Internet DRAFT - draft-kjsun-dmm-gap-analysis-3gpp
draft-kjsun-dmm-gap-analysis-3gpp
Distributed Mobility Management Kyoungjae Sun
Internet Draft Younghan Kim
Intended status: Informational Soongsil University
Expires: April 2018 Jaehwoon Lee
Dongguk University
October 30, 2017
Gap Analysis for Adapting the Distributed Mobility Management
Models in 4G/5G Mobile Networks
draft-kjsun-dmm-gap-analysis-3gpp-02.txt
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Abstract
In this document, we provide a gap analysis to apply DMM deployment
models to a 3GPP mobile core network. The DMM deployment models are
described into five models for separation control and data plane,
and the 3GPP mobile core network is a 4G-based extended architecture
and 5G core network study architecture. We conduct the gap analysis
to describe the technology that requires current standards-based
applicability and extension for technical interoperability between
two standardization organizations.
Table of Contents
1. Introduction ................................................ 2
2. 3GPP 4G/5G Studies Overview ................................. 3
3. Gap Analysis for Adapting DMM in 4G/5G Mobile Core Network .. 5
3.1. Split Home Anchor Model ................................ 5
3.2. Separated Control and User Plane ....................... 6
3.3. Centralized Control Plane .............................. 6
3.4. Data Plane Abstraction ................................. 8
3.5. On-demand Control Plane Orchestration .................. 8
3.6. Mapping DMM Deployment Model in to 4G/5G Core Network
Architecture ........................................... 9
4. Security Considerations...................................... 9
5. IANA Considerations ......................................... 9
6. References ................................................. 10
6.1. Normative References....................................10
6.2. Informative References..................................10
7. Acknowledgments .............................................10
1. Introduction
The Distributed Mobility Management (DMM) solution has been
investigated to re-locate the current anchor functions in a
distributed manner and to provide different IP session management
characteristics for each mobile node session. For deploying DMM,
five different models are described in [dmm-deployment-models] based
on the network entities according to the location(access or home)
and functionality(control or data).
3GPP has the responsibility to standardize cellular mobile networks,
and the functional separation of the gateway in 4G Evolved Packet
Core(EPC) network has also been studied to divide the gateway into
a control and data plane, defining an interface between them, and
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configuring a data path from the control plane entities to the data
plane entities by exchanging signaling messages between the control
plane entities. Furthermore, future mobile core network architecture
called 5G NextGen has been also studied. For flexible service
continuity, 5G NextGen have integrated the current distributed
gateway entities (SGW and PGW) that are deployed in a hierarchical
manner into a combined gateway to separate the control and data
plane function. In addition, to provide on-demand session
management, they separate the attachment procedure of the mobile
node and the session establishment procedure so that different
sessions of the mobile node with different service characteristics
can connect through a network slice. However, mobility management
solution when the IP anchor function is changing is not described
clearly yet.
This document provides a gap analysis to adapt the DMM deployment
model into the 4G/5G mobile network architectures studied in 3GPP.
Based on studies of the network architecture evolution in 3GPP, we
analyze whether each scenario of the DMM deployment model can be
adapted to the 3GPP network architecture under study by showing the
corresponding mapping table.
2. 3GPP 4G/5G Studies Overview
The 4G EPC network includes several components that provide IP
connectivity to mobile subscribers and accommodate the use of
various network access technologies. In mobility management, many
different kinds of handover can occur in the EPC network
architecture. IP mobility is occurred in the Inter-MME handover,
which occurs between different SGWs, the traffic forwarding path
between the SGW and PGW should be changed, so the IP mobility scheme
should be needed. For this, the 3GPP standard can use the GTP or
PMIP protocol to update the location of the mobile node, establish
the tunnel between the SGW and PGW, and forward data traffic.
To improve the flexibility during deployment and operation of the
mobile core network, 3GPP provides several options to modify the
gateway deployment. First, the combined gateway entity is defined
by integrating the SGW and PGW function into a single component in
[3GPP TR 23.401]. Second, the control plane and the data plane are
separated for the gateway functions in [3GPP TR 23.714]. The
operation of the interface between control plane and data plane
includes managing the state of the data plane in the control plane,
configuring the session path between the GW-DPs according to the
service request of the mobile node, and reporting the measurement
information from the data plane to the control plane.
