[ale] wgr614V6 router https issue resolved?

[Watson, Keith R.]

> -----Original Message-----
> From: ale-bounces at ale.org [mailto:ale-bounces at ale.org] On Behalf Of
Paul
> Cartwright
> Sent: Wednesday, April 25, 2007 13:17
> To: Atlanta Linux Enthusiasts
> Subject: [ale] wgr614V6 router https issue resolved?
> 
> ok, I screwed around and screwed around and THOUGHT it was working,
then
> it
> stopped again. So I did another google search and found this:
> http://www.daniweb.com/techtalkforums/printthread73860.html
> 
> basically I could not connect to my.yahoo.com, my bank, or any https
site
> that
> required logging in or sending data back.
> I did as the web site poster suggested, changed my MTU from the
original
> 1500,
> to 1400, and... IT WORKED.
> can someone explain WHY???
> 
> --
> Paul Cartwright
> Registered Linux user # 367800
> Ubuntu User number is # 12459
> _______________________________________________
> Ale mailing list
> Ale at ale.org
> http://www.ale.org/mailman/listinfo/ale

Paul,

HTTPS uses an encrypted data stream. It is the equivalent of digitally
signing each packet. If a packet is fragmented it looks as if it was
tampered with. This would be like the checksum of downloaded code not
matching the checksum posted on the source site.

There are many things you can do to a packet that require information to
be added to the header. Once the data in the packet plus the header
exceed the MTU of the network the packet will be fragmented.

I first noticed this problem when trying to connect to an HTTPS:// URL
over a VPN. I could pull up any HTTP:// URL but an HTTPS:// would hang.
I could map to SMB shares but I couldn't transfer any files greater than
about 1K in size. Lowering the MTU solved the problem.

Lowering the MTU lowers the efficiency of network transfers because the
ratio of data size to header size has gone down. Maximum efficiency is
achieved by setting MTU to the largest size that doesn't cause packet
fragmentation.

keith

-- 

Keith R. Watson                        Georgia Institute of Technology
Systems Support Specialist IV          College of Computing
keith.watson at cc.gatech.edu             801 Atlantic Drive NW
(404) 385-7401                         Atlanta, GA  30332-0280