115 lines
5.2 KiB
Perl
115 lines
5.2 KiB
Perl
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.\" Copyright (c) 1983, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)e.t 8.1 (Berkeley) 6/8/93
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.\"
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.\".ds RH "Network configuration options
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.bp
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.LG
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.B
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.ce
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APPENDIX E. NETWORK CONFIGURATION OPTIONS
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.sp
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.R
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.NL
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.PP
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The network support in the kernel is self-configuring
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according to the protocol support options (INET and NS) and the network
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hardware discovered during autoconfiguration.
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There are several changes that may be made to customize network behavior
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due to local restrictions.
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Within the Internet protocol routines, the following options
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set in the system configuration file are supported:
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.IP \fBGATEWAY\fP
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.br
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The machine is to be used as a gateway.
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This option currently makes only minor changes.
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First, the size of the network routing hash table is increased.
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Secondly, machines that have only a single hardware network interface
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will not forward IP packets; without this option, they will also refrain
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from sending any error indication to the source of unforwardable packets.
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Gateways with only a single interface are assumed to have missing
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or broken interfaces, and will return ICMP unreachable errors to hosts
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sending them packets to be forwarded.
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.IP \fBTCP_COMPAT_42\fP
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.br
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This option forces the system to limit its initial TCP sequence numbers
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to positive numbers.
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Without this option, 4.4BSD systems may have problems with TCP connections
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to 4.2BSD systems that connect but never transfer data.
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The problem is a bug in the 4.2BSD TCP.
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.IP \fBIPFORWARDING\fP
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.br
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Normally, 4.4BSD machines with multiple network interfaces
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will forward IP packets received that should be resent to another host.
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If the line ``options IPFORWARDING="0"'' is in the system configuration
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file, IP packet forwarding will be disabled.
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.IP \fBIPSENDREDIRECTS\fP
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.br
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When forwarding IP packets, 4.4BSD IP will note when a packet is forwarded
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using the same interface on which it arrived.
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When this is noted, if the source machine is on the directly-attached
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network, an ICMP redirect is sent to the source host.
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If the packet was forwarded using a route to a host or to a subnet,
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a host redirect is sent, otherwise a network redirect is sent.
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The generation of redirects may be inhibited with the configuration
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option ``options IPSENDREDIRECTS="0".''
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.br
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.IP \fBSUBNETSARELOCAL\fP
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TCP calculates a maximum segment size to use for each connection,
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and sends no datagrams larger than that size.
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This size will be no larger than that supported on the outgoing
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interface.
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Furthermore, if the destination is not on the local network,
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the size will be no larger than 576 bytes.
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For this test, other subnets of a directly-connected subnetted
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network are considered to be local unless the line
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``options SUBNETSARELOCAL="0"'' is used in the system configuration file.
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.LP
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The following options are supported by the Xerox NS protocols:
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.IP \fBNSIP\fP
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.br
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This option allows NS IDP datagrams to be encapsulated in Internet IP
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packets for transmission to a collaborating NSIP host.
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This may be used to pass IDP packets through IP-only link layer networks.
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See
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.IR nsip (4P)
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for details.
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.IP \fBTHREEWAYSHAKE\fP
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.br
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The NS Sequenced Packet Protocol does not require a three-way handshake
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before considering a connection to be in the established state.
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(A three-way handshake consists of a connection request, an acknowledgement
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of the request along with a symmetrical opening indication,
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and then an acknowledgement of the reciprocal opening packet.)
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This option forces a three-way handshake before data may be transmitted
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on Sequenced Packet sockets.
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