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Network Working Group                                        D. von Hugo
Internet-Draft                           Telekom Innovation Laboratories
Intended status: Informational                               B. Sarikaya
Expires: March 18, 2017                                           Huawei
                                                      September 14, 2016

  Review on issues in discussion of next generation converged networks
                     (5G) from an IP point of view


   This document discusses considerations related to open and upcoming
   issues with upcoming new communication systems denoted as 5G.  The
   draft reviews currently investigated topics, including both inputs
   from IETF and from other SDOs as well as research activities.
   Further the outcome of recent discussions at side sessions during
   IETF meetings are recaptured to help identifying a starting point for
   future thoughts.

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 March 18, 2017.

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
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   to this document.  Code Components extracted from this document must
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Problem Space and Typical Use Cases . . . . . . . . . . . . .   4
     2.1.  Ubiquitous Broadband Access Use Case  . . . . . . . . . .   4
     2.2.  Massive Deployment of Machines Use Case . . . . . . . . .   4
     2.3.  Critical Communications Use Case  . . . . . . . . . . . .   4
   3.  Requirements to Future Communication Systems  . . . . . . . .   4
   4.  Current Activities and Areas of Work within IETF/IRTF . . . .   5
   5.  Future Internet Architecture  . . . . . . . . . . . . . . . .   6
   6.  Edge Network with no Tunneling  . . . . . . . . . . . . . . .   7
   7.  Logical Network Isolation (Slicing) Concepts  . . . . . . . .   8
   8.  Location Identification Separation and Naming . . . . . . . .   9
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  10
   10. Security Considerations . . . . . . . . . . . . . . . . . . .  10
   11. Privacy Considerations  . . . . . . . . . . . . . . . . . . .  10
   12. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  10
   13. References  . . . . . . . . . . . . . . . . . . . . . . . . .  11
     13.1.  Normative References . . . . . . . . . . . . . . . . . .  11
     13.2.  Informative References . . . . . . . . . . . . . . . . .  11
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  12

1.  Introduction

   This document focuses on IP architecture and protocol aspects related
   to upcoming new communication system dubbed as 5G.  Originally
   foreseen to be available from 2020 onwards such a converged ICT
   system for a broad spectrum of fixed and mobile services will be
   characterised mainly by improved flexibility and efficient usage of
   available resources to support services' demands with partially
   contradicting requirements.  A new highly re-configurable
   architecture in both heterogeneous access and a converged core
   network shall allow for key features as

   o  Stable selectable low latency

   o  Granted reliability and availability according to user and service

   o  Potential (adaptive) mobility support (i.e. on demand): in case of
      change in device or service location or as countermeasure to
      partial failures /outage

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   o  Low cost (i.e. affordable and related to service characteristics)
      with respect to both investment and operational expenses:
      efficiency in terms of resource consumption and effort

   o  Adaptive support of service quality in terms of (raw network)
      performance and individual user experience (requiring end-to-end
      monitoring and feedback)

   o  Selectable inbuilt security: different measures to be chosen from
      a tool box

   o  Improved resource efficiency (e.g. in terms of energy consumption,
      processing power, data storage, and radio spectrum usage)

   o  High flexibility for new services (and service features)
      introduction and deployment

   o  Much better scalability in terms of amount of supported end
      devices and transferred data rates and volume

   o  Higher bandwidth, data rate and throughput shall be achieved with
      new radio technologies (multiple antennas) and usage of multiple
      potentially heterogeneous technologies in concurrence
      (multiaccess), bandwidth/ broadband access values exceeding 1Gbps.

   A network to serve diverse demands ranging between very strict and
   quite relaxed requirements asks for dynamic feature selection per
   network functionality and thus will be much more software centric.
   Only an architecture with modular control plane functions will enable
   service tailored selection or adaptation of network characteristics
   in terms of functionalities.

   Also the expected high flexibility and resource efficiency demands
   for exploitation of SDN and NFV together with computation and storage
   space provision in central or distributed cloud environments.

