Enhanced Feasible-Path Unicast Reverse Path Filtering
draft-sriram-opsec-urpf-improvements-02

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Last updated 2017-10-30
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Opsec Working Group                                            K. Sriram
Internet-Draft                                             D. Montgomery
Intended status: Best Current Practice                           US NIST
Expires: May 3, 2018                                             J. Haas
                                                  Juniper Networks, Inc.
                                                        October 30, 2017

         Enhanced Feasible-Path Unicast Reverse Path Filtering
                draft-sriram-opsec-urpf-improvements-02

Abstract

   This document identifies a need for improvement of the unicast
   Reverse Path Filtering techniques (uRPF) [BCP84] for source address
   validation (SAV) [BCP38].  The strict uRPF is inflexible about
   directionality, the loose uRPF is oblivious to directionality, and
   the current feasible-path uRPF attempts to strike a balance between
   the two [BCP84].  However, as shown in this draft, the existing
   feasible-path uRPF still has short comings.  This document proposes
   an enhanced feasible-path uRPF technique, which aims to be more
   flexible (in a meaningful way) about directionality than the
   feasible-path uRPF.  It can potentially alleviate ISPs' concerns
   about the possibility of disrupting service for their customers, and
   encourage greater deployment of uRPF techniques.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on May 3, 2018.

Copyright Notice

   Copyright (c) 2017 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

Sriram, et al.             Expires May 3, 2018                  [Page 1]
Internet-Draft              Enhanced FP-uRPF                October 2017

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  Review of Existing Source Address Validation Techniques . . .   3
     2.1.  SAV using Access Control List . . . . . . . . . . . . . .   4
     2.2.  SAV using Strict Unicast Reverse Path Filtering . . . . .   4
     2.3.  SAV using Feasible-Path Unicast Reverse Path Filtering  .   5
     2.4.  SAV using Loose Unicast Reverse Path Filtering  . . . . .   6
   3.  Proposed New Technique: SAV using Enhanced Feasible-Path uRPF   7
     3.1.  Description of the Method . . . . . . . . . . . . . . . .   7
     3.2.  Operational Recommendations . . . . . . . . . . . . . . .   8
     3.3.  A Challenging Scenario  . . . . . . . . . . . . . . . . .   9
     3.4.  Overcoming the Above Challenge: Algorithm with Full
           Flexibility Across Customer Cone  . . . . . . . . . . . .  10
     3.5.  Implementation Considerations . . . . . . . . . . . . . .  11
       3.5.1.  Impact on FIB Memory Size Requirement . . . . . . . .  11
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .  12
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  12
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  13
   7.  Informative References  . . . . . . . . . . . . . . . . . . .  13
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  14

1.  Introduction

   This internet draft identifies a need for improvement of the unicast
   Reverse Path Filtering (uRPF) techniques [RFC2827] for source address
   validation (SAV) [RFC3704].  The strict uRPF is inflexible about
   directionality, the loose uRPF is oblivious to directionality, and
   the current feasible-path uRPF attempts to strike a balance between
   the two [RFC3704].  However, as shown in this draft, the existing
   feasible-path uRPF still has short comings.  Even with the feasible-
   path uRPF, ISPs are often apprehensive that they may be dropping
   customers' data packets with legitimate source addresses.
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