[c-nsp] Replace CDP

[Mark Boolootian]

regarding LLDP:

> That looks like the answer to my (geekier) dreams... does anyone
> actually implement it?

HP has implemented it in their ProCurve switches (at least).  Foundry
has it on the roadmap.  Extreme has a white paper touting its glories,
though I wasn't clear on whether they actually had working code.  Cisco
was supposed to have support for it in Q4 this year (35xx/37xx/29xx
switches) and Q1 next year in 65xx.  It didn't appear that it was on the
roadmap for their routed products, though I've not yet confirmed.