[fpc-other] Re: FPC website

[Programming]

An update, after several months.

After the last message, I adjusted the MTU size down to 1400. Doing a 
tracert, after this change, to forum.lazarus.freepascal.org now 
succeeds, but I am still unable to connect via my desktop (Win 7 Pro 
64bit) to the address from neither Chrome nor Firefox (I get a timeout). 
I can connect without a problem via the original Kindle Fire tablet from 
the same LAN, so that seems to eliminate the router as a problem.

At that point I tried to figure out what is wrong without bothering the 
folks here on the list.

I have taken up the habit of every time I get access to someone's 
desktop or other device to try accessing the forum. About 1 out of 4 
Win-7 desktop computers I have tried will not connect (I did not check 
which versions of Win-7). The few Linux boxes I have tried have all 
succeeded in connecting. Same successful connection via the Mac and 
Android/Linux tablets and phones I have tried. I have not tried any iOS, 
XP, or Win 8 devices/laptops/boxes. In the computers that did not 
connect, it did not seem to matter if I used Chrome, Firefox, or IE (if 
one failed, they all failed).

Using the IP address explicitly does not seem to make a difference.

Using Wireshark for monitoring, the connection seems to hit a wall once 
a SYN packet is sent during the handshake (no SYN-ACK packet is returned 
from 80.123.225.56, the IP of the forum).
192.168.1.3 → 80.123.225.56, TCP protocol, length 66B, port 51683→80
[SYN] Seq=0; Win=8192; Len=0; MSS=1360; WS=4; SACK_PERM=1
After the packet doesn't get acknowledged, it retransmits the same 
packet twice, then transmits the packet *without* the Window Scaling=4 
parameter (other information is the same) twice. Then it repeats the 
entire process until the timeout hits.

I have tried figuring this out, but after several months, I seem to not 
be getting any further in solving this. I am not sure what else I need 
to check.

On 1/31/2015 4:26 PM, Helmut Hartl wrote:
> hi, i am helmut
>
> i am one of the admins of the hosting facility that the lazarus website
> lives in.
> The lazarus website/mailinglist is hosted here in graz/austria.
> the servers external ip is 80.123.225.56, while the firewalls ip is
> 80.120.208.116 ( here your packets seem to end, so you are
> just 2 feet away from the data :-) )
>
> The firewall disallows icmp packet to go through to the webserver.
>
> I changed this now because the firewall drops also fragmented packets,
> icmp is needed for mtu path discovery to work - It
> may be a problem that you emit fragmented packets along your path,
> which reach us but then get dropped (for security reasons).
>
> Maybe my change helps you.
>
> You can also try to use lazarus.firmos.at, which is the same ip
> and may rule out some strange dns problems.
>
> Another thing you could do is to try to change the mtu of
> your networking equipment (network card that you are using
> to browse to the site) downwards (say from 1500 -> 1400
> to test).
> Just google or
> http://www.networkworld.com/article/2224654/cisco-subnet/mtu-size-issues.html
>
>
> HTH,
>
>  helmut 

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