Re: [Dctc-general] Rollback resuming?

[eric]

Hi,

In fact, there is 3 main reasons to obtain a corrupted file after a download 
(GDL or any other xfer type):
1) the original file is corrupted. This explanation is so easy that nobody 
thinks of it. However, you will tell me that if the original file is 
corrupted, one day, someone has had the uncorrupted file and I agree.
2) an uncorrected error during a transfer is another explanation. The checksum 
used in ethernet is not perfect, it can detect a lot of errors but if you 
check the specs, you will see one bit on 10^8 (ethernet standard) is not 
corrected. It is very very small but it is one bit for 100,000,000 and a 
700MB CD (mode 1) has 5,872,025,600 bits this means if you transfer a CD, you 
may have 58 corrupted bits... Ouch!!! Hopefully, uncorrected bit does not 
mean corrupted bit. On intel gigabit switch web page, they report they have 
one corrupted bit for 10^12bits = one bit for 1,000,000,000,000. This means 1 
corrupted bit for ~170 transferred CD. 170CD seems quite a lot for a user... 
but not for the whole internet.
3) a buggy program or OS... I remember a program named hotline running on 
win98 (first of the name) which sometimes, for an unknown reason, corrupts 
the packet content but have a valid CRC (checksum) thus packets are assumed 
to be ok by the remote client. It was not hotline fault (the same binary 
works perfectly on NT) and the problem appears very randomly. It can also 
came from stupid thing in a language like "I want the byte 1 of the file. VB 
returns the first byte of the file but AFAIK, any other language will return 
the second because all kernels (including windoz) has file first byte at the 
position 0) [this looks stupid but it is a real case... direct connect works 
like this :) ].

Eric