afdebce3f6
This will make FreeBSD boxes better behaved 'MBONE Citizens', based on a couple of the comments about the severity of fixes.. Agreed to by: wollman, fenner@parc.xerox.com
405 lines
15 KiB
Groff
405 lines
15 KiB
Groff
'\"COPYRIGHT 1989 by The Board of Trustees of Leland Stanford Junior University.
|
|
'\"$Id: mrouted.8,v 3.8 1995/11/29 22:37:21 fenner Rel $
|
|
.TH MROUTED 8
|
|
.UC 5
|
|
.SH NAME
|
|
mrouted \- IP multicast routing daemon
|
|
.SH SYNOPSIS
|
|
.B /etc/mrouted
|
|
[
|
|
.B \-p
|
|
] [
|
|
.B \-c
|
|
.I config_file
|
|
] [
|
|
.B \-d
|
|
[
|
|
.I debug_level
|
|
]]
|
|
.SH DESCRIPTION
|
|
.I Mrouted
|
|
is an implementation of the Distance-Vector Multicast Routing
|
|
Protocol (DVMRP), an earlier version of which is specified in RFC-1075.
|
|
It maintains topological knowledge via a distance-vector routing protocol
|
|
(like RIP, described in RFC-1058), upon which it implements a multicast
|
|
datagram forwarding algorithm called Reverse Path Multicasting.
|
|
.PP
|
|
.I Mrouted
|
|
forwards a multicast datagram along a shortest (reverse) path tree
|
|
rooted at the subnet on which the datagram originates. The multicast
|
|
delivery tree may be thought of as a broadcast delivery tree that has
|
|
been pruned back so that it does not extend beyond those subnetworks
|
|
that have members of the destination group. Hence, datagrams
|
|
are not forwarded along those branches which have no listeners of the
|
|
multicast group. The IP time-to-live of a multicast datagram can be
|
|
used to limit the range of multicast datagrams.
|
|
.PP
|
|
In order to support multicasting among subnets that are separated by (unicast)
|
|
routers that do not support IP multicasting,
|
|
.I mrouted
|
|
includes support for
|
|
"tunnels", which are virtual point-to-point links between pairs of
|
|
.IR mrouted s
|
|
located anywhere in an internet. IP multicast packets are encapsulated for
|
|
transmission through tunnels, so that they look like normal unicast datagrams
|
|
to intervening routers and subnets. The encapsulation
|
|
is added on entry to a tunnel, and stripped off
|
|
on exit from a tunnel.
|
|
By default, the packets are encapsulated using the IP-in-IP protocol
|
|
(IP protocol number 4).
|
|
Older versions of
|
|
.I mrouted
|
|
tunnel using IP source routing, which puts a heavy load on some
|
|
types of routers.
|
|
This version does not support IP source route tunnelling.
|
|
.PP
|
|
The tunnelling mechanism allows
|
|
.I mrouted
|
|
to establish a virtual internet, for
|
|
the purpose of multicasting only, which is independent of the physical
|
|
internet, and which may span multiple Autonomous Systems. This capability
|
|
is intended for experimental support of internet multicasting only, pending
|
|
widespread support for multicast routing by the regular (unicast) routers.
|
|
.I Mrouted
|
|
suffers from the well-known scaling problems of any distance-vector
|
|
routing protocol, and does not (yet) support hierarchical multicast routing.
|
|
.PP
|
|
.I Mrouted
|
|
handles multicast routing only; there may or may not be unicast routing
|
|
software running on the same machine as
|
|
.IR mrouted .
|
|
With the use of tunnels, it
|
|
is not necessary for
|
|
.I mrouted
|
|
to have access to more than one physical subnet
|
|
in order to perform multicast forwarding.
|
|
.br
|
|
.ne 5
|
|
.SH INVOCATION
|
|
.PP
|
|
If no "\-d" option is given, or if the debug level is specified as 0,
|
|
.I mrouted
|
|
detaches from the invoking terminal. Otherwise, it remains attached to the
|
|
invoking terminal and responsive to signals from that terminal. If "\-d" is
|
|
given with no argument, the debug level defaults to 2. Regardless of the
|
|
debug level,
|
|
.I mrouted
|
|
always writes warning and error messages to the system
|
|
log demon. Non-zero debug levels have the following effects:
|
|
.IP "level 1"
|
|
all syslog'ed messages are also printed to stderr.
|
|
.IP "level 2"
|
|
all level 1 messages plus notifications of "significant"
|
|
events are printed to stderr.
|
|
.IP "level 3"
|
|
all level 2 messages plus notifications of all packet
|
|
arrivals and departures are printed to stderr.
