When it comes - as it must - it'll be ugly. It will be a long drawn-out, knockdown battle between the two biggest bruisers in town. The fight of the century - and it's coming soon, to your IT department.
In the red corner: Microsoft - the company with the avowed intention of taking over the world, whatever the Department of Justice and Judge Penfield Jackson might say. In the blue corner: Cisco - the other company vying for world domination.
For now, the two are allies. Uneasy allies, but allies nonetheless. They co-operate at every level, and particularly in products such as Microsoft's Active Directory.
Publicly, Cisco stresses the partnership aspects of the relationship.
Privately, it will let no opportunity to disparage Microsoft pass - a sign of the tensions to come.
How the companies converge
While the two companies remain in completely different markets, there seems little likelihood of friction. But that will change as the strategies of the two companies move closer together over the next two to five years.
It will work like this. Cisco has two main planks to its overall corporate strategy. The first is to make Internet Protocol (IP) pervasive, not just for the transmission of data, but for voice and video as well.
The company is pushing IP telephones out of the door as fast as it can - 50,000 last year, 10 times that number this year. It is promoting IP everywhere - on the largest scale with the telcos and into niches such as storage area networks, where the company is trying to straight-arm the incumbents into accepting a Cisco-driven, IP standard.
The second strand of the strategy emerged last month when Cisco pulled together the works of three software companies it had purchased into the Internet Communications Software Group.
That group has a five-point plan to develop a standards-based software architecture - a Cisco standard but open to the industry - for linking every kind of device to every kind of distributed application. It is designed to enable application developers to put together applications that can be accessed by everything from a telephone to a PC, without the requirement for the application to have awareness of what kind of device is accessing it.
Ambitious? Absolutely. That puts it squarely in competition with Microsoft and Sun Microsystems.
The first two of the five points - IP messaging services and IP communications services - are already in place. The next two - applications and content services, and transactions services - will be available "within a year", Cisco says. The fifth, independent software vendor application development services, will follow.
A complete architecture for developing completely distributed applications will be up and running within two years.
The impact on Microsoft
Microsoft will not be best pleased with this. For the Redmond company, the most pressing problem is where to go from Windows NT. An increasing number of disparate devices - phones, personal digital assistants, set-top boxes, and the rest - are used for tasks that for a long time were only possible with computers, usually running Microsoft software. But the new devices are starting to seriously encroach on Microsoft's business.
The company will then be faced with owning an industry standard that gradually becomes less and less relevant. Some analysts believe this is already happening.
Essentially, if Cisco is successful, the important standard moves one step away from the device and onto the network. The communications software infrastructure is the only standard that will matter, and Cisco will want to own that standard.
Microsoft will want to own it too, but its approach is from the opposite direction - making a standard across all the devices from telephones to servers.
As the head of Cisco's ICSG, Eugene Lee, puts it: "Microsoft is a partner so we don't compete, but if you think that Microsoft is the sort of company that wants to own the industry standards, then yes, you can see that we will compete."
As Cisco moves up from the network, and Microsoft moves down from the desktop, there is going to be an almighty collision. It will be the biggest battle of the campuses - Redmond versus San Jose.
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