(Note that the following email may contain biased opinions, as I'm an
employee of the company manufacturing the items in question.)

tv@pobox.com (Todd Vierling) writes:

> The P15 is a terminal adapter a la the Motorola BitSURFR Pro. 
>It's more or less the next generation of Ascend's NetWARP Pro

Actually, the two are architecturally unrelated (and very different)
beasts (the NetWarp guys like to think that it is a newer generation
product than the P15, but really each has its own unique place). The
NetWARP interfaces directly to the ISA bus (rather than through an
RS-232 port) and therefore doesn't need to do the async<->sync PPP
conversion that the P15 does. Also, the NetWarp is a "passive" device -
it has few smarts of its own, and all line communications are handled at
a very low level by software on the PC; the P15 is a standalone unit
with an M68302 CPU, and it handled all details of sending stuff over the
line, as well as speaking (synchronous) PPP to the remote end and
speaking (asynchronous) PPP to the local host.

The result is that a NetWARP gives you better performance (on systems
that support it) because the rs232 bottleneck is missing, but at the
expense of more CPU time. I think the NetWARP only has drivers for MS
operating systems at present.

>It can be
>used like any other modem directly with NetBSD, but as far as I know,
>there's no STAC compression, multichannel support, blah, blah, blah, for
>NetBSD right now. 

As far as I know, the P15 does synchronous MPP to the remote end, and
converts this into standard (single line) async PPP before sending it to
the host. So it shouldn't matter if the host supports MPP or not. (Don't
take my word on this, though - I haven't actually used the thing
myself).

As far as STAC compression, I could be wrong about this as well, but the
information I have indicates the P15 doesn't support STAC compression
under any circumstances, regardless of host OS.

>My suggestion to the original poster:  If you have a P15, trade it up for a
>P75 and use an Ethernet card instead.  For the speed and flexibility, you
>won't regret it.  :)  (Note I don't mention the P25:  it's a product Ascend
>intends to dump in the near future.)

I agree with this whole paragraph (although I don't know anything about
dumping the P25). Async<->Sync ISDN terminal adapters are okay when an
async serial port is all you've got (or you're low on cash), but you'll
get better performance and more features with a real router every time.
I've got a P75 at home and it serves me very well (I even have a modem
plugged into one of the P75 POTS ports and into an old Morning Star
router, giving me an analog dialin that comes over one of my B
channels).