📄 cs427 zebra overview.htm
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<Br>
<h2>Overview</h2>
Traditional routing software programs are designed to be one-process programs that provide all of the routing protocol functionality. Zebra is unique in its design because it has a process for each protocol that runs on a multi-threaded UNIX kernel. Zebra uses multi-thread technology under multi-thread supported Unix kernels. However, Zebra can be run under non-multithread supported UNIX kernels. Thus Zebra provides flexibility and reliability. Each module can be upgraded independently of the others, allowing for quick upgrades as well as protection from the case of a failure in one protocol affecting the entire system.
Zebra is made from a collection of several daemons that work together to build a routing table. There may be several protocol-specific routing daemons and zebra the kernel routing manager. The ripd daemon handles the RIP protocol, while ospfd is a daemon which supports OSPF protocol, 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 zebra daemon. Zebra is the routing manager. It provides kernel routing table updates, interface lookups and redistribution of routes between different routing protocols.
Each daemon has its own routing table. Zebra daemon is responsible for kernel routing table update (service) and its redistribution between different protocol (e.g. RIPd). Other daemons are for protocol handling. [[[FENG > Zebra References]]
Zebra protocol is used between protocol daemon and zebra. Each protocol daemon sends selected routes to the zebra daemon. The zebra daemon manages which route is installed into the forwarding table. Zebra protocol is a TCP based protocol.
All the daemons listen on a particular port for incoming VTY (Virtual Terminal Interface). VTY is a command line interface (e.g. telnet) to change or view the current configuration. Zebra抯 daemon抯 have their own VTY.
<br>
[http://wiki.cs.uiuc.edu/cs427/DOWNLOAD/Zebra_comps.gif]
Zebra architecture has been geared towards achieving modularity, extensibility, and maintainability. This approach has several advantages as well as disadvantages.[[[Zebra Home > Zebra References]]
<b>Advantages</b>
* Modularity: due to the multi-process nature of the Zebra software, it is easily upgraded and maintained. Each protocol can be upgraded separately, leaving the other protocols and the router online. This will save network administrators time in upgrading and maintenance.
* Speed: packet routing is carried out at a faster rate than with traditional software. Zebra software allows routers to transfer more data more quickly. The need for the ability to transfer large amounts of data quickly is increasing as the internet grows and global networks form. Zebra software will meet that need.
* Reliability: in the event of failure of any of the software modules, the router can remain online and the other protocol daemons will continue to operate. The failure can then be diagnosed and corrected without taking the router offline.
<b>Disadvantage </b>
* Inter-process communication (Zebra) vs. intra-process communication (GateD).
* Kernel routing table updates and redistribution would be slow.
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<P>
<HR>
<P><BR>
<P>
<H2>Overview</H2>
<P>Traditional routing software programs are designed to be one-process programs
that provide all of the routing protocol functionality. Zebra is unique in its
design because it has a process for each protocol that runs on a multi-threaded
UNIX kernel. Zebra uses multi-thread technology under multi-thread supported
Unix kernels. However, Zebra can be run under non-multithread supported UNIX
kernels. Thus Zebra provides flexibility and reliability. Each module can be
upgraded independently of the others, allowing for quick upgrades as well as
protection from the case of a failure in one protocol affecting the entire
system.
<P>Zebra is made from a collection of several daemons that work together to
build a routing table. There may be several protocol-specific routing daemons
and zebra the kernel routing manager. The ripd daemon handles the RIP protocol,
while ospfd is a daemon which supports OSPF protocol, 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
zebra daemon. Zebra is the routing manager. It provides kernel routing table
updates, interface lookups and redistribution of routes between different
routing protocols.
<P>Each daemon has its own routing table. Zebra daemon is responsible for kernel
routing table update (service) and its redistribution between different protocol
(e.g. RIPd). Other daemons are for protocol handling. [<A
href="http://wiki.cs.uiuc.edu/cs427/Zebra+References">FENG</A>]
<P>Zebra protocol is used between protocol daemon and zebra. Each protocol
daemon sends selected routes to the zebra daemon. The zebra daemon manages which
route is installed into the forwarding table. Zebra protocol is a TCP based
protocol.
<P>All the daemons listen on a particular port for incoming VTY (Virtual
Terminal Interface). VTY is a command line interface (e.g. telnet) to change or
view the current configuration. Zebra抯 daemon抯 have their own VTY.
<P><BR>
<P>
<P><IMG src="cs427 Zebra Overview_files/Zebra_comps.gif" border=0>
<P>
<P>Zebra architecture has been geared towards achieving modularity,
extensibility, and maintainability. This approach has several advantages as well
as disadvantages.[<A href="http://wiki.cs.uiuc.edu/cs427/Zebra+References">Zebra
Home</A>]
<P><B>Advantages</B>
<P>
<UL>
<LI>Modularity: due to the multi-process nature of the Zebra software, it is
easily upgraded and maintained. Each protocol can be upgraded separately,
leaving the other protocols and the router online. This will save network
administrators time in upgrading and maintenance. </LI></UL>
<UL>
<LI>Speed: packet routing is carried out at a faster rate than with
traditional software. Zebra software allows routers to transfer more data more
quickly. The need for the ability to transfer large amounts of data quickly is
increasing as the internet grows and global networks form. Zebra software will
meet that need. </LI></UL>
<UL>
<LI>Reliability: in the event of failure of any of the software modules, the
router can remain online and the other protocol daemons will continue to
operate. The failure can then be diagnosed and corrected without taking the
router offline. </LI></UL>
<P><B>Disadvantage </B>
<P>
<UL>
<LI>Inter-process communication (Zebra) vs. intra-process communication
(GateD).
<LI>Kernel routing table updates and redistribution would be slow.
</LI></UL><BR>
<P>
<P>
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