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Conference bulova::decw_jan-89_to_nov-90

Title:	DECWINDOWS 26-JAN-89 to 29-NOV-90
Notice:	See 1639.0 for VMS V5.3 kit; 2043.0 for 5.4 IFT kit
Moderator:	STAR::VATNE

Created:	Mon Oct 30 1989
Last Modified:	Mon Dec 31 1990
Last Successful Update:	Fri Jun 06 1997
Number of topics:	3726
Total number of notes:	19516

1451.0. "DECwindows, modems, and asynch DECnet?" by PHDVAX::FEENY () Fri Sep 15 1989 16:42

    the customer at which i'm a resident has the following configuration:
    
    VS3100 & VAX 6310 in a LAVc;  the 6310 processes medical images (xrays,
    etc) and communicates, via DECnet, with the VAXstation to get those
    images displayed via DECwindows.  i would guess this is a fairly
    standard DECwindows server-client approach, yes? 
    
    in the not-too-distant future, the 6310 will be moved to a remote site
    (1000+ miles away) for installation as a prototype site.  the customer
    would like to be able to connect to the 6310, on an *occasional* basis,
    with a local VAXstation 2000, and bring up the same server-client
    software.  such connections would be infrequent, and of short
    durations (to duplicate reported problems, etc.).  the customer
    is looking for the most (surprise) cost-effective way to pull this
    off.

    my questions (to anyone still listening) are:    

    o would it be *technically* possible to do this via modems, dialup
    lines and the VAXstation 2000's comm port? 
    
    o if so, any guesses as to performance?  would the performance be so
    dreadful that even an occasional session would be too painful to be
    productive? 

    o the customer may have a spare DECrouter 200 that could be ethernetted
    together with the local VS 2000.  would this buy them anything?
    
    thx for any sugs.
    
    michael

T.R	Title	User	Personal Name	Date	Lines
1451.1	Note, I haven't actually tried it.	STAR::BECK	The question is - 2B or D4?	`Fri Sep 15 1989 17:33`	13
	> o would it be technically possible to do this via modems, dialup > lines and the VAXstation 2000's comm port? Not if, as you say, > such connections would be ... of short duration There have been several discussions of this. Bottom line on dialups is, the bandwidth of a DECwindows display requires a lot of bytes to be transmitted. It's technically feasible (a DECnet connection is a DECnet connection is a DECnet connection), but you need to be VERY patient. Bring along a good book. Like War and Peace.
1451.2	But at 9600 baud?	WJG::GUINEAU	Impossible Concentration	`Mon Sep 18 1989 14:15`	6
	Will some form of serial line transport be in DECwindows? XTerminal must use LAT protocol, right? John
1451.3		PSW::WINALSKI	Careful with that VAX, Eugene	`Mon Sep 18 1989 19:26`	8
	LAT is an ethernet-only protocol, as far as I know. DECnet supports links over serial lines, so you could use DECnet transport operating over a 9600 baud line (or even a 300 baud line, if you're not picky about performance). --PSW
1451.4	Service class 3	MIPSBX::thomas	The Code Warrior	`Mon Sep 18 1989 20:01`	2
	is for the X protocol and is used between DECwindow Terminals and VMS.
1451.5		WJG::GUINEAU	Impossible Concentration	`Mon Sep 18 1989 23:26`	7
	> is for the X protocol and is used between DECwindow Terminals and VMS. So, theoretically, one could dial up to a LAT and run DECwindows? John
1451.6	Not without a bunch of help.	MIPSBX::thomas	The Code Warrior	`Tue Sep 19 1989 03:19`	11
	if you dialed up, you would be connecting out from the terminal server as SC1 (tty type service class). Other problems is that X expects to be running on a reliable transport (such as TCP, NSP, TP4, LAT) which an async dialup does not provide for. So underneath you'd have to run a reliable datalink protocol such as DDCMP or a reliable transport (TCP over SLIP). By now you're eating away at the bandwidth that X so deperately needs. BTW, assuming a LAT terminal server session offers one credit every 80ms (standard), then the thruput to that session is 825012 bits/seconds or 48Kb/sec. This is just getting tolerable for using X.
1451.7		KONING::KONING	NI1D @FN42eq	`Tue Sep 19 1989 11:35`	6
	If you want to run over anything other than Ethernet, you'll need to use some transport other than LAT. TCP/IP comes to mind, or DECnet. It will have to be something the target understands, of course. paul
1451.8		ERIS::CALLAS	The Torturer's Apprentice	`Tue Sep 19 1989 12:54`	8
	"If you want to run over anything other than Ethernet, you'll need to use some transport other than LAT." Unless, of course, the target speaks LAT. I know that for example Macintoshs speak LAT over their twisted-pair LocalTalk. Jon
1451.9	You caught me... :-)	KONING::KONING	NI1D @FN42eq	`Tue Sep 19 1989 19:15`	6
	Ok, ok, so I was using sloppy terminology. Replace "Ethernet" by "a LAN, such as Ethernet". paul
1451.10		GIBSON::DICKENS	What are you pretending not to know ?	`Wed Sep 20 1989 13:33`	11
	How about if the transport was a pair of 9600 baud error correcting modems between the server and client, using the asynch terminal muxes that both already have (in my case) ? That's a sort of "reliable transport", no ? Is there any other (maybe better) way to get the "x server at the end of a skinny pipe" effect ? -Jeff