Internet DRAFT - draft-sfc-sinha-5g-bearer-dc-ran

draft-sfc-sinha-5g-bearer-dc-ran



Service Function Chaining                              Sunil Kumar Sinha
Internet-Draft                              Infinite Computing Solutions
Intended status: Informational                            Amardeep Sinha
Expires: December 7, 2018                  Reliance Jio Infocomm Limited
                                                      Dharmendra Dwivedi
                                                                Ericsson
                                             Harsh Vardhan Singh Chauhan
                                                                   Nokia
                                                            June 8, 2018

       5G-System Bearer Offloading for Dual Connectivity for RAN
                draft-sfc-sinha-5g-bearer-dc-ran-00

Abstract

   This document attempts the case for new work that needs to be 
   developed for 5G users to improve faster download and upload of the
   user's data in a scenario of dual-connectivity 3GPP access outlining
   the poor radio coverage issues. This document also outlines the
   faster user data mechanism accompanying 3GPP access of 5G user
   device via bearer offloading in case of a poor coverage.

Status of This Memo

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   This Internet-Draft will expire on December 7, 2018

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Table of Contents:

   1. Introduction...................................................2
   2. Conventions and Terminology....................................2
   3. User data flow for Dual Connectivity for 3GPP access and
      problem statement..............................................2
      3.1 5G System architecture.....................................2
      3.2 QoS........................................................3
      3.3 Dual Connectivity..........................................3
      3.4 Problem Statement..........................................4
   4. Proposal of Bearer Offloading Dual-Connectivity with 3GPP
      access ........................................................4
   5. IANA Considerations............................................6
   6. Security Considerations........................................6
   7. Privacy Considerations ........................................6
   8. Acknowledgements...............................................6
   9. References.....................................................7
      9.1 Normative References.......................................7
      9.2 Informative References.....................................7
   Authors' Addresses................................................8

1. Introduction

   5G system has been evolved to serve the user in more efficient way
   of meeting higher download and upload of user data for 5G Users
   accessing the network via wireline and wireless, in addition to
   Residential Gateway RG and IoT support. In 5G system Access and
   user experience is challenging for poor radio coverage (for both
   wi-fi and RAN) and the proposal in this document addresses to the
   problem of dual-connectivity of 3GPP access with Master-gNB having
   poor coverage.

2.  Conventions and Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [1].

3. User data flow for Dual Connectivity for 3GPP access and problem 
   statement

3.1 5G system architecture
   
   A simplified 5G-system architecture shown in Figure-1 in the case of 
   UE in non-roaming scenario with RAN access(3GPP).



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                       +-------------------------------+
                       |                               |
                       | +------------------+          |
                       | |                  |          |
                       | |                  |N8        |N15
                       | |                  |          |
          +------+     | | +------+  N13  +-----+      |
          | NSSF |---+ | | | AUSF |-------| UDM |      |
          +------+   | | | +------+       +-----+      |
                     | | |     |             |         | 
                     | | |     |             |         | 
                  N22| | |     |N12          |N10   +-----+  N5  +----+
                     | | | +---+             |      | PCF |------| AF |
                     | | | |                 |      +-----+      +----+
                     | | | |                 |         |
                     | | | |                 |         |
      +-----+       +-------+            +-----+       |
 UE---| RAN |-------|  AMF  |------------| SMF |-------+
      +-----+  N2   +-------+    N11     +-----+    N7
         |                                  |
         |                                  |
         |                                  |N4
         |                                  |
         |                                  |
         |          N3                   +-----+   N6   +-------------+
         +-------------------------------| UPF |--------| Service N/W |
                                         +-----+        +-------------+

        Figure 1 : Simplified 5G-system Architecture for RAN access

   For clarity in the current document proposal, multiple node/
   function like UDSF, NRF, and interfaces N9, N14 are not shown.

3.2 QoS 

   QFI is defined as Qos Flow ID is an identity to QoS flow in the 5G 
   system. All data traffic within a PDU session are labelled or 
   identified by QFI, it implies same QFI labelled data flow will 
   receive same traffic forwarding treatment like scheduling, priority
   etc.