|
|
.PP
|
|
Upon startup, mrouted writes its pid to the file /etc/mrouted.pid .
|
|
.SH CONFIGURATION
|
|
.PP
|
|
.I Mrouted
|
|
automatically configures itself to forward on all multicast-capable
|
|
interfaces, i.e., interfaces that have the IFF_MULTICAST flag set (excluding
|
|
the loopback "interface"), and it finds other
|
|
.IR mrouted s
|
|
directly reachable
|
|
via those interfaces. To override the default configuration, or to add
|
|
tunnel links to other
|
|
.IR mrouted s,
|
|
configuration commands may be placed in
|
|
/etc/mrouted.conf (or an alternative file, specified by the "\-c" option).
|
|
There are four types of configuration commands:
|
|
.nf
|
|
|
|
phyint <local-addr> [disable] [metric <m>]
|
|
[threshold <t>] [rate_limit <b>]
|
|
[boundary (<boundary-name>|<scoped-addr>/<mask-len>)]
|
|
[altnet <network>/<mask-len>]
|
|
|
|
tunnel <local-addr> <remote-addr> [metric <m>]
|
|
[threshold <t>] [rate_limit <b>]
|
|
[boundary (<boundary-name>|<scoped-addr>/<mask-len>)]
|
|
|
|
cache_lifetime <ct>
|
|
|
|
pruning <off/on>
|
|
|
|
name <boundary-name> <scoped-addr>/<mask-len>
|
|
|
|
.fi
|
|
.PP
|
|
The file format is free-form; whitespace (including newlines) is not
|
|
significant.
|
|
The
|
|
.I boundary
|
|
and
|
|
.I altnet
|
|
options may be specified as many times as necessary.
|
|
.PP
|
|
The phyint command can be used to disable multicast routing on the physical
|
|
interface identified by local IP address <local-addr>, or to associate a
|
|
non-default metric or threshold with the specified physical interface.
|
|
The local IP address <local-addr> may be replaced by the
|
|
interface name (e.g le0).
|
|
If a phyint is attached to multiple IP subnets, describe each additional subnet
|
|
with the altnet keyword.
|
|
Phyint commands must precede tunnel commands.
|
|
.PP
|
|
The tunnel command can be used to establish a tunnel link between local
|
|
IP address <local-addr> and remote IP address <remote-addr>, and to associate
|
|
a non-default metric or threshold with that tunnel.
|
|
The local IP address <local-addr> may be replaced by the
|
|
interface name (e.g. le0). The remote IP address <remote-addr> may
|
|
be replaced by a host name, if and only if the host name has a single
|
|
IP address associated with it.
|
|
The tunnel must be set
|
|
up in the mrouted.conf files of both routers before it can be used.
|
|
'\"For backwards compatibility with older
|
|
'\".IR mrouted s,
|
|
'\"the srcrt keyword specifies
|
|
'\"encapsulation using IP source routing.
|
|
.PP
|
|
The cache_lifetime is a value that determines the amount of time that a
|
|
cached multicast route stays in kernel before timing out. The value of this
|
|
entry should lie between 300 (5 min) and 86400 (1 day). It defaults to 300.
|
|
.PP
|
|
The pruning <off/on> option is provided for
|
|
.IR mrouted
|
|
to act as a non-pruning router. It is also possible to start
|
|
.IR mrouted
|
|
in a non-pruning mode using the "-p" option on the command line. It is
|
|
expected that a router would be configured in this manner for test
|
|
purposes only. The default mode is pruning enabled.
|
|
.PP
|
|
You may assign names to boundaries to make configuration easier with
|
|
the name keyword. The boundary option on phyint or tunnel commands
|
|
can accept either a name or a boundary.
|
|
.PP
|
|
The metric is the "cost" associated with sending a datagram on the given
|
|
interface or tunnel; it may be used to influence the choice of routes.
|
|
The metric defaults to 1. Metrics should be kept as small as possible,
|
|
because
|
|
.I mrouted
|
|
cannot route along paths with a sum of metrics greater
|
|
than 31.
|
|
.LP
|
|
The threshold is the minimum IP time-to-live required for a multicast datagram
|
|
to be forwarded to the given interface or tunnel. It is used to control the
|
|
scope of multicast datagrams. (The TTL of forwarded packets is only compared
|
|
to the threshold, it is not decremented by the threshold. Every multicast
|
|
router decrements the TTL by 1.) The default threshold is 1.
|
|
.LP
|
|
In general, all
|
|
.IR mrouted s
|
|
connected to a particular subnet or tunnel should
|
|
use the same metric and threshold for that subnet or tunnel.