   In addition a new architecture with modular control plane functions
   is required to enable service tailored selection or adaptation of
   network characteristics in terms of functionalities.

   Decoupling and abstraction of access and core domains to allow for
   heterogeneity enabling higher flexibility and resource usage
   efficiency is a request to 5G systems.

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2.  Problem Space and Typical Use Cases

   The design of the new 5G system faces challenging requirements which
   are derived from potential prospective services to be provisioned via
   the 5G ecosystem.  To illustrate the broad range of diverse demands
   out of the plentitude of use cases as identified e.g. in [NGMN] a set
   of three exemplary use case families is presented below following

   Generally all such services cannot and have not to be provided within
   one specifically configured logical network.  Flexibility to allow
   different adaptations of the same physical infrastructure to fulfill
   one tenants or verticals (service providers) requests is essential
   for an appropriate 5G system concept.

2.1.  Ubiquitous Broadband Access Use Case

   These group of use cases covers fixed, portable, and mobile
   applications between user equipment and servers in the network which
   may be characterized by large bandwidth requirements, support of
   moving devices, typical multimedia services between humans and
   between humans and content in the network to only name a few.

2.2.  Massive Deployment of Machines Use Case

   The MTC or IoT use cases cover generally a large amount and dense
   deployment of devices (sensors, metering) as smart grid or of
   Industry 4.0 type, but also vehicular communication.

2.3.  Critical Communications Use Case

   Here a strict latency and reliability limit has to be considered
   since services are time-critical or need high delivery probability.

3.  Requirements to Future Communication Systems

   Derived from the use case scenarios a list of requirements for 5G has
   been established by several organisations as e.g.  NGMN or 3GPP
   denoting as key issues or key design principles or key drivers, for
   details see e.g. 3GPP [TR23.799].  Also ITU has identified key
   capabilities of IMT-2020, i.e. the International Mobile
   Telecommunications (IMT) system for 2020 and beyond, which can be
   found in [M.2083].

   Beside quantitatively measurable Expected enhancement of performance
   parameters as

   o  User experienced data rate: 100 vs. 10 Mbit/s

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   o  Spectrum efficiency 3 times that of IMT Advanced

   o  Mobility support for up to 500 km/h instead of 350 (only)

   o  Latency (of 1 vs. 10 ms), Latency down to 1ms could be foreseen
      for 5G

   o  Connection density of 1 Million vs. 100000 devices/km )

   o  Network energy efficiency of 100 times improved

   o  Area traffic capacity of 10 vs. 0.1 Mbit/s/m2

   o  Peak data rate of 20 instead of below 1 Gbit/s

   Other key improvements which are not always direct quantitatively
   measurable cover so-called soft features are also essential for 5G:

   o  Network scalability and flexibility

   o  Consistent customer experience

   o  Service and network trust, reliability and security

   o  Operational efficiency

   o  Openness for innovation

4.  Current Activities and Areas of Work within IETF/IRTF

   Although a vertical topic as 5G is seen not as IETF topic ( providing
   standardized building blocks for specific engineering challenges
   "horizontals."  IETF does not define or adapt "vertical" frameworks
   like "Smart Cities," "Internet of Things," or "5G networks."  It is
   implicitly assumed that the participants will apply the building
   blocks within the verticals
   [I-D.arkko-ietf-trends-and-observations].), the topic creates issues
   on multiple horizontal levels as is reflected within drafts and
   discussions in WGs such as LISP (Locator/Identifier Separation
   Protocol), NVO3 (Network Virtualization Overlays).  Furthermore IRTF
   RGs with focus on 5G topics are NFV(Network Function Virtualization),
   SDN (Software Defined Networking), and ICN (Information Centric

   The current activities there contribute to one or more of the
   following issues addressed in more detail during the preceding side
   meetings of the 5GangIP mailing list archive.

