311 lines
11 KiB
Groff
311 lines
11 KiB
Groff
.\" Copyright (c) 1996-1999 Whistle Communications, Inc.
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.\" All rights reserved.
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.\"
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.\" Subject to the following obligations and disclaimer of warranty, use and
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.\" redistribution of this software, in source or object code forms, with or
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.\" without modifications are expressly permitted by Whistle Communications;
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.\" provided, however, that:
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.\" 1. Any and all reproductions of the source or object code must include the
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.\" copyright notice above and the following disclaimer of warranties; and
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.\" 2. No rights are granted, in any manner or form, to use Whistle
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.\" Communications, Inc. trademarks, including the mark "WHISTLE
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.\" COMMUNICATIONS" on advertising, endorsements, or otherwise except as
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.\" such appears in the above copyright notice or in the software.
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.\"
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.\" THIS SOFTWARE IS BEING PROVIDED BY WHISTLE COMMUNICATIONS "AS IS", AND
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.\" TO THE MAXIMUM EXTENT PERMITTED BY LAW, WHISTLE COMMUNICATIONS MAKES NO
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.\" REPRESENTATIONS OR WARRANTIES, EXPRESS OR IMPLIED, REGARDING THIS SOFTWARE,
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.\" INCLUDING WITHOUT LIMITATION, ANY AND ALL IMPLIED WARRANTIES OF
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.\" MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, OR NON-INFRINGEMENT.
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.\" WHISTLE COMMUNICATIONS DOES NOT WARRANT, GUARANTEE, OR MAKE ANY
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.\" REPRESENTATIONS REGARDING THE USE OF, OR THE RESULTS OF THE USE OF THIS
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.\" SOFTWARE IN TERMS OF ITS CORRECTNESS, ACCURACY, RELIABILITY OR OTHERWISE.
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.\" IN NO EVENT SHALL WHISTLE COMMUNICATIONS BE LIABLE FOR ANY DAMAGES
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.\" RESULTING FROM OR ARISING OUT OF ANY USE OF THIS SOFTWARE, INCLUDING
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.\" WITHOUT LIMITATION, ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
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.\" PUNITIVE, OR CONSEQUENTIAL DAMAGES, PROCUREMENT OF SUBSTITUTE GOODS OR
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.\" SERVICES, LOSS OF USE, DATA OR PROFITS, HOWEVER CAUSED AND UNDER ANY
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.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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.\" THIS SOFTWARE, EVEN IF WHISTLE COMMUNICATIONS IS ADVISED OF THE POSSIBILITY
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.\" OF SUCH DAMAGE.
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.\"
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.\" Author: Archie Cobbs <archie@whistle.com>
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.\"
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.\" $FreeBSD$
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.\" $Whistle: ng_ppp.8,v 1.3 1999/01/25 23:46:27 archie Exp $
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.\"
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.Dd January 19, 1999
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.Dt NG_PPP 8
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.Os FreeBSD
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.Sh NAME
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.Nm ng_ppp
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.Nd PPP protocol netgraph node type
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.Sh SYNOPSIS
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.Fd #include <netgraph/ng_ppp.h>
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.Sh DESCRIPTION
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The
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.Nm ppp
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node type performs multiplexing for the PPP protocol. It handles
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only packets that contain data, and forwards protocol negotiation
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and control packets to a separate controlling entity (e.g., a
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user-land daemon). This approach combines the fast dispatch of
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kernel implementations with the configuration flexibility of a
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user-land implementations. The PPP node type supports multi-link
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PPP, Van Jacobsen compression, PPP compression, and PPP encryption.
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A single PPP node corresponds to one PPP multi-link bundle.
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.Sh ENABLING FUNCTIONALITY
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In general, the PPP node enables a specific link or functionality when
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(a) a
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.Dv NGM_PPP_SET_CONFIG
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message has been received which enables it, and
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(b) the corresponding hook(s) are connected.
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This allows the controlling entity to use either method (a) or (b)
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(or both) to control the node's behavior.
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.Sh LINK HOOKS
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During normal operation, the individual PPP links are connected to hooks
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.Dv link0 ,
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.Dv link1 ,
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etc. Up to
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.Dv NG_PPP_MAX_LINKS
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links are supported.
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These device-independent hooks transmit and receive full PPP
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frames, which include the PPP protocol field, but no address, control
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or checksum fields.
