GWIA Architecture

GWIA architecturethe way in which the GWIA works with the rest of the GroupWise systemis best understood in terms of general gateway architecture. All GroupWise gateways perform one or more of the following functions:

• Translation

• Transport

• Mailbox access

The functions performed by the gateway determine the way in which the gateway connects to the rest of the system. The GWIA performs all three of these functions. The following sections look at each of the functions in turn.

Translation

The GWIA translates messages from Simple Mail Transfer Protocol (SMTP) format or Multipurpose Internet Mail Extensions (MIME) format into GroupWise format. It also translates GroupWise messages from the proprietary GroupWise format into SMTP or MIME format. This allows messages sent by GroupWise users to be read by users of email systems that can receive SMTP or MIME email messages.

Note

Other gateways that perform translation include the GroupWise API gateway and the GroupWise gateways for Exchange, Notes, and the Messaging Architect's GWFax software.

The translation function requires that the GWIA receive messages from the GroupWise system. The message transfer agent (MTA) handles this by dropping Internet-bound messages into the GWIA's input queues. When messages are sent to the GroupWise system from the Internet, the MTA transfers those messages after the GWIA has translated them into GroupWise format.

Transport

Translated messages originating in the GroupWise system must be transported to the correct mail host on the Internet. The GWIA performs this function independently of the GroupWise MTA. The GWIA functions as a sendmail host, which means it can communicate with any other sendmail host on the Internet (assuming that a connection is established).

This transport is performed in TCP/IP through port 25, the industry-standard sendmail TCP port. The GWIA performs the appropriate domain name system/service (DNS) lookup to locate the recipient's mail host, and then connects and transfers the translated message. For inbound messages, the GWIA is always "listening" for similar connections from other sendmail hosts.

Mailbox Access

The GWIA can give users access to their mailboxes from alternative clients, such as Eudora, Netscape Messenger, or Microsoft Outlook Express, as well as other POP3 clients on handheld computers. The GWIA supports two forms of mailbox access: Post Office Protocol (POP3) and Internet Message Access Protocol (IMAP4). The GWIA also allows users to access the GroupWise address book via the Lightweight Directory Access Protocol (LDAP).

To do this, the GWIA must be able to connect directly to the users' post offices. This can be accomplished by the GWIA talking directly to the post office based on UNC direct access, or by using TCP/IP to the Post Office Agent (POA). Typically and preferably, the GWIA connects to the POA in client/server mode for every user who needs POP3 or IMAP4 access and thus acts as an intermediary between the POA and the third-party mail client.

LDAP address-book access is provided a little differently. The GWIA reads the necessary address-book information directly from the domain database. The GWIA is hard-coded to look to its parent domain directory for the necessary domain database file.

Architectural Summary

When the GWIA is functioning in its capacity as a sendmail host (translation and transport), it connects with the GroupWise system via the MTA and standard file-polling. When the GWIA functions as a POP3 or IMAP4 host (mailbox access), it connects with the GroupWise system via the POA in client/server or direct access mode. When the GWIA functions as an LDAP host, it connects with the GroupWise system via a UNC mapping to the domain database.