overview.texi

大名鼎鼎的路由器源码。程序分ZEBRA、OSPFRIP等3个包。程序框架采用一个路由协议一个进程的方式

@node Overview, Installation, Top, Top
@comment  node-name,  next,  previous,  up
@chapter Overview
@cindex Overview

  Zebra is a routing software package that provides TCP/IP based
routing services with routing protocols support such as RIPv1, RIPv2,
RIPng, OSPFv2, OSPFv3, BGP-4, and BGP-4+ (@pxref{Supported RFC}).
Zebra also supports special BGP Route Reflector and Route Server
behavior.  In addition to traditional IPv4 routing protocols, Zebra
also supports IPv6 routing protocols.  With SNMP daemon which supports
SMUX protocol, Zebra provides routing protocol MIBs (@pxref{SNMP
Support}).

  Zebra uses an advanced software architecture to provide you with a
high quality, multi server routing engine.  Zebra has an interactive
user interface for each routing protocol and supports common client
commands.  Due to this design, you can add new protocol daemons to Zebra
easily.  You can use Zebra library as your program's client user
interface.

  Zebra is an official @sc{gnu} software and distributed under the
@sc{gnu} General Public License.

@menu
* About Zebra::                 Basic information about Zebra
* System Architecture::         The Zebra system architecture
* Supported Platforms::         Supported platforms and future plans
* Supported RFC::               Supported RFCs
* How to get Zebra::            
* Mailing List::                Mailing list information
* Bug Reports::                 Mail address for bug data
@end menu

@node About Zebra, System Architecture, Overview, Overview
@comment  node-name,  next,  previous,  up
@section About Zebra
@cindex About Zebra

  Today, TCP/IP networks are covering all of the world.  The Internet
has been deployed in many countries, companies, and to the home.  When
you connect to the Internet your packet will pass many routers which
have TCP/IP routing functionality.

  A system with Zebra installed acts as a dedicated router.  With Zebra,
your machine exchanges routing information with other routers using
routing protocols.  Zebra uses this information to update the kernel
routing table so that the right data goes to the right place.  You can
dynamically change the configuration and you may view routing table
information from the Zebra terminal interface.

  Adding to routing protocol support, Zebra can setup interface's flags,
interface's address, static routes and so on.  If you have a small
network, or a stub network, or xDSL connection, configuring the Zebra
routing software is very easy.  The only thing you have to do is to set
up the interfaces and put a few commands about static routes and/or
default routes.  If the network is rather large, or if the network
structure changes frequently, you will want to take advantage of Zebra's
dynamic routing protocol support for protocols such as RIP, OSPF or BGP.
Zebra is with you.

  Traditionally, UNIX based router configuration is done by
@command{ifconfig} and @command{route} commands.  Status of routing
table is displayed by @command{netstat} utility.  Almost of these
commands work only if the user has root privileges.  Zebra has a different
system administration method.  There are two user modes in Zebra.  One is
normal mode, the other is enable mode.  Normal mode user can only view
system status, enable mode user can change system configuration.  This
UNIX account independent feature will be great help to the router
administrator.

  Currently, Zebra supports common unicast routing protocols.  Multicast
routing protocols such as BGMP, PIM-SM, PIM-DM will be supported in
Zebra 2.0.  MPLS support is going on.  In the future, TCP/IP filtering
control, QoS control, diffserv configuration will be added to Zebra.
Zebra project's final goal is making a productive, quality free TCP/IP
routing software.

@node System Architecture, Supported Platforms, About Zebra, Overview
@comment  node-name,  next,  previous,  up
@section System Architecture
@cindex System architecture
@cindex Software architecture
@cindex Software internals

  Traditional routing software is made as a one process program which
provides all of the routing protocol functionalities.  Zebra takes a
different approach.  It is made from a collection of several daemons
that work together to build the routing table.  There may be several
protocol-specific routing daemons and zebra the kernel routing manager.

  The @command{ripd} daemon handles the RIP protocol, while
@command{ospfd} is a daemon which supports OSPF version 2.
@command{bgpd} supports the BGP-4 protocol.  For changing the kernel
routing table and for redistribution of routes between different routing
protocols, there is a kernel routing table manager @command{zebra}
daemon.  It is easy to add a new routing protocol daemons to the entire
routing system without affecting any other software.  You need to run only
the protocol daemon associated with routing protocols in use.  Thus,
user may run a specific daemon and send routing reports to a central
routing console.