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5.  Future Internet Architecture

   Currently the efforts are in its beginning stages of defining,
   designing or optimizing protocols for a more efficient internet to
   provide mobility, scale, security and ease of deployment required for
   a connected society beyond the year 2020.  But the industry seems to
   be divided by what should qualify as a true 5G.  One approach to 5G

   5G radio + 4G Core (with improvements)

   This approach takes 4G/LTE core, i.e. the current core network as 5G
   core.  However, what is in demand should be

   5G radio + 5G Core

   As a truly 5G, the real distinguisher lies in designing a new core to
   meet the 5G requirements.  The new core may also allow for connection
   via enhanced 4G radio for reasons of operational continuity.

   The current IP is connectivity-centric.  Additional features such as
   mobility and security are added as optional patches and fix-ups.
   Moreover, protocols have been designed in a segmented way instead of
   an architectural way.

   Future Internet Architecture attempts to look at the current user/
   data plane protocol stack that is in use in both fixed and mobile
   networks and redesign it.  One issue the future internet architecture
   addresses is the number of layers below the IP layer.

   If we consider the current LTE radio protocol stack, we can easily
   find that there are 6-plus layers, with PDCP, RLC, MAC and PHY being
   the ones below IP layer.  Each layer adds some bytes to the header,
   some layers have their own checksums, i.e. more overhead.  However,
   in cellular Internet of Things, (IoT) a packet may have only 1 byte
   payload.  In this case, we would not call it efficient, the
   efficiency rate is less than 1%, with the efficiency rate defined as
   (payload length)/(packet size).

   Future internet architecture deals with data plane protocol stack
   reduction issues like:

   Which layers could be reduced?

   How can we deal with multiple checksums, since it is very expensive
   to compute checksums, remembering we only have 1ms latency budget?

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   Should we design a new type of protocol that does not reuse the
   existing ones to make the network more efficient?  Such a clean slate
   approach would expose a high degree of disruption.

   What would happen if we take away GTP, LTE's tunneling protocol?  For
   more discussion on this see Section 6.

   Future internet architecture proposes a unified layering for both
   fixed and mobile networks.  In the IP layer, we have Identifier
   Oriented Networking or IP protocol.  Below this, we have the next
   generation medium access control protocol providing a unified medium
   access to 5G radio, 802.11 or Wi-Fi and Ethernet type of fixed access
   technologies.  The lowest layer is the next generation physical layer
   protocol unifying all physical accesses to 5G-era.

   In the control plane, there are even much more we need to consider.
   For example, the current internet is operated by routing protocols
   and their extensions.  These protocols are usually driven by Command
   Line Interfaces (CLIs) on the first hand, e.g. for protocols like
   OSPF [RFC5340] will work as instructed by the commands in CLI.

   However, in 5G, there will be many moving things, perhaps with low-
   power so that at one instant they are up and at the next instant they
   are down.  The traditional operation model won't work any more, since
   we can't easily configure them and we don't want their mobility and
   status change affecting the routing tables, Routing Information Base
   (RIB) frequently.

   In this case, mobility issue will arise.  A cell phone moves, but its
   identifier (ID) doesn't change.  Can we re-think about ID related
   protocols such as LISP?  Can we re-scope it to just mobility?  ID
   plays a central role in mobility.  Can we design a new protocol, say
   ID-Oriented Networking Protocol?  In future, more and more mobile
   things are connected to the internet: connected cars, connected
   drones, etc.

   For more discussion on this see Section 8.

6.  Edge Network with no Tunneling

   In fixed network, PPPoE protocol [RFC2516] is used between the
   residential gateway and broadband network gateway to transport the
   residential users IP packets to the fixed network gateway to the
   Internet.  PPPoE protocol requires 8 octets of header in every IP
   packet, thereby reducing the MTU size by 8 octets to usually 1492
   octets.  PPPoE protocol is carried in Ethernet frames with 18 octet
   headers where the destination address is the broadband network
   gateway address.

