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!

Enjoy The TCP/IP Guide? Get the complete PDF!
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
                     9  ICMP Version 6 (ICMPv6) Informational Message Types and Formats

Previous Topic/Section
ICMP Version 6 (ICMPv6) Informational Message Types and Formats
Previous Page
Pages in Current Topic/Section
1
2
Next Page
ICMPv6 Router Advertisement and Router Solicitation Messages
Next Topic/Section

ICMPv6 Echo Request and Echo Reply Messages
(Page 1 of 2)

IP is a relatively simple protocol that does not itself include any method for performing tests between devices to help in diagnosing internetwork problems. This means that this job, like other support tasks, falls to ICMP. The simplest test performed when there is a problem using TCP/IP is usually a check that a pair of devices is able to send datagrams to each other. This is most often done by an initiating device sending a test message to a second device, which receives it and replies back to tell the first device it received the message.

Like ICMPv4, ICMPv6 includes a pair of messages specifically for connection testing. To use them, Device A begins the test process by sending an ICMPv4 Echo Request message to Device B. Device B responds back to Device A with an Echo Reply message. When Device A receives this message, it knows that it is able to communicate (both send and receive) successfully with Device B.

Note: As a side note, in ICMPv4, the first message type was named just Echo but was often called Echo Request instead. In ICMPv6 they finally just added the “Request” to the message name and were done with it. A modest but useful improvement from a clarity standpoint.



Previous Topic/Section
ICMP Version 6 (ICMPv6) Informational Message Types and Formats
Previous Page
Pages in Current Topic/Section
1
2
Next Page
ICMPv6 Router Advertisement and Router Solicitation 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.