24 Jun
2021
24 Jun
'21
1:41 p.m.
Does anyone know anything about the "Serial Multisession" that the VT
LAN 40, and presumably other terminals, supports?
I've not heard about it before and intend to do some research. But I
figured that it was an interesting enough topic, that is multiplexing
terminal sessions over a single serial link, to warrant further discussion.
--
Grant. . . .
unix || die
24 Jun
24 Jun
2:10 p.m.
On Thu, Jun 24, 2021 at 1:41 PM Grant Taylor via cctalk
<cctalk at classiccmp.org> wrote:
Does anyone know anything about the "Serial Multisession" that the VT
LAN 40, and presumably other terminals, supports?
I've not heard about it before and intend to do some research. But I
figured that it was an interesting enough topic, that is multiplexing
terminal sessions over a single serial link, to warrant further discussion.
https://en.wikipedia.org/wiki/TD/SMP
TD/SMP, short for Terminal Device/Session Management Protocol, was a
terminal multiplexer system introduced by DEC on their VT330/340
terminals in 1987. The terminal-side was referred to as SSU. TD/SMP
allowed data from two separate host sessions to be sent to a
compatible computer terminal over a single serial port. The format was
patented and never described in depth, limiting it to DEC's own
terminal servers and terminals.
Also supported by the VT420, VT510, VT520, VT525
Terminal device session management protocol
https://patents.google.com/patent/US4791566
https://patents.google.com/patent/US5165020
SSU software was available on OpenVMS
2:25 p.m.
Also supported by the VT420, VT510, VT520, VT525
Actually as far as I can tell the VT510 does not support TD/SMP
(Terminal Device/Session Management Protocol). No mention of multiple
sessions in this VT510 manual as there are in this VT520 manual.
http://www.bitsavers.org/pdf/dec/terminal/vt5xx/
http://www.bitsavers.org/pdf/dec/terminal/vt5xx/598-0013866_VT510_Installat…
http://www.bitsavers.org/pdf/dec/terminal/vt5xx/EK-VT520-IN_VT520_Installat…
4:42 p.m.
The patent goes into considerable depth on the "preferred embodiment"
with descriptions of the protocol with flow control etc. and it looks
like it could be pretty easy to reverse engineer if the actual
implementation is similar to the description in the patent. If one had
a working example to play with of course. Could be a fun little
project.
The flow control is kinda interesting. The receiver sends "transmit
credits" to the sender who will consume them in the process of sending
data and then stop until more credits are received.
On Thu, Jun 24, 2021 at 4:25 PM Glen Slick via cctalk
<cctalk at classiccmp.org> wrote:
Also supported by the VT420, VT510, VT520, VT525
Actually as far as I can tell the VT510 does not support TD/SMP
(Terminal Device/Session Management Protocol). No mention of multiple
sessions in this VT510 manual as there are in this VT520 manual.
http://www.bitsavers.org/pdf/dec/terminal/vt5xx/
http://www.bitsavers.org/pdf/dec/terminal/vt5xx/598-0013866_VT510_Installat…
http://www.bitsavers.org/pdf/dec/terminal/vt5xx/EK-VT520-IN_VT520_Installat…
26 Jun
26 Jun
2:34 p.m.
Thank you for the links Glen. I'll add them to my reading like.
--
Grant. . . .
unix || die
1226
days inactive
1228
days old
4 comments
3 participants
participants (3)
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cctalk＠gtaylor.tnetconsulting.net -
gavin＠learn.bio -
glen.slick＠gmail.com