openssh unix dev - Nov 2018 - openssh-based file transfers (e.g. rsync, scp, ...) are running 40 (!!) times faster via IPv4 than IPv6

Servus Philipp,


Unfortunately the traceroute(6) results are both more or less random. Sometimes
traceroute "hangs" a while, wherever,
sometimes traceroute6. Sometimes traceroute is faster, sometimes traceroute6.
Not reliable.

Your MTU question, tried as adviced:

Maximum size for IPv4 is 1466, and max size for IPv6 is 1444. Exceeding these
values leads to a "ping: local error:
Message too long, mtu=1492" in both cases.

My Fritzbox says "Native IPv6", no tunnel, no underlying "IPv4
via DS-Lite". These are the default settings for ISP
"Deutsche Telekom", VDSL-50.


VINCENZO: Tried as adviced to test with FTP, installed pure-ftpd and opened
VPS's ftp port in firewall. Maximum IPv4
speed was much slower (1.5-2 MB/sec) than other tests, maybe temporary issue or
virtualization. But again: IPv6 was MUCH
slower than IPv4.





Am 07.11.18 um 20:57 schrieb Philipp Marek:
> 
>> first post to list, hopefully on-topic. Haven't found anything on
the
>> net, tried to ask at first in OpenSuse forums a
>> while ago
>>
(https://forums.opensuse.org/showthread.php/533588-rsnapshot-rsync-massive-performance-decrease)
>> and today
>> opened a bug in OpenSuse's Bugzilla
>> (https://bugzilla.opensuse.org/show_bug.cgi?id=1115075)
>>
>> As written in bug report, as general network issues could be excluded,
>> any hints where to start, how to narrow down if
>> this is a specific openssh issue or something else?
> 
> Your IPv6 _route_ has 3 times the latency:
> 
> ? $ time /usr/sbin/traceroute vserver.domain.tld
> ? ...
> ?? 7? domain.tld (IPv4)? 26.002 ms !X? 24.859 ms !X? 25.230 ms !X
> 
> ? $ time /usr/sbin/traceroute6 vserver.domain.tld
> ? ...
> ?? 8? domain.tld (IPv6)? 80.430 ms !X? 79.301 ms !X? 80.444 ms !X
> 
> The big time waster seems to be this link:
> ?? 6? nug-d-i40-v6.telia.net (2001:2000:3018:8d::1)? 32.046 ms? 23.850 ms?
24.097 ms
> ?? 7? contabo-ic-305268-ffm-b11.c.telia.net (2001:2000:3080:953::2)? 74.829
ms? 77.704 ms? 78.066 ms
> 
> I'll now speculate that you might as well have some MTU mismatches,
> meaning that packages have to get split up along the way, further
> slowing down your connection.
> 
> Do you have native IPv6 all the way, or is there an 6-in-4 tunnel
> inbetween (from the fritzbox on)?
> 
> Please try
> ?? # ping -M do -s <size> <ip>
> for sizes between 1300 and 1500 and find the largest (even) packet size
> that still works, and then do the same with ping6 as well.
> 
> Also note whether some packetsize works, but just larger ones vanish
> along the way.

> Unfortunately the traceroute(6) results are both more or less random.
> Sometimes traceroute "hangs" a while, wherever,
> sometimes traceroute6. Sometimes traceroute is faster, sometimes
> traceroute6. Not reliable.
That might just as well be DNS issue; the reported latency
values are the interesting data.

> Your MTU question, tried as adviced:
> 
> Maximum size for IPv4 is 1466, and max size for IPv6 is 1444.
> Exceeding these values leads to a "ping: local error:
> Message too long, mtu=1492" in both cases.
Hmmm, the IPv6 header is 20 bytes longer than IPv4 -- so there
are still 2 bytes missing.

Please try to set the MTU manually smaller, eg. to 1400,
and test once more.

Philipp,


thank you so much for your valuable hints!!

BUT as this list's topic is OpenSSH, and as I now know that my issue has
NOTHING to do with OpenSSH, I would like to
stop here, not wasting anyone's time.

Thanks to Vincenco's FTP hint I've now tested with a Debian based
"rescue live system" instead of my OpenSuse based VPS,
on server side, offered by my VPS's hosting company. And on the client side
with my Android smartphone and the (FOSS)
"Ghost Commander" instead of my OpenSuse box at home. To be sure that
my issue has also nothing to do with OpenSuse, as my
preferred Linux flavor.

And in fact it has nothing to do with either OpenSSH or OpenSuse....


Thanks again,
Michael


Am 07.11.18 um 22:18 schrieb Philipp Marek:
> 
>> Unfortunately the traceroute(6) results are both more or less random.
>> Sometimes traceroute "hangs" a while, wherever,
>> sometimes traceroute6. Sometimes traceroute is faster, sometimes
>> traceroute6. Not reliable.
> That might just as well be DNS issue; the reported latency
> values are the interesting data.
> 
> 
>> Your MTU question, tried as adviced:
>>
>> Maximum size for IPv4 is 1466, and max size for IPv6 is 1444.
>> Exceeding these values leads to a "ping: local error:
>> Message too long, mtu=1492" in both cases.
> Hmmm, the IPv6 header is 20 bytes longer than IPv4 -- so there
> are still 2 bytes missing.
> 
> Please try to set the MTU manually smaller, eg. to 1400,
> and test once more.