Locator/ID Separation Protocol Alternative Logical Topology (LISP+ALT)
RFC 6836

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Internet Engineering Task Force (IETF)                         V. Fuller
Request for Comments: 6836
Category: Experimental                                      D. Farinacci
ISSN: 2070-1721                                                 D. Meyer
                                                                D. Lewis
                                                           Cisco Systems
                                                            January 2013

 Locator/ID Separation Protocol Alternative Logical Topology (LISP+ALT)

Abstract

   This document describes a simple distributed index system to be used
   by a Locator/ID Separation Protocol (LISP) Ingress Tunnel Router
   (ITR) or Map-Resolver (MR) to find the Egress Tunnel Router (ETR)
   that holds the mapping information for a particular Endpoint
   Identifier (EID).  The MR can then query that ETR to obtain the
   actual mapping information, which consists of a list of Routing
   Locators (RLOCs) for the EID.  Termed the Alternative Logical
   Topology (ALT), the index is built as an overlay network on the
   public Internet using the Border Gateway Protocol (BGP) and Generic
   Routing Encapsulation (GRE).

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for examination, experimental implementation, and
   evaluation.

   This document defines an Experimental Protocol for the Internet
   community.  This document is a product of the Internet Engineering
   Task Force (IETF).  It represents the consensus of the IETF
   community.  It has received public review and has been approved for
   publication by the Internet Engineering Steering Group (IESG).  Not
   all documents approved by the IESG are a candidate for any level of
   Internet Standard; see Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc6836.

Fuller, et al.                Experimental                      [Page 1]
RFC 6836                        LISP+ALT                    January 2013

Copyright Notice

   Copyright (c) 2013 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Fuller, et al.                Experimental                      [Page 2]
RFC 6836                        LISP+ALT                    January 2013

Table of Contents

   1. Introduction ....................................................3
   2. Definition of Terms .............................................5
   3. The LISP-ALT Model ..............................................8
      3.1. Routability of EIDs ........................................8
           3.1.1. Mechanisms for an ETR to Originate EID-Prefixes .....9
           3.1.2. Mechanisms for an ITR to Forward to EID-Prefixes ....9
           3.1.3. Map-Server Model Preferred ..........................9
      3.2. Connectivity to Non-LISP Sites ............................10
      3.3. Caveats on the Use of Data-Probes .........................10
   4. LISP+ALT: Overview .............................................10
      4.1. ITR Traffic Handling ......................................11
      4.2. EID Assignment - Hierarchy and Topology ...................12
      4.3. Use of GRE and BGP between LISP-ALT Routers ...............14
   5. EID-Prefix Propagation and Map-Request Forwarding ..............14
      5.1. Changes to ITR Behavior with LISP+ALT .....................15
      5.2. Changes to ETR Behavior with LISP+ALT .....................15
      5.3. ALT Datagram Forwarding Failure ...........................16
   6. BGP Configuration and Protocol Considerations ..................16
      6.1. Autonomous System Numbers (ASNs) in LISP+ALT ..............16
      6.2. Subsequent Address Family Identifier (SAFI) for LISP+ALT ..17
   7. EID-Prefix Aggregation .........................................17
      7.1. Stability of the ALT ......................................18
      7.2. Traffic Engineering Using LISP ............................18
      7.3. Edge Aggregation and Dampening ............................19
      7.4. EID Assignment Flexibility vs. ALT Scaling ................19
   8. Connecting Sites to the ALT Network ............................20
      8.1. ETRs Originating Information into the ALT .................20