December 2005
Intermediate to advanced
1066 pages
33h 38m
English
Content preview from Understanding Linux Network InternalsBecome 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.
IP-over-IP
IP-over-IP, also called IP tunneling (or IPIP), consists of transmitting IP packets inside other IP packets. This protocol is useful in some very interesting cases, including in a Virtual Private Network (VPN). Of course, nothing comes for free; you can well imagine the extra weight of the doubling of the protocol: because each IP packet has two IP headers, the overhead becomes huge for small packets. There are subtle complexities in implementation, too. For instance, what is the relationship between the IP options of the two headers?
If you consider just the IPv4 and IPv6 protocols, you already have four possible combinations of tunneling. But not all of these combinations are likely to be used.
To make things more complex (I should actually say "flexible"), keep in mind that there is no limit to the number of recursions in tunneling.[*]
The different tunnel interfaces that can be created in Linux are not covered in this book. However, given the background on the IP implementation in this part of the book, you can study the code in net/ipv4/ipip.c and include/net/ipip.h to derive the implementation details.
[*] IPv6 defines the "tunnel encapsulation limit" as the maximum number of nested encapsulations. See section 6.6 of RFC 2473.
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.