Last year a large number of users with older Macintosh computers suddenly called Microcomputer Services to complain that their Internet connectivity had stopped working.
Upon further investigation, we found that older Macs running system software prior to 7.6, and using Apple's classic networking called "MacTCP," failed to connect to most Internet sites outside the UO. We later discovered that one of our upstream Internet providers had enabled a feature called "Type of Service," which causes problems for older Macs. Unfortunately, this feature is required for services like voice over IP (using the Internet to make phone calls) and for wide-area traffic shaping.
As time passes, few Internet providers will be able to accommodate older Macs, and Apple does not intend to update the older Macintosh system and networking software. The bottom line is that Mac users must upgrade to System 7.6 or higher to continue interruption-free access to the Internet through the UO--and in the long term, from any provider.
We recommend users with 24Mb or more memory upgrade to MacOS 8.1 or higher, and those with less than 24Mb upgrade to 7.6.1 or higher.