Subject: Re: FTP Service Discontinuance / RSYNC IPV6

From: Doug Royer <[email-masked]>
Date: Tue, 19 May 2015 18:36:47 -0600

And on a related note.

  My ISP recently started issuing IPv6 addresses.

  I switched from FTP to RSYNC, all seemed to work.

  Until my ISP switched to also providing me a IPV6 address.

  Ubuntu or RSYNC, seem to look for the DNS AAAA record before the DNS A 
record.
  It finds the AAAA record for  for rsync.ietf.org (2001:1900:3001:11::2c).

  RSYNC connects to the correct RSYNC port at 2001:1900:3001:11::2c, 
then hangs.

  I sent an email to [email-masked] in an attempt to figure out 
if it is me, my ISP, RSYNC, or IETF.org - in progress...

Anyone else tried RSYNC with rsync.ietf.org via IPv6? Does it work for you?

Thanks!

-- 

Doug Royer - (http://K7DMR.us / http://DougRoyer.US)
[email-masked]
714-989-6135

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From: Christopher Morrow <[email-masked]>
Date: Tue, 19 May 2015 20:49:15 -0400

On Tue, May 19, 2015 at 8:36 PM, Doug Royer <[email-masked]> wrote:
> rsync.ietf.org

$ rsync -6  rsync.ietf.org::
charter         - Repository of WG Charters
concluded-wg-ietf-mail-archive  - Older list text archives
conflict-reviews        - Repository of Conflict Review documents
everything-ftp  - The entire IETF FTP Archive

sure, v6 works. if you see connect but hang I'd suspect pmtu problems
(at first guess).

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From: Doug Royer <[email-masked]>
Date: Tue, 19 May 2015 20:37:35 -0600

On 05/19/2015 06:49 PM, Christopher Morrow wrote:
>> rsyn

Thanks for the quick reply, this also works for me:

	rsync -6  rsync.ietf.org::

This does not (getting the data, I have tried turning off -z, -v, and -a):

         rsync -6 -avz --progress rsync.ietf.org::rfc

Checking into pmtu ...

Has anyone done an IPv6 RSYNC ?

--

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From: "John Levine" <[email-masked]>
Date: 20 May 2015 02:58:17 -0000

>Has anyone done an IPv6 RSYNC ?

Just did this from my T-W cable modem, worked fine:

 rsync -6 -avz --exclude='*/scanned/*' --del ftp.rfc-editor.org::rfcs .

R's,
John

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From: Doug Royer <[email-masked]>
Date: Tue, 19 May 2015 21:04:39 -0600

>   rsync -6 -avz --exclude='*/scanned/*' --del ftp.rfc-editor.org::rfcs .

THANKS!

--

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From: Doug Royer <[email-masked]>
Date: Tue, 19 May 2015 21:17:37 -0600

> sure, v6 works. if you see connect but hang I'd suspect pmtu problems 

Don't understand why yet. By moving the MTU from 1500 (the default 
value) to 1420, it works.

--

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From: Christopher Morrow <[email-masked]>
Date: Tue, 19 May 2015 23:22:34 -0400

On Tue, May 19, 2015 at 11:17 PM, Doug Royer <[email-masked]> wrote:
>> sure, v6 works. if you see connect but hang I'd suspect pmtu problems (at
>> first guess).
>
>
> Don't understand why yet. By moving the MTU from 1500 (the default value) to
> 1420, it works.

clearly there's a lower mtu (perhaps tunneled?) path between you and
the ietf rsync host. traceroute6 ?

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From: Michael Richardson <[email-masked]>
Date: Wed, 20 May 2015 10:26:32 -0400

obiwan-[~] mcr 10012 %telnet rsync.ietf.org rsync
Trying 2001:1900:3001:11::2c...
Connected to rsync.ietf.org.
Escape character is '^]'.
@RSYNCD: 30.0

so that works for me.  I have native IPv6 at my home office from storm.ca.

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From: Nico Williams <[email-masked]>
Date: Wed, 20 May 2015 10:49:51 -0500

On Tue, May 19, 2015 at 09:17:37PM -0600, Doug Royer wrote:
> >sure, v6 works. if you see connect but hang I'd suspect pmtu
> >problems (at first guess).
> 

Make sure ICMP isn't getting filtered.

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From: Brian E Carpenter <[email-masked]>
Date: Thu, 21 May 2015 08:02:36 +1200

> Make sure ICMP isn't getting filtered.

Or fragments being dropped.
https://tools.ietf.org/html/draft-ietf-v6ops-ipv6-ehs-in-real-world

Or MSS negotiation failing.

   Brian

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From: "Joe Abley" <[email-masked]>
Date: Wed, 20 May 2015 16:12:33 -0400

> Or MSS negotiation failing.

Yeah.

At the risk of stating the obvious, lowering your MTU and declaring the 
problem fixed is like fixing a broken window by sticking a poster over 
it. The window is still broken, even if the immediate signs that there 
is a problem to fix have gone away.

Path MTU discovery being broken is endemic in the v4 network, mainly I 
think because of the common wisdom in enterprise networks that ICMP is a 
security! risk! and must! be! blocked! The fact that these kinds of 
problems persist in v6 is perhaps a sign that enterprises are deploying 
it? Trying hard to see the glass as half full, here. :-)

Joe