PC Ext Gen: Questions Asked About X.25 and External [Part II]

MORE INFORMATION

1. Q. Can one Multitasking Message Transfer Agent (MMTA) service X.25 and Async External instances simultaneously, for more than the home postoffice?
   
   A. Yes, but every instance of External can handle only one connection method in the Admin program (Direct via either MS-DOS Drive, Modem, or X.25). The X.25 instance can service many permanent drives or dynamic drive connections (both MS-DOS Direct Drives). The number of these connections are limited largely by the memory on the OS/2 computer. Dynamic Drives can use DynAdmin tables only on the home postoffice. DrivesUNC or DrivesNovell do not use the DynAdmin tables.
   
   NOTE: The EXTERNAL.INI options DrivesDirectPO, DrivesDynamic, DrivesHomePO, and DrivesNovell are not available for the Multitasking MTA for Windows NT Server version 3.5 (NT MMTA).
2. Q. How do you configure an MMTA to service more than one home PO?
   
   A. Use the DriveHomePO option with different DirectDrives in the EXTERNAL.INI as follows:

   [External - Instance1]
   DriveHomePO=M
   
   [External - Instance2]
   DriveHomePO=N

3. Q. Can one instance of External handle both an X.25 and an Async call?
   
   A. No, choosing "CommType=X25Eicon", precludes using asynchronous (async) communication for the same instance, and vice-versa. The External program, for example, can launch either ASYNC.OVL or the X25<card-type>.OVL, but not both in the same instance. Only one X.25 session can be done at any time by one External instance.
4. Q. What happens when two remote postoffices or remote users dial-in at the same time to one DOS MTA, or one instance of External on an MMTA?
   
   A. One PO or remote user will connect, and the second user will fail to connect, receiving a busy signal. Concurrent connections are only possible with:
   • Multiple instances of External on one OS/2 machine.
   • Several instances on a Windows NT Server version 3.51 running the Multitasking MTA (NT MMTA).
   • Multiple MS-DOS machines running the MTA.
5. Q. Can one instance of External (MS-DOS or MMTA) connecting to multiple postoffices via multiple directly attached permanent drives (DrivesDirectPO), support remote mail for all users on all postoffices?
   
   A. Yes, provided that they are not dialing in at the same time. To avoid this limitation, multiple instances would need to be setup. Each instance would need to be connecting to a separate set of direct drive mappings. If Instance1 was connecting to drives M, N, and O, Instance2 would need to connect to a different set of direct drives. For example, Instance2 could connect to drives P, Q, and S.
6. Q. Are there any special flags or attributes in the \MAILDATA directory to prevent file locking (in a Novell environment), when using X.25?
   
   A No, there are no special flags or access rights for the Novell NetWare environment for X.25. Flags and rights are the same as for "direct drive" connections. For details, refer to the Microsoft Mail for PC Networks "Administrator's Guide", Appendix G Troubleshooting Guide.
7. Q. What is the command line for each External instance, used for X.25, to differentiate it from the others?
   
   A. The best way to differentiate the instances is to add "X25" (without the quotes) to the beginning of the instance name. For example, to initiate the instance from a command line use the instance name from the EXTERNAL.INI file with the /InstanceName command line parameter:

   EXTERNAL /InstanceName=<X25Instance_Name>

8. Q. Can I specify the last X.25 channel specifically for outbound and the rest of the channels for inbound mail?
   
   A. Yes, but you control the Virtual Circuits (VC) by specifying the Comm options of the External instance using this VC. Given the fact that you can not specify the "Virtual Circuit" with the X25PortNumber, you are still able to include CommOutOnly (-KO) and CommInOnly (-KI) EXTERNAL.INI options (-KO and -KI External command line parameters). When you configure the Eicon card, specify one-way or two-way in External_Admin, Setup, VCs by number. The other option is to use the -KI, -KO switches with X.25. It is recommended to use a single two-way virtual circuit in the Eicon setup (the default), rather than using -KI and -KO switches in the External command line.
9. Q. What are X.25 subaddresses, and how do they relate to External_Admin, Setup and to the EXTERNAL.INI file entries?
   
   A. When an X.25 application, such as the MTA is on a LAN workstation, and the X.25 card and software are installed on a second computer, the X.25 card software (Eicon or Atlantis) needs a way of identifying which LAN process it is establishing a X.25 virtual circuit.
   
   The subaddress is an arbitrary but unique two-digit number assigned by the mail Admin that is added to the end of the original X.21 subaddress.
   
   ADMIN PROGRAM
   An X.25 connection is defined under the Admin program by selecting External-Admin, Create, Network, Postoffice, Direct/X.25.
   
   EXTERNAL.INI FILE
   In the EXTERNAL.INI file, the required entries look similar to the following for the Eicon X.25 card and software:

   [External - X.25]
   CommType=X25Eicon
   X25PortNumber=255 ; 255 is for a DOS MTA
   X25SubAddress=234187654321XX ; where XX is a unique 2-digit number