Technical Considerations for Internet Service Blocking and Filtering
RFC 7754

Document Type RFC - Informational (March 2016; No errata)
Last updated 2016-03-03
Replaces draft-barnes-blocking-considerations
Stream IAB
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Stream IAB state Published RFC
Consensus Boilerplate Yes
RFC Editor Note (None)
Internet Architecture Board (IAB)                              R. Barnes
Request for Comments: 7754                                     A. Cooper
Category: Informational                                       O. Kolkman
ISSN: 2070-1721                                                D. Thaler
                                                             E. Nordmark
                                                              March 2016

  Technical Considerations for Internet Service Blocking and Filtering

Abstract

   The Internet is structured to be an open communications medium.  This
   openness is one of the key underpinnings of Internet innovation, but
   it can also allow communications that may be viewed as undesirable by
   certain parties.  Thus, as the Internet has grown, so have mechanisms
   to limit the extent and impact of abusive or objectionable
   communications.  Recently, there has been an increasing emphasis on
   "blocking" and "filtering", the active prevention of such
   communications.  This document examines several technical approaches
   to Internet blocking and filtering in terms of their alignment with
   the overall Internet architecture.  When it is possible to do so, the
   approach to blocking and filtering that is most coherent with the
   Internet architecture is to inform endpoints about potentially
   undesirable services, so that the communicants can avoid engaging in
   abusive or objectionable communications.  We observe that certain
   filtering and blocking approaches can cause unintended consequences
   to third parties, and we discuss the limits of efficacy of various
   approaches.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   This document is a product of the Internet Architecture Board (IAB)
   and represents information that the IAB has deemed valuable to
   provide for permanent record.  It represents the consensus of the
   Internet Architecture Board (IAB).  Documents approved for
   publication by the IAB are not 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/rfc7754.

Barnes, et al.                Informational                     [Page 1]
RFC 7754          Blocking and Filtering Considerations       March 2016

Copyright Notice

   Copyright (c) 2016 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.

Barnes, et al.                Informational                     [Page 2]
RFC 7754          Blocking and Filtering Considerations       March 2016

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   4
   2.  Filtering Examples  . . . . . . . . . . . . . . . . . . . . .   5
   3.  Characteristics of Blocking Systems . . . . . . . . . . . . .   7
     3.1.  The Party Who Sets Blocking Policies  . . . . . . . . . .   8
     3.2.  Purposes of Blocking  . . . . . . . . . . . . . . . . . .   8
       3.2.1.  Blacklist vs. Whitelist Model . . . . . . . . . . . .   9
     3.3.  Intended Targets of Blocking  . . . . . . . . . . . . . .   9
     3.4.  Components Used for Blocking  . . . . . . . . . . . . . .  10
   4.  Evaluation of Blocking Design Patterns  . . . . . . . . . . .  11
     4.1.  Criteria for Evaluation . . . . . . . . . . . . . . . . .  11
       4.1.1.  Scope: What set of hosts and users are affected?  . .  12
       4.1.2.  Granularity: How specific is the blocking?  Will
               blocking one service also block others? . . . . . . .  12
       4.1.3.  Efficacy: How easy is it for a resource or service to
               avoid being blocked?  . . . . . . . . . . . . . . . .  13
       4.1.4.  Security: How does the blocking impact existing trust
               infrastructures?  . . . . . . . . . . . . . . . . . .  14
     4.2.  Network-Based Blocking  . . . . . . . . . . . . . . . . .  15
       4.2.1.  Scope . . . . . . . . . . . . . . . . . . . . . . . .  16
       4.2.2.  Granularity . . . . . . . . . . . . . . . . . . . . .  17
       4.2.3.  Efficacy and Security . . . . . . . . . . . . . . . .  17
       4.2.4.  Summary . . . . . . . . . . . . . . . . . . . . . . .  20
     4.3.  Rendezvous-Based Blocking . . . . . . . . . . . . . . . .  20
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