AOL dominates the instant message market but is blocking rivals' attempts to send messages to its tens of millions of users, writes Jack Schofield

You can phone anyone you like, if they have a phone. You can e-mail anyone with an e-mail address, or send a letter to anyone with a postal address. But you can't send an instant message to anyone who uses instant messaging, especially if they use AOL's Instant Messenger (AIM).

For the past three years, the company that dominates the market has been intermittently blocking its rivals' attempts to send messages to its tens of millions of users. Last month, AOL more or less thumbed its nose at the American government. It said in a filing that technical difficulties meant it would try alternative approaches to the server-to-server links stipulated by the Federal Communications Commission when it allowed AOL to take over CNN Time Warner.

AOL now thought gateways "would require further significant expenditures of time and resources to develop". Boiled down to the bones, AOL's position is that it is not worth giving up any of the speed, privacy or security features enjoyed by the majority to provide interoperability for a minority who could simply download the AIM software (free) to send their messages (also free).

That may limit consumer choice, but AOL is keen to do deals, and Apple has just unveiled iChat software that can replace AOL's client software on Macs. However, companies that won't play by AOL's rules, such as Microsoft, Yahoo, Odigo and Trillian, have had messages blocked.

This has infuriated users and turned Trillian's authors, Mr Scott Werndorfer and Mr Kevin Kurtz, into folk heroes. They recognised that users did not want to download separate messaging programs to send instant messages to people using AIM, ICQ, Microsoft Messenger, Yahoo Messenger or the internet's system, IRC (Internet Relay Chat), so they created Trillian to work with all of them. It's convenient, it's free and it isn't even adware.

Users seem to love it. AOL doesn't love it, because its users are typing their AIM names and passwords into someone else's software, which it says could compromise security.

Also, since Trillian (Cerulean Studios) does not provide its own servers and network, critics say it is getting a free ride. Mr Werndorfer says: "We view ourselves as a bridge solution to the ultimate goal of server-based interoperability, \ will require more technical work and more inter-company collaboration before it becomes a reality. In the meantime, products like Trillian help consumers combine the instant messaging services now."

But Mr Rob Batchelder, a research director with Gartner in the US, says bluntly: "Trillian has no right to send its traffic over AOL's network without AOL's permission, and unpleasant as it may be, it's perfectly within AOL's rights to block them. They've built a large network, which costs money to run and, quite legitimately, they don't feel compelled to share that asset with their competitors. Trillian is trying to get something for nothing."

Mr Batchelder, who used to run an internet service provider, also supports AOL's position on server-to-server connections, which, he says, have fundamental problems. "If you stick gateways in the middle of a network, you degrade its performance so that in some instances, instant messaging becomes no better than e-mail. Gartner's position is that gateways probably are not the solution to interoperability."

Gateways are a way of connecting incompatible networks by translating between their different sets of protocols. It wouldn't be such a problem if almost everyone used the same protocols, and standards are coming into use. The best known are the Internet Engineering Task Force's (IETF's) SIP (Session Internet Protocol), widely used by phone companies, and Simple (SIP for Instant Messaging and Presence Leverage). Microsoft has contributed to the Simple standard, and has based the Windows Messenger built into Windows XP on SIP.

Unfortunately, this was the type of gateway AOL prototyped to test interoperability with IBM's Sametime system, and now regards as unsatisfactory. Although it may look like a proprietary supplier balking at standards, AOL does have a point. Mr Derek Atkins, president of IHTFP Consulting and co-chair of the IETF's Instant Messaging and Presence Protocol working group, said the group still needed "closure" on some issues, including security, and that while it could provide interoperability if everyone used it, not everyone believed in the SIP model.

The IETF's instant messaging "design contest" had failed to come up with a single standard, he said, and efforts had been split into three subgroups: Simple, Apex (Application Exchange Core) and Prim (Presence and Instant Messaging protocol).

But if you can't connect your client software to AOL's network, and you can't connect your network to AOL's network, that just leaves AOL dominating the market. When instant messaging was mostly teenagers chatting, hardly anyone cared about that. Things are different now the market is exploding - Gartner reckons instant messaging will be bigger than e-mail - and people think there could be money in it.

Instant messaging is penetrating the business market, and companies need much more sophisticated systems than AOL provides. For example, traders discussing share purchases want their messages encrypted so they cannot be read if intercepted. They want messages logged to provide audit trails.

Software developers are free to write for Windows Messenger or AOL or both, so Microsoft's strategy is to make it easier for them to write more exciting applications for Windows Messenger. Users will follow.

With Microsoft and AOL already competing in portals (Microsoft has MSN) and browsers (AOL owns Netscape), instant messaging looks like another battle between Tweedledum and Tweedledee over a nice new rattle. But there are alternatives emerging from the free software movement based around GNU/Linux, and one that has come to the fore over the past year is a peer-to-peer system called Jabber.

Mr Peter Saint-Andre, executive director of the Jabber Software Foundation, says: "A lot of people don't really want their identity to be wrapped up in AOL or MSN, and part of what Jabber does is that you can run your own server for your own community. It's a grassroots, bottom-up approach, like the weblogging phenomenon."

So at the moment we have a stand-off between the usual parties: a dominant proprietary supplier, a group of rivals trying to displace it by backing an IETF standard, and a grassroots, peer-to-peer approach that could subvert both. As with early phone networks and incompatible e-mail systems, the battle should lead eventually to the sort of interoperable network users want.

"But how you get there from here is still very much a muddle," says Mr Batchelder. "In the long run, it's going to be very exciting, but in the short run, it's anarchy. It's a street riot."