Comment by belthesar

With my v.92 soft modem, I was able to regularly connect at 48k, and sometimes 53.3k. I never connected at theoretical max of 56k.

Worthwhile to also mention that ISDN was full duplex, instead of half-duplex like dialup. The modems on either end would need to time-slice to allow bi-directional communication, which in a TCP laden world like the web meant that every interaction was orders of magnitude more latent than on ISDN, in which you had symmetrical, full-duplex 56k of bandwidth between you and the ISDN modem. That's the biggest reason why you had a significant decrease in latency.