Sync serial bridging over Ethernet, was Re: [HECnet] Multi-floor household (DECnet) routing help needed

[Dave McGuire]

On 01/18/2013 01:48 AM, John Wilson wrote:
I'd do it with an HDLC/SDLC-capable chip like a Z8530...offload as
much from the firmware as possible, leave those cycles for protocol
handling.

FWIW, I'm in the middle of writing a Z8530 driver for E11 (in heavily
commented x86 code), which I'd be happy to contribute (after modifying
as needed) if you aren't already neck-deep in SCC code.

  I built a Z8530-based AX.25 PAD for ham packet radio...but that was 25
years ago!   I remember being thoroughly impressed with the Z8530, and
I've used it in several projects since then...but only in async mode.
So yes...if you're doing sync stuff with it, that might be very handy if
we do this and it goes this route.

  We could certainly do the framer in firmware; there's a certain appeal
to that...but I'm a big fan of distributed processing, and as the iOS
device saying goes, "there's a chip for that".

Wrapping the data in UDP is simple.   The HDLC layer could deal with
error detection/correction.

Yes!

Careful -- UDP doesn't guarantee in-order delivery.
How does HDLC feel about little surprises?

  I would imagine it'd be offended. ;)   However if memory serves, HDLC
frames contain a few bits' worth of sequence numbers.   These could be
checked and buffered/re-issued to recover from most bad situations, I
would think.

                      -Dave

-- 
Dave McGuire, AK4HZ
New Kensington, PA