  There is no need for these daemons to be running on the same machine.
You can even run several same protocol daemons on the same machine.  This
architecture creates new possibilities for the routing system.

@example
@group
+----+  +----+  +-----+  +-----+
|bgpd|  |ripd|  |ospfd|  |zebra|
+----+  +----+  +-----+  +-----+
                            |
+---------------------------|--+
|                           v  |
|  UNIX Kernel  routing table  |
|                              |
+------------------------------+

    Zebra System Architecture
@end group
@end example

  Multi-process architecture brings extensibility, modularity and
maintainability.  At the same time it also brings many configuration
files and terminal interfaces.  Each daemon has it's own configuration
file and terminal interface.  When you configure a static route, it must
be done in @command{zebra} configuration file.  When you configure BGP
network it must be done in @command{bgpd} configuration file.  This can be a
very annoying thing.  To resolve the problem, Zebra provides integrated
user interface shell called @command{vtysh}.  @command{vtysh} connects to
each daemon with UNIX domain socket and then works as a proxy for user input.

  Zebra was planned to use multi-threaded mechanism when it runs with a
kernel that supports multi-threads.  But at the moment, the thread
library which comes with @sc{gnu}/Linux or FreeBSD has some problems with
running reliable services such as routing software, so we don't use
threads at all.  Instead we use the @command{select(2)} system call for
multiplexing the events.

  When @command{zebra} runs under a @sc{gnu} Hurd kernel it will act as a
kernel routing table itself.  Under @sc{gnu} Hurd, all TCP/IP services are
provided by user processes called @command{pfinet}.  Zebra will provide
all the routing selection mechanisms for the process.  This feature will
be implemented when @sc{gnu} Hurd becomes stable.

@node Supported Platforms, Supported RFC, System Architecture, Overview
@comment  node-name,  next,  previous,  up
@section Supported Platforms

@cindex Supported platforms
@cindex Zebra on other systems
@cindex Compatibility with other systems
@cindex Operating systems that support Zebra

  Currently Zebra supports @sc{gnu}/Linux, BSD and Solaris.  Below is a list
of OS versions on which Zebra runs.  Porting Zebra to other platforms is
not so too difficult.  Platform dependent codes exist only in
@command{zebra} daemon.  Protocol daemons are platform independent.
Please let us know when you find out Zebra runs on a platform which is not
listed below.

@sp 1
@itemize @bullet
@item
GNU/Linux 2.2.x
@item
GNU/Linux 2.4.x
@item
FreeBSD 4.x
@item
FreeBSD 5.x
@item
NetBSD 1.6.x
@item
OpenBSD 3.x
@item
Solaris 8
@end itemize

@sp 1
  Some IPv6 stacks are in development.  Zebra supports following IPv6
stacks.  For BSD, we recommend KAME IPv6 stack.  Solaris IPv6 stack is
not yet supported.
@sp 1
@itemize @bullet
@item
Linux IPv6 stack for GNU/Linux 2.2.x and higher.
@item
KAME BSD IPv6 stack
@end itemize

@node Supported RFC, How to get Zebra, Supported Platforms, Overview
@comment  node-name,  next,  previous,  up
@section Supported RFC

  Below is the list of currently supported RFC's.

@table @asis
@item @asis{RFC1058}
@cite{Routing Information Protocol. C.L. Hedrick. Jun-01-1988.}

@item @asis{RF2082}
@cite{RIP-2 MD5 Authentication. F. Baker, R. Atkinson. January 1997.}

@item @asis{RFC2453}
@cite{RIP Version 2. G. Malkin. November 1998.}

@item @asis{RFC2080}
@cite{RIPng for IPv6. G. Malkin, R. Minnear. January 1997.}

@item @asis{RFC2328}
@cite{OSPF Version 2. J. Moy. April 1998.}

@item @asis{RFC2740}
@cite{OSPF for IPv6. R. Coltun, D. Ferguson, J. Moy. December 1999.}

@item @asis{RFC1771} 
@cite{A Border Gateway Protocol 4 (BGP-4). Y. Rekhter & T. Li. March 1995.}

