Subscriber and Performance Policy Identifier Context Headers in the Network Service Header (NSH)
RFC 8979

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Internet Engineering Task Force (IETF)                       B. Sarikaya
Request for Comments: 8979                                              
Category: Standards Track                                    D. von Hugo
ISSN: 2070-1721                                         Deutsche Telekom
                                                            M. Boucadair
                                                                  Orange
                                                           February 2021

  Subscriber and Performance Policy Identifier Context Headers in the
                      Network Service Header (NSH)

Abstract

   This document defines the Subscriber and Performance Policy
   Identifier Context Headers.  These Variable-Length Context Headers
   can be carried in the Network Service Header (NSH) and are used to
   inform Service Functions (SFs) of subscriber- and performance-related
   information for the sake of policy enforcement and appropriate
   Service Function Chaining (SFC) operations.  The structure of each
   Context Header and their use and processing by NSH-aware nodes are
   described.

Status of This Memo

   This is an Internet Standards Track document.

   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).  Further information on
   Internet Standards is available in Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   https://www.rfc-editor.org/info/rfc8979.

Copyright Notice

   Copyright (c) 2021 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
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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction
   2.  Conventions and Terminology
   3.  Subscriber Identifier NSH Variable-Length Context Header
   4.  Performance Policy Identifier NSH Variable-Length Context
           Headers
   5.  MTU Considerations
   6.  IANA Considerations
   7.  Security Considerations
   8.  References
     8.1.  Normative References
     8.2.  Informative References
   Acknowledgements
   Authors' Addresses

1.  Introduction

   This document discusses how to inform Service Functions (SFs)
   [RFC7665] about subscriber and service policy information when
   required for the sake of policy enforcement within a single
   administrative domain.  In particular, subscriber-related information
   may be required to enforce subscriber-specific SFC-based traffic
   policies.  However, the information carried in packets may not be
   sufficient to unambiguously identify a subscriber.  This document
   fills this void by specifying a new Network Service Header (NSH)
   [RFC8300] Context Header to convey and disseminate such information
   within the boundaries of a single administrative domain.  As
   discussed in Section 3, the use of obfuscated and non-persistent
   identifiers is recommended.

   Also, traffic steering by means of SFC may be driven, for example, by
   Quality of Service (QoS) considerations.  Typically, QoS information
   may serve as an input for the computation, establishment, and
   selection of the Service Function Path (SFP).  Furthermore, the
   dynamic structuring of Service Function Chains and their subsequent
   SFPs may be conditioned by QoS requirements that will affect the
   identification, location, and sequencing of SF instances.  Hence, the
   need arises to provide downstream SFs with a performance policy
   identifier in order for them to appropriately meet the QoS
   requirements.  This document also specifies a new NSH Context Header
   (Section 4) to convey such policy identifiers.

   The context information defined in this document can be applicable in
   the context of mobile networks (particularly in the 3GPP-defined
   (S)Gi interface) [CASE-MOBILITY].  Typically, because of the
   widespread use of private IPv4 addresses in those networks, if the
   SFs to be invoked are located after a NAT function, the
   identification based on the internal IPv4 address is not possible
   once the NAT has been crossed.  NAT functionality can reside in a
   distinct node.  For a 4G 3GPP network, that node can be the Packet
   Data Network (PDN) Gateway (PGW) as specified in [TS23401].  For a 5G