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Tuesday, Jan 17, 2017 - 5:43:36 - Current software version: : 3.10.0.2

MODE Z - zlib

What is zlib ?

zlib is a compression method which can greatly decrease the size of data, similar to popular compression format like Zip.

You can refer to the author's website for more information : http://www.gzip.org/zlib/


How to use zlib with Gene6 FTP Server ?

zlib can be used in Gene6 FTP Server thanks to the newly implemented MODE Z command.

This command and format have been discussed with and already adopted by popular FTP software developers like SmartFTP, RaidenFTPd, FTP Voyager, GetIt to name a few.

Once activated, zlib compression will be transparent to users, no additional software to install.
MODE Z is on the fly data compression.

Note : MODE Z is optional and will not break compatibility with non-zlib enabled FTP software.


What is the benefit ?

Faster data transfers!

Directory listing, which is text, can be highly compressed with zlib thus boosting the server and client network speed and reactivity.

Webmasters and server administrators will see an increase in productivity : transfers of html, scripts or large logfiles (which are text) no longer needs to be zipped before being sent via ftp and should generally experience a 3-4 times gain in data transfers. Enjoy sending your websites update from home!

For example, a 60MB log file can turn into a 5MB data exchange when transferred with MODE Z enabled.

Depending on the file content, you will see different results.


Typical gains


  • text files : ~15-20% of original size !
  • html files : ~25-30% of original size !
  • media, video, sound : ~90-95% of original size

Note : already compressed documents with Zip, Rar, Ace etc. will see virtually no gain at all.


How to implement ?

If you are a FTP software developer, we recommend you to follow this implementation :
http://www.ietf.org/internet-drafts/draft-preston-ftpext-deflate-03.txt

Here is a typical server-client exchange (C = FTP client, S = FTP server) :

S : 220 Gene6 FTP Server v3.0.3 (Build 45) ready...
C : USER anonymous
S : 331 Password required for anonymous.
C : PASS ****
S : 230 User anonymous logged in.

C : FEAT
S : 211-Extensions supported:
[..]
MODE Z
[..]
211 End.

C : MODE Z
S : 200 MODE Z ok

C : PASV
S : 227 Entering Passive Mode (192,168,0,1,195,172)
C : TYPE A
S : 200 Type set to A.
C : LIST
S : 150 Data connection accepted from 192.168.0.1:33269; transfer starting.
C : 226-Compression : 30,2% (971 Bytes/3,14 KBytes).
S : 226 Transfer ok.

Once sent, MODE Z commands the server to send zlib compressed data, so all directory listings and file exchanges between server and client will be compressed.




Now you can