ePipe Product Documentation: 2000 Family Performance Tuning

ePipe 2000 Family Additional Information

ePipe 2000 Family Performance Tuning

Internet Connections
Intelligent Internet Bonding (I2B)
Connection Bundles
End to End Bonding (E2B)
VPN Client (PPTP)

Performance Tuning

This document provides information that will help you to obtain the best possible performance from ePipe and your network.

Internet Connections

To ensure you obtain the best performance from dial-up internet connections:

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 available modems.
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.

Connection Bundles

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).

Filter troubleshooting:
If you suspect that your filters are preventing some network application from working, you can:
- Turn on detailed filter trace (see SET SERVER SYSLOG) and watch to see if the traffic generated by your application is being rejected, or
- Temporarily add a filter rule "* accept 0" to see if this remedies the problem (be sure to remove the rule and replace it with a more appropriate one when the test is completed as a "wide-open" rule is a serious security risk).
For critical VPN bundles choose a high number of dialer retries, and a low retry time, to reduce the risk that a temporary telecommunications failure will cause the VPN to go down due to too many retries.
You should adjust the number or retries and retry time on the bundle to best suit your particular application (espcially for ISDN as the defaults are choosen to be reasonable for modem configurations).
If your Bundle appears to have stopped it has most likely disabled due to too many retries. Check the status with the "Status-RAW Stats-Bundle" screen.

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 too often.
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 as "dynamic").

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 Transport.
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 latency connection.

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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