lauren@vortex.UUCP (Lauren Weinstein) (05/28/83)
Greetings. Sorry to send this message to two groups, but I felt that it should have as broad a distribution as possible. I've been watching UUCP dialup patterns on several sites (including vortex) and am beginning to suspect that some (many?) sites are using too SHORT an interval for their dialing timeout for calling other sites. I've noticed a pattern of some sites that ring once and then immediately hang up, or which hang up *immediately* after getting carrier (before ACU transfer to the modem could be completed, essentially). I believe that the issue here is an underestimate of the time required to establish a connection to some sites. Remember that there are a variety of factors that can effect call setup time. If you are calling a site on a step-by-step telephone exchange, the connection interval can be greatly increased. The same goes for numbers on Direct Inward Dialing Trunks which are using pulse dialing (there are lots of these still around and still being installed!) Note that I am talking about the site you are CALLING in both cases -- not the site making the call. Another important factor is that many modems (including Bell 212A's) require a FULL RING before they will answer. If you happen to partially ring the line when you first connect, there will be a full inter-ring pause and another ring before the modem answers, and a bit more delay before carrier is sent by the answering modem and detected by the originating modem. The upshot of all this is that, I believe, a more liberal timeout interval could help decrease the number of "almost connects", which might be wasting a substantial amount of time. Nobody really knows, of course, since most sites do not and cannot log such events (since the answering modem never realized a call came in, and the originating modem would assume a "no-answer" or "busy" situation.) I would recommend a full 45 second timeout after dialing has completed for all long distance calls to help avoid these problems. Depending upon your ACU arrangement, you may be able to force a longer interval by putting some dialing "pauses" into your L.sys line for the appropriate sites (this will not work with some ACU's, so be careful.) Others may have to change the actual interval inside UUCP, but I expect this would be fairly rare. I believe that many people have already "played around" with the timeout interval, possibly even to SHORTEN it, judging from some of my observations. Just because a short interval works for MOST calls, it doesn't mean that it'll work for ALL calls! Thanks much. --Lauren--
msc@qubix.UUCP (Mark Callow) (06/03/83)
I too have noticed systems calling us and not waiting long enough for an answer. I have modified conn.c so that the timeout is calculated based on the length of the number. (10 digits is assumned to be long distance and gets a big timeout.) I then program the dialer with this value (a Hayes Smartmodem 1200) and add 10 secnds and use the new value for the alarm call. I have used timeouts as long as 75 seconds because I was trying to call the East Coast via Sprint/MCI. These calls never worked and I abandoned the attempt. I now use a 50 second timeout on long distance calls via Ma Bell. [The reason Sprint/MCI is NBG (I believe) is because they use half duplex statistical multiplexers in their networks which obviously don't allow full duplex 212a modems to work over the same lines.] Mark Callow
martin@vax135.UUCP (06/03/83)
For sites with Bell 801 ACU's there is an option switch that controls how long the ACU will wait for the carrier. I dont have the manual at hand but your local Bell Operating Company will probably be able to tell you what the setting should be. The best setting is for the longest timeout, 56 second timeout. Then the code inside uucp conn.c should be changed to match the new timeout. For people with Bell 212A modems there is an option to allow the modem to answer on the first ring. martin.
smh@mit-eddi.UUCP (06/04/83)
Not to mention, some supposedly clever autodial modems feature automatic call abort if carrier is not returned within, say, 24 seconds. This is definitely not long enough for some calls. In the modems with which I am familiar, this feature can be disabled by cutting jumpers.