gwyn.tux.org.www: S 2282647321:2282647321(0) win 16384 <mss 1460,nop,wscale 0,nop,nop,timestamp 40917 0>
15:17:09.183626 public.XFree86.Org.www > obelix.premium.com.au.1340: . ack 308 win 16616 (DF)
15:17:09.548745 gwyn.tux.org.www > obelix.premium.com.au.1347: S 4133123402:4133123402(0) ack 2282647322 win 32736 <mss 1460>
15:17:09.548860 obelix.premium.com.au.1347 > gwyn.tux.org.www: . ack 1 win 17520
15:17:09.549601 obelix.premium.com.au.1347 > gwyn.tux.org.www: P 1:258(257) ack 1 win 17520
15:17:09.707448 obelix.premium.com.au.1113 > echidna.premium.com.au.domain: 47804+ (43)
15:17:10.252736 gwyn.tux.org.www > obelix.premium.com.au.1347: . ack 258 win 32736 (DF)
15:17:11.426488 echidna.premium.com.au.domain > obelix.premium.com.au.1113: 47804* 1/3/3 (223)

...and nothing further.  <ESC>, retry the URL, and what happens?

15:18:06.006756 obelix.premium.com.au.1347 > gwyn.tux.org.www: F 258:258(0) ack 1 win 17520
15:18:06.503604 gwyn.tux.org.www > obelix.premium.com.au.1347: . ack 259 win 32735 (DF)
15:18:07.865974 obelix.premium.com.au.1354 > gwyn.tux.org.www: S 2316673760:2316673760(0) win 16384 <mss 1460,nop,wscale 0,nop,nop,timestamp 41034 0>
15:18:08.404717 gwyn.tux.org.www > obelix.premium.com.au.1354: S 155680838:155680838(0) ack 2316673761 win 32736 <mss 1460>
15:18:08.404816 obelix.premium.com.au.1354 > gwyn.tux.org.www: . ack 1 win 17520
15:18:08.405497 obelix.premium.com.au.1354 > gwyn.tux.org.www: P 1:258(257) ack 1 win 17520
15:18:09.078334 gwyn.tux.org.www > obelix.premium.com.au.1354: . ack 258 win 32736 (DF)

...then nothing further!

FWIW, echidna is running an incarnation of named; obelic (my machine)
has no named running, but has echidna listed in /etc/resolv.conf.

How am I losing out here?

--Kevin.

[1] Netscape Communicator 4.05 (BSD 1.0)