ePipe 2000 Family Additional Information
ePipe 2000 Family Performance Tuning
This document provides information that will help you to obtain
the best possible performance from ePipe and your network.
To ensure you obtain the best performance from dial-up internet
- Ensure that data compression and error correction are turned on in your
modem (refer to your modem manual).
- Ensure the serial port to which the modem is attached is set to a speed
faster than your modem's top speed. If your modem has compression enabled,
set the serial port at least twice as fast as the modem's top speed.
- Set serial ports to 8 data bits, No parity, 1 stop bit.
Finer points of 56k modems.
The so-called "56kbps" modems only achieve 56k when dialled in to special
digital equipment at an ISP. Even then, the 56k data rate applies only in
the "downstream" direction, that is, from the ISP to the client. In other
cases (upstream, or when a 56k modem dials another 56k modem) the maximum
possible data rate is 33.6 kbps. Note also, that the stated speed of a modem
is only the maximum possible speed, and that the actual speed achieved may
be considerably lower due to problems related to line quality and distance
from the local exchange. It is not uncommon for modems to be limited to speeds
as low as 24kbps due to poor quality telephone lines. In some rural areas,
lines can be so bad that even 10kbps is unlikely. The speed achieved by a
modem connection can vary from time to time, even from the same location.
When a modem is connected, you can use the ePipe WWW status report to show
the true speed at which the connection was established. The console commands
SHOW INTERNET DOD and SHOW PORT x STATUS also
display the actual modem speed.
Intelligent Internet Bonding (I2B)
I2B operates by intercepting each HTTP connection, and rerouting it over a specific
modem link. Thus the time taken to downloading a single large file cannot be
improved by I2B. However, the time taken to download the average WWW page will
be improved greatly, as most WWW pages consist of multiple files---one HTML
file per frame, plus all the images, animations and Java applets. Here are some
things you can do to get the best results with I2B:
- Configure your WWW browser to use multiple simultaneous connections. Many
WWW browsers do this by default (Netscape Navigator often uses four connections.
Microsoft Internet Explorer seems to only use two much of the time.).
- Ensure that your modems are set up to report DCE speed on connection,
not the DTE speed (see your modem manual, particularly with respect to the
"ATWx" command). If your ePipe has accurate knowledge of the speed of each
modem connection, it can more efficiently share new connections across the
- Use a local caching proxy server. If you have a proxy server on your local
network, ensure clients use it. The proxy server can maintain a large cache
of files, and connections from the proxy server to the internet will be
shared across available modems just as simply and automatically as connections
from a desktop WWW browser.
Some hints on effective configuration of dial-on-demand bundles
- Analog modems take some time to establish connections (dialling time,
ring time, negotiation time, PPP setup etc.). This time delay should be
kept in mind when tuning the Bandwidth-On-Demand settings, in particular
UPPER TIMEBASE and LOWER TIMEBASE.
- If you have problems with intermittent unsuccessful modem connections,
pay attention to the TIMEOUT setting in the chat script. Remember that it
can sometimes take a long time for modems to connect under adverse condtions
(as long as 60 seconds).
- If you have a line with a fixed IP-address, then this is the best choice
to be marked as the Default-Route.
- Use the minimum number of filter rules needed for your environment. The
filter wizard is the best way to create your starting filter set, as this
is a complex subject.
- Choose reasonable up-times for Dial-on-Demand filter rules. As for timeout
choice, start with liberal values and tune by experimentation.
- When using dial-up lines, start with 5 minutes, or a value slightly
shorter than the telecommunications provider's time-charging interval.
- When using time-charged ISDN, choose rather short up-time values.
- When using un-timed local calls and flat-rate ISP connections, you
can use long up-times. If you have a "semi-permanent" connection mark
all lines as static (which will keep all connections up all the time).
Getting the most from ePipe's Bandwidth-on-Demand features
- Choosing a the UPPER THRESHOLD parameter: due to protocol
overhead and line quality concerns it is unlikely that any modem line will
ever achieve full (100%) utilization. When choosing the utilization threshold
that triggers addition of another dial-up line, a value in the range of
50-80 percent is most appropriate.
- Choosing the LOWER THRESHOLD parameter: choose a value in
the range of 20-30 percent. A higher value may result in lines being dropped
- The best way to fine-tune your bandwidth limits is by experimentation.
Start with liberal settings (say UT=50, LT=20), and observe the behaviour.
- To test your maximum achievable bandwidth, temporarily mark all lines
as "static" (causing them to be dialled immediately until disabled or re-configured
End-to-End Bonding (E2B)
Some hints on tuning E2B parameters.
- For VPNs with 1 or 2 lines, use a fragment length (fraglen) of 1428 bytes
(this is the optimal value for this situation).
- If IPSEC transport performance is poor, consider switching to E2B TCP
- Pay close attention to modem quality---not all modems are created equal.
If a poor quality or damaged modem is causing packet loss, the performance
of your network will undoubtedly suffer.
- To get the best performance in a VPN situation, consider a many-to-one
configuration---i.e. VPN clients (eg. branch offices) have several modem
or ISDN links, VPN servers (eg. head office) have a single high-speed, low
VPN Client (PPTP)
- As noted above, use quality modems, and attempt to rectify packet loss
due to modem or line quality issues.
- Remember that 56k modems are only 56k downstream (from ISP to modem).
If the VPN server uses 56k modems, one client performing a download with
one 56k modem can possibly saturate two 56k modems at the server,
as they only achieve (a maximum of) 33.6kbps in the "upstream" direction.
Plan your modem acquisition appropriately (or use a dedicated internet connection
at the server end).
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