My friend Ronald sent me this comment:
I don't drink this Cisco Kool Aid about interconnecting data centres using an IP backbone. Rather use FC directly over DWDM instead of FCIP on MPLS.
This time I could agree with him wholeheartedly ... assuming you already have DWDM gear (or infinite budget to buy some) and you can get dark fiber when and where you need it. Unfortunately not everyone is so lucky and/or rich, so we have to compromise.
His comment also reminded me of the comments I’ve heard from SNA gurus more than 15 years ago when Cisco introduced SDLC-over-IP and later LLC2-over-IP tunneling. We’ve spent years trying to persuade them to drink the DLSw Kool-Aid … and in the end they all gave up their precious SDLC leased lines and Front-End Processors as the market realities forced them to consolidate their infrastructure and migrate to routed networks. Not to mention that most of the gear they supported (including ATM machines) got replaced by newer models supporting IP (or even having IP as the only connectivity option).
A similar story played out in the Service Provider world, where the idea of offering Frame Relay or ATM service on top of an IP backbone was a heresy … until it became cheaper to migrate the legacy services to a router-based network than to pay the maintenance fees for the Frame Relay gear.
Moral of the story: whenever you propose to tunnel a well-established protocol using a new entrant in a particular technology area, people will tell you that it’s all a marketing plot and that they prefer to stick with the tested scenario … until the business pressures force them to change their mind. The tricky part is figuring out the right time to jump: if you’re too early, you could get burnt; if you’re too late, you might have lost a fortune.
Last but not least, don’t forget that not all tunneling scenarios were worth pursuing: IP-over-APPN never really took hold.