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+-----+ +-----+ +-----+ +-----+ +----+
| NEF | | NRF | | PCI | | UDM | | AF |
+-----+ +-----+ +-----+ +-----+ +----+
| | | | |
-----------------------------------------------
| | |
+-----+ +-----+ +-----+
| AUF | | AMF | | SMF |
+-----+ +-----+ +-----+
: : : control-plane
==============:=====:=============:====================
: : : user-plane
+----+ +-----+ +-----+ +----+
| UE |----| RAN |---------| UPF |-------| DN |
+----+ +-----+ +-----+ +----+
Fig 1. 5G Core Network Architecture
The 5G mobile core network architecture is designed in a service-
oriented manner described in Fig.1. 5G mobile core network design
separates control and user plane functions for allowing independent
scaling of both functions and it allows control plane dynamically
configures user-plane functions to provide the traffic handling
functionality. Unlike SGW/PGW in 4G network, user plane function of
5G is defined as a unified entity. All the control plane functions
are separated into different standalone entities to enable
independent scalability and flexibility. For example, unlike the 4G
mobile core network, authentication and mobility management function
which were combined into the MME are separated and also mobility
management and session management function are separated. The
interfaces between control functions are defined as a service-based
interface which is independent on the communication protocol so that
the interoperation in the control plane is more flexible that the 4G
mobile core network.
For the mobility management, since that mobility management and
session management functions are separated, they consider supporting
different levels of data session continuity based on the mobility on
demand concept as similar with DMM works. It allows selection of
anchor point to achieve efficient user plane path, as well as
enablement of reselection of anchor point to achieve efficient user
plane path with minimum service interruption. In the 5G mobile core
architecture, IP anchor function is separated into control and user
plane function. Control plane of anchor function which is allocation
of UE IP address is performed by the Session Management Function
(SMF) and user plane of anchor functions such as external PDU
session point, packet forwarding, and anchor point for mobility are
assigned to user plane function. When the IP mobility of the mobile
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nodes traffic occurs between the different access networks or by
changing the IP anchor in the core network, the SMF processes the
signaling to provide session mobility for the mobile node and
configures the forwarding policies to the data plane. There is more
than one data plane functions in the core network, and these are
included in the path of the mobile nodes traffic to the data network
but it may not perform the separate roles as with the SGW/PGW in the
existing 4G network.
3. Gap Analysis for Adapting DMM in 4G/5G Mobile Core Network
Following five deployment models in [dmm-deployment-model], we
provide a conformance and gap analysis to apply the IETF DMM
deployment model to 4G/5G mobile network architectures. Detailed
description of DMM deployment model is not provided in this
document.
3.1. Split Home Anchor Model
In the 4G EPC network, we can deploy the PGW as the home anchor with
CP/DP separation and the SGW as an Access Node with a legacy entity
without CP/DP separation. For that, terminology of Home-CPA is
mapped to PGW-CP, Home-DPA to PGW-DP, Access-CPN to SGW-CP, and
Access-CPN to SGW-DP. In this case, the current interface between
SGW and PGW is separated into two interfaces for the control and
data planes. However, since the SGW is implemented as an existing
CP/DP combined entity, the destinations of the control and data
packets must be set differently in the SGW. Figure 2 describes
architecture of this model in EPC network. Between PGW-CP and
PGW-DP, several protocols can be used to configure forwarding
policy. Mobility management signaling such as GTP-C or PMIP will be
exchanged using S5-C interface and data traffic will be forwarded on
the S5-D using various forwarding method such as GTP/PMIP tunnel,
SDN-based forwarding, etc.
+-------+ S5-C (GTP/PMIP) +-------+
| |-----------------| PGW-C |
| | +---^---+
| SGW | : FPC / OpenFlow /...
| | S5-D (tunnel) +---v---+
| |-----------------| PGW-D |
+-------+ +-------+
Figure 2. Split Home Anchor Model for 4G EPC
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In the 5G core network study architecture, the data plane functions
are not separated into Home and Access. Even though one or more data
plane functions may be included in the data traffic path of the
mobile node between the access network and the data network, it is
not clear whether this separates the roles of Access and Home.
