My Throughput Check (Updated 19-Nov-99)
CURRENT FINDINGS: The Lucent LT Win Modem gives me far better performance than my USR External Faxmodem (1786-02 with 5.0.0 firmware), even though the USR reports a higher connect rate.
A lower connect rate on a Lucent modem gives better throughput to 3Com server modems than a higher connect rate with a 3Com modem!
I get better throughput calling the 'poorer' of my ISP's access numbers! (The 'Super POP' CLEC-provided number, adding RBS impairments and a lower connect rate gives better performance than the ILEC-provided number to 3Com Total Control Access Equipment.)
ILEC (GTE)-provided access number - physically located in Hilo; ISP - Shaka.com has 3Com Total Control access equipment connected via frame relay data-line to server in Honolulu. Call encounters no RBS links and a 3db digital pad.
3Com Modem gets a CONNECT rate of 49.3k on every call; peak speed at end of call usually reported at 50666. Modem will usually retrain within the first 5 minutes of connection. Throughput for the first several minutes may be very poor - even after initial retrain. Testing done after the modem has "warmed up". Final rate usually 49333. Throughput average - approx. 4400 bytes/second - equivalent to a 39kbps true connect rate.
Lucent Modem (with 5.54 firmware) gets a CONNECT rate of 48-49.3k on every call. It will retrain on every call down to a rate of 46.6k, so I limit the maximum connect rate to 46.6k. If the CONNECT isn't limited, initial throughput will be poor as the modem will retrain within the first 60 seconds. With CONNECT limited at 46.6k, initial throughput is as good as final throughput. Throughput average - approx. 4800 bytes/sec, equivalent to a 43kbps true connect rate.
CLEC (GST)-provided access number - Hilo 'virtual' number - the call is passed to CLEC facilities in Hilo. The digital telco facilities have recently been upgraded eliminating RBS links. The call encounters a 6db digital pad; the call effectively goes 'long-distance' to Honolulu to 3Com Total Control Access Equipment.
3Com Modem gets a CONNECT rate of 48k on most calls; Will usually retrain within the first 5 minutes of connection. Peak rate will usually be 50666, and final rate 46.6-49.3k. The modem has initially poor throughput as described previously. Testing done after "warm-up". Throughput average - approx. 4500 bytes/second - equivalent to a 40kbps true connect rate.
Lucent Modem gets a reliable connection with the rate limited to 46.6k. Throughput average - approx. 4900 bytes/sec, equivalent to a 44kbps true connect rate.
HOW I'M TESTING - I've put a 1.1mb file on my personal space at my ISP's Honolulu server. Running only CuteFTP, I download the file and record the throughput. As of 13-Nov-99, I've made over 10 calls with each modem to each line on different days and times, and timed the download at least 2 times on each call. I'm continuing to test - and will be adding the Courier v.Everything external, as well as the result of Limiting the Connect Speed on the 3Com. I'll also be doing some testing of the upstream throughput.
YOUR RESULTS MAY VARY - The combination of your modem, firmware revision, extra init strings, telephone facilities, and server access equipment and firmware may produce different results.