So we have covered a teeny bit of DEC VAX, and a little of this new fangled world of IP, why not drop back again in to a world of the past and talk about IPX?

For those that don’t know, before IP really took over there was a bit of a battle going on between Microsoft and Novell in the application/server space with a resultant impact on networking – Microsoft saying you should run IP and Novell saying IPX/SPX. Unix, yes, was all IP yet was limited in deployment. IBM were very keen on something called SNA at the time. If ever a paragraph was written that would inflame technical people on that Internet, that was it. Sorry, I’m summarising badly. Fortunately this is a book, so flaming capability is limited.

IPX in itself held some rarely appreciated beauty in it’s design. It had a built in equivalent of DHCP without needing a centralised server to provide addressing. Your address was a combination of your MAC address and your network address, allowing routers to route to the network and switches to switch by examining specific parts of the frame or packet as appropriate. All without anything happening, addressing by turning on a machine. Magic if you will. What could go wrong?

As it turns out, quite a lot. When dealing with remote access, it turned out more things could go wrong than expected but I learnt a huge lesson.

In this new world, we now have less physical modems and have moved to chassis based modems (4 per card) with ISDN 30 delivery and a router card to deal with the interaction between the modems and the network. The RAS server has effectively become redundant and users are connecting directly to the network when they dial in.

Great news if you appreciate that at this point my IP routing skills have advanced somewhat and I now have a clue about networks. He thinks.

As it turns out the remote workers are now sales people – similar idea, different demands. Their resources are not via terminal servers, SNA sessions or local servers, they are generally on Netware file shares and accessed via IPX.

The fault condition reported is that it can take minutes before people can access their files. If they are lucky. Sometimes they can’t see their files at all. Brilliant - intermittent unprovable nonsense, the dream of any IT professional. It went on for so long though we had to start to try to fathom this one out.

I hand all credit on this one to someone else who introduced me to a tool, which in it’s day was called Network Monitor. A Microsoft tool which today we would recognise as Wireshark or TCPDump. Watching this over a dial-up connection was a revelation to me. I could see the entirety of a conversation from computer to computer and that meant I could decode what on earth was going on. And it was simple.

Computer says “Hi, can you tell me where my nearest server is?” and this would be sent (for simplicity sake) as a wide area network broadcast. Whomever responded first won. That meant if someone’s files were actually in Liverpool they could easily be served by a server in London that was less loaded at the time but didn’t hold the files. That as a result meant the visibility of files, shares and resources were as per that local London area, not from Liverpool. Hence mixed results. That only took a fair few weeks of hell to find.