Interleaving is forward error correction. Your packet bits are spread in time and interleaved with bits from other packets, so that a noise spike has less chance of causing data loss. This is a design feature, which makes video streaming (a la "video on demand) more robust. Remember that ADSL was originally developed for "cable TV on copper loops" but when that didn't take off it was (is) used for highspeed Internet access. TCP/IP has it's own error correcting facilities and interleaving is not nearly as important. Fast Path disables or greatly reduces the interleaving "spread" of the bits.

Decreased latency (ping times) can improve performance of streaming content and makes browsing snappier. It can also help with FTP and other densely packed file transfer protocols. Low pings are critical for online gaming.

If you changed over, you probably would not see any problems unless your line is marginal. TCP/IP retransmits packets, which are corrupted and unless your line has high packet loss, can handle the occasional noise burst quite nicely. If you have a very noisy line your modem could lose sync, which is not good at all. This is unlikely.

FAQ by kadar