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.
Open Shortest Path First (OSPF)
Interior routing protocols using
routing algorithm, such as the Routing
Information Protocol (RIP), have a long
history and work well in a small group of routers. However, they also
have some serious limitations in both scalability and performance that
makes them poorly-suited to larger autonomous systems or those with
specific performance issues. Many organizations that start out using
RIP quickly found that its restrictions and issues made it less than
To solve this problem, a new routing
protocol was developed in the late 1980s that uses the more capable
(and more complex) link-state
or shortest path first routing algorithm.
This protocol is called Open Shortest Path First (OSPF). It fixes
many of the issues with RIP and allows routes to be selected dynamically
based on the current state of the network, not just a static picture
of how routers are connected. It also includes numerous advanced features,
including support for a hierarchical topology and automatic load sharing
amongst routes. On the downside, it is a complicated protocol, which
means it is often not used unless it is really needed. This makes it
the complement of RIP and is the reason they both have a place in the
spectrum of TCP/IP routing protocols.
In this section I provide a condensed
explanation of the concepts and operation behind OSPF. As usual, I begin
with an overview of the protocol, discussing how it was developed, its
versions and the standards that define them. I describe the concepts
behind OSPF, including basic topology and the link state database. I
then discuss the more complex optional hierarchical topology of routers,
and the roles routers play when this topology is used. I briefly explain
the method used for determining routes in OSPF, and the general operation
and messaging used in the protocol, including a description of the five
OSPF message types. I conclude with an illustration of the formats used
for OSPF messages.
Note: The difficult thing about networking is that so many protocols and technologies are so involved that each deserves its own book. This is certainly the case with OSPF itself, which is sufficiently complex that the RFC defining OSPF Version 2 is over 240 pages long. Thus, as you have heard me say before, this section, despite including six topics, can only be considered a high-level description of OSPF.
|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!|
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.