221 lines
6.5 KiB
Groff
221 lines
6.5 KiB
Groff
.\" Copyright (c) 1990, 1991 The Regents of the University of California.
|
|
.\" All rights reserved.
|
|
.\"
|
|
.\" Redistribution and use in source and binary forms, with or without
|
|
.\" modification, are permitted provided that the following conditions
|
|
.\" are met:
|
|
.\" 1. Redistributions of source code must retain the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer.
|
|
.\" 2. Redistributions in binary form must reproduce the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer in the
|
|
.\" documentation and/or other materials provided with the distribution.
|
|
.\" 3. All advertising materials mentioning features or use of this software
|
|
.\" must display the following acknowledgement:
|
|
.\" This product includes software developed by the University of
|
|
.\" California, Berkeley and its contributors.
|
|
.\" 4. Neither the name of the University nor the names of its contributors
|
|
.\" may be used to endorse or promote products derived from this software
|
|
.\" without specific prior written permission.
|
|
.\"
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
|
|
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
|
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
|
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
|
|
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
|
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
|
|
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
|
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
|
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
|
|
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
|
.\" SUCH DAMAGE.
|
|
.\"
|
|
.\" @(#)esis.4 6.2 (Berkeley) 3/28/91
|
|
.\"
|
|
.Dd March 28, 1991
|
|
.Dt ESIS 4
|
|
.Os
|
|
.Sh NAME
|
|
.Nm es-is
|
|
.Nd End System to Intermediate System Routing Protocol
|
|
.Sh SYNOPSIS
|
|
.Sy pseudo-device
|
|
.Nm ether
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Nm ES-IS
|
|
routing protocol is used to dynamically map between
|
|
.Tn ISO NSAP
|
|
addresses and
|
|
.Tn ISO SNPA
|
|
addresses; to permit End and Intermediate Systems
|
|
to learn of each other's existence; and to allow Intermediate Systems
|
|
to inform End Systems of (potentially) better routes to use when
|
|
forwarding
|
|
.Tn NPDU Ns s
|
|
to a particular destination.
|
|
.Pp
|
|
The mapping between
|
|
.Tn NSAP
|
|
addresses and
|
|
.Tn SNPA
|
|
addresses is accomplished by
|
|
transmitting hello
|
|
.Tn PDU Ns s
|
|
between the cooperating Systems. These
|
|
.Tn PDU Ns s
|
|
are transmitted whenever the
|
|
.Em configuration
|
|
timer expires.
|
|
When a hello
|
|
.Tn PDU
|
|
is received, the
|
|
.Tn SNPA
|
|
address that it conveys is stored in the routing table for as long as the
|
|
.Em holding time
|
|
in the
|
|
.Tn PDU
|
|
suggests. The default
|
|
.Em holding time
|
|
(120 seconds) placed in the hello
|
|
.Tn PDU ,
|
|
the configuration timer value,
|
|
and the system type (End System or Intermediate System) may be changed by
|
|
issuing an
|
|
.Dv SIOCSSTYPE
|
|
.Xr ioctl 2 ,
|
|
which is defined in
|
|
.Pa /sys/netiso/iso_snpac.h.
|
|
.Pp
|
|
The protocol behaves differently depending on whether the System is
|
|
configured as an End System or an Intermediate System.
|
|
.Sh END SYSTEM OPERATION
|
|
When an interface requests a mapping for an address not in the cache,
|
|
the
|
|
.Tn SNPA
|
|
of any known Intermediate System is returned. If an Intermediate
|
|
System is not known, then the
|
|
.Em all end systems
|
|
multicast address
|
|
is returned. It is assumed that the intended recipient of the NPDU will
|
|
immediately transmit a hello
|
|
.Tn PDU
|
|
back to the originator of the
|
|
.Tn NPDU .
|
|
.Pp
|
|
If an
|
|
.Tn NPDU
|
|
is forwarded by the End System, a redirect
|
|
.Tn PDU
|
|
will not be
|
|
generated.
