RFC 1853 (rfc1853) - Page 2 of 8

IP in IP Tunneling

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