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Final version of documentation (famous last words)

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Pavel Machek 2000-06-08 14:06:20 +00:00
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@ -52,7 +52,7 @@ the IPv4 or the IPv6 protocol). Routers are devices which forward packets betwee
networks in order to allow hosts not connected directly to the same local area network to
communicate with each other. They also communicate with the other routers in the Internet to discover
the topology of the network which allows them to find optimal (in terms of some metric) rules for
forwarding of packets (which will be called routes in the rest of this document) and to adapt themselves to the
forwarding of packets (which are called routing tables) and to adapt themselves to the
changing conditions such as outages of network links, building of new connections and so on. Most of
these routers are costly dedicated devices running obscure firmware which is hard to configure and
not open to any changes (on the other hand, their special hardware design allows them to keep up with lots of high-speed network interfaces, better than general-purpose computer does). Fortunately, most operating systems of the UNIX family allow an ordinary
@ -62,8 +62,8 @@ a statically configured table.
<p>A <em/Routing Daemon/ is in UNIX terminology a non-interactive program running on
background which does the dynamic part of Internet routing, that is it communicates
with the other routers, calculates routing tables and sends them to the OS kernel
which does the actual packet forwarding. There already exist other such routing daemons: routed (rip only), GateD<HTMLURL URL="http://www.gated.org/">
(non free), Zebra<HTMLURL URL="http://www.zebra.org"> and MRTD<HTMLURL URL="http://www.zcu.cz/ftp/mirrors/mmrz/mrtd">, but their capabilities are limited and
which does the actual packet forwarding. There already exist other such routing daemons: routed (RIP only), GateD<HTMLURL URL="http://www.gated.org/">
(non-free), Zebra<HTMLURL URL="http://www.zebra.org"> and MRTD<HTMLURL URL="http://www.zcu.cz/ftp/mirrors/mmrz/mrtd">, but their capabilities are limited and
they are relatively hard to configure and maintain.
<p>BIRD is an Internet Routing Daemon designed to avoid all of these shortcomings,
@ -75,7 +75,7 @@ protocols to be incorporated easily. Among other features, BIRD supports:
<item>both IPv4 and IPv6 protocols
<item>multiple routing tables
<item>the Border Gateway Protocol (BGPv4)
<item>the Routing Interchange Protocol (RIPv2)
<item>the Routing Information Protocol (RIPv2)
<item>the Open Shortest Path First protocol (OSPFv2)
<item>a virtual protocol for exchange of routes between different routing tables on a single host
<item>a command-line interface allowing on-line control and inspection
@ -137,16 +137,15 @@ options. The most important ones are:
<chapt>About routing tables
<p>BIRD has one or more routing tables, which may or may not be
synchronized with kernel and which may or may not be synchronized with
each other (see the Pipe protocol). Each routing table contains list of
<p>BIRD has one or more routing tables which may or may not be
synchronized with OS kernel and which may or may not be synchronized with
each other (see the Pipe protocol). Each routing table contains a list of
known routes. Each route consists of:
<itemize>
<item>network prefix this route is for (consists of network address and number of bits forming the network part of the address)
<item>preference of this route (taken from preference of
protocol and possibly altered by filters)
<item>IP address of router who told us about this route
<item>network prefix this route is for (network address and prefix length -- the number of bits forming the network part of the address; also known as a netmask)
<item>preference of this route
<item>IP address of router which told us about this route
<item>IP address of router we should forward the packets to
using this route
<item>other attributes common to all routes
@ -154,23 +153,23 @@ known routes. Each route consists of:
may not be present (typically protocol metrics)
</itemize>
Routing table maintains more than
one entry for a network, but at most one entry for one network and one
protocol. The entry with biggest preference is used for routing. If
Routing table maintains multiple entries
for a network, but at most one entry for one network and one
protocol. The entry with the highest preference is used for routing (we
will call such an entry the <it/selected route/). If
there are more entries with the same preference and they are from the same
protocol, protocol decides (typically according to metrics). If not,
internal ordering is used to decide. You can
get list of route attributes in "Route attributes" section in
filters.
protocol, the protocol decides (typically according to metrics). If they aren't,
an internal ordering is used to break the tie. You can
get the list of route attributes in the Route attributes section.
<p>Protocols are connected to routing tables through filters. Routes
that come from other routers go to the protocol, it then passes them to
filters, if import filter accepts route, it gets to main routing
table. It is then broadcasted to all other protocols (filtered through
their export filters), which typically send it to other routers.
Filters can alter routes passed between routing tables and
protocols.
<p>Each protocol is connected to a routing table through two filters
which can accept, reject and modify the routes. An <it/export/
filter checks routes passed from the routing table to the protocol,
an <it/import/ filter checks routes in the opposite direction.
When the routing table gets a route from a protocol, it recalculates
the selected route and broadcasts it to all protocols connected to
the table. The protocols typically send the update to other routers
in the network.
<chapt>Configuration
@ -235,7 +234,7 @@ protocol rip {
<tag>filter <m/name local variables/{ <m/commands/ }</tag> Define a filter. You can learn more about filters
in the following chapter.
<tag>function <m/name (parameters) local variables/ { <m/commands/ }</tag> Define a function. You can learn more
<tag>function <m/name/ (<m/parameters/) <m/local variables/ { <m/commands/ }</tag> Define a function. You can learn more
about functions in the following chapter.
<tag>protocol rip|ospf|bgp|... <m/[name]/ { <m>protocol options</m> }</tag> Define a protocol
@ -351,7 +350,7 @@ BIRD and <file/birdc/ is stable (see the programmer's documentation).
<tag>show symbols</tag>
Show the list of symbols defined in the configuration (names of protocols, routing tables etc.).
