How does Traffic Shaping work?
cFos Traffic Shaping reduces delays during data transfer and allows you
to surf the Internet up to three times faster. So you can use the full
bandwidth of your connection!
During TCP/IP transfer, a certain amount of data needs to be confirmed
upon reception before more can be sent. Stalling data confirmation
results in delays and transfer-rate slowdowns, thus forcing the sender
to wait. Especially for DSL and cable, it is possible to slow a
download to a crawl by choking the upstream channel (which has the
smaller bandwidth anyway) with an upload. This is because in such a
scenario there is not enough upstream bandwidth left for data
confirmation.
The standard solution so far has been to try and compensate for this by
increasing TCP window size, thereby allowing more data to be sent
without immediate confirmation. The main problem here is that this also
leads to high ping times (latency) and significant delays during
Webpage rendering. Latency of up to 2 seconds is not uncommon for TCP
windows with a size of 64k. In short, huge window sizes just won´t let
you achieve full download speed.
By contrast, cFos Traffic Shaping prioritizes data traffic in such a
fashion that important packets zip past regular packets. This way,
receipts always arrive in time, and uploads won't ever choke your
broadband connection again!
cFos Traffic-Shaping technology recognizes a number of important packet
types and prioritizes them not only to keep Internet traffic running
smoothly but also to ensure particularly low ping times. This not only
accelerates surfing and download speeds significantly, but it is also a
decisive advantage for online gaming.
With cFos Traffic Shaping, you will notice measurable improvements and benefits like:
* Full download rate during upload
* Consistently quick response time while surfing the Web or running other applications
* Improved VoIP speech quality
High speed, low ping
Without Traffic Shaping, ping times can easily reach a horrific 2
seconds, which will make participating in Telnet or SSH sessions a
chore if not outright impossible. But with cFos Traffic Shaping,
latency remains normal.
This alone should make for a totally new surfing experience!
It also means that while surfing the Web, you will be hard-pressed to
even notice that there are any data transfers running in the
background. Again, such drastically reduced latency will come in
especially handy for online gaming.
First, cFos Traffic Shaping measures upstream and downstream rates as
well as ping delays for each Internet connection. It then uses this
information to control the scheduling of all Internet data transfer. In
addition, Traffic Shaping does assign the available bandwidth
dynamically to each individual connection as needed.
Not only does cFos Traffic Shaping prioritize ACKs, but also other
important packets like those used for Telnet and SSH. Thus, with cFos
Traffic Shaping, filesharing programs or mail uploads choking your
connection will finally be a thing of the past!
But don't take our word for it; just see for yourself.
What else does Traffic Shaping do?
Besides prioritizing ACK packets, Traffic Shaping performs or lets you perform the following:
* RX Shaping
ensures ping times remain low even during downloads, while keeping one download from choking other simultaneous downloads.
* ACK-Filter
optimizes TCP/IP acknowledgements, thus making more bandwidth available in the upstream channel.
* Prioritizing individual programs
like games while assigning lower priority to others is especially
useful when trying to reserve some extra bandwidth for important
applications.
* Voice over IP (VoiP) speech quality
is improved by recognition and prioritization of RTP packets.
* Prioritizing other protocols through layer-7 analysis,
like HTTP, FTP, POP3, SMTP, ICMP, SSH, Telnet, and DNS can be done using built-in, programmable filtering rules.
Test it on your own!
First, keep in mind that tests with just one upload or download can
only measure your connection's maximum up or downstream transfer rate.
That is why you will need to generate at least two simultaneous data
streams to gauge the effect of cFos Traffic Shaping:
Both cFos and cFosSpeed will calibrate themselves with respect to the
connection. This means best results are usually achieved after having
used those programs for several days, during which you should run as
many uploads and downloads as possible at full speed.
Now send yourself an e-mail with an attachment of at least 5 MB. On a
standard connection, this should give you about 5 minutes you can use
for measuring. For each test, you should flush your browser cache and
keep track of the loading times for your Web sites. All tests should be
repeated several times for maximum accuracy.