|
|
.PP
|
|
The rate_limit option allows the network administrator to specify a
|
|
certain bandwidth in Kbits/second which would be allocated to multicast
|
|
traffic. It defaults to 500Kbps on tunnels, and 0 (unlimited) on physical
|
|
interfaces.
|
|
.PP
|
|
The boundary option allows an interface
|
|
to be configured as an administrative boundary for the specified
|
|
scoped address. Packets belonging to this address will not
|
|
be forwarded on a scoped interface. The boundary option accepts either
|
|
a name or a boundary spec.
|
|
.PP
|
|
.I Mrouted
|
|
will not initiate execution if it has fewer than two enabled vifs,
|
|
where a vif (virtual interface) is either a physical multicast-capable
|
|
interface or a tunnel. It will log a warning if all of its vifs are
|
|
tunnels; such an
|
|
.I mrouted
|
|
configuration would be better replaced by more
|
|
direct tunnels (i.e., eliminate the middle man).
|
|
.SH "EXAMPLE CONFIGURATION"
|
|
.PP
|
|
This is an example configuration for a mythical multicast router at a big
|
|
school.
|
|
.sp
|
|
.nf
|
|
#
|
|
# mrouted.conf example
|
|
#
|
|
# Name our boundaries to make it easier
|
|
name LOCAL 239.255.0.0/16
|
|
name EE 239.254.0.0/16
|
|
#
|
|
# le1 is our gateway to compsci, don't forward our
|
|
# local groups to them
|
|
phyint le1 boundary EE
|
|
#
|
|
# le2 is our interface on the classroom net, it has four
|
|
# different length subnets on it.
|
|
# note that you can use either an ip address or an
|
|
# interface name
|
|
phyint 172.16.12.38 boundary EE altnet 172.16.15.0/26
|
|
altnet 172.16.15.128/26 altnet 172.16.48.0/24
|
|
#
|
|
# atm0 is our ATM interface, which doesn't properly
|
|
# support multicasting.
|
|
phyint atm0 disable
|
|
#
|
|
# This is an internal tunnel to another EE subnet
|
|
# Remove the default tunnel rate limit, since this
|
|
# tunnel is over ethernets
|
|
tunnel 192.168.5.4 192.168.55.101 metric 1 threshold 1
|
|
rate_limit 0
|
|
#
|
|
# This is our tunnel to the outside world.
|
|
# Careful with those boundaries, Eugene.
|
|
tunnel 192.168.5.4 10.11.12.13 metric 1 threshold 32
|
|
boundary LOCAL boundary EE
|
|
.fi
|
|
.SH SIGNALS
|
|
.PP
|
|
.I Mrouted
|
|
responds to the following signals:
|
|
.IP HUP
|
|
restarts
|
|
.I mrouted .
|
|
The configuration file is reread every time this signal is evoked.
|
|
.IP INT
|
|
terminates execution gracefully (i.e., by sending
|
|
good-bye messages to all neighboring routers).
|
|
.IP TERM
|
|
same as INT
|
|
.IP USR1
|
|
dumps the internal routing tables to /usr/tmp/mrouted.dump.
|
|
.IP USR2
|
|
dumps the internal cache tables to /usr/tmp/mrouted.cache.
|
|
.IP QUIT
|
|
dumps the internal routing tables to stderr (only if
|
|
.I mrouted
|
|
was invoked with a non-zero debug level).
|
|
.PP
|
|
For convenience in sending signals,
|
|
.I mrouted
|
|
writes its pid to /etc/mrouted.pid upon startup.
|
|
.bp
|
|
.SH EXAMPLE
|
|
.PP
|
|
The routing tables look like this:
|
|
.nf
|
|
|
|
Virtual Interface Table
|
|
Vif Local-Address Metric Thresh Flags
|
|
0 36.2.0.8 subnet: 36.2 1 1 querier
|
|
groups: 224.0.2.1
|
|
224.0.0.4
|
|
pkts in: 3456
|
|
pkts out: 2322323
|
|
|
|
1 36.11.0.1 subnet: 36.11 1 1 querier
|
|
groups: 224.0.2.1
|
|
224.0.1.0
|
|
224.0.0.4
|
|
pkts in: 345
|
|
pkts out: 3456
|
|
|
|
2 36.2.0.8 tunnel: 36.8.0.77 3 1
|
|
peers: 36.8.0.77 (2.2)
|
|
boundaries: 239.0.1
|
|
: 239.1.2
|
|
pkts in: 34545433
|
|
pkts out: 234342
|
|
|
|
3 36.2.0.8 tunnel: 36.6.8.23 3 16
|
|
|
|
Multicast Routing Table (1136 entries)
|
|
Origin-Subnet From-Gateway Metric Tmr In-Vif Out-Vifs
|
|
36.2 1 45 0 1* 2 3*
|
|
36.8 36.8.0.77 4 15 2 0* 1* 3*
|
|
36.11 1 20 1 0* 2 3*
|
|
.