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On outgoing frames, when protocol compression
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has been enabled and the protocol number is suitable for compression,
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the protocol field will be compressed (i.e., sent as one byte
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instead of two). Either compressed or uncompressed protocol fields
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are accepted on incoming frames.
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.Pp
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Since all negotiation is handled outside the PPP node, the links
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should not be connected and enabled until the corresponding link
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has reached the network phase (i.e., LCP negotiation and authentication
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have completed successfully) and the PPP node has been informed of
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the link parameters via the
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.Dv NGM_PPP_LINK_CONFIG
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message.
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.Sh COMPRESSION AND ENCRYPTION
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.Pp
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Compression is supported via two hooks,
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.Dv compress
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and
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.Dv decompress .
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When enabled and connected, the PPP node writes outgoing frames on the
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.Dv comp
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hook and expects to receive back the compressed frame on the same hook.
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Similarly, the
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.Dv decompress
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hook is used to uncompress incoming frames when decompression is
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negotiated (compression and decompression are independenly negotiable).
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The type of node attached to these hooks should correspond
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to the type of compression negotiated, e.g., Deflate, Predictor-1, etc.
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.Pp
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Encryption works exactly analogously via the
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.Dv encrypt
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and
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.Dv decrypt
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nodes. Data is always compressed before being encrypted,
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and decrypted before being decompressed.
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.Pp
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Only bundle-level compression and encryption is directly supported;
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link-level compression and encryption can be handled transparently
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by downstream nodes.
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.Sh VAN JACOBSEN COMPRESSION
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When all of the
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.Dv vjc_ip ,
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.Dv vjc_vjcomp ,
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.Dv vjc_vjuncomp ,
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and
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.Dv vjc_vjip
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hooks are connected, and the corresponding configuration flag is
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enabled, Van Jacobsen compression and/or decompression will become active.
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Normally these hooks connect to the corresponding hooks of a single
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.Xr ng_vjc 8
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node. The PPP node is compatible with the ``pass through'' modes of the
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.Xr ng_vjc 8
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node type.
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.Sh BYPASS HOOK
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When a frame is received on a link with an unsupported protocol,
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or a protocol which is disabled or for which the corresponding hook
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is unconnected, the PPP node forwards the frame out the
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.Dv bypass
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hook, prepended with a four byte prefix. This first two bytes of
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the prefix indicate the link number on which the frame was received
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(in network order).
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For such frames received over the bundle (i.e., encapsulated in the
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multi-link protocol), the special link number
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.Dv NG_PPP_BUNDLE_LINKNUM
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is used. After the two byte link number is the two byte PPP protocol number
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(also in network order).
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The PPP protocol number is two bytes long even if the original frame
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was protocol compressed.
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.Pp
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Conversely, any data written to the
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.Dv bypass
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hook is assumed to be in this same format. The four byte header is
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stripped off, the PPP protocol number is prepended (possibly compressed),
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and the frame is delivered over the desired link.
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If the link number is
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.Dv NG_PPP_BUNDLE_LINKNUM
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the frame will be delivered over the multi-link bundle; or, if multi-link
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is disabled, over the (single) PPP link.
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.Pp
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Typically when the controlling entity receives a packet on the bypass
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hook it responds either by dropping the frame (if it's not ready for
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the protocol) or with an LCP protocol reject (if it doesn't recognize
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or expect the protocol).
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.Sh MULTILINK OPERATION
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To enable multi-link PPP, the corresponding configuration flag must be set
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and at least one link connected. The PPP node will not allow more than
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one link to be connected if multi-link is not enabled, nor will it allow
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certain multi-link settings to be changed while multi-link operation is
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active (e.g., short sequence number header format).
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.Pp
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Because packets are sent as fragments across multiple individual links,
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it is important that when a link goes down the PPP node is notified
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immediately, either by disconnecting the corresponding hook or disabling
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the link via the
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.Dv NGM_PPP_SET_CONFIG
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control message.
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.Pp
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Each link has configuration parameters for latency (specified in
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miliseconds) and bandwidth (specified in tens of bytes per second).
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The PPP node can be configured for
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.Em round-robin
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or
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.Em optimized
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packet delivery.
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.Pp
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When configured for round-robin delivery, the latency and bandwidth
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values are ignored and the PPP node simply sends each frame as a
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single fragment, alternating frames across all the links in the
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bundle. This scheme has the advantage that even if one link fails
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silently, some packets will still get through. It has the disadvantage
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of sub-optimal overall bundle latency, which is important for
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interactive response time, and sub-optimal overall bundle bandwidth
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when links with different bandwidths exist in the same bundle.
