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Network Working Group                                         T. Fossati
Internet-Draft                                                     Nokia
Intended status: Standards Track                            G. Fairhurst
Expires: June 19, 2019                            University of Aberdeen
                                                     P. Aranda Gutierrez
                                        Universidad Carlos III de Madrid
                                                           M. Kuehlewind
                                                              ETH Zurich
                                                       December 16, 2018


         A Loss-Latency Trade-off Signal for the Mobile Network
                      draft-fossati-tsvwg-lola-00

Abstract

   This document proposes a marking scheme for tagging low-latency flows
   (for example: interactive voice and video, gaming, machine to machine
   applications) that is safe to use by the mobile network for matching
   such flows to suitable per-hop behaviors (EPS bearers defined by
   3GPP) in its core and radio segments.  The suggested scheme re-uses
   NQB, a DiffServ-based signalling scheme with compatible rate-delay
   trade-off semantics that has been recently introduced in the context
   of fixed access to allow differential treatment of non-queue building
   vs queue building flows.

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 June 19, 2019.

Copyright Notice

   Copyright (c) 2018 IETF Trust and the persons identified as the
   document authors.  All rights reserved.




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   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://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
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   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  DiffServ Code . . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  Marking . . . . . . . . . . . . . . . . . . . . . . . . . . .   4
   5.  Relationship to a Mobile DiffServ Domain  . . . . . . . . . .   4
   6.  On Remarking and Bleaching  . . . . . . . . . . . . . . . . .   4
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   9.  Privacy Considerations  . . . . . . . . . . . . . . . . . . .   5
   10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   5
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     11.1.  Normative References . . . . . . . . . . . . . . . . . .   5
     11.2.  Informative References . . . . . . . . . . . . . . . . .   6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   Today's mobile networks are configured to bundle all flows to and
   from the Internet into a single "default" EPS bearer whose buffering
   characteristics are not compatible with low-latency traffic.  The
   established behaviour is partly rooted in the desire to prioritise
   operators' voice services over competing over-the-top services.  Of
   late, said business consideration seems to have lost momentum and the
   incentives might now be aligned towards allowing a more suitable
   treatment of Internet real-time flows.  However, a couple of
   preconditions need to be satisfied before we can move on from the
   status quo.  First, the real-time flows must be efficiently
   identified so that they can be quickly assigned to the "right" EPS
   bearer.  This is especially important with the rising popularity of
   encrypted and multiplexed transports, which has the potential of
   increasing the cost/accuracy ratio of Multi-Field (MF) based
   classification over the acceptable threshold.  Second, the signal
   must be such that malicious or badly configured nodes can't abuse it.
   Today's mobile networks take a rather extreme posture in this respect
   by actively discarding (remarking or bleaching [Custura]) DiffServ
   signalling coming from an interconnect.  Therefore, the signal must



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   be modelled in a way that the mobile network can either trust it or,
   even better, avoid the need of trusting it in the first place.  The
   Rate-Delay trade-off [Podlesny] satisfies the above requirements and
   has been shown [Fossati] to integrate well with a simplified LTE QoS
   setup that uses one dedicated low-latency bearer in addition to the
   default.

   This document suggests reusing the Non Queue Building (NQB)
   signalling protocol described in [I-D.white-tsvwg-nqb] as the method
   employed by endpoints to mark their real-time flows and by the LTE
   network to classify and route these flows via a suitable (low-
   latency) bearer through the LTE core network and E-UTRAN.

2.  Terminology

   o  DPI: Deep Packet Inspection

   o  EPS bearer: Evolved Packet System bearer, a virtual circuit with a
      given set of QoS attributes which spans the entire mobile network
      including the LTE core and E-UTRAN segments;

   o  GBR: Guaranteed Bit Rate.  EPS bearers can be GBR, in which case
      they are guaranteed to not drop packets under congestion, or non-
      GBR, in which case no guarantee of delivery is made by the mobile
      network;

   o  LTE: 3GPP Long Term Evolution, aka 4G;

   o  E-UTRAN: LTE Radio Access Network;

   o  QCI: QoS Class Identifier.  In LTE networks, EPS bearers are
      partitioned into equivalency classes modulo the QoS treatment they
      receive.  QCI is an integer that labels a specific QoS class.  Its
      semantics is consistently understood by all network elements
      involved in packet forwarding;

   o  UE: User Equipment, any device (e.g., smartphone, laptop, tablet)
      attached to an LTE network.

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.