   Data flow is via N3 (N3 and N9) interface, being encapsulated
   end-to-end. This flow is controlled by SMF, who provides QoS profile 
   during session establishment to R(AN) and provide the PDR to the UPF.
   Please Note that like 4G system, default QoS flow is applied to each
   PDU session and retain till lifetime span of connectivity. In case
   of non-3GPP access QFI is delivered to N3IWF entity (or NG-RAN) for 
   every time User Plane of the PDU session is established, modified or
   activated.

3.3 Dual Connectivity

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   Dual connectivity (DC) concept developed for 3GPP access, functional
   support the network to make use of additional radio resource to 
   achieve required throughput in downlink and uplink of user data. This
   was introduced in 4G system support 5G data speed by addition of dual
   connectivity of UE with eNBs , master eNB and Secondary eNB and /or 
   eNodeB in congestion with gNB. This is achieved by addition of 
   Secondary eNodeB to the Master eNodeB. Master-eNB has full control
   to add, delete and HO (handover) of eNodeBs as and when needed.

3.4 Problem Statement

   Problem statement 1: Inspite in a Dual connectivity of 5G system user
   experience is impacted because of Master-gNB may have degrade radio
   condition and another Master-gNB is not available for handover where
   as Secondary-gNB is available with sufficient radio resource.

4. Proposal of Bearer Offloading Dual-Connectivity with 3GPP access

   The solution proposed in this document to solve the degrade Rf 
   condition at Master-gNB while handover to another Master-gNB is
   not possible and UE have better or improved Rf condition with 
   Secondary-gNB(as compared to Master-gNB).

   Figure 2, show below shows how radio resource control can be handed
   over from Master-gNB to Secondary-gNB.

   - 5G user (UE) is being served by Master-gNB
   - Master-gNB adds Secondary-gNB for delivering user data to UE
   - UE is register to 5G-core via Master-gNB , whereas there is no
     user context available between Secondary-gNB and AMF
   - There is X2 interface between master-gNB and Secondary-gNB defined
     in 3GPP specification.
   - User data is deliver over N3 interface between UPF and Master-gNB
   - Master-gNB splits the partial User data over x2 interface to 
     Secondary-gNB.




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     +--+           +-----+    +-----+    +---+     +---+   +---+
     |UE|           |M-gNB|    |S-gNB|    |AMF|     |SMF|   |UPF|          
     +--+           +-----+    +-----+    +---+     +---+   +---+
       |               |          |         |        |         |
       |               |          |         |        |         |
       |<==User Data==>|<==============User Data==============>|
       |               |          |         |        |         |
       |  Measurement  |          |         |        |         |
       |<--------------|          |         |        |         |
       |   Control     |          |         |        |         |
       |               |          |         |        |         |
       | Measurement   |          |         |        |         |
       |-------------->|          |         |        |         |
       | Report        |          |         |        |         |
       |               |          |         |        |         |
       |           -------------  |         |        |         |
       |          | HO Decision | |         |        |         |
       |           -------------  |         |        |         |
       |               |          |         |        |         |
       |               |          |         |        |         |
       |               |  S-gNB HO Request  |        |         |
       |               |--------->|         |        |         |
       |               | (carry SCG configinfo)      |         |
       |               |          |         |        |         |
       |               |          |         |        |         |
       |               |          |         |        |         |
       |               | S-gNB HO Req.Ack   |        |         |
       |               |<---------|         |        |         |
       |               |          |         |        |         |
       |               |          |         |        |         |
       |<-----RRC procedure------>|         |        |         |
       |               |          |         |        |         |
       |               |          |         |        |         |
       |             --------------------------------------------
       |            |     PATH UPDATE PROCEDURE and FILTER       |
       |             --------------------------------------------
       |                          |                            |
       |<========User Data=======>|<==========User Data=======>|
       |                          |                            |
 
    Figure 2: Bearer Offloading Dual-Connectivity with 3GPP access only

   - Based on Measurement report, Master-gNB take decision to execute a
     procedure of handover to Secondary-gNB with SCG configuration. 
   - Secondary-gNB establish connection with AMF to cater user's all 
     signalling and data traffic. 
   - Master-gNB also provides a radio (Rf) bearer splitting template
     termed as 'FILTER'. This bearer template FILTER is delivered to
     UPF via SMF. 
   - UPF now shift the user data on N3 interface from Master-gNB to 
     Secondary-gNB. This Secondary-gNB will act as new Master-gNB.