<tag>show route [<m/prefix/|for <m/prefix or IP/] [primary] [table <m/sym/] [all] [stats|count] [filter <m/name/|where <m/condition/] [(import|proto) <m/sym/]</tag>
<tag>show route [[for] <m/prefix/|<m/IP/] [table <m/sym/] [filter <m/f/|where <m/c/] [(import|proto) <m/p/] [<m/options/]</tag>
Show contents of a routing table (by default of the main one),
that is routes, their metrics and (in case the <cf/all/ switch is given)
all their attributes.
@ -602,10 +601,10 @@ defined by using the <cf>defined( <m>attribute</m> )</cf> operator.
Next hop packets routed using this route should be forwarded to.
<tag><m/enum/ source</tag>
what protocol has told me about this route. Possible values: <cf/RTS_DUMMY, RTS_STATIC, RTS_INHERIT, RTS_DEVICE, RTS_STATIC_DEVICE, RTS_REDIRECT, RTS_RIP, RTS_OSPF, RTS_OSPF_EXT, RTS_OSPF_IA, RTS_OSPF_BOUNDARY, RTS_BGP, RTS_PIPE/.
what protocol has told me about this route. Possible values: <cf/RTS_DUMMY/, <cf/RTS_STATIC/, <cf/RTS_INHERIT/, <cf/RTS_DEVICE/, <cf/RTS_STATIC_DEVICE/, <cf/RTS_REDIRECT/, <cf/RTS_RIP/, <cf/RTS_OSPF/, <cf/RTS_OSPF_EXT/, <cf/RTS_OSPF_IA/, <cf/RTS_OSPF_BOUNDARY/, <cf/RTS_BGP/, <cf/RTS_PIPE/.
<tag><m/enum/ cast</tag>
Route type (<cf/RTC_UNICAST/ for normal routes, <cf/RTC_BROADCAST, RTC_MULTICAST, RTC_ANYCAST/ for broadcast, multicast and anycast routes). Read-only.
Route type (<cf/RTC_UNICAST/ for normal routes, <cf/RTC_BROADCAST/, <cf/RTC_MULTICAST/, <cf/RTC_ANYCAST/ for broadcast, multicast and anycast routes). Read-only.
<tag><m/enum/ dest</tag>
Type of destination the packets should be sent to (<cf/RTD_ROUTER/ for forwarding to a neighboring router, <cf/RTD_NETWORK/ for routing to a directly-connected network, <cf/RTD_BLACKHOLE/ for packets to be silently discarded, <cf/RTD_UNREACHABLE/, <cf/RTD_PROHIBIT/ for packets that should be returned with ICMP host unreachable / ICMP administratively prohibited messages). Read-only.
@ -1420,17 +1419,43 @@ protocol static {
}
</code>
<chapt>Problems
<chapt>Conclusions
<p>BIRD is relatively young system, and probably contains some
bugs. You can report bugs at bird-users mailing list (<HTMLURL URL="mailto:bird-users@bird.network.cz" name="bird-users@bird.network.cz">), but before you do,
please make sure you have read available documentation, make sure are running latest version (available at <HTMLURL
URL="ftp://bird.network.cz/pub/bird" name="bird.network.cz:/pub/bird">). (Of course, patch
which fixes the bug along with bug report is always welcome). If you
want to use BIRD, join mailing list by sending
<tt/subscribe bird-users/ to <HTMLURL URL="mailto:majordomo@bird.network.cz" name="majordomo@bird.network.cz">. Main home page of bird is <HTMLURL URL="http://bird.network.cz/" name="http://bird.network.cz/">. When
trying to understand, what is going on, Internet standards are
relevant reading; you can get them from <HTMLURL URL="ftp://ftp.rfc-editor.org/" name="ftp.rfc-editor.org"> (or nicely sorted version from <HTMLURL URL="ftp://atrey.karlin.mff.cuni.cz/pub/rfc" name="atrey.karlin.mff.cuni.cz:/pub/rfc">).
<sect>Future work
<p>Although BIRD supports all the commonly used routing protocols,
there are still some features which would surely deserve to be
implemented in future versions of BIRD:
<itemize>
<item>OSPF for IPv6 networks
<item>OSPF NSSA areas and opaque LSA's
<item>Route aggregation and flap dampening
<item>Generation of IPv6 router advertisements
<item>Multipath routes
<item>Multicast routing protocols
<item>Ports to other systems
</itemize>
<sect>Getting more help
<p>If you use BIRD, you're welcome to join the bird-users mailing list
(<HTMLURL URL="mailto:bird-users@bird.network.cz" name="bird-users@bird.network.cz">)
where you can share your experiences with the other users and consult
your problems with the authors. To subscribe to the list, just send a
<tt/subscribe bird-users/ command in a body of a mail to
(<HTMLURL URL="mailto:majordomo@bird.network.cz" name="majordomo@bird.network.cz">).
The home page of BIRD can be found at <HTMLURL URL="http://bird.network.cz/" name="http://bird.network.cz/">.
<p>BIRD is a relatively young system and it probably contains some
bugs. You can report any problems to the bird-users list and the authors
will be glad to solve them, but before you do so,
please make sure you have read the available documentation and that you are running the latest version (available at <HTMLURL
URL="ftp://bird.network.cz/pub/bird" name="bird.network.cz:/pub/bird">). (Of course, a patch
which fixes the bug is always welcome as an attachment.)
<p>If you want to understand what is going inside, Internet standards are
a good and interesting reading. You can get them from <HTMLURL URL="ftp://ftp.rfc-editor.org/" name="ftp.rfc-editor.org"> (or a nicely sorted version from <HTMLURL URL="ftp://atrey.karlin.mff.cuni.cz/pub/rfc" name="atrey.karlin.mff.cuni.cz:/pub/rfc">).
<p><it/Good luck!/