[CentOS] Disable window scaling during kickstart

Fri May 11 08:09:32 UTC 2007
Plant, Dean <dean.plant at roke.co.uk>

Ray Van Dolson wrote:
> On Thu, May 10, 2007 at 07:04:51PM +0100, Plant, Dean wrote:
>> Weird... Tell me about it, I spent a lot of time head scratching
>> trying to figure out why network connections would just mysteriously
>> hang. Eventually found reference to a problem with
>> tcp_window_scaling and firewalls and after disabling
>> tcp_window_scaling on my test CentOS 5 box, everything started
>> working. 
>> The install does not get far enough for the shell console to be
>> available, it hangs at the transferring stage2.img.
> Ah, probably before %pre even has run (?)  Well you could rebuild the
> kernel on the install CD to disable window scaling by default. :)  Ok,
> not a particularly useful option... maybe someone else will have a
> suggestion.
> In HP-UX you can pass kernel parameters at boot-time, I wonder if
> anything similar could be done?  Probably not.
> Have you captured a tcpdump of what happens when the "freeze" occurs
> with an intermediary system?  Maybe a setting could be changed on your
> switch?  Although I would doubt the switch would be a factor.  Are
> your packets going through an intermediary router?
> I plan to do some network installs of CentOS 5 soon, will be
> interesting to see if this issue occurs.

I don't think this is a issue with CentOS/RHEL. The kickstart in this
instance is passing through a firewall appliance, which I think is
Open/FreeBSD based and we now believe is breaking tcp window scaling. It
seems that CentOS3&4 was unaffected by this but with v5 network
connections hang after transferring about 500k. On a network that does
not pass through this firewall v5 works as expected.