Mobility Support for Nimrod : Challenges and Solution Approaches
RFC 2103

Document Type RFC - Informational (February 1997; No errata)
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Network Working Group                                      R. Ramanathan
Request for Comments: 2103                  BBN Systems and Technologies
Category: Informational                                    February 1997

   Mobility Support for Nimrod :  Challenges and Solution Approaches

Status of this Memo

   This memo provides information for the Internet community.  This memo
   does not specify an Internet standard of any kind.  Distribution of
   this memo is unlimited.

Abstract

   We discuss the issue of mobility in Nimrod.  While a mobility
   solution is not part of the Nimrod architecture, Nimrod does require
   that the solution have certain characteristics.  We identify the
   requirements that Nimrod has of any solution for mobility support.
   We also classify and compare existing approaches for supporting
   mobility within an internetwork and discuss their advantages and
   disadvantages.  Finally, as an example, we outline the mechanisms to
   support mobility in Nimrod using the scheme currently being developed
   within the IETF - namely, the Mobile-IP protocol.

Table of Contents

   1  Introduction...................................................  1
   2  Mobility :  A Modular Perspective..............................  2
   3  Effects of Mobility............................................  4
   4  Approaches.....................................................  6
   5  Solution using IETF Mobile-IP.................................. 10
      5.1 Overview .................................................. 10
      5.2 Protocol Details........................................... 11
   6  Security Considerations........................................ 15
   7  Summary........................................................ 16
   8  Acknowledgements............................................... 16
   9  Author's Address............................................... 17

1  Introduction

   The nature of emerging applications makes the support for mobility
   essential for any future routing architecture.  It is the intent of
   Nimrod to allow physical devices as well as networks to be mobile.

   Nimrod, as a routing and addressing architecture, does not directly
   concern itself with mobility.  That is, Nimrod does not propose a
   solution for the mobility problem.  There are two chief reasons for

Ramanathan                   Informational                      [Page 1]
RFC 2103                Nimrod Mobility Support            February 1997

   this.  First, mobility is a non-trivial problem whose implications
   and requirements are still not well understood and will perhaps be
   understood only when a mobile internetwork is deployed on a large
   scale.  Second, a number of groups (for instance the Mobile-IP
   working group of the IETF) are studying the problem by itself and it
   is not our intention to duplicate those efforts.

   This attitude towards mobility is consistent with Nimrod's general
   philosophy of flexibility, adaptability and incremental change.

   While a mobility solution is not part of the "core" Nimrod
   architecture, Nimrod does require that the solution have certain
   characteristics.  It is the purpose of this document to discuss some
   of these requirements and evaluate approaches towards meeting them.

   We begin by identifying the precise nature of the functionality
   needed to accommodate mobile entities (section 2).  Following that,
   we discuss the effects of mobility on Nimrod (section 3).  Next, we
   classify current and possible approaches to a solution for mobility
   (section 4) and finally (in section 5) we describe how mobility can
   be implemented using the IETF's Mobile-IP protocol.

   This document uses many terms and concepts from the Nimrod
   Architecture document [CCS96] and some terms and concepts (in section
   5) from the Nimrod Functionality document [RS96].  Much of the
   discussion assumes that you have read at least the Nimrod
   Architecture document [CCS96].

2  Mobility :  A Modular Perspective

   Nimrod has a basic feature that helps accommodate mobility in a
   graceful and natural manner, namely, the separation of the endpoint
   naming space from the locator space.  The Nimrod architecture [CCS96]
   associates an endpoint with a globally unique endpoint identifier
   (EID) and an endpoint label (EL). The location of the endpoint within
   the Internetwork topology is given by its locator.  When an endpoint
   moves, its EID and EL remain the same, but its locator might change.
   Nimrod can route a packet to the endpoint after the move, provided it
   is able to obtain its new locator.

Ramanathan                   Informational                      [Page 2]
RFC 2103                Nimrod Mobility Support            February 1997

   Thus, providing a solution to mobility in the context of Nimrod may
   be perceived as one of maintaining a dynamic association between the
   endpoints and the locators.  Extending this viewpoint further, one
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