该软件的工作特点是完全将可使用的 DSL/ISDN等物理连接模拟成一个标准的老式调制解调器，这样不管你使用哪种线路连接，只需要安装cFos以后当作56KModem来用就可以，不用考虑网络配置等等，全部由cFos自动配置协调。该软件因为是模拟普通Modem所以需要操作系统的拨号网络来协同工作。因此安装之前要检查是否已经安装了拨号网络（拨号适配器）并且该软件要求使用的拨号网络版本最低必须是MSDUN1.3 ,否则即使完成了安装过程，也不能正常工作。程序体积小巧,自带网络防火墙和计费统计功能。

cFos 7.50 build 3045 -- 18-Jan-2008

* Added rx-priorisation. It works as follows:

Each class (high, default, low, lowest) has a weight assigned. Furthermore,
all TCP streams are mapped to a certain class (this only applies for bulk
data; e.g. ACKs are always sent out in the higher class), according to
filter rules. The class weight is used when TCP windows for rx-shaping are
computed. A TCP stream with weight 100 gets a window that is about 4 times
bigger than a stream with weight 25. This should *usually* translate into
more speed on that stream, but not necessarily (e.g. the sending server
might not be fast enough).

The pre-set weights are:

class high -weight 400
class default -weight 100
class low -weight 25
class lowest -weight 6

I.e. regular browser downloads (class default) should get about 16 times
the speed than Torrents (class lowest).

The weighting needs some time (some seconds) to be through, so a newly
created higher-than-average TCP stream needs these seconds to come to full
speed.

* Now you can set MAXimum rx-speed and tx-speed!

Just use "cfo set rx_limit " resp. "cfo set tx_limit ". The
value is in bytes as cFos calculates them. This might be up to some
percent more than what your software shows you. It's best to look at maxrx
resp. maxtxraw ("cfo set maxrx" resp. "cfo set maxtxraw") and then set the
limit accordingly. The value is automatically saved. To set no limit, set
it to "inf" (like "cfo set rx_limit inf").

The tx_limit is quite accurate, but the rx_limit is only met statistically,
i.e. it's possible you receive more than the limit, but shortly afterwards
you'll receive less.

It is a good idea to give your client one full blast upload and download
before setting one of those limits. Otherwise, it will have problems
calculating, because it doesn't know the "true" line speeds.

* Speeded DSL transmit/receive speed and lowered CPU utilisation.

+ ctrace.txt is now in UTF-8 coding, but without a byte-order marker at the
beginning. Use e.g. notepad for viewing.

+ Added a way to change and save rtt_tab's. Thanks to Darko Grskovic for
inspiration.

+ Increased way too small buffer limits from 32k to 512k.

+ Added "cfo ati " command to see the ATIx modem command outputs.
and improved ATI7 PPP statistics.

+ Variable shaper will regain full speed quicker after it slowed down when
congestion was detected.

+ Added "cfo cperf" command to switch on or off class traffic dumping. By
setting "cfo cperf on" cFos will dump about once per second how many
bytes were sent in what priority class. This can help in testing filter
rules or finding performance problems.

+ When cFos' variable shaper is sending slow because of tx congestion
and that congestion goes away, cFos will now return to its old tx speed
quicker.

+ Now UDP checksums are checked as well.

+ Added "cfo timerstyle" command to query (just "cfo timerstyle"), set
"cfo timerstyle " or list supported values ("cfo timerstyle -?").
Changes to timerstyle are only active after a restart of cFos.

+ Added layer-7 protocols SSL_S_BULK and SSL_C_BULK. Switching of SSL
sessions between bulk and regular mode is done automatically based
on speed and packet sizes.

Added l7-protocol SSH_BULK. SSH sessions are automatically switched to this
protocol, if they transfer mostly data in large blocks, so we presume they
are doing some file transfer. Thanks to ghorvath for inspiration.

+ Added gset variable fwlog. Setting it to 0 ("cfo gset fwlog 0 -save")
will disable fwlog.txt logging of firewalled packets. Thanks to danny
for inspiration.

+ Straightened evaluation of which filter rules determine the class of a
connection. Now rules like -tcp-dport, etc. work as well. The third column
of a "cfo filter" output is 'c' for rules that set the class.

+ Added additional column with MSS to "cfo cons". It is included in
"cfo -speed", can be added with "-mss" option and has the column key 'm'
for -show, -addshow resp. -sort parameters.

Added additional columns for average tcp segment size (ass) to "cfo cons".
They are included in "cfo -speed", can be added with "-ass" option and have
the column keys 'a' for tx ass and 'A' for rx ass for -show, -addshow resp.
-sort parameters.

+ Now the class of UDP pseudo-connections is displayed, too, when you use
"cfo cons -class" or the "current connections" dialog.

+ Added global option 'relaxed_discr' to relax the check of discriminators of
Multilink-PPP (MPPP) bundles. It's set to 1 by default. With this option
on, only the class must match, not the whole discriminator.

+ Now you can display the class most packets of a TCP connection are classified
to (higher, high, default, low or lowest). Use "cfo cons -class" or -show:c,
-addshow:c or -sort:c options. See other "cons" or "-sort:" entries here
in whatsnew.txt for more details.

The "current connections" dialog show the class as well.

+ Added a proper "cfo cons -?" help screen.

+ New filter rules -tcp-seq and -tcp-cnt to match on bytes of sequence space
transmitted or number of packets in this connection, respectively. Thanks
to pogowurst for inspiration.

+ More changes in rx-shaping: cFos should now work much better with very
many connections, like with BitTorrent. Please report if it works for you!

+ Added an experimental new way to detect if cfosdnt.exe is running on "the"
console. cfosdnt.exe on "the" console is the one that e.g. loads
capi2032.dll and makes it available to kernelmode cfosnt.sys.

To use this alternative method, open cfos.ini and in section [cfos] set
new_console_detect=1. You need to restart cfosdnt.exe afterwards.

x Buttons in the icon skins where not working under Windows Vista. Fixed.

x Fixed a skin problem.

x Fixed warning that is displayed if too many connections cause rx-shaping
to be inefficient. It was displayed regardless of the number of
connections.

x Fixed a problem where downloads would be slowed too much. Thanks to FR.

x FTPS (FTP with SSL, FTP with TLS) command sessions are now identified
as FTPCMD in layer-7 detection. Thanks to ghorvath.

x Changing l7-protocol priority to "Normal" didn't work. Fixed.

x Fixed two possible causes for non-MSS aligned RWINs.

x Fixed problems with main_class display.

x Fixed a problem under Vista where skin settings would not be written to
disk after modification.

- Discontinued support of Windows 9x/Me and Windows NT 4.0. Now at least
Windows 2000 is required.

- FTPDATA protocol can now be set to high or higher priority, regardless of
its packet sizes.

- Removed tracing of minimal RTT ping packets.

- Module "ackfilter" is now disabled by default. Set "ackfilter=1" in
section [param] in cfos.ini to enable it again. This does only
switch off the filtering of presumably superfluous TCP ACKs, not the
regular priorisation of TCP ACKs.