|
|
.
|
|
.
|
|
|
|
.fi
|
|
In this example, there are four vifs connecting to two subnets and two
|
|
tunnels. The vif 3 tunnel is not in use (no peer address). The vif 0 and
|
|
vif 1 subnets have some groups present; tunnels never have any groups. This
|
|
instance of
|
|
.I mrouted
|
|
is the one responsible for sending periodic group
|
|
membership queries on the vif 0 and vif 1 subnets, as indicated by the
|
|
"querier" flags. The list of boundaries indicate the scoped addresses on that
|
|
interface. A count of the no. of incoming and outgoing packets is also
|
|
shown at each interface.
|
|
.PP
|
|
Associated with each subnet from which a multicast datagram can originate
|
|
is the address of the previous hop router (unless the subnet is directly-
|
|
connected), the metric of the path back to the origin, the amount of time
|
|
since we last received an update for this subnet, the incoming vif for
|
|
multicasts from that origin, and a list of outgoing vifs. "*" means that
|
|
the outgoing vif is connected to a leaf of the broadcast tree rooted at the
|
|
origin, and a multicast datagram from that origin will be forwarded on that
|
|
outgoing vif only if there are members of the destination group on that leaf.
|
|
.bp
|
|
.PP
|
|
.I Mrouted
|
|
also maintains a copy of the kernel forwarding cache table. Entries
|
|
are created and deleted by
|
|
.I mrouted.
|
|
.PP
|
|
The cache tables look like this:
|
|
.nf
|
|
|
|
Multicast Routing Cache Table (147 entries)
|
|
Origin Mcast-group CTmr Age Ptmr IVif Forwvifs
|
|
13.2.116/22 224.2.127.255 3m 2m - 0 1
|
|
>13.2.116.19
|
|
>13.2.116.196
|
|
138.96.48/21 224.2.127.255 5m 2m - 0 1
|
|
>138.96.48.108
|
|
128.9.160/20 224.2.127.255 3m 2m - 0 1
|
|
>128.9.160.45
|
|
198.106.194/24 224.2.135.190 9m 28s 9m 0P
|
|
>198.106.194.22
|
|
|
|
.fi
|
|
Each entry is characterized by the origin subnet number and mask and the
|
|
destination multicast group. The 'CTmr' field indicates the lifetime
|
|
of the entry. The entry is deleted from the cache table
|
|
when the timer decrements to zero. The 'Age' field is the time since
|
|
this cache entry was originally created. Since cache entries get refreshed
|
|
if traffic is flowing, routing entries can grow very old.
|
|
The 'Ptmr' field is simply a dash if no prune was sent upstream, or the
|
|
amount of time until the upstream prune will time out.
|
|
The 'Ivif' field indicates the
|
|
incoming vif for multicast packets from that origin. Each router also
|
|
maintains a record of the number of prunes received from neighboring
|
|
routers for a particular source and group. If there are no members of
|
|
a multicast group on any downward link of the multicast tree for a
|
|
subnet, a prune message is sent to the upstream router. They are
|
|
indicated by a "P" after the vif number. The Forwvifs field shows the
|
|
interfaces along which datagrams belonging to the source-group are
|
|
forwarded. A "p" indicates that no datagrams are being forwarded along
|
|
that interface. An unlisted interface is a leaf subnet with are no
|
|
members of the particular group on that subnet. A "b" on an interface
|
|
indicates that it is a boundary interface, i.e. traffic will not be
|
|
forwarded on the scoped address on that interface.
|
|
An additional line with a ">" as the first character is printed for
|
|
each source on the subnet. Note that there can be many sources in
|
|
one subnet.
|
|
.SH FILES
|
|
/etc/mrouted.conf
|
|
.br
|
|
/etc/mrouted.pid
|
|
.br
|
|
/usr/tmp/mrouted.dump
|
|
.br
|
|
/usr/tmp/mrouted.cache
|
|
.SH SEE ALSO
|
|
.BR mrinfo (8) ,
|
|
.BR mtrace (8) ,
|
|
.BR map-mbone (8)
|
|
.sp
|
|
DVMRP is described, along with other multicast routing algorithms, in the
|
|
paper "Multicast Routing in Internetworks and Extended LANs" by S. Deering,
|
|
in the Proceedings of the ACM SIGCOMM '88 Conference.
|
|
.SH AUTHORS
|
|
Steve Deering, Ajit Thyagarajan, Bill Fenner
|