For instance, during one upload and one download, a "typical" DSL
connection of 768 kbit/s should reach a download rate of about 87
kbytes/s and an upstream rate of roughly 16 kbytes/s. 11.5 kbytes/s of
the latter are available for uploads, while the remaining 4.5 kbytes/s
are used to handle data confirmation for the download session.
One easy and accurate way to keep track of ping times is to use our hrPing freeware utility.
What alternative Internet tuning methods are there?
Broadband users in particular want to get the absolute max out of their
connection. But even narrowband users may benefit from Internet tuning
on their low-speed connections.
What tuning methods are there?
Registry-Tweaks
An entire line of so-called "registry-tweak" programs has sprung up
based on the assumption that changing various Internet protocol
parameters may boost data-transfer speed. In essence, what such
programs do is simply change the values of certain parameters rather
than have the user edit the corresponding registry entries manually.
Typically, the following parameters are thus adjusted:
* MTU/MSS:
Transmission of each packet entails a certain packet overhead, which is
always the same - regardless of what size the transmitted packet may
be. Thus, sending out packets that are as large as possible would seem
to be one probable way to cut back on overall overhead. For instance, a
TCP/IP packet sent via DSL/PPPoE has an overhead of 48 bytes (i.e.,
almost 10 percent for a 500-byte packet). If no value for Maximum
Transfer/Transmission Unit (MTU) is specified in the registry, TCP will
determine packet size itself through a process called "Path MTU
Discovery." It will do so in such a manner that packets sent will
always be of the largest size that can still be handled by all
intervening transmission nodes. For DSL/PPPoE, maximum MTU is 1,492
bytes, which corresponds to an overhead of approximately 3 percent.
This value really doesn't need to be set, since Windows already
maximizes it through Path MTU Discovery. MSS usually equals MTU-40.
* TcpWindowSize:
This parameter controls the maximum number of bytes the remote TCP may
send before an acknowledgment must be received. Lacking such
acknowledgment, the sender is forced to wait, thus resulting in
dramatic drops in transfer rate. Unless the user specifies otherwise,
Windows determines the value for this parameter based on packet size
(12 * MSS). The greater the latency, the larger the TcpWindowSize needs
to be to avoid having the sender wait. Thus, assuming a connection
speed of 1,024 kbit/s and 150ms of ping time to server, TcpWindowSize
must at least be 2,000 bytes. Should further delays occur, even that
wouldn't suffice anymore. This is why a lot of tuning programs tend to
jack TcpWindowSize up inordinately. The problem is that while running
an upload, the upload competes with acknowledgments for available
bandwidth, meaning the transfer rate will plummet nevertheless.
Furthermore, huge TcpWindowSize does also increase latency, which can
quickly turn VoIP or online gaming into an exercise in frustration. For
instance, at a TcpWindowSize of 64k or higher, latency will rise to
more than 400ms, which is absolutely unacceptable for VoIP.
* TTL:
This value indicates how often any given packet may be passed on from
node to node until it reaches its destination. Changing this value has
no appreciable effect whatsoever on transfer speed. Can you spell
"placebo software?"
Traffic Shaping
So, in a nutshell, some registry tweaks may sometimes yield greater
speed (though often at the cost of significantly higher latency).
Traffic Shaping is then the next logical step in improving
data-transfer speed without sacrificing performance elsewhere. It works
by sorting data packets according to importance prior to sending them,
thereby ensuring all time-critical data are being sent out first. TCP
acknowledgments, for example, are highly prioritized so that they are
always received in time, which means download data can be transmitted
without interruption.
However, the more data are transmitted simultaneously, the more data
congestion will likely occur. Therefore, effective Traffic Shaping
should ensure not too much data are being sent simultaneously, as this
also tends to affect ping times and VoIP speech quality. The more
protocols Traffic Shaping can distinguish, the more responsively a
system will perform while multiple applications are being run on it at
the same time. For instance, Traffic Shaping can be used to accelerate
surfing speed by having the corresponding DNS requests prioritized. FTP
command, Telnet, SSH and similar protocols can also be prioritized in
this fashion.