3.2. Separated Control and User Plane
This model separates the control plane and the data plane from both
the Access and Home nodes, and it can be applied as a CP/DP
separation architecture between the SGW and the PGW when applied in
the 4G EPC network. The parameters for the tunnel configuration,
such as the TEID according to the bearer information generated
through the control plane and the QoS-related information, are
transmitted to the data plane by using the interface between the
control plane and the data plane, and traffic measurement
information is transmitted to the control plane for billing and
policy management. Figure 3 describes EPC network architecture
using this model.
+-------+ S5-C (GTP/PMIP) +-------+
| SGW-C |------------------| PGW-C |
+---^---+ +---^---+
: FPC / OpenFlow /... :
+---v---+ +---v---+
| SGW-D |------------------| PGW-D |
+-------+ S5-D (tunnel) +-------+
Figure 3. Separated Control and User Plane Model for 4G EPC
Since there is no definition for an access node in the 5G core
architecture, we cannot find a clear adaptable scenario to apply
that model. By considering the network slice concept, the 5G
architecture separates the mobile node attachment and the service
request process for the authentication and connection state
management according to the attachment of the mobile node through
the Common CP function and selects an appropriate network slice when
the mobile node requests session connectivity to the network. In
this case, several control planes can exist in the core network, but
this is not related to mobility management and there is no data
plane function that is mapped with the Common CP.
3.3. Centralized Control Plane
In [3GPP TR 23.401], the 3GPP standard allows to integrate the SGW
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and PGW into a single entity called Combined GW. In the CP/DP
separation architecture, each plane entity can be deployed as a
combined or separated entity, and the architecture with a combined
control plane and separate data plane entities can be applied. For
the combined GW-CP function, the interface between control plane
functions is no longer required because the SGW-CP and PGW-CP
functions are combined as a single physical entity. Figure 4 shows
EPC architecture using this model.
+-----------------------------+
| SGW-C + PGW-C |
+---^---------------------^---+
: FPC / OpenFlow /... :
+---v---+ +---v---+
| SGW-D |-------------| PGW-D |
+-------+ S5-D +-------+
Figure 4. Centralized Control Plane Model for 4G EPC
With the 5G core architecture, there may be an architecture for a
single control plane entity to manage multiple data plane entities,
even without an access node definition. According to
[3GPP TS23.501], 3GPP specifications support deployments with a
single User Plane Function(UPF) or multiple UPFs for a given PDU
session. In the latter case, UPF in the middle of path may be
performed as a access data plane node. When mobility is occurred,
session management function can assign other access UPF to forward
packet to the anchor UPF. Figure 5 is described this model for 5G
core network architecture.
In particular case, [3GPP TR 23.799] defines a data plane branching
a GW entity between the access network and the different data plane
functions. The branching GW maintains the session between the
respective anchor data plane nodes and uses the tunnels for traffic
forwarding.
+-------+
| SMF |
+---^---+
: FPC / OpenFlow /...
:---------------:--------------:
+---v---+ +---v---+ +---v---+
| UPF |_______| UPF |______| Anchor|
| | | | | UPF |
+-------+ +-------+ +-------+
Figure 5. Centralized Control Plane Model for 5G Core
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3.4. Data Plane Abstraction
SDN-based EPC networks and forwarding configuration schemes between
the data plane entities can be possible. In several studies, all
EPC control plane functions, including the SGW-CP and the PGW-CP,
are implemented in the SDN controller as an SDN application, and the
data traffic path in the data plane network is set utilizing
southbound protocol such as the OpenFlow. The SDN-based EPC
architecture has an advantage in that the traffic path between the
data plane entities can be abstracted from the control plane while
maintaining each GW role, so a flexible forwarding path
configuration may be possible.
The 5G core network architecture document also considers SDN-based
data plane abstraction. In [3GPP TR23.799], they described about
SDN-based approach for user plane forwarding. In that document, the
CP function updates the forwarding table of the switches in the path
between access network and UP function. When UE moves to another
access network node, the CP-Function determines which switch need to
be updated and do the forwarding table update accordingly. Even
though there is no definition for Anchor and Access node, the data
plane GW entities and the switches in the core network are
abstracted through the SDN controller to manage the traffic path
from the access network to the data network. FPC protocol defined in
[draft-ietf-dmm-fpc-cpdp-08] may be used for configuring forwarding
policy and mobility policy to UP functions.
