Newsgroup: it.comp.retrocomputing
Titolo: Protocolli, circuiti intercontinentali e collaborazione online 25 anni fa (roba Digital)

Negli ultimi giorni – un po' per interesse e un po' per noia – ho letto e
studiato diverso materiale su DDCMP (Digital Data Communications Message
Protocol), cioè il protocollo Digital a livello data link su cui si basava
DECnet prima dell'avvento di Ethernet (e anche dopo, almeno in ambito WAN).
 
DDCMP è un protocollo orientato ai caratteri, studiato sia per collegamenti
seriali sincroni e asincroni sia per collegamenti paralleli, e fa parte della
grande famiglia che ricomprende anche SLIP, PPP e BSC nonché i classici SDLC,
HDLC e LAPB (ma questi ultimi sono bit oriented).
 
A proposito: chi era quello che qui aveva un VAX senza Ethernet e non sapeva
come fare per metterlo in contatto col resto del mondo? :)
 
Va be', tutto questo per introdurre il seguente post – trovato in una "Notes
conference" (vedi oltre) – che racconta come potesse essere un collegamento
dati intercontinentale nel 1988, cioè quasi l'altro ieri:
 
    If you are wondering what I'm doing in Seoul, I'm working with the
    Associated Press for the Olympic games. We have about 80 Gold Star
    IBM PC clones in a big room where the AP's writers use them as word
    processors. The stories are sent to a MV 3600 which acts as a file
    server and message router. We have DECnet circuits to New York where
    the stories are distributed to the various AP newswire circuits
    by another bunch of VAX, PDP-8 and PDP-11 computers. Don't ask about
    the New York end -- it's real ugly.
 
    The Gold Star micros are connected to the VAX using reverse LAT
    application ports. Don't ask why -- it's even uglier than New York!
    The MODEM connections in question are used by the writers at the
    game venues who use Tandy Model 200 portables to  write their stories
    and then send them into the VAX in our Olympic bureau.
 
    We have three circuits back to New York -- a 4800 bps async DECnet
    connection via Tokyo connecting two DECrouter 200's -- a  9600 bps
    synchronous DDCMP connecting our VAX to another in New York through
    various Infotron muxers which goes via satellite either direct to New
    York or through London, depending on what kind of mood the Infotrons
    are in -- and a 56 kbps T1 chunk via satellite to California and fiber
    back to New York. The 4800 bps circuit seems rock solid, the 9600 bps
    circuit is a little dodgy and the 56KB circuit has not worked right yet.
 
    We have three MV 3600 machines -- a live, a backup and a spares kit.
    The whole computer room was put together within two weeks by the AP
    communications staff of about  10 technicians from all over the world
    who will have roughly two days after the closing ceremonies to get it
    all back on the plane to the States. The local DEC distributor FS
    operation has been very helpful although it's a good thing we brought
    our spares kit! 
 
    I'm coming to you through a SET HOST connection to New York, a VAXNET
    connection to CCA's terminal network to a dial-out modem in Cambridge.
    So far I've only had three disconnects in the hour it has taken
    me to write this story!
 
La stessa persona – in un post di tre anni dopo – rispondendo a qualcuno che
domandava un parere sull'affidabilità di certi modem, scrisse così:
 
    I think it depends on how your luck runs. When I worked the '88
    Olympics in Seoul for The AP, we had three circuits back to New York
    for DECnet: A 56 kbps satellite link, a 9600 bps synchronous circuit
    on the fancy new MUX equipment with a special DDCMP card to make the
    DECnet work, and a 2400 (or was it 1200) asynch circuit that wandered
    all over the world, via Tokyo, Bahrain and London, through more
    STAT-MUXERs and what-not than anyone could figure out.
 
    We never did get the 56 kbps circuit running. The 9600 circuit worked
    most of the time, but was a lot of trouble. The slow-speed circuit was
    rock-solid from the minute we started it until we packed up and came
    home, and was the only available circuit often enough that we would
    have been most embarassed if it had not been there.
 
Come ho scritto sopra, entrambi questi messaggi li ho trovati in una
conference, cioè nell'equivalente di un newsgroup nell'ambito di VAX Notes
(poi rinominato DEC Notes), ovvero uno dei primissimi esempi di groupware,
immesso sul mercato col nome di Notes-11 quando appunto girava su PDP-11.
 
Una buona descrizione di Notes si può trovare qui:
 
 
http://goo.gl/k2xEl
 
 
Le conference in questione sono quelle del DECUS (lo user group americano dei
clienti e utenti Digital) – mantenute accessibili in massima parte per ragioni
storiche (ma c'è chi le usa ancora) – e si possono leggere comodamente anche
in forma anonima grazie a un'interfaccia web accessibile da qui:
 
 
https://mail.encompasserve.org/anon/notes/
 
 
Per altre informazioni sull'ex DECUS (oggi Encompass), vedere qui:
 
 
http://www.encompasserve.org/
 
 
Il tutto gira su EISNER cioè l'Alpha con VMS su cui – fra le varie cose – ci
si iscrive gratuitamente per ottenere altrettanto gratuitamente le licenze del
programma Hobbyist per VMS... E per poter scrivere nelle conference. :)
 
Ciao,
G.
 
 
P.S. I due messaggi riportati qui sopra sono rispettivamente estratti delle
note 33.35 e 82.19 della conference DEC_NETWORKING ospitata su EISNER.


Grazie "G.", davvero interessanti questi link.