On a different, older tangent ... coming from my possibly (probably) flawed memories:
A looong time ago ... back in 1996-97 or so ...
A cisco rep promised a smallish VAR I onced worked for that a new code base was being developed alongside 11.x and that it would likely become the Next Generation IOS someday if it "worked out".
It was supposed to be a complete ground up re-write in an OO language and it would have the ability to link new modules or shared objects in at run time, and it would unify the existing router (25xx / 4xx / 75xx) family with the Grand Junction acquisition - the CAT5K switch family into one code tree and one IOS to run them all.
Instead we saw a flurry of new hardware (26xx, 16xx, 72xx, 36xx) which seemed to be a little more buggy than the older hardware
especially when comparing the early 26xx and 36xx releases to the 4xx routers.
I remember having some strange issues with early 26xx routers - like the t1 wics wedging, the ip route cache getting corrupt, and 36xx routers refusing to recognize NMs when you swapped them into new slots or added new NMs. I always wondered exactly what those routers were running - was it some of the "NG" code backported or just normal bugs you expect when you are using all new chips, flash, and cpus (probably the latter) ?
Anyway, I asked the cisco rep why they didn't just port *bsd or linux and use that and he said there were some "smart people that had already considered that and ruled it out as a bad idea."
Wonder if cisco regrets this (I dont have any idea, I'm just wondering aloud). Would cisco have been smarter to already be running, say OpenBSD as its kernel and then its IOS services as daemons ? Might have opened up licensing problems for them that would have been a huge headache too.
Is cisco the only major router/switch vendor running a home grown (i.e. not commercial rtos or *bsd / linux based derivative) for its core OS ?
Do folks that control purchasing decisions care whether their selected vendors use a general purpose or proprietary OS when they are evaluating products ?
I know that personally I dont like to buy gear that uses Microsoft win2(x) or winCE as its host (whether its a pbx, firewall, router - remember MS Steelhead?, etc). But thats just me ... Do people stop to think about what is really inside their router or network appliance when they buy it or do they only care what the *printed* manual says can be done with their shiny new box ?
(Dislaimer - I like cisco gear a *lot* and I guess I am one that always considered IOS pretty secure though I do always put interface and vty acls for limiting access to the control plane when permitted by the end customer).