LANs in office networks were certainly entirely mainstream in the first half of the 1990s. When I started my first job in London in 1991, we had just one client who _didn't_ have an office network. That was considered unusual but it was an intentional management decision, intended to slow the possible spread of malware and increase real-life face-to-face staff communication.

What wasn't mainstream was them being based on TCP/IP.

These days, networking and TCP/IP seem synonymous, but that's just how it happens to be this century. Networking, mostly over Ethernet, initially Thin Ethernet (10base-2), in wide use as a common office tool predated the rise of TCP/IP by a good 15 years or so. Some early adopters were using it 20+ years earlier.

Network protocols then were a bit like OSes are now. Many people use Windows but lots use Macs, some use *BSD, a few still use commercial UNIX, etc., and there are things like ChromeOS, thin clients over RDP, and stuff. It's not at all homogenous and it's hard to even say there's a clear majority for any one OS: Windows has the edge, but not by a lot any more.

Well, in the era of MS-DOS, Novell was the server OS of choice for almost everyone, with rivalry from 3Com and its 3+Share MS-DOS-based server OS; 3+Share was related to MS LAN Manager, which was in OS/2 and led to 3+Open. They all used NetBEUI. LAN Manager also ran on VMS thanks to DEC Pathworks, running over DECnet, which was handy because it also supported terminal sessions -- remember, this is before SSH -- and X.11 and DEC email and more.

Focussing on big businesses was Banyan VINES, with its own protocol derived from Xerox's Alto and so on. This had the first network directory. Novell designed Netware 4, with NDS, as a direct response to Banyan's StreetTalk, and in the NT 3.x era it kicked Microsoft's behind in the market; the tide only turned with NT 4.

Speaking of big enterprises, email was common long before LANs or TCP/IP. All big DEC users and IBM users had those companies' email systems. Small firms used dial-up to pre-Internet service providers -- I used CIX, which dominated in Britain. My 1991 CIX email address is still live and still works. Americans favoured CompuServe, AKA Compu$erve, but it was too expensive in Europe where we pay for local calls too.

This stuff is, ballpark, a quarter of a century older than TCP/IP and Internet-based networking. And given that that is only about 25 years old, what I am saying is that widespread LAN use didn't begin with Win98.

At the time, Win98 wasn't even a blip; it was nicknamed "GameOS" in enterprise IT circles and few companies even considered it. NT 4 was where it was at, and it launched with full TCP/IP support two whole years before Win98.

So no, Win98's networking didn't begin anything at all. It wasn't significant in any way, then or now. Win98 was a home OS for standalone PCs with dial-up, but it merely took over from Win95 which created that market.

The rise of TCP networking in business LANs arguably began with Windows NT, but NT 3.x wasn't very significant, and NT itself arrived about half way through the lifetime of business use of machine-to-machine communications, email, groupware, etc. from its beginning to now.

If you want to argue that integrated networking in Windows was a significant turn, that I won't argue with. But it began 5 years before Win98, with Windows for Workgroups and Windows NT.

The fact that _now_ it looks big and significant that it's when TCP/IP became the default is an emergent artifact of the current focus on IP. It wasn't at the time.

Email is a 1960s thing. The Internet started to become significant in the 1970s, long after email. Corporate LANs rose in prominence in the 1980s and by the 1990s were almost a given. Macintosh-based companies (mostly in design, print, repro etc.) did direct peer-to-peer comms over ISDN.

In the 1990s, for most people, TCP/IP only ran over dial-up modem connections, and it was contemporaneous with the industry moving to 10base-T: Ethernet over UTP replacing Ethernet over Coax.

For a time, the obvious successor to 10base-T looked to be ATM, which is a protocol at well as a cabling system; TCP/IP had to be tunnelled over ATM, but it looked clear for a while that ATM was the future. 100base-T (Fast Ethernet) was just one contender among several.

But actually, as it happened, TCP/IP rose vastly in importance, and networking switched to 100base-T and then wifi.

LANs switched to IP in the 21st century but they were a roughly 20-year-old, established, totally normal technology then.