IP Tunnels in the Internet Architecture
draft-ietf-intarea-tunnels-08
Internet Area WG J. Touch
Internet Draft
Intended status: Best Current Practice M. Townsley
Updates: 4459 Cisco
Expires: July 2018 January 19, 2018
IP Tunnels in the Internet Architecture
draft-ietf-intarea-tunnels-08.txt
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Abstract
This document discusses the role of IP tunnels in the Internet
architecture. An IP tunnel transits IP datagrams as payloads in non-
link layer protocols. This document explains the relationship of IP
tunnels to existing protocol layers and the challenges in supporting
IP tunneling, based on the equivalence of tunnels to links. The
implications of this document are used to derive recommendations that
update MTU and fragment issues in RFC 4459.
Table of Contents
1. Introduction...................................................3
2. Conventions used in this document..............................6
2.1. Key Words.................................................6
2.2. Terminology...............................................6
3. The Tunnel Model..............................................10
3.1. What is a Tunnel?........................................11
3.2. View from the Outside....................................13
3.3. View from the Inside.....................................14
3.4. Location of the Ingress and Egress.......................15
3.5. Implications of This Model...............................15
3.6. Fragmentation............................................16
3.6.1. Outer Fragmentation.................................16
3.6.2. Inner Fragmentation.................................18
3.6.3. The Necessity of Outer Fragmentation................19
4. IP Tunnel Requirements........................................20
4.1. Encapsulation Header Issues..............................20
4.1.1. General Principles of Header Fields Relationships...20
4.1.2. Addressing Fields...................................21
4.1.3. Hop Count Fields....................................21
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4.1.4. IP Fragment Identification Fields...................22
4.1.5. Checksums...........................................23
4.2. MTU Issues...............................................24
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