[Info-vax] SFTP hang - from VMS to Windows

[Simon Clubley]

On 2013-02-25, GerMarsh <marsh.family at tirhir.com> wrote:
> Anyone seen anything like this?
>

Yes, but only in heavy packet loss situations with protocols other than sftp
and, for once :-), not on VMS.

Do your site security policies allow you to use Wireshark on a third
machine so that you can see what is really going on ?

> We get intermittent hangs during file transfers - nothing consistent about which file will be affected nor their sizes.
>
> Windows is running an OpenText (Hummingird) server. VMS is TCPIP Services V5.6 - ECO 2.
>
> The "hang" can be kicked into life by trying an FTP connection to the same server!
>

FTP or SFTP ?

Regardless, that would suggest a possible candidate is faulty TCP packet
loss recovery logic in a TCP stack somewhere especially since it appears to
be happening at the end of a transfer.

>
> The transfer sits at 99% with no throughput - and the associated average rate decreasing. 
>

You really need to have a look at what is going on by using Wireshark if your
site security policies allow it. You need to capture, and keep, a successful
transfer and compare it with a failed transfer. You can also see what is
actually going on when your second transfer starts up.

Simon.

-- 
Simon Clubley, clubley at remove_me.eisner.decus.org-Earth.UFP
Microsoft: Bringing you 1980s technology to a 21st century world