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   In mobile network, IP packets are tunneled using GTP data plane
   protocol called GTP-U.  First eNodeB or the base station tunnels UE's
   IP packets to the Serving Gateway, in S1 GTP tunnel and then the
   serving gateway tunnels to the Packet Gateway, called S5 tunnel.
   Both of them are UDP tunnels which adds 8 octet header and GTP
   protocl header is 12 octets, so a total of 20 octets are used.  In
   addition also an IPSec header should be accounted for between eNodeB
   and SGW.

   Tunneling in both fixed and mobile networks has the purpose of
   directing the user traffic to the correct gateway.  As exemplarily
   shown above, however, tunneling adds a lot of overhead to the user IP
   packets and therefore inefficiencies arise including reducing the MTU

   If tunneling can be avoided, i.e. if edge networks can be designed
   with no tunneling, a corrollary of this would be no gateways would be
   needed, leading to edge networks with no tunneling or no gateway.
   The means to avoid gateways and tunneling a direct end-to-end routing
   has to be established in the edge network.

   With routing support edge networks can direct the user traffic to the
   correct destinations, rather than tunneling to the gateways.  In
   order to deal with user mobility, ID-oriented networking protocol
   would be needed.  So it needs to be evaluated if using ID-oriented
   networking protocol with routing will lead to more efficient delivery
   of user IP packets in the edge network compared with 4G edge network
   techniques of tunneling with gateways.

7.  Logical Network Isolation (Slicing) Concepts

   Within the framework of 5G a network slice is seen as an independent
   logical end-to-end network, defined by a set of specific network
   functions providing service-specific network characteristic
   (performance).  The basic Network Functions can be both physical and
   virtual in nature, and comprise C-plane and D-plane tasks (maybe
   supplemented by Management), and should be independently instantiated
   and operated.  Identified related work in IETF on aspects of single
   virtualized network control cover the ACTN (Abstraction and Control
   of Traffic Engineered Networks) activity in TEAS (Traffic Engineering
   Architecture and Signaling) WG.

   Corresponding discussion is also under way in IRTF NFVRG analysing
   gaps of current approaches with respect to virtual network instances'
   operation and inter-operation.

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8.  Location Identification Separation and Naming

   With both physical and logical mobility of (an extremely high number
   of) entities and virtualization of network functions the traditional
   usage of IP addresses for identification of name and address or
   logical entity and location as source or destination of data packets
   becomes cumbersome.  New approaches to solve the issues are proposed
   in LISP WG in terms of [RFC6830] and ICN RG (see [RFC7476]) but also
   ILNP [RFC6740] and ILA [I-D.herbert-nvo3-ila] address this challenge.

   By separating a Routing LOCator (RLOC) from a unique Identity (EID)
   LISP keeps a single address to each session endpoint even in multi-
   homing but requires new mapping mechanisms at borders to the
   Internet.  ILNP (and ILNP-based ILA) do neither tunneling and
   encapsulation nor require changes in higher layers (except the
   transport layer) re-using part of an (IPv6) Address as Identifier and

   LISP has two forms of split EID/RLOC collocated in same entity: EID
   mobile, RLOC static.  Predictive RLOCs can be used if LISP entity
   knows where the user going so that the system can mitigate mobility
   impacts.  LISP can be used between the Serving and Packet data
   Gateways.  Best solution is to keep LISP close to the moving entity
   with the functions as close to the edge as possible.

   ILNP defines minimal changes on IPv4 and IPv6, it requires changes on
   the domain name system and the transport layer [RFC6740].  ILNP does
   not require any changes on the routing system or LTE core network.
   LISP requires routing system changes, it is implemented on the
   routers, possibly on the edge routers.  That means LISP requires
   changes on LTE core network.  ILNP does not use encapsulation so it
   is light weight.  LISP is UDP encapsulated so in IPv6, LISP messages
   incur 52 bytes of overhead.

