2 .\" Copyright (c) 1997, 2001 Joerg Wunsch
4 .\" All rights reserved.
6 .\" Redistribution and use in source and binary forms, with or without
7 .\" modification, are permitted provided that the following conditions
9 .\" 1. Redistributions of source code must retain the above copyright
10 .\" notice, this list of conditions and the following disclaimer.
11 .\" 2. Redistributions in binary form must reproduce the above copyright
12 .\" notice, this list of conditions and the following disclaimer in the
13 .\" documentation and/or other materials provided with the distribution.
15 .\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY EXPRESS OR
16 .\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
17 .\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
18 .\" IN NO EVENT SHALL THE DEVELOPERS BE LIABLE FOR ANY DIRECT, INDIRECT,
19 .\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
20 .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
21 .\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
22 .\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23 .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
24 .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
26 .\" $FreeBSD: src/share/man/man4/sppp.4,v 1.8.2.5 2002/04/24 18:55:35 joerg Exp $
33 .Nd point to point protocol network layer for synchronous lines
35 .Cd "pseudo-device sppp"
39 network layer implements the state machine and the Link Control
41 .Em point to point protocol (PPP)
42 as described in RFC 1661. Note that this layer does not provide
43 network interfaces of its own, it is rather intended to be layered on
44 top of drivers providing a synchronous point-to-point connection that
45 wish to run a PPP stack over it. The corresponding network interfaces
46 have to be provided by these hardware drivers.
50 layer provides three basic modes of operation. The default mode,
51 with no special flags to be set, is to create the PPP connection
54 event to the LCP layer) as soon as the interface is taken up with the
56 command. Taking the interface down again will terminate the LCP layer
57 and thus all other layers on top. The link will also terminate itself as
58 soon as no Network Control Protocol (NCP) is open anymore, indicating
59 that the lower layers are no longer needed.
61 Setting the link-level flag
65 will cause the respective network interface to go into
67 mode. This means, the administrative
69 event to the LCP layer will be delayed until after the lower layers
74 This can be used by lower layers to support
75 a dialin connection where the physical layer isn't available
76 immediately at startup, but only after some external event arrives.
79 event from the lower layer will not take the interface completely down
82 Finally, setting the flag
84 will cause the interface to operate in
86 mode. This is also only useful if the lower layer supports the notion
87 of a carrier. Upon configuring the
88 respective interface, it will delay the administrative
90 event to the LCP layer until either an outbound network packet
91 arrives, or until the lower layer signals an
93 event, indicating an inbound connection. As with passive mode, receipt
96 event (loss of carrier) will not automatically take the interface down,
97 thus it remains available for further connections.
103 interface flag that can be set with
105 If this flag is set, the various control protocol packets being
106 exchanged as well as the option negotiation between both ends of the
107 link will be logged at level
109 This can be helpful to examine configuration problems during the first
110 attempts to set up a new configuration. Without this flag being set,
111 only the major phase transitions will be logged at level
114 It is possible to leave the local interface IP address open for
115 negotiation by setting it to 0.0.0.0. This requires that the remote
116 peer can correctly supply a value for it based on the identity of the
117 caller, or on the remote address supplied by this side. Due to the
118 way the IPCP option negotiation works, this address is being supplied
119 late during the negotiation, which might cause the remote peer to make
122 In a similar spirit the remote address can be set to the magical
125 which means that we don't care what address the remote
126 side will use, as long as it is not 0.0.0.0.
127 This is useful if your ISP has several dial-in
128 servers. You can of course
129 .Nm route Cm add Ar something_or_other 0.0.0. Ns Em *
130 and it will do exactly what you would want it to.
132 The PAP and CHAP authentication protocols as described in RFC 1334,
133 and RFC 1994 resp., are also implemented. Their parameters are being
138 VJ header compression is implemented, and enabled by default. It can be
143 .It <ifname><ifnum>: <proto> illegal <event> in state <statename>
144 An event happened that should not happen for the current state
145 the respective control protocol is in. See RFC 1661 for a description
146 of the state automaton.
147 .It <ifname><ifnum>: loopback
148 The state automaton detected a line loopback (that is, it was talking
149 with itself). The interface will be temporarily disabled.
150 .It <ifname><ifnum>: up
151 The LCP layer is running again, after a line loopback had previously
153 .It <ifname><ifnum>: down
154 The keepalive facility detected the line being unresponsive.
155 Keepalive must be explicitly requested by the lower layers in order to
165 .%A W. Simpson, Editor
166 .%T "The Point-to-Point Protocol (PPP)"
171 .%T "The PPP Internet Protocol Control Protocol (IPCP)"
177 .%T "PPP Authentication Protocols"
182 .%T "PPP Challenge Handshake Authentication Protocol (CHAP)"
187 The original implementation of
189 was written in 1994 at Cronyx Ltd., Moscow by
190 .An Serge Vakulenko Aq Mt vak@cronyx.ru .
191 .An J\(:org Wunsch Aq Mt joerg_wunsch@uriah.heep.sax.de
192 rewrote a large part in 1997 in order
193 to fully implement the state machine as described in RFC 1661, so it
194 could also be used for dialup lines. He also wrote this man page.
196 later on wrote a basic implementation for PAP and CHAP, which
197 served as the base for the current implementation, done again by
206 network protocol is supported.
207 More NCPs should be implemented, as well as other control protocols
208 for authentication and link quality reporting.
210 Negotiation loop avoidance is not fully implemented. If the negotiation
211 doesn't converge, this can cause an endless loop.
213 The various parameters that should be adjustable per RFC 1661 are
214 currently hard-coded into the kernel, and should be made accessible
219 mode has not been tested extensively.
221 Link-level compression protocols should be supported.