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.Pp
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When configured for optimal delivery, the PPP node distributes the
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packet across the links in a way that minimizes the time it takes
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for the completed packet to be received by the far end. This
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involves taking into account each link's latency, bandwith, and
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current queue length. Therefore these numbers should be
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configured as accurately as possible. The algorithm does require
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some computation, so may not be appropriate for very slow machines
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and/or very fast links.
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.Pp
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As a special case, if all links have identical latency and bandwidth,
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then the above algorithm is disabled (because it is unnecessary)
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and the PPP node simply fragments frames into equal sized portions
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across all of the links.
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.Sh HOOKS
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This node type supports the following hooks:
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.Pp
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.Bl -tag -compact -width vjc_vjuncomp
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.It Dv link<N>
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Individual PPP link number
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.Dv <N>
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.It Dv compress
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Connection to compression engine
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.It Dv decompress
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Connection to decompression engine
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.It Dv encrypt
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Connection to encryption engine
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.It Dv decrypt
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Connection to decryption engine
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.It Dv vjc_ip
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Connection to
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.Xr ng_vjc 8
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.Dv ip
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hook
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.It Dv vjc_vjcomp
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Connection to
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.Xr ng_vjc 8
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.Dv vjcomp
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hook
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.It Dv vjc_vjuncomp
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Connection to
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.Xr ng_vjc 8
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.Dv vjuncomp
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hook
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.It Dv vjc_vjip
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Connection to
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.Xr ng_vjc 8
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.Dv vjip
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hook
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.It Dv inet
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IP packet data
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.It Dv atalk
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AppleTalk packet data
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.It Dv ipx
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IPX packet data
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.It Dv bypass
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Bypass hook; frames have a four byte header consisting of
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a link number and a PPP protocol number.
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.El
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.Pp
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.Sh CONTROL MESSAGES
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This node type supports the generic control messages, plus the following:
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.Bl -tag -width foo
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.It Dv NGM_PPP_SET_CONFIG
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This command configures all aspects of the node. This includes enabling
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multi-link PPP, encryption, compression, Van Jacobsen compression, and IP,
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AppleTalk, and IPX packet delivery. It includes per-link configuration,
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including enabling the link, setting latency and bandwidth parameters,
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and enabling protocol field compression. Note that no link or functionality
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is active until the corresponding hook is also connected.
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This command takes a
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.Dv "struct ng_ppp_node_config"
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as an argument.
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.It Dv NGM_PPP_GET_CONFIG
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Returns the current configuration as a
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.Dv "struct ng_ppp_node_config" .
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.It Dv NGM_PPP_GET_LINK_STATS
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This command takes a two byte link number as an argument and returns a
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.Dv "struct ng_ppp_link_stat"
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containing statistics for the corresponding link. Here
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.Dv NG_PPP_BUNDLE_LINKNUM
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is a valid link number corresponding to the multi-link bundle.
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.It Dv NGM_PPP_CLR_LINK_STATS
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This command takes a two byte link number as an argument and
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clears the statistics for that link. If
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.Dv NG_PPP_BUNDLE_LINKNUM
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is given,
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.Em all
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statistics are cleared.
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.El
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.Pp
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This node type also accepts the control messages accepted by the
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.Xr ng_vjc 8
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node type. When received, these messages are simply forwarded to
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the adjacent
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.Xr ng_vjc 8
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node, if any.
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.Sh SHUTDOWN
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This node shuts down upon receipt of a
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.Dv NGM_SHUTDOWN
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control message, or when all hooks have been disconnected.
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.Sh SEE ALSO
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.Xr netgraph 4 ,
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.Xr ng_async 8 ,
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.Xr ng_iface 8 ,
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.Xr ng_vjc 8 ,
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.Xr ngctl 8 .
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.Rs
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.%A W. Simpson
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.%T "The Point-to-Point Protocol (PPP)"
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.%O RFC 1661
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.Re
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.Rs
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.%A K. Sklower
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.%A B. Lloyd
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.%A G. McGregor
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.%A D. Carr
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.%A T. Coradetti
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.%T "The PPP Multilink Protocol (MP)"
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.%O RFC 1990
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.Re
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.Sh AUTHOR
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Archie Cobbs <archie@whistle.com>
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