HAL/MISSLINKS/MikeB%Traveling_Software;_Inc.@MCIMAIL.COM (MikeB) (06/29/91)
What does the CONNECT xxx message mean? It seems that the xxx part has no conclusive meaning anymore. For example: 1) Hayes CONNECT messages reflect the DTE speed regardless of what the previous speed was. 2) MNP class modems, (I have a PP 2400SA MNP Level 5) returns a CONNECT 2400/REL message after negotiating an MNP class connect, carrier 2400, even though the DTE speed is at the last AT command DTE speed, up to 9600. 3) I also have a PP 2400SA V.42bis modem that returns a CONNECT 2400 (by default although this can be changed) message after negotiating a V.42, V.42bis, carrier 2400 connection and will have a DTE speed of last AT command, again up to 9600. Can we assume that, in general, an error control connection will stay at the last AT command DTE speed? If not, what assumptions can be made on what the DTE speed should be following a CONNECT command? Any?
davidg%aegis.or.jp@kyoto-u.ac.jp (Dave McLane) (06/29/91)
HAL/MISSLINKS/MikeB%Traveling_Software;_Inc.@MCIMAIL.COM (MikeB) writes: > What does the CONNECT xxx message mean? It seems that the xxx part has no > conclusive meaning anymore. For example: [* examples deleted *] > Can we assume that, in general, an error control connection will stay at the > last AT command DTE speed? If not, what assumptions can be made on what the > DTE speed should be following a CONNECT command? Any? According to my experience unless you know 1) the exact model of modem, 2) the options that have been set in the DIP and/or memory switches and 3) what kind of speed you are connecting at ... best make no assumptions about what a modem is going to do. If you know those things, the results are totally predictable but without them, you don't know if the speed indicated is the speed of 1) the link between the modems, 2) the speed of the port. To know what the speed of the DTE should be you need to know if the modem set to lock the speed to the port or not, and, if so, under what conditions. Even when you have that all figured out, there are sometimes significant differences between two modems with from the same of the same make and model but with different serial numbers. Fun, huh? Dave -- Dave McLane <davidg%aegis.or.jp@kyoto-u.ac.jp>
gandrews@netcom.COM (Greg Andrews) (06/30/91)
In article <95910628172559.0004025717NB1EM@mcimail.com> HAL/MISSLINKS/MikeB%Traveling_Software;_Inc.@MCIMAIL.COM (MikeB) writes: > >What does the CONNECT xxx message mean? It seems that the xxx part has no >conclusive meaning anymore. For example: > >1) Hayes CONNECT messages reflect the DTE speed regardless of what the >previous speed was. > That's not completely true. If I disable call progress reporting (W0), my V-2400 will report the modulation speed. If call progress reporting is enabled, I get three messages: "CARRIER xxxx", "PROTOCOL:xxxx", and "CONNECT xxxx". As you can see, there is a separate message describing the carrier (modulation) speed, so the connect speed is given to notify the comm software which speed the modem will use on the RS232 port. > >2) MNP class modems, (I have a PP 2400SA MNP Level 5) returns a CONNECT >2400/REL message after negotiating an MNP class connect, carrier 2400, even >though the DTE speed is at the last AT command DTE speed, up to 9600. > >3) I also have a PP 2400SA V.42bis modem that returns a CONNECT 2400 (by >default although this can be changed) message after negotiating a V.42, >V.42bis, carrier 2400 connection and will have a DTE speed of last AT >command, again up to 9600. > >Can we assume that, in general, an error control connection will stay at the >last AT command DTE speed? If not, what assumptions can be made on what the >DTE speed should be following a CONNECT command? Any? > No assumptions. The modem manual should tell you how the modem will behave under various conditions. You can probably program your modem to stay at the speed of the last AT command, or to shift down to the connection speed - it all depends on the capabilities of that particular modem. Historical note: The first 2400 bps modems didn't have error control capabilities. Therefore, they didn't have the ability to support an RS232 speed different from the modulation speed. If you dialed out at 2400 but got a connection at 1200, the modem reported "CONNECT 1200" and shifted speeds down to 1200. If your comm software didn't shift speeds also, you couldn't communicate. This means there are thousands (millions?) of copies of comm programs in people's machines that take the number reported in "CONNECT xxxx" and shift to that speed. So now what happens when an error control modem gets an error-controlled connection? It wants to report the connection, but keep the RS232 port at the original speed. What does it report? If it gives the modulation speed, the comm software may change speeds by mistake. The answer is that the modem reports the RS232 speed it intends to use for this particular connection. It's safe, because the comm software won't shift to the wrong speed like it would if the modem reported the modulation speed in the "CONNECT xxxx" message. -- .------------------------------------------------------------------------. | Greg Andrews | UUCP: {apple,amdahl,claris}!netcom!gandrews | | | Internet: gandrews@netcom.COM | `------------------------------------------------------------------------'
root@zswamp.uucp (Geoffrey Welsh) (06/30/91)
In a letter to All, MikeB (HAL/MISSLINKS/MikeB%Traveling_Software;_Inc.@MCIMAIL.COM ) wrote: >Can we assume that, in general, an error control connection >will stay at the >last AT command DTE speed? If not, what assumptions can be >made on what the >DTE speed should be following a CONNECT command? Any? The port speed will remain fixed only if the modem is configured to do so (on some modems, including USRobotics, the command is &B1). Factory default is to switch the DTE speed to match the connect speed, because that's what years of software has been accustomed to. -- Geoffrey Welsh - Operator, Izot's Swamp BBS (FidoNet 1:221/171) root@zswamp.uucp or ..uunet!watmath!xenitec!zswamp!root 602-66 Mooregate Crescent, Kitchener, ON, N2M 5E6 Canada (519)741-9553 "He who claims to know everything can't possibly know much" -me
flinton@eagle.wesleyan.edu (07/01/91)
In article <1991Jun29.172655.3066@netcom.COM>, gandrews@netcom.COM (Greg Andrews) writes: > So now what happens when an error control modem gets an error-controlled > connection? > The answer is that the modem reports the RS232 speed it intends to use for > this particular connection. Not so my Acer MNP4 external -- when I have the RS232 speed locked at 9600 it reports the modem-to-modem communication speed -- 2400, 1200, 300, whatever -- and whether or not the connection is /RELiable. But 9600 just isn't in its CONNECT vocabulary. > .------------------------------------------------------------------------. > | Greg Andrews | UUCP: {apple,amdahl,claris}!netcom!gandrews | > | | Internet: gandrews@netcom.COM | > `------------------------------------------------------------------------' -- Fred <FLinton@eagle.Wesleyan.EDU>