Sierra Wireless DART 300 manual Using PPP Service, Closing a PPP Session

Configuration and Use DART 300 Modem

9.2.2.Using PPP Service

With a modem configured as noted immediately above, the local host needs to do the following to connect to the network.

(AT is omitted for brevity):

1.On start-up, either monitor the DART 300 for the OK result code, or check for an assertion of the CTS control line to indicate the modem is ready.

2.Optionally verify CDPD channel acquisition and registration. You can manage this process as suits your need. If manual registration is selected, the Dial command can handle the network registration process using the NEI indexed by the auto-register index. See the AT Command Reference for details.

3.D (Dial); any parameters are ignored. This command forces the modem to attempt to register regardless of the setting of auto-registration. This allows the modem to go on-line using just the one command, but network registration is not guaranteed unless +WS179 was set to 1 in the configuration.

The modem will reply with CONNECT at which point PPP is used to negotiate the session parameters between the modem and local host. If the host does not handshake the PPP negotiation promptly, the modem will drop the connection and revert to command state with the OK result code.

An alternative process is to issue O to go on-line (start the session). This should only be used if you know the modem has successfully registered on the CDPD network.

The modem is now operating under PPP control to pass host packets to the network. Any incoming packets, from any calling client or responding server, will be passed to the local host. This allows the host to send and receive packets to and from multiple destinations asynchronously provided the host can manage multiple socket connections.

Once in data state, the modem acts as a pipe through which data passes. All PAD and IP protocol stacks as well as PPP framing must be implemented on the local host (DTE) system. Windows Dial-up Networking can provide these services.

9.2.2.1.Transmitting

Data packets received from the local host (DTE) are forwarded to the network in 128 byte segments. They can be buffered on the modem up to 14 segments (1792 bytes). Beyond this, there is local hardware flow control (RTS/CTS) with the host to prevent overflow.

9.2.2.2.Receiving

Incoming data from the network is buffered (up to 14 x 128 bytes) and is passed to the local host as it arrives. If the modem has been placed in command state but is still in on-line condition, incoming data will be buffered. There is an automatic remote flow control between the modem and the network to prevent overflow when the modem’s buffers are full.

9.2.3.Closing a PPP Session

To end a PPP session, escape data state via PPP or by using DTR in conjunction with the &D2 DTR option.

If the PPP escape sequence or the &D1 DTR option is used then you must hang-up with either H or H1 to close the session. Both of these will close the current session. If the modem is set to manual registration, it will also be de-registered by both of these commands.

H1 will force de-registration of the modem even if auto-registration is enabled. The modem will remain de-registered. Although auto-registration remains enabled, the modem will not resume auto-registration until the register is reset (+WS173=1) or the modem itself resets or power cycles.

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