[Full-disclosure] abnormal behavior Gmail logon

[Valdis.Kletnieks at vt.edu (Valdis.Kletnieks@xxxxxx)]

On Wed, 31 May 2006 09:23:08 BST, Edward Pearson said:
> This isn't abnormal or weird, It happens when your internet connection
> is fairly slow and its because you sometimes receive incomplete headers
> for the page (broken or garbled)

If you have noisy hardware that's mangling data in transit, the mangling will
*usually* be detected by the checksums on each IP packet.  The reason your
connection gets slow is because if a corruption is detected, the packet gets
thrown out, and needs to be retransmitted by the sending system.

If you're still on dialup, a noisy phone line will also make things go slower,
as the modem will probably drop back to slower and slower speeds (which are
more noise resistant.  Getting 56K through a 56K modem requires near-perfect
copper - but it will drop back to 44K, 33K, 19.2K. By the time you get down to
9600/4800/1200/300 baud, it can survive incredible amounts of clicks, hums, and
other noises.

Incidentally, the TCP checksums are *not* perfect.  Usually, it doesn't
matter, but you *should* verify the MD5 hash on a large file you've
downloaded (like a .ISO image, etc).  The average .iso is big enough that
you have a fairly good chance of getting an undetected bad packet.

So always check those md5sums.. :)
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