Please Whitelist This Site?

I know everyone hates ads. But please understand that I am providing premium content for free that takes hundreds of hours of time to research and write. I don't want to go to a pay-only model like some sites, but when more and more people block ads, I end up working for free. And I have a family to support, just like you. :)

If you like The TCP/IP Guide, please consider the download version. It's priced very economically and you can read all of it in a convenient format without ads.

If you want to use this site for free, I'd be grateful if you could add the site to the whitelist for Adblock. To do so, just open the Adblock menu and select "Disable on tcpipguide.com". Or go to the Tools menu and select "Adblock Plus Preferences...". Then click "Add Filter..." at the bottom, and add this string: "@@||tcpipguide.com^$document". Then just click OK.

Thanks for your understanding!

Sincerely, Charles Kozierok
Author and Publisher, The TCP/IP Guide


NOTE: Using software to mass-download the site degrades the server and is prohibited.
If you want to read The TCP/IP Guide offline, please consider licensing it. Thank you.

The Book is Here... and Now On Sale!

Get The TCP/IP Guide for your own computer.
The TCP/IP Guide

Custom Search







Table Of Contents  The TCP/IP Guide
 9  TCP/IP Lower-Layer (Interface, Internet and Transport) Protocols (OSI Layers 2, 3 and 4)
      9  TCP/IP Internet Layer (OSI Network Layer) Protocols
           9  TCP/IP Routing Protocols (Gateway Protocols)
                9  TCP/IP Interior Routing Protocols (RIP, OSPF, GGP, HELLO, IGRP, EIGRP)
                     9  Open Shortest Path First (OSPF)

Previous Topic/Section
Open Shortest Path First (OSPF)
Previous Page
Pages in Current Topic/Section
1
2
Next Page
OSPF Basic Topology and the Link State Database (LSDB)
Next Topic/Section

OSPF Overview, History, Standards and Versions
(Page 1 of 2)

In the early days of TCP/IP, the Routing Information Protocol (RIP) became the standard protocol for routing within an autonomous system (AS), almost by default. RIP had two big things going for it: it was simple and easy to use, and it was included in the popular Berkeley Standard Distribution (BSD) of UNIX starting in 1982. Most organizations using TCP/IP started out with relatively small networks, and were able to use RIP with some degree of success.

However, as we discussed in our look at RIP, that protocol has some serious technical issues, and these are exacerbated when it is used on a larger AS. Many of its problems are due to it being a distance-vector protocol—the algorithm itself simply limits the ability of RIP to choose the best route and adapt to changing network conditions. Other problems with RIP were based on its implementation, such as the selection of a value of 16 for “infinity” that made it impossible to use RIP in a situation where more than 15 hops might occur between devices. Problems such as the lack of classless addressing support were addressed in Version 2 of RIP, but the basic difficulties with the protocol as a whole persist.

Development and Standardization of OSPF

The Internet Engineering Task Force (IETF) recognized that RIP by itself simply would not meet the needs of all autonomous systems on the Internet. They formed a working group in 1988 to develop a new routing protocol based on the more capable link-state algorithm, also called shortest path first (SPF). Research into this type of protocol had already begun as early as the 1970s, with some of it conducted on the ARPAnet, the predecessor of the Internet upon which much of TCP/IP was developed.

This new protocol was called Open Shortest Path First, or OSPF, and its name conveys two of its most important characteristics. The first word refers to the fact that the protocol, like all TCP/IP standards, was developed using the open and public RFC process, so it is not proprietary and no license is required to use it. The SPF portion of the name refers to the type of algorithm it uses, which is designed to allow routers to dynamically determine the shortest path between any two networks.

The first version of OSPF was described in RFC 1131, published in October 1989. This was quickly replaced by OSPF Version 2 in July 1991, described in RFC 1247. Since then there have been several revisions to the OSPF Version 2 standard, in RFCs 1583, 2178, and 2328, with the last of these the current standard. OSPF Version 2 is the only version in use today, so it is usually what is meant when people (including myself) refer to “OSPF”.


Previous Topic/Section
Open Shortest Path First (OSPF)
Previous Page
Pages in Current Topic/Section
1
2
Next Page
OSPF Basic Topology and the Link State Database (LSDB)
Next Topic/Section

If you find The TCP/IP Guide useful, please consider making a small Paypal donation to help the site, using one of the buttons below. You can also donate a custom amount using the far right button (not less than $1 please, or PayPal gets most/all of your money!) In lieu of a larger donation, you may wish to consider purchasing a download license of The TCP/IP Guide. Thanks for your support!
Donate $2
Donate $5
Donate $10
Donate $20
Donate $30
Donate: $



Home - Table Of Contents - Contact Us

The TCP/IP Guide (http://www.TCPIPGuide.com)
Version 3.0 - Version Date: September 20, 2005

© Copyright 2001-2005 Charles M. Kozierok. All Rights Reserved.
Not responsible for any loss resulting from the use of this site.