PPP-layer Echo

[Crist J. Clark]

I want to do something rather simple, but a quick look at
documentation ("man ppp") didn't give me an answer, and I'm
rather pressed for time.

All I want to do is send an echo-request and listen for the
echo-reply at the PPP layer. Note that I am talking about
pings _at the link layer,_ not IP layer pings. A quick look
at the ppp(8) manpage didn't seem to indicate any tools for
sending or receiving PPP-layer echoes. If ppp(8) doesn't have
the ability, does anyone have any other _simple_ suggestions
for doing this (e.g. dunno if it's worth writing a netgrap(4)
node for this unless its really simple)?

(BTW, support for PPP-layer echoes seems to be required by
RFC1661. Anyone know to what extent real-world PPP implementations
really handle them correctly?)
-- 
Crist J. Clark                     |     cjclark at alum.mit.edu