Network Working Group W. Simpson Request for Comments: 1853 Daydreamer Category: Informational October 1995 IP in IP Tunneling Status of this Memo This memo provides information for the Internet community. It does not specify an Internet standard. Distribution of this memo is unlimited. IESG Note: Note that this memo is an individual effort of the author. This document reflects a current informal practice in the internet. There is an effort underway within the IETF Mobile-IP Working Group to provide an appropriate proposed standard to address this issue. Abstract This document discusses implementation techniques for using IP Protocol/Payload number 4 Encapsulation for tunneling with IP Security and other protocols. Table of Contents 1. Introduction .......................................... 2 2. Encapsulation ......................................... 3 3. Tunnel Management ..................................... 5 3.1 Tunnel MTU Discovery ............................ 5 3.2 Congestion ...................................... 6 3.3 Routing Failures ................................ 6 3.4 Other ICMP Messages ............................. 6 SECURITY CONSIDERATIONS ...................................... 7 REFERENCES ................................................... 7 ACKNOWLEDGEMENTS ............................................. 8 AUTHOR'S ADDRESS ............................................. 8 Simpson Informational