   ILNP nodes send Locator Update messages which are ICMPv4/v6 messages
   to its correspondent nodes when its Locator value changes during an
   active session.  Correspondent node could be a fixed node such as
   Google server which means ILNP has to be implemented by the fixed
   nodes as well.

   ILA is a major update to ILNP [I-D.herbert-nvo3-ila].  It is
   originally designed for network virtualization to be used in cloud
   networks.  ILA can encode a virtual network identifier (VNID) and
   virtual address as an ILNP identifier.  ILA can be adopted for
   mobility and it can be applied to LTE network, the result can be
   called mobile-ILA.  This effort is undergoing.  These aspects of ILA
   are described in [I-D.mueller-ila-mobility].

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   LISP, ILA and mobile ILA are candidate protocols for ID-oriented
   networking protocol.  These protocols may also serve as the basis of
   an ID-oriented networking protocol for 5G yet to be designed and

   As none of the mentioned existing proposals fully covers the 5G
   requirements consistently, in this document, the authors propose the
   following steps for investigations on further enhancements that have
   to be performed.

   Problem statement on the need for ID-oriented networking protocol,
   exploiting LISP, ILNP and ILA efforts.

   Requirements on a new ID-oriented network protocol in view of 5G
   requirements such as in Section 3, and issues such as in Section 6.

   A document on possible solution space investigations.

9.  IANA Considerations


10.  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

11.  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 (details have to be added).

12.  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.

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13.  References

13.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,

13.2.  Informative References

              Arkko, J., Atlas, A., Doria, A., Gondrom, T., Kolkman, O.,
              olshansky@isoc.org, o., Schliesser, B., Sparks, R., and R.
              White, "IETF Trends and Observations", draft-arkko-ietf-
              trends-and-observations-00 (work in progress), February

              Herbert, T., "Identifier-locator addressing for network
              virtualization", draft-herbert-nvo3-ila-02 (work in
              progress), March 2016.

              Mueller, J. and T. Herbert, "Mobility Management for 5G
              Network Architectures Using Identifier-locator
              Addressing", draft-mueller-ila-mobility-00 (work in
              progress), July 2016.

   [M.2083]   ITU-R, "Rec. ITU-R M.2083-0, IMT Vision-Framework and
              overall objectives of the future development of IMT for
              2020 and beyond", September 2015.

   [METIS]    Elayoubi, S. and et al., "5G Service Requirements and
              Operational Use Cases: Analysis and METIS II Vision",
              Proc. euCNC, 2016.

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

   [RFC2516]  Mamakos, L., Lidl, K., Evarts, J., Carrel, D., Simone, D.,
              and R. Wheeler, "A Method for Transmitting PPP Over
              Ethernet (PPPoE)", RFC 2516, DOI 10.17487/RFC2516,
              February 1999, <http://www.rfc-editor.org/info/rfc2516>.

   [RFC5340]  Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF
              for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008,

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   [RFC6740]  Atkinson, RJ. and SN. Bhatti, "Identifier-Locator Network
              Protocol (ILNP) Architectural Description", RFC 6740,
              DOI 10.17487/RFC6740, November 2012,

   [RFC6830]  Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "The
              Locator/ID Separation Protocol (LISP)", RFC 6830,
              DOI 10.17487/RFC6830, January 2013,

   [RFC7476]  Pentikousis, K., Ed., Ohlman, B., Corujo, D., Boggia, G.,
              Tyson, G., Davies, E., Molinaro, A., and S. Eum,
              "Information-Centric Networking: Baseline Scenarios",
              RFC 7476, DOI 10.17487/RFC7476, March 2015,

              "3GPP TR23.799, Study on Architecture for Next Generation
              System (Release 14)", August 2016.

Authors' Addresses

   Dirk von Hugo
   Telekom Innovation Laboratories
   Deutsche-Telekom-Allee 7
   D-64295 Darmstadt

   Email: Dirk.von-Hugo@telekom.de

   Behcet Sarikaya
   5340 Legacy Dr.
   Plano, TX  75024

   Email: sarikaya@ieee.org

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