@item @asis{RFC1965}
@cite{Autonomous System Confederations for BGP. P. Traina. June 1996.}

@item @asis{RFC1997}
@cite{BGP Communities Attribute. R. Chandra, P. Traina & T. Li. August 1996.}

@item @asis{RFC2545}
@cite{Use of BGP-4 Multiprotocol Extensions for IPv6 Inter-Domain Routing. P. Marques, F. Dupont. March 1999.}

@item @asis{RFC2796}
@cite{BGP Route Reflection An alternative to full mesh IBGP. T. Bates & R. Chandrasekeran. June 1996.}

@item @asis{RFC2858}
@cite{Multiprotocol Extensions for BGP-4. T. Bates, Y. Rekhter, R. Chandra, D. Katz. June 2000.}

@item @asis{RFC2842}
@cite{Capabilities Advertisement with BGP-4. R. Chandra, J. Scudder. May 2000.}

@end table

  When SNMP support is enabled, below RFC is also supported.

@table @asis

@item @asis{RFC1227}
@cite{SNMP MUX protocol and MIB. M.T. Rose. May-01-1991.}

@item @asis{RFC1657}
@cite{Definitions of Managed Objects for the Fourth Version of the
Border Gateway Protocol (BGP-4) using SMIv2. S. Willis, J. Burruss,
J. Chu, Editor. July 1994.}

@item @asis{RFC1724}
@cite{RIP Version 2 MIB Extension. G. Malkin & F. Baker. November 1994.}

@item @asis{RFC1850}
@cite{OSPF Version 2 Management Information Base. F. Baker, R. Coltun.
November 1995.}

@end table

@node How to get Zebra, Mailing List, Supported RFC, Overview
@comment  node-name,  next,  previous,  up
@section How to get Zebra

  Zebra is still beta software and there is no officially
released version.  So currently Zebra is distributed from Zebra beta ftp
site located at:

@url{ftp://ftp.zebra.org/pub/zebra}

  Once Zebra is released you can get it from @sc{gnu} FTP site and
its mirror sites.  We are planning Zebra-1.0 as the first released
version.

  Zebra's official web page is located at:

@url{http://www.gnu.org/software/zebra/zebra.html}.

  There is a Zebra beta tester web page at: 

@url{http://www.zebra.org/}.

  You can get the latest beta software information from this page.

@node Mailing List, Bug Reports, How to get Zebra, Overview
@comment  node-name,  next,  previous,  up
@section Mailing List
@cindex How to get in touch with Zebra
@cindex Mailing Zebra
@cindex Contact information
@cindex Mailing lists

  There is a mailing list for discussions about Zebra.  If you have any
comments or suggestions to Zebra, please send mail to
@email{zebra@@zebra.org}.  New snapshot announcements, improvement
notes, and patches are sent to the list.

  To subscribe to the @email{zebra@@zebra.org, Zebra mailing list},
please send a mail to @email{zebra-request@@ml.zebra.org} with a message with a subject:

@quotation
subscribe
@end quotation

  To unsubscribe from the list, please send a mail to
@email{zebra-request@@ml.zebra.org} with a message body that includes only:

@quotation
unsubscribe
@end quotation

@node Bug Reports,  , Mailing List, Overview
@comment  node-name,  next,  previous,  up
@section Bug Reports

@cindex Bug Reports
@cindex Bug hunting
@cindex Found a bug?
@cindex Reporting bugs
@cindex Reporting software errors
@cindex Errors in the software

  If you think you have found a bug, please send a bug report to
@email{bug-zebra@@gnu.org}.  When you send a bug report, please be
careful about the points below.

@itemize @bullet
@item 
Please note what kind of OS you are using.  If you use the IPv6 stack
please note that as well.
@item
Please show us the results of @code{netstat -rn} and @code{ifconfig -a}.
Information from zebra's VTY command @code{show ip route} will also be
helpful.
@item
Please send your configuration file with the report.  If you specify
arguments to the configure script please note that too.
@end itemize

  Bug reports are very important for us to improve the quality of Zebra.
Zebra is still in the development stage, but please don't hesitate to
send a bug report to @email{bug-zebra@@gnu.org}.