Routing problem?

Matthew Seaman m.seaman at infracaninophile.co.uk
Tue Nov 19 12:14:52 GMT 2002


On Tue, Nov 19, 2002 at 11:25:23AM +0000, Lou Kamenov wrote:
> In some email I received from Matthew Seaman
> <m.seaman at infracaninophile.co.uk> on Tue, 19 Nov 2002 09:23:04 +0000 :
> > On Tue, Nov 19, 2002 at 08:09:38AM +0000, Frank Shute wrote:
> > > 18  193.ATM6-0.GW6.TCO1.ALTER.NET (152.63.37.37)  215.447 ms 
> > > 207.485 ms  209.401 ms 19 * * *
> > 
> > Looks like that router is kaput.
> >  
> 
> Erm who knows, my route is different.
> 
> -- my traceroute --
> 14  193.ATM7-0.GW6.TCO1.ALTER.NET (152.63.37.53)  98.324 ms  95.686 ms 
> 97.938 ms
> 15  pbs-gw.customer.ALTER.NET (157.130.32.130)  97.744 ms  98.016 ms 
> 100.161 ms 16  * * *
> -- end --
> 
> AFAICS {www.}pbs.org doesnt reply to any icmps, however we know how
> traceroute works /icmp/udp/.

Since traceroute can send out whatever sort of packet you want (tcp,
udp, gre (whatever that is), defaults to udp) and it's the
interveining gateways that send back the ICMP TTL exceeded or
destination unreachable responses, I tried a a few different options.
None worked.  It's not unreasonable for them to filter out packets to
random UDP or TCP high ports... Even so, seems they're filtering ICMP
echo {request,reply} as well. Probably all ICMP types. Grrr... I hate
sites that just blindly do that.
 
> > > ie. it seems to get stuck at alter.net's Godforsaken network.
> > > Anybody got an idea what's going on here? 
> I think that it`s only a filter... 

Looks like they've got at least two routers on some sort of load
balance:

    193.ATM7-0.GW6.TCO1.ALTER.NET (152.63.37.53)
    193.ATM6-0.GW6.TCO1.ALTER.NET (152.63.37.37)

> I can access www.pbs.org (149.48.192.134) with my browser..

Yeah --- I can access the site by IP number.  Slow, and it looks to me
like my system is having to do some retries to retrieve all the images
on the site: maybe one of those routers is sending stuff into
never-never land.

They've got another problem though:

    happy-idiot-talk:~:% dig @8496-gslb.nyc3.aens.net www.pbs.org IN AAAA
    
    ; <<>> DiG 8.3 <<>> @8496-gslb.nyc3.aens.net www.pbs.org IN AAAA 
    ; (1 server found)
    ;; res options: init recurs defnam dnsrch
    ;; res_nsend to server 8496-gslb.nyc3.aens.net  63.240.96.196: Operation timed out

Stupid nameservers that won't respond *at all* to AAAA requests, even
if it's just to say "Huh?".  That will put the kybosh on any
application that uses getaddrinfo(3), like Mozilla.

	Cheers,

	Matthew

-- 
Dr Matthew J Seaman MA, D.Phil.                       26 The Paddocks
                                                      Savill Way
                                                      Marlow
Tel: +44 1628 476614                                  Bucks., SL7 1TH UK




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