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If you spend any time on any of the various Mac OS X Administration - related mailing lists, you will soon see the question, "Is there anything like Citrix or Windows Terminal Server available for Mac OS X?" This question will get many responses, well thought out, and reasoned recommending Apple Remote Desktop, (ARD), Timbuktu Pro, VNC, or NetBoot. These response will tout the advantages and disadvantages of each, with firm technical arguments marshaled in support of their arguments. The problem is, the only correct answer to that question is: "No, there is currently nothing like Citrix or Windows Terminal Services for Mac OS X unless you mean a client for a Citrix or Windows Terminal Services server", although NetBoot comes the closest. Which is a real shame.

What Citrix/WTS do is give you X11 - like capabilities on Windows. In essence, they make Windows a true multi-user OS. Now, I can hear the flames starting now, so let me clarify. Windows supports multiple users. In the right configurations, thousands. But, we are talking about things like email, file/print services, application serving, even remote home directories. When you log into your Windows machine, without Citrix/WTS, you are logging into your local machine, which then may, (if you use roaming profiles), talk to the domain controller to authenticate you and connect to your home directory. Your home directory is then downloaded/synchronized to your local machine home directory and you work. When you log out, the local home is uploaded/synchronized to your network home directory. (This is how it works up through Windows 2000 to the best of my knowledge. If this is changed/fixed in 2003 server let me know. I don't care about Longhorn Server, it's still two years from being anything but ExpoWare.)

However, with Citrix/WTS, it's different. First, your local machine is only used to connect to the Citrix/WTS server, and provide minimal local services, such as input device, display, etc. Everything else happens on the server. You have your own user session on the server. You have remote home directories, but they stay on the server. Your applications run on the server. In other words, the box you are using locally is a terminal. (Hence the name, Windows Terminal Server) You are logged into the server and all your actions happen on the server. This can be done from almost any platform, be it the Mac OS, WIndows, *nix, etc. So with the former, you're simply using the server to get work done locally. With the latter, you're logged into the server, and that's where you do all your work.

This is analogous, although not a perfect comparison to using X11. (X11 does a lot more, but this type of use is a subset of what X11 is for.) It makes a Windows server a true multi-user server. In fact, Citrix started out to bring X11 - like functionality to OS/2, and later Windows. Versions of Citrix that ran on Windows 3.5.1 actually had a custom kernel, so it was more CitWin than Windows with Citrix. This means that you can have hundreds of users logged into a Citrix/WTS server or server farm, all with remote graphical displays all running off of the server (farm). The actual bandwidth used is quite small, to the point that you can, with minor tweaking, get a usable session over a dialup. (This is really handy for email and surfing from a hotel with only dialup. You run Citrix/WTS over dialup and use the faster connection at the server to do your email and web work. You end up working a LOT faster.)

In addition to not being bandwidth - intensive, Citrix/WTS support disconnected operation. When you end your Citrix/WTS session, you can do it two ways: Logout, or Disconnect. If you log out, the session is done, just like it is when you log out of a Mac OS X box. Your processes end, your session is terminated, your work on that server is done.

However, if you just disconnect, well, then everything you started continues to run. Disconnect from work, reconnect from home, and bang, you're right back where you were. It's ALMOST like Fast User Switching, only much cooler and better. So, you start a long process, like a Really Big Database Operation in Oracle at work. Ruh-roh, quitting time, and it's still running. Normally, you have to stay logged on to your box. But not if you run this in a Citrix/WTS session. Just disconnect, and go home. Now from home, connect via the VPN, (of course you use a VPN, because we're all thinking securely here), fire up your Citrix/WTS client and reconnect. BAM!, you're back watching your Really Big Database Operation in Oracle do its thing. It's been chugging away while you drove home, ate dinner, etc.

Disconnected.Operation.Rocks

You can also just publish applications so that your Citrix/WTS users don't get the full Windows desktop, but just specific applications. This is, BTW, a fantastic solution for Mac shops needing access to Windows vertical market applications. No need to buy PC hardware, and copies of windows. Just use Citrix/WTS, and publish the applications. Makes licensing a breeze.

What about Mac OS X ? This is all neat stuff, but don't we have this on Mac OS X already?

Well, no, no we don't.

NetBoot kind of comes close, but there's some things it doesn't support, and I triple dog - dare you to try NetBoot on a wonky modem line from a Motel 6. ARD, Timbuktu, and VNC are all remote control applications. They're designed to let one person remotely control one or more client boxes from a single station. They are not designed to allow multiple clients run interactive user sessions from a single machine. They're all fairly bandwidth intensive, although Timbuktu is better than most, having been around a verrrrrrrrrrrrry long time. They sort of support disconnected operations, in that, if no one else connects, or sits down at the console, the machine will be left in the state it was in when you disconnected. But that's not really the same as what Citrix/WTS do.

So there's nothing like Citrix/WTS on Mac OS X. (Ironically, Citrix does have its Metaframe server ported to Solaris, and HP-UX, so you can use a single client to talk to Windows Servers, or Unix servers, and the client side is tons simpler to set up than X11.) This is a shame, because giving Mac OS X this capability would really help sell things like Mac OS X Server, Xserves and Xserve RAIDS.

For example, if you have a school with older macs that can't afford to upgrade the clients AND the servers, but can do one, then, with Citrix/WTS capabilities, they could get an Xserve, and turn even ancient Macs into clients. That way, they'd be able to phase in Mac OS X clients in a way that was less abusive to their budgets. If you have a lab full of windows machines, and you wanted to use iMovie and iDVD to teach the basics of Video production, then with Citrix/WTS services, you could buy a set of Xserves and Xserve RAIDs, put a MacTerminalServices client on the lab machines, and bang! you're running. You'd still have limits on burning DVDs, but that's hardware. If you put burners in the Xserves, then you could get around that somewhat.

It would be great for FCP jockeys, Maya Jockeys, etc. With FCP, once you have all the footage moved from tape to disk, you could run FCP on some big, fat G5 Xserves via the MacTerminalServices client from almost anything. Got a 24 hour render job? Go home. Log in here and there and check on it. It'll run, and you don't have to leave your main machine on.

What's nice is that it allows you to have longer client upgrade cycles. (Yes, obviously a single server won't support 200 FCP jockeys. But there's this concept of load balancing, and this thing called a server farm that can help you with that.) Citrix/WTS capabilities in Mac OS X and Mac OS X Server would greatly expand the platform, and give companies that are considering the platform another reason to write the check for it. It could also be a HUGE push of Xserve and Xserve RAID sales as well. I know when I'm at this year's WWDC, I'm going to prod quite a few people about it.

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