|
|
However, redirect
|
|
.Tn PDU Ns s
|
|
received will be processed. This processing
|
|
consists of adding an entry in the routing table. If the
|
|
redirect is towards an Intermediate System, then an entry is made in the
|
|
routing table as well.
|
|
The entry in the routing table will may mark the
|
|
.Tn NSAP
|
|
address contained in the redirect
|
|
.Tn PDU
|
|
as the gateway for the destination
|
|
system (if an NET is supplied), or will create a route with
|
|
the NSAP address as the
|
|
destination and the
|
|
.Tn SNPA
|
|
address (embodied as a link-level sockaddr) as the
|
|
gateway.
|
|
.Pp
|
|
If the System is configured as an End System, it will report all the
|
|
.Tn NSAP Ns s
|
|
that have been configured using the ifconfig command, and no others.
|
|
It is possible to have more than one
|
|
.Tn NSAP
|
|
assigned to a given interface,
|
|
and it is also possible to have the same
|
|
.Tn NSAP
|
|
assigned to multiple
|
|
interfaces.
|
|
However, any
|
|
.Tn NSAP
|
|
containing an NSEL that is consistent with the
|
|
nsellength option (default one) of any interface will be accepted as
|
|
an
|
|
.Tn NSAP
|
|
for this System.
|
|
.Sh INTERMEDIATE SYSTEM OPERATION
|
|
When an interface requests a mapping for an address not in the routing table,
|
|
an error is returned.
|
|
.Pp
|
|
When an
|
|
.Tn NPDU
|
|
is forwarded out on the same interface that the
|
|
.Tn NPDU
|
|
arrived upon,
|
|
a redirect
|
|
.Tn PDU
|
|
is generated.
|
|
.Sh MANUAL ROUTING TABLE MODIFICATION
|
|
.Pp
|
|
To facilitate communications with systems which do not use
|
|
.Nm ES-IS,
|
|
one may add a route whose destination is a sockaddr_iso containing
|
|
the
|
|
.Tn NSAP
|
|
in question, and the gateway being a link-level sockaddr,
|
|
either by writing a special purpose program, or using the
|
|
.Xr route 8
|
|
command e.g.:
|
|
.Bd -literal
|
|
route add -iface -osi 49.0.4.8.0.2b.b.83.bf \
|
|
-link qe0:8.0.2b.b.83.bf
|
|
.Ed
|
|
.Pp
|
|
If the
|
|
System is configured as an End System and has a single network interface
|
|
which does not support multicast reception,
|
|
it is necessary to manually configure the location of an
|
|
.Tn IS ,
|
|
using the route command in a similar way.
|
|
There, the destination address should be
|
|
.Dq default
|
|
(spelled
|
|
out literally as 7
|
|
.Tn ASCII
|
|
characters), and the gateway should be
|
|
once again be a link-level sockaddr specifying the
|
|
.Tn SNPA
|
|
of the
|
|
.Tn IS .
|
|
.Sh SEE ALSO
|
|
.Xr un 4 ,
|
|
.Xr iso 4 ,
|
|
.Xr route 8 ,
|
|
.Xr ifconfig 8
|
|
.Rs
|
|
.%T "End system to Intermediate system routing exchange protocol for use in conjunction with the Protocol for providing the connectionless-mode network service"
|
|
.%R ISO
|
|
.%N 9542
|
|
.Re
|
|
.Sh HISTORY
|
|
The
|
|
.Nm
|
|
protocol implementation
|
|
.Ud
|
|
.Sh BUGS
|
|
Redirect
|
|
.Tn PDU Ns s
|
|
do not contain options from the forwarded
|
|
.Tn NPDU
|
|
which generated
|
|
the redirect. The multicast address used on the 802.3 network is taken from
|
|
the
|
|
.Tn NBS
|
|
December 1987 agreements. This multicast address is not compatible
|
|
with the 802.5 (Token Ring) multicast addresses format. Therefore, broadcast
|
|
addresses are used on the 802.5 subnetwork.
|
|
Researchers at the University of Wisconsin are constructing an implementation
|
|
of the
|
|
.Tn IS-IS
|
|
routing protocol.
|