July 2002
Beginner
360 pages
11h 19m
English
Content preview from IPv6 Essentials
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.
ICMP Informational Messages
In RFC 2463, two types of informational messages are defined: the Echo Request and the Echo Reply messages. Other ICMP informational messages are used for Path MTU Discovery and neighbor discovery. These messages are discussed at the end of this chapter and defined in RFC 2461, “Neighbor Discovery for IP Version 6,” and RFC 1981, “Path MTU Discovery for IP version 6.”
The Echo Request and Echo Reply messages are used for one of the most common TCP/IP utilities: Packet INternet Groper (ping). Ping is used to determine if a specified host is available on the network and ready to communicate. The source host issues an Echo Request message to the specified destination. The destination host, if available, responds with an Echo Reply message. In Chapter 11, you can find a screenshot that shows you what an IPv6 ping looks like in the trace file, as well as the command you need to ping over IPv6.
Echo Request Message
The format of the Echo Request message is shown in Figure 4-6.
Figure 4-6. Format of the Echo Request message
The Type Field is set to 128, the value for the Echo Request. The Code Field is not used for this message and is therefore set to zero. The Identifier and Sequence Number fields are used to match requests with replies. The reply must always contain the same numbers as the request. Whether an identifier and a sequence number are used and ...
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
and much more.
Read now
Unlock full access
More than 5,000 organizations count on O’Reilly
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.