The command to enter Serial Line Internet Protocol mode (SLIP) is used when an external stack configuration is needed. SLIP is useful if the stack resides in the host computer, multiple sessions and complete control over all aspects of each session can be obtained. SLIP is one of the more common protocols used for splitting the functionality between the modem and the host. SLIP does, however, require certain parameters to be set up prior to activating a session. SLIP does not extract the IP address from the modem. This must be set up in dial-up-networking before starting. SLIP is less flexible than Point to Point Protocol (PPP) which is quickly winning over most users.
The SLIP session is usually controlled by DTR, unless the modem has been configured to ignore DTR by programming register S211. DTR, when used, must be asserted to initiate a session and de-asserted to terminate a session. If the modem has been programmed not to use DTR Control, then the command AT\ASLIP can be sent without asserting DTR. To exit SLIP in this case, the host must either power down the modem or use the escape sequence. To terminate a SLIP session, DTR must be de-asserted or the escape sequence can be activated or the modem can be powered down.