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 $
27 .\" $DragonFly: src/share/man/man4/sppp.4,v 1.2 2003/06/17 04:36:59 dillon Exp $
34 .Nd point to point protocol network layer for synchronous lines
36 .Cd "pseudo-device sppp"
40 network layer implements the state machine and the Link Control
42 .Em point to point protocol (PPP)
43 as described in RFC 1661. Note that this layer does not provide
44 network interfaces of its own, it is rather intended to be layered on
45 top of drivers providing a synchronous point-to-point connection that
46 wish to run a PPP stack over it. The corresponding network interfaces
47 have to be provided by these hardware drivers.
51 layer provides three basic modes of operation. The default mode,
52 with no special flags to be set, is to create the PPP connection
55 event to the LCP layer) as soon as the interface is taken up with the
57 command. Taking the interface down again will terminate the LCP layer
58 and thus all other layers on top. The link will also terminate itself as
59 soon as no Network Control Protocol (NCP) is open anymore, indicating
60 that the lower layers are no longer needed.
62 Setting the link-level flag
66 will cause the respective network interface to go into
68 mode. This means, the administrative
70 event to the LCP layer will be delayed until after the lower layers
75 This can be used by lower layers to support
76 a dialin connection where the physical layer isn't available
77 immediately at startup, but only after some external event arrives.
80 event from the lower layer will not take the interface completely down
83 Finally, setting the flag
85 will cause the interface to operate in
87 mode. This is also only useful if the lower layer supports the notion
88 of a carrier (like with an ISDN line). Upon configuring the
89 respective interface, it will delay the administrative
91 event to the LCP layer until either an outbound network packet
92 arrives, or until the lower layer signals an
94 event, indicating an inbound connection. As with passive mode, receipt
97 event (loss of carrier) will not automatically take the interface down,
98 thus it remains available for further connections.
104 interface flag that can be set with
106 If this flag is set, the various control protocol packets being
107 exchanged as well as the option negotiation between both ends of the
108 link will be logged at level
110 This can be helpful to examine configuration problems during the first
111 attempts to set up a new configuration. Without this flag being set,
112 only the major phase transitions will be logged at level
115 It is possible to leave the local interface IP address open for
116 negotiation by setting it to 0.0.0.0. This requires that the remote
117 peer can correctly supply a value for it based on the identity of the
118 caller, or on the remote address supplied by this side. Due to the
119 way the IPCP option negotiation works, this address is being supplied
120 late during the negotiation, which might cause the remote peer to make
123 In a similar spirit the remote address can be set to the magical
126 which means that we don't care what address the remote
127 side will use, as long as it is not 0.0.0.0.
128 This is useful if your ISP has several dial-in
129 servers. You can of course
130 .Nm route Cm add Ar something_or_other 0.0.0. Ns Em *
131 and it will do exactly what you would want it to.
133 The PAP and CHAP authentication protocols as described in RFC 1334,
134 and RFC 1994 resp., are also implemented. Their parameters are being
139 VJ header compression is implemented, and enabled by default. It can be
144 .It <ifname><ifnum>: <proto> illegal <event> in state <statename>
145 An event happened that should not happen for the current state
146 the respective control protocol is in. See RFC 1661 for a description
147 of the state automaton.
148 .It <ifname><ifnum>: loopback
149 The state automaton detected a line loopback (that is, it was talking
150 with itself). The interface will be temporarily disabled.
151 .It <ifname><ifnum>: up
152 The LCP layer is running again, after a line loopback had previously
154 .It <ifname><ifnum>: down
155 The keepalive facility detected the line being unresponsive.
156 Keepalive must be explicitly requested by the lower layers in order to
166 .%A W. Simpson, Editor
167 .%T "The Point-to-Point Protocol (PPP)"
172 .%T "The PPP Internet Protocol Control Protocol (IPCP)"
178 .%T "PPP Authentication Protocols"
183 .%T "PPP Challenge Handshake Authentication Protocol (CHAP)"
188 The original implementation of
190 was written in 1994 at Cronyx Ltd., Moscow by
191 .An Serge Vakulenko Aq vak@cronyx.ru .
193 .Aq joerg_wunsch@uriah.heep.sax.de
194 rewrote a large part in 1997 in order
195 to fully implement the state machine as described in RFC 1661, so it
196 could also be used for dialup lines. He also wrote this man page.
197 Serge later on wrote a basic implementation for PAP and CHAP, which
198 served as the base for the current implementation, done again by
207 network protocol is supported.
208 More NCPs should be implemented, as well as other control protocols
209 for authentication and link quality reporting.
211 Negotiation loop avoidance is not fully implemented. If the negotiation
212 doesn't converge, this can cause an endless loop.
214 The various parameters that should be adjustable per RFC 1661 are
215 currently hard-coded into the kernel, and should be made accessible
220 mode has not been tested extensively.
222 Link-level compression protocols should be supported.