Recommendations for Forwarding Packets Marked with EXP/LU DSCPs in Diffserv Networks
draft-blake-explu-dscp-rec-00

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Author Steven Blake 
Last updated 2020-04-25
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Internet Engineering Task Force                                 S. Blake
Internet-Draft                                             25 April 2020
Intended status: Informational                                          
Expires: 27 October 2020

   Recommendations for Forwarding Packets Marked with EXP/LU DSCPs in
                           Diffserv Networks
                     draft-blake-explu-dscp-rec-00

Abstract

   Some network operators implementing Diffserv are purported to remark
   some IP packets with non-zero DSCP values to the default DSCP value
   '000000' at their ingress network boundaries.  This behavior is often
   not strictly necessary to protect an operator's network resources,
   and it impedes end-to-end experimentation of new differentiated
   services.  This document recommends that Diffserv network operators
   refrain from remarking packets received with an EXP/LU DSCP value
   [RFC2474][RFC8436] that is not in use within the operator's network,
   and recommends that operators forward these packets at each Diffserv
   node (DS-node) using the Default "best-effort" PHB.

Status of This Memo

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   This document is subject to BCP 78 and the IETF Trust's Legal
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Blake                    Expires 27 October 2020                [Page 1]
Internet-Draft    Forwarding Packets with EXP/LU DSCPs        April 2020

   Please review these documents carefully, as they describe your rights
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  EXP/LU DSCPs  . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  End-to-End Diffserv Experiments Using EXP/LU DSCP Values  . .   3
   4.  Recommendations For Forwarding Packets With EXP/LU DSCP
           Values  . . . . . . . . . . . . . . . . . . . . . . . . .   4
   5.  Recommendations For Allocating EXP/LU DSCP Values . . . . . .   4
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   The Differentiated Service (Diffserv) architecture defines the
   differentiated services field codepoint (DSCP) in IP packets to
   select among a set of per-hop forwarding behaviors (PHBs) in Diffserv
   nodes (DS-nodes) [RFC2474][RFC2475].  Network operators enforce
   traffic conditioning specifications (TCSs) [RFC3260] at network
   ingress boundaries to regulate the traffic parameters of ingressing
   Diffserv behavior aggregates (BAs) marked with specific DSCP values
   to deliver differentiated services to these BAs according to the
   traffic provisioning and PHB configuration policies the operator has
   enacted.

   One aspect of a TCS is regulating which packet flows are admitted to
   the operator's network while using a non-default (i.e., non-zero)
   DSCP value.  If such a BA is in violation of a TCS, or if no TCS is
   in effect for this BA, then the network operator may need to discard
   or remark the associated packets of the BA to preserve network
   resources.  Some network operators are purported to remark packets in
   such a BA to the default DSCP value '000000'.  This behavior is
   referred to as "DSCP bleaching" [CVF][CSF][BWEDIG].

   Packets in a BA that is in violation of an operator's TCS generally
   should not be forwarded at DS-nodes using an enhanced PHB, but should
   instead be forwarded using the Default "best-effort" PHB
   [RFC2474][RFC2475], if they are not discarded according to some
   security policy.  However, this does not automatically imply that
   such packets must be DSCP bleached.  If the BA's packets are marked
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