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3.  DiffServ Code

   Given the semantic equivalence of a Loss-Latency trade-off with the
   Non Queue Building (NQB) behaviour, this document reuses the NQB DSCP
   (Section 4 of [I-D.white-tsvwg-nqb]) as-is.

4.  Marking

   Endpoints SHOULD mark packets that belong to the Best Effort class
   and are latency sensitive by assigning the NQB DSCP value to the DS
   field.

   The marking could also be added to other BE traffic if the default
   class could be reclassified by the network to use the NQB DSCP before
   the packet enters the mobile domain - for example by a classifier in
   the SGi-LAN or in an LTE router.

5.  Relationship to a Mobile DiffServ Domain

   The Mobile network is configured to give UEs a dedicated, low-
   latency, non-GBR, EPS bearer with QCI 7 in addition to the default
   EPS bearer.

   A packet carrying the NQB DSCP shall be routed through the dedicated
   low-latency EPS bearer.  A packet that has no associated NQB marking
   shall be routed through the default EPS bearer.

6.  On Remarking and Bleaching

   NQB markings SHOULD be preserved when forwarding via an interconnect.

   The NQB DSCP can have end-to-end semantics and this might benefit any
   NQB-marked traffic if utilised by other path elements (e.g. allowing
   DS treatment if a bottleneck link happens to be in the part of the
   path outisde the mobile access network segment).

7.  IANA Considerations

   This document makes no request to IANA.

8.  Security Considerations

   Internet applications cannot benefit from wrongly indicating low-
   latency as they have to pay the expense of high loss as a trade-off.
   Hence there is no incentive for Internet applications to set the
   wrong code-point.





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   The NQB signal is not integrity protected and could be flipped by an
   on-path attacker.  This might negatively affect the QoS of the
   tampered flow.

9.  Privacy Considerations

   As described in [Shbair] state of art encrypted traffic analysis
   based machine learning can successfully identify the type of
   transported application (e.g., HTTPS, SMTP, P2P, VoIP, SSH, Skype)
   with good accuracy and without any need to access the clear-text.  In
   this context, despite it being coarse grained, a 1-bit signal such as
   the one described in this document might be used to improve the
   precision of the classifier.

10.  Acknowledgments

   We would like to thank the authors of the "Latency Loss Tradeoff PHB
   Group" draft: Jianjie You, Michael Welzl, Brian Trammell and Kevin
   Smith.  Big thanks to Chris Seal, Dan Druta, Diego Lopez, Shamit
   Bhat, Georg Mayer, Florin Baboescu, James Gruessing for the help.

   This work is partially supported by the European Commission under
   Horizon 2020 grant agreement no. 688421 Measurement and Architecture
   for a Middleboxed Internet (MAMI), and by the Swiss State Secretariat
   for Education, Research, and Innovation under contract no. 15.0268.
   This support does not imply endorsement.

11.  References

11.1.  Normative References

   [I-D.white-tsvwg-nqb]
              White, G., "Identifying and Handling Non Queue Building
              Flows in a Bottleneck Link", draft-white-tsvwg-nqb-00
              (work in progress), October 2018.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.







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11.2.  Informative References

   [Custura]  Custura, A., Venne, A., and G. Fairhurst, "Exploring DSCP
              modification pathologies in mobile edge networks", TMA ,
              2017.

   [Fossati]  Fossati, T., Aranda Gutierrez, P., Kuehlewind, M., and D.
              Lopez, "Loss Latency Tradeoff and the Mobile Network",
              2018, <https://github.com/mami-
              project/roadshows/blob/master/ietf-103-lola/hotrfc/build/
              main.pdf>.

   [Podlesny]
              Podlesny, M. and S. Gorinsky, "Rd Network Services:
              Differentiation Through Performance Incentives", SIGCOMM ,
              2008.

   [Shbair]   Shbair, W., Cholez, T., Francois, J., and I. Chrisment, "A
              Multi-Level Framework to Identify HTTPS Services", NOMS ,
              2016.

Authors' Addresses

   Thomas Fossati
   Nokia

   Email: thomas.fossati@nokia.com


   Gorry Fairhurst
   University of Aberdeen

   Email: gorry@erg.abdn.ac.uk


   Pedro A. Aranda Gutierrez
   Universidad Carlos III de Madrid

   Email: paranda@it.uc3m.es


   Mirja Kuehlewind
   ETH Zurich

   Email: mirja.kuehlewind@tik.ee.ethz.ch






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