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!

Searchable, convenient, complete TCP/IP information.
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  Internet Control Message Protocol (ICMP/ICMPv4 and ICMPv6)
                9  ICMP Message Types and Formats

Previous Topic/Section
ICMPv6 Parameter Problem Messages
Previous Page
Pages in Current Topic/Section
1
Next Page
ICMPv6 Echo Request and Echo Reply Messages
Next Topic/Section

ICMP Version 6 (ICMPv6) Informational Message Types and Formats

In the previous section we explored a number of ICMPv6 error messages, which are sent back to the originator of an IPv6 datagram when an error is detected in it that makes it impossible to be delivered. Just as was the case with the original version of ICMP (ICMPv4), ICMPv6 also defines another class of message: informational messages. These ICMPv6 messages are used not to report errors, but to allow the sharing of information required to implement various test, diagnostic and support functions critical to the operation of IPv6.

In this section I describe eight different ICMPv6 informational messages in five topics (six of these messages are used in matching pairs, and the pairs are described together). I begin by describing ICMPv6 Echo Request and Echo Reply messages, used for network connectivity testing. I explain the format of Router Advertisement and Router Solicitation messages, used to let hosts discover local routers and learn necessary parameters from them. I then describe ICMPv6 Neighbor Advertisement and Neighbor Solicitation messages, used for various communications between hosts on a local network, including IPv6 address resolution. I discuss IPv6 Redirect messages, which let routers inform hosts of better first-hop routers, and IPv6 Router Renumbering messages.

Several of the ICMPv6 informational messages include additional information that is either optional, recommended or mandatory, depending on the circumstances under which the message is generated. Some of these are shared between message types, so they are described in a separate topic at the end of the section.

In IPv4, the use of many of the ICMP informational messages was described in a variety of different standards. In IPv6, many of the functions using informational messages have been gathered together and formalized in the IPv6 Neighbor Discovery (ND) Protocol. The solicitation and advertisement of local routers and neighboring hosts, as well as communication of redirection information are both examples of activities for which ND is responsible. In fact, five of the ICMP messages described in this section are actually defined in the Neighbor Discovery standard, RFC 2461.

ND and ICMPv6 are obviously closely related, given that ND describes the use of several of the ICMP messages: Router Advertisement, Router Solicitation, Neighbor Advertisement, Neighbor Solicitation and Redirect. Thus, just as ICMPv4 is an important “assistant” to IPv4, both ICMPv6 and ND are important helpers for IPv6. In this Guide, I provide most of the description of how these messages are used in the detailed section on ND. In this section, I provide only a brief summary of their use, while focusing primarily on message format and the meaning of each of the fields in that format.

Note: In ICMPv6, the Redirect message is informational, and no longer considered an error message as it was in ICMPv4.


Quick navigation to subsections and regular topics in this section



Previous Topic/Section
ICMPv6 Parameter Problem Messages
Previous Page
Pages in Current Topic/Section
1
Next Page
ICMPv6 Echo Request and Echo Reply Messages
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.