Well, the J-series are fully software-based routers. Still, they have their own routing daemons and such.
The difference is that Juniper, even on th J-series box, completely separates the control plane and fowarding plane. The forwarding plane on a M or T series is going to be a ppc based chip along with ASIC to do the real lifitng. In the J-series it is a emulated FPC running on real-time BSD. The control plane on both platform is freebsd based. This is also what an Olive is. The control plane with no FPC. You'll also note horrible forwarding performance on an Olive. So a J-series it cannot be compared to a Vyatta or Imagestream even though it's software based. I think IOS can be compared more so (combined fowarding and control planes on software routers) -Brandon http://www.juniper.net/company/presscenter/pr/2005/pr-050131.html http://www.linuxdevices.com/news/NS4066781213.html