Black Box Console Server user guide 74
Configuring a dial in line

Introduction to SLIP and PPP connections

This section deals with setting up SLIP and PPP connections on a line. There is also
a summary of the configurable features of modems.

Deciding whether to use SLIP or PPP

If you require any of the features listed below, use PPP, otherwise SLIP sh ould be
sufficient.
IP Address Negotiation. SLIP provides no mechanism for informi ng the other end of a
link of its IP address, whereas PPP will do so.
Error Checking. SLIP does not error check whereas PPP does. This is not necessarily a
problem in SLIP since most upper layer protocols have their own error checking.
Some systems exchange UDP packets with checksum disabl ed, which would cause
problems should that part of an IP packet get corrupted.
Authentication. Once SLIP has started you cannot authenticate the remote device,
whereas as PPP provides the option of using security protocols PAP or CHAP. See
Configuring PPP on page 82, then sub-section ‘Security’ for further details.
Software Flow Control. You cannot use software flow control on SLIP links since there
is no way of escaping control characters from the data stream. PPP has a facility (calle d
ACCM) which allows specific control characters to be escaped from the data stream.
See Configuring PPP on page 82 for more details.
For more information on the SLIP and PPP protocols see Configuring a dial in line on
page 74.