6 Dec
2004
6 Dec
'04
11:38 a.m.
On Tue, 7 Dec 2004, Michael Sokolov wrote:
Probably because that was a test link; the production system (with the
same driver) connected to a real DDMCP network. The choice was to either
change the WAN to HDLC/PPP, or make that one box talk IP over DDMCP.
Such a driver has existed in standard BSD since 4.2,
except that it's
for the DMC-11/DMR-11/DMV-11 (which do all DDCMP processing on board and
can't be made to talk any other protocol to my knowledge) rather than
for the DMF32 that this thread is presumably about.
Indeed. I run DMV11's
here. I know.
The DMF32 sync port supports DDCMP too, but it leaves
more work to
the host and supports HDLC as well.
Correct. Still, it offloads a LOT of the
enframe and deframe work
to the board CPU.
with a
modified IOS running at the other end, on a Cisco 2501.
If you needed to connect
the DMF32 sync port to a Cisco router, why didn't
you implement Cisco HDLC on the VAX side instead? (As I've done in 2000
in 4.3BSD-Quasijarus0b on a DSV11.) I'm sure you
know the frame format:
<flag> <addr> 00 <Ethertype> packet <FCS-16> <flag>
addr is 0F for unicast or 8F for multicast/broadcast*.
After 17 years of
networking, I guess I'm aware of the various
frame formats, yes.
*The only thing that I never understood is what the
hell did Cisco mean
by multicast or broadcast on a point-to-point link. I guess it dates from
Frame
filtering.
the days before people realised that a point-to-point
link is not a network
(no ARP, etc.) and does not need to burn up a net/subnet number, and people
would map a net number (hopefully a /30 subnet) to each point-to-point link.
Then .1 and .2 addrs would be assigned to the ends and I guess the 8F addr
byte was generated on packets addressed to .3... My driver always puts
There are
very good reasons for assigning IP addresses to both ends of
a WAN connection, especially in multipath environments and/or networks
that use link-state routing protocols. We dont all use "route add
default wan0" you know.
The approach of using a /30 subnet for a
point-to-point link now has to
be used only when you are forced to use an Ethernet as a point-to-point
link without PPPoE, which is stupid but unfortunately used by some DSL
providers.
Actually, by most xDSL providers in Europe. So, apparently it's
not
THAT stupid. Its a cheap 10Mbps (or even 100Mbps, if needed) leased
line technology with baseband encoding to them :)
USR Courier V.Everything (external of course) supports
sync mode on its
DB25 port. The problem is with the other end of the call... I'm using
such modem for my PPP connection, and while I would love to run sync PPP,
I doubt that the ISP's POP will support it.
If they use TotalControl or akin
racks, they will. I used to run that
over my USR Courier I-Modem (ISDN V.Everything with both digital and
analog protocols.)
--f