what is routing information protocol?how is it used? what is its
advantages and disadvantages?

Hi there,

In this instance the "define:" function for Google searching works
very well to provide definitions of RIP:


RIP Defined
-----------
A distance vector, as opposed to link state, routing protocol. It is
an Internet standard IGP defined in STD 34, RFC 1058 (updated by RFC
1388).
http://www.red.net/glossary/r.php

The Routing Information Protocol is a commonly used routing protocol
under both IPX and IP. RIP is a distance-vector protocol, and it
calculates the shortest distance (and therefore most desirable path)
between the source and destination addresses based on the lowest hop
count. See Distance Vector Protocols.
http://www.networkbuyersguide.com/search/105491.htm

A distance vector, as opposed to link state, routing protocol. It is
an Internet standard IGP defined in RFC 1058. See also: Interior
Gateway Protocol, Open Shortest-Path First. [RFC 1983]
http://www.direct.bigpond.com/glossaryL-Z.cfm

A UDP protocol (RFC 1058) that propagates routing information
throughout an internetwork, so that each router (or gateway) knows
where the next hop is for any destination. Updated in RFC 2453.
http://www.clock.org/~jss/glossary/r.html

An interior routing protocol supplied with Unix systems. 
http://dsg.port.ac.uk/mab/Teaching/ARCH3/Glossary.html

One of the protocols used by routers to exchange routing information
and thus update their network routing tables.
http://www.prenhall.com/divisions/bp/app/stamper/bdc/student/glossary4.html

(RIP) An interior Gateway Protocol used by TCP/IP to exchange routing
information on a small computing network.
http://www.connectworld.net/cgi-bin/iec/02GLSR.html

RIP. A protocol in which routers periodically exchange information
with one another so that they can determine minimum distance paths
between sources and destinations.
http://manuals.sharecom.ca/rt314/applications/glossary.html

A protocol that uses distance-vector algorithms to determine routes.
With RIP, routers transfer information among other routers to update
their internal routing tables and use that information to determine
the best routes based on hop counts between routers. TCP/IP and IPX
support RIP.
http://www.gckschools.com/users/thompsons/temp/Tools/glossary/glossary_R.htm

An Interior Gateway Protocol supplied with UNIX and most routers. As
"routed" (pronounced route-dee), it was developed for the Berkeley
UNIX (BSD) operating system. It lets a group of hosts, located on a
local network, share routing information. RIP is used on many LANs and
is also called local routing process.
http://homepages.bw.edu/~kweiss/glossary/r.html

from searching for [define:"routing information protocol"]
://www.google.com/search?q=define%3A%22routing+information+protocol%22


How RIP is used
---------------
Here is some background info on how routers work, followed by detailed
explanations from Cisco and Network Sorcery:

Howstuffworks "How Routers Work"
http://www.howstuffworks.com/router.htm

Cisco provide information on how the RIP protocol works:
http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/rip.htm

A more technical view comes from Network Sorcery:
http://www.networksorcery.com/enp/protocol/rip.htm


Advantages and Disadvantages of RIP
----------------------------------
Advantages:

* Simple to implement
* Low requirement in processing and memory at the nodes
* Suitable for small networks

Disadvantages:

* Slow convergence
* Bouncing effect
* Counting to infinity problem

from Routing Basics, RIP
http://www.ceenet.org/workshops99/Iskra_Djonova-Popova/basicrout/sld026.htm



RIP Advantages:

* Router interworking. Some routers do not support OSPF, and RIP may
be the only common dynamic discovery protocol in a heterogeneous
environment. This often applies to workstations, Unix machines or PC
file servers used as routers.
* Router discovery. Many end user devices listen to RIP traffic to
discover the local router interface(s).
* Simplicity. RIP is simple to set up, and if a router has no complex
choices to make on alternate paths, then RIP is good enough.

Note that some of these "advantages" cause problems in real networks.
Misconfiguration of a Unix machine may generate illegal routes, and
RIP will propagate these through the internet unless route filters are
used.


RIP Disadvantages:

* Trust. The RIP protocol does not support checking for common faults
and errors. All routes sent by a router to others are assumed correct,
even if no traffic can flow on the return path.
* Slow convergence. RIP does not find new routes quickly when known
routes fail. In addition, more complex topologies with resilient
routers can produce count to infinity problems, where a spurious route
is used and not discovered for several minutes.
* Poor metrics. RIP only supports a hop count metric, with a maximum
value of 15 hops. It is not practical to cost different speed links to
bias traffic towards better routes unless the network is simple and
small.

from: NCAT RIP Information:
http://www.ncat.co.uk/Net_Lib/ripinfo.htm


RIP Problems
------------

Counting-to-infinity problem: 

* Simple configuration A->B->C. If C fails, B needs to update and
thinks there is a route through A. A needs to update and thinks there
is a route thru B.
* No clear solution, except to set infinity to be small (eg 16 in RIP) 
* Split-horizon: If A?s route to C is thru B, then A advertises C?s
route (only to B) as infinity.

Slow convergence after topology change: 

* Due to count to infinity problem 
* Also information cannot propogate thru node until it recalculates routing info.

Black-holes: 
* If one node goes broke and advertises route of zero to several key
networks, all nodes immediately point to it.
* General problem in distance-vector methods (also the cause for the
recent Internet-brownout in BGP-4)

Does not support VLSMs. 

No authentication 

from Interior Gateway Protocols: RIP & OSPF
http://www.ecse.rpi.edu/Courses/S98/35696/i11_rip/tsld011.htm


More info
---------

Managing IP Networks with Cisco Routers: Sample Chapter 5: Routing
Protocol Selection (complete chapter from an O'Reilly book):
http://www.oreilly.com/catalog/cisco/chapter/ch05.html

Wikipedia: Routing Information Protocol:
http://en.wikipedia.org/wiki/Routing_Information_Protocol

Cisco: 68 articles on RIP
http://www.cisco.com/pcgi-bin/Support/browse/psp_view.pl?p=Technologies:RIP


Search keywords: advantages disadvantages "routing information protocol"


Best wishes,
robertskelton-ga