RFC 1853 (rfc1853) - Page 2 of 8
IP in IP Tunneling
Alternative Format: Original Text Document
RFC 1853 IP Tunnelling October 1995
1. Introduction
The IP in IP encapsulation Protocol/Payload number 4 [RFC-1700] has
long been used to bridge portions of the Internet which have disjoint
capabilities or policies. This document describes implementation
techniques used for many years by the Amateur Packet Radio network
for joining a large mobile network, and also by early implementations
of IP Security protocols.
Use of IP in IP encapsulation differs from later tunneling techniques
(for example, protocol numbers 98 [RFC-1241], 94 [IDM91a], 53
[swIPe], and 47 [RFC-1701]) in that it does not insert its own
special glue header between IP headers. Instead, the original
unadorned IP Header is retained, and simply wrapped in another
standard IP header.
This information applies principally to encapsulation of IP version
4. Other IP versions will be described in separate documents.
Simpson Informational