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   Please note that this FILTER value in this scenario of handover from
   Master-gNB to Secondary-gNB MUST empty or NULL, implies that user
   traffic segregation is completely governed by AMF and SMF based on
   PCC rules and policies.

5.  IANA Considerations

   None.

6.  Security Considerations

   Security considerations related to the 5G systems are discussed in
   [NGMN].  Due to the request for intrinsic realization of security
   such aspects have to be considered by design for architecture and
   protocols.

   Especially as a joint usage of resources and network functions by
   different separate logical network slices (e.g. in terms of virtual
   network functions) seems to be inevitable in the framework of 5G the
   need for strong security measures in such an environment is a major
   challenge.

7.  Privacy Considerations

   Support of full privacy of the users (customers and tenants / end
   service providers) is a basic feature of the next generation trusted
   and reliable communications offering system.  Such a high degree of
   ensured privacy shall be reflected in the proposed architecture and
   protocol solutions.

   Especially as Identifiers and mapping of locators to them are
   addressed some privacy concerns arise.  Mobility solutions tend to
   expose unique identifiers.  A solution inside the mobile network
   exposes these identifiers to the network operator, which is not a big
   deal since the network operator already has information about the
   device's location.  In contrast, an IP level solution exposes both
   the identifiers and the locations at the IP layer.  That means that
   web sites, for example, can now track the device's successive
   locations by watching the IP address.  Solutions such as transporting
   the identifiers not as part of the IP header should be considered.

8.  Acknowledgements

   This work has been partially performed in the framework of the
   cooperation Config.  Contributions of the project partners are
   gratefully acknowledged.  The project consortium is not liable for
   any use that may be made of any of the information contained therein.

   Comments, constructive critisms from Karthik Palaniswamy and 
   Nagesh V. J. are respectfully acknowledged.

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9.  References

9.1.  Normative References

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

9.2.  Informative References

   [TS23.501]
              "3GPP TS23.501, System Architecture for the 5G System
              (Release 15)", March 2018.

   [TS36.300]
              "3GPP TS36.300, Evolved Universal Terrestrial Radio Access
               (E-UTRA) and Evolved Universal Terrestrial Radio Access
               Network (E-UTRAN); Overall description", March 2018.

   [TS23.502]
              "3Procedures for the 5G System", March 2018.

   [TS23.228]
              "IP Multimedia Subsystem (IMS)", March 2018.

   [TR38.801]
              "Study on new radio access technology: Radio
               access architecture and interfaces", March 2017.

   [TR23.793]
              "Study on Access Traffic Steering, Switch and Splitting
               support in the 5G system architecture.", April 2018.

   [TR23.793]
              "Study on Access Traffic Steering, Switch and Splitting
               support in the 5G system architecture.", April 2018.

   [ETSI GR NGP 004]
              "Next Generation Protocol (NGP):Evolved Architecture for
               mobility using. Identity Oriented Networks.",January 2018

   [ETSI GR NGP 001]
              "Next Generation Protocol (NGP); Scenario Definitions".
               ,May 2017

   [NGMN]     NGMN Alliance, "NGMN White Paper", February 2015.




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Authors' Addresses


   Sunil Kumar Sinha
   FF-01, Rainbow Residency,
   Green Glan layout,
   Bellandur, Bangalore
   Karnataka, India

   Email: sunilkumarsinha9@gmail.com


   Amardeep Sinha
   C-1003, Yashodeep Heights,
   Sec-29C, Airoli,
   Navi-Mumbai, Maharashtra
   India

   Email: sinha.amardeep@gmail.com


   Dharmendra Dwivedi
   Ericsson Global Service, India
   EGI, Mahadev Pura,
   EMC Square, Outer Ring Road,
   Bengaluru, India

   Email: dharmendra.dwivedi78@gmail.com



   Harsh Vardhan Singh Chauhan
   Gwalior, MP

   Email: vardhan.chauhan@gmail.com















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