3.5. On-demand Control Plane Orchestration
This model can be deployed through an EPC network structure with an
NFV-based virtualization environment and Management & Orchestration
(MANO) function. In an NFV-based virtualized EPC (vEPC) environment,
all control plane functions can be installed on a general-purpose
cloud server using a Virtualized Network Function (VNF), and the
data plane entities can be physically located in the switch or
router. Regarding mobility, the Mobility Controller defined in the
DMM deployment model is an entity that provides mapping information
of the mobility control plane and data plane functions as needed.
This is a method to generate mobility services by including VNFs
according to the mobility in the network.
The 5G architecture research also discusses methods to provide
on-demand services in a virtualization-based environment. In
different sets of core network functions by selecting network slices
according to the type of traffic for a given service, even if they
are from the same mobile node.
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Network slicing is a one of key technology of 5G and it can provide
customized network to optimize for different network services.
Network slicing has the advantage of providing QoS to meet various
service requirements. From mobility management perspective,
different network slice can support different kinds of mobility
management. For example, network slice for vehicle network needs to
support mobility management functions enhanced for reducing handover
latency by locating the anchor function closed to the access
network. In other case, for traditional mobile core network, they
can make network slice including one or more anchor UPF depending on
their needs. Thus, for the various services and subscriber types,
network operator can support on-demand mobility management using
different network slices.
3.6. Mapping DMM Deployment Model in to 4G/5G Core Network Architecture
Table 1 shows whether five DMM deployment models are applicable to
the 4G EPC network and 5G core network study architecture.
+==============+===================================================+
| | DMM Deployment Models (Described Chapter) |
| 3GPP +---------------------------------------------------+
| | 3.1 | 3.2 | 3.3 | 3.4 | 3.5 |
+========================+=========+=========+==========+==========+
| 4G EPC Core | | | | YES | YES |
| with CP/DP | YES | YES | YES | with | with |
| Separation | | | | SDN | NFV |
+--------------+---------+---------+---------+----------+----------+
| 5G Core | | | | YES | YES |
| Network Study| NO | NO | YES | with | with |
| Architecture | | | | SDN | NFV |
+==============+=========+=========+=========+==========+==========+
Table 1: Mapping DMM Deployment Model in to 3GPP Mobile Core Network
4. Security Considerations
T.B.D
5. IANA Considerations
T.B.D
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6. References
6.1. Normative References
[dmm-deployment-models] S. Gundavelli, and S. Jeon, "DMM Deployment
Models and Architectural Considerations", I.D. draft-ietf
-dmm-deployment-models-02, Aug. 2017.
[3GPP TR 23.401] 3GPP, "LTE: General Packet Radio Service(GPRS)
enhancements for Evolved Universal Terrestrial Radio
Access Network (E-UTRAN) access", 3GPP TR 23.401
(v.14.2.0), Dec. 2016.
[3GPP TR 23.714] 3GPP, "Study on Control and User Plane
Separation of EPC nodes", 3GPP TR 23.714 (v.14.0.0).
Jun.2016.
[3GPP TR 23.799] 3GPP, "Study on Architecture for Next Generation
System", 3GPP TR 23.799 (v.1.0.2), Sep. 2016.
[draft-ietf-dmm-fpc-cpdp-08] S. Matsushima, L. Bertz, M. Liebsch,
S. Gundavelli, D. Moses and C. Perkins, "Protocol for
Forwarding Policy Configuration (FPC) in DMM", I.D.
draft-ietf-dmm-fpc-cpdp-08, Sep. 2017.
6.2. Informative References
7. Acknowledgments
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Authors' Addresses
Kyoungjae Sun
Soongsil University
369, Sangdo-ro, Dongjak-gu
Seoul 156-743, Korea
Email: gomjae@ssu.ac.kr
Jaehwoon Lee
Dongguk University
26, 3-ga Pil-dong, Chung-gu
Seoul 100-715, KOREA
Email: jaehwoon@dongguk.edu
Younghan Kim
Soongsil University
369, Sangdo-ro, Dongjak-gu
Seoul 156-743, Korea
Email: younghak@dcn.ssu.ac.kr
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