Enhanced Feasible-Path Unicast Reverse Path Filtering
draft-sriram-opsec-urpf-improvements-00

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Last updated 2016-10-31
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Opsec Working Group                                            K. Sriram
Internet-Draft                                                      NIST
Intended status: Best Current Practice                     D. Montgomery
Expires: May 4, 2017                                             US NIST
                                                        October 31, 2016

         Enhanced Feasible-Path Unicast Reverse Path Filtering
                draft-sriram-opsec-urpf-improvements-00

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 is expected to alleviate ISPs' concerns about
   the possibility of disrupting service for their customers, and
   encourage greater deployment of uRPF.

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
   Task Force (IETF).  Note that other groups may also distribute
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   Internet-Drafts are draft documents valid for a maximum of six months
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   This Internet-Draft will expire on May 4, 2017.

Copyright Notice

   Copyright (c) 2016 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

Sriram & Montgomery        Expires May 4, 2017                  [Page 1]
Internet-Draft              Enhanced FP-uRPF                October 2016

   This document is subject to BCP 78 and the IETF Trust's Legal
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   (http://trustee.ietf.org/license-info) in effect on the date of
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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 . . . . . . . . . . . . . .   3
     2.2.  SAV using Strict Unicast Reverse Path Filtering . . . . .   4
     2.3.  SAV using Feasible-Path Unicast Reverse Path Filtering  .   4
     2.4.  SAV using Loose Unicast Reverse Path Filtering  . . . . .   6
   3.  Proposed New Technique: SAV using Enhanced Feasible-Path uRPF   6
     3.1.  Customer Cone Consideration . . . . . . . . . . . . . . .   7
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
   6.  Informative References  . . . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Introduction

   This internet draft identifies a need for improvement of the unicast
   Reverse Path Filtering techniques (uRPF) [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 denying
   customers' data packets with legitimate source addresses.  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 is based on the principle that if
   BGP updates for multiple prefixes with the same origin AS were
   received on different interfaces, then data packets with source
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