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DMM Working Group                                                S. Jeon
Internet-Draft                                   Sungkyunkwan University
Intended status: Standards Track                          March 13, 2017
Expires: September 14, 2017

                      Stateless mobility functions


   This draft presents two use cases to start a talk of stateless
   mobility function architecture in IETF DMM WG.

Status of This Memo

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   This Internet-Draft will expire on September 14, 2017.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Mobility function architecture  . . . . . . . . . . . . . . .   3
     2.1.  Integrated state with mobility function . . . . . . . . .   3
     2.2.  Separated state from mobility function  . . . . . . . . .   3
   3.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   5.  Informative References  . . . . . . . . . . . . . . . . . . .   4
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   4

1.  Introduction

   A mobility function could be categorized stateful function and
   stateless function.  The stateful function maintains the state
   information associated with a terminal or network situation while the
   stateless function does not keep the state information but only
   focusing on processing received signaling messages or data packets,
   as a worker.

   Combing the state with the worker in the mobility function has
   basically been considered in many network architectures for easier
   implementation and negligible latency for accessing the state
   database without external signaling messages.  However, it is
   nowadays challenging as it tackles the flexibility for network
   scaling and other enhanced operation support.

   Separating the control-plane and user-plane makes a progress for the
   flexible network control and provisioning.  That is, a routing
   controller with holistic view can take a decision of forwarding
   behavior in the network entities.  Stateless user-plane architecture
   is proposed in [I-D.matsushima-stateless-uplane-vepc], suggesting a
   mobile architecture that the user-plane network is governed by
   virtualized EPC decorated with mobility control-plane functions only.
   The state information the vEPC is holding is transferred by BGP
   routing to the user-plane architecture.  Therefore, the user-plane
   architecture is totally abstracted and becomes state free, supporting
   high flexibility in network scaling.

   Mobility architecture is composed of many control-plane functions.
   Scale-in/scale-out of those functions is of importance for elastic
   function resource handling and management (e.g., load balancing).
   User-plane functions does not generically hold the state information
   much, so it is relatively easier to do scaling but it is challenging
   to scale with mobility control-plane functions.  Separating the state
   information from the control-plane functions could facilitate
   flexible function resource provisioning and expect further enhanced
   scenarios such as VNF mobility and migration procedure easier.

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   The main objective of this draft is to bring a broad discussion in
   IETF DMM WG, identifying what needs and requirements for the state
   separation from a mobility function are existing and what use cases
   could be meaningful, finally bearing a work item.  In this draft, we
   start with two cases; i) mobility control-plane function integrated
   with the state information and ii) mobility control-plane function
   separated from the state information.  From the two cases, we check
   the mentioned aspects.

2.  Mobility function architecture

2.1.  Integrated state with mobility function

   Fig. 1 shows the state information is integrated in the mobility
   control-plane function.  Suppose that the mobility control-plane
   function is composed of state and worker where the work is dedicated
   to the processing of signaling messages or data packets without
   concerning or maintaining the state.  When the function is
   instantiated, the state is also initialized within the function.  On
   the other hand, the function needs to be shut down due to some
   maintenance purpose and the same kinds of a new function is supposed
   to be initiated, the managed mobility state associated with mobile
   terminals should be moved to the newly initiated mobility control-
   plane function through a migration procedure in this case.

             +-------------+        +-------------+
             | State info. |        | State info. |
             +-------------+        +-------------+
             | Worker for  |        | Worker for  |
             | MCP function|        | MCP function|
             +-------------+        +-------------+

   Fig. 1.  The mobility function integrated with the state information

2.2.  Separated state from mobility function

   Fig. 2 shows the state information is separated from the mobility
   control-plane function, thus the worker for mobility control-plane
   function remains in the function.  The relationship between the state
   database and worker can be defined by internal interface or external
   interface.  Following the same scenario described in 2.1, for a need
   of replacing with a new worker or for scaling out/in, maintaining the
   state is not constrained, so facilitating various flexibility

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                         | State info. |
                          | ^       ^ |
                          | |       | |
                          v |       | v
               +-------------+     +-------------+
               | Worker for  |     | Worker for  |
               | MCP function|     | MCP function|
               +-------------+     +-------------+

   Fig. 2.  The mobility function separated from the state information

3.  IANA Considerations

   This document currently makes no request of IANA.

4.  Security Considerations

5.  Informative References

              "Network Functions Virtualisation (NFV); Virtual Network
              Functions Architecture, ETSI GS NFV-SWA 001, v1.1.1",
               Proceedings of GlobeCom Workshop on Seamless Wireless
              Mobility, December 2014.

              Matsushima, S. and R. Wakikawa, "Stateless user-plane
              architecture for virtualized EPC (vEPC)", draft-
              matsushima-stateless-uplane-vepc-06 (work in progress),
              March 2016.

Author's Address

   Seil Jeon
   Sungkyunkwan University
   2066 Seobu-ro, Jangan-gu
   Suwon, Gyeonggi-do

   Email: seiljeon@skku.edu

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