Since Traffic Shaping boosts transfer rates by reducing latency, it
does yield higher speed irrespective of how much bandwidth may be
available. This is especially valuable seeing how latency problems
during simultaneous use of multiple Internet connections cannot be
compensated for by additional bandwidth.
ACK filtering
During each download, acknowledgments take up about 5 percent of the
available download bandwidth in upstream direction. The problem here is
that upstream bandwidth is much lower than downstream bandwidth for
ADSL and broadband cable. This also means there may not be enough
upload bandwidth left to achieve full download speed, not to mention
that it is always desirable to have some upstream bandwidth available
for other uses. For this reason, ACK filtering reduces the size of
acknowledgment packets as much as possible without decreasing download
rates. In this manner, the bandwidth needed for handling
acknowledgments can often be cut in half.
Data compression
It is always nice to be able to compress user and/or protocol data. For
Web servers, so-called "GZIP compression" lends itself particularly
well to this. With it, the text on Web pages can be compressed to about
half the original size prior to transmission. Leading Web browsers like
the Internet Explorer or Mozilla Firefox do support GZIP compression.
The Web server is also smart enough to send uncompressed data instead
when dealing with old browsers that do not support GZIP. Therefore,
there is to our knowledge no drawback to using GZIP. Unfortunately, it
can only be activated by a Web server's administrator.
Modems and ISDN make use of V.42bis and Stac data compression,
respectively. Both reduce the amount of text data transmitted between
dial-in node and modem or ISDN board by roughly one half. Thus, these
compression methods could conceivably double transfer speed in both
direction for types of data (like text) that can be compressed well.
But because image files account for most of the data servers must
transmit for today's Web sites, our experience has generally been that
this kind of compression makes very little difference. The same is true
if a server is sending data already compressed in GZIP format.
In contrast, VJ compression (also known as IP-header compression) does
not minimize the size of user data but only that of protocol data.
Assuming a standard narrowband packet size of 576 bytes, this can
effectively cut TCP/IP header size from 40 to 3 bytes, resulting in a
reduction of packet overhead from approximately 7 to 0.5 percent. While
this is of great interest for low-speed modem and ISDN connections, it
is very rarely if ever used for broadband connections. DSL and cable
providers would much rather sell their clients more bandwidth.
Download accelerator
Many servers permit downloads at no more than a predefined maximum
download rate. The idea behind most download accelerators is to
circumvent this by downloading a file in several segments at the same
time through multiple connections to the same server. This does indeed
often lead to higher download rates.
Web accelerator
The ability to use cell phones for wireless (yet typically very slow)
Internet access has dramatically increased the demand for having
Web-page data compressed prior to transmission. Such precompression
might also be useful for modem or ISDN connections. Providers of Web
accelerator software maintain their own servers with broadband
connections to the Internet. These are needed to first load the desired
data, compress it, and then send it through the bottleneck of the
modem, ISDN or radio-network connection.
But due to the large image files involved, the gain thus yielded by
conventional compression methods can only be marginal at best. This is
why more and more Web accelerators have begun to manipulate image data
as well. To make some headway there, images are usually reduced in
color depth and resolution. Given the small size of their displays,
this poses little if any problem with respect to cell phones. But on
desktop computers it may well result in a clearly discernible loss in
quality for desktop applications.
Installation of the respective browser add-on is required for using the
services of a Web accelerator - as is in most cases payment of a
monthly fee or surcharge. Using web accelerators does yield little
appreciable gain in speed on broadband connections. Countervailing this
is a possible increase in latency, since the Web accelerator is
interposed between server and client.
Faster Connection
Switching to a rate plan that gives you higher connection speed is
still the safest way to improve bandwidth and thus achieve better data
transmission rates. This as such won?t improve ping times though. And
neither will it prevent downloads from slowing dramatically, even
stalling altogether, when data is being uploaded at the same time.
That?s why it is ideal to combine any bandwidth upgrade with Traffic
Shaping technology.
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