OpenAirInterface Core Network: Recent enhancements in OAI ... · the DiffServ Code Point, based on...

OpenAirInterface Core Network: Recent enhancements in OAI-CN,

MME, SPGW, HSSBeken Dincer, BLACKNED

and

Gauthier Lionel, EURECOM

Outline

12/12/2018 - - p 1

EPC fundamentals

OAI Core Network

Recent developments

Testing (testers ng4T and 3 eNB connected to a box –attenuation/mobility scenarios )

Future plans

Wish list

Outline

EPC fundamentals3GPP picture of network function and interfaces.Releases and features

OAI Core Network

Recent developments

Testing (testers ng4T and 3 eNB connected to a box –attenuation/mobility scenarios )

Future plans

Wish list

12/12/2018 - - p 2

Core Network Fundamentals – Purpose of CN

Evolved Packet Core Network Purpose Evolved Packet Core (EPC) is a framework for providing converged

voice and data on a 4G Long-Term Evolution (LTE) network.

12/12/2018 - - p 3

Source http://www.3gpp.org/technologies/keywords-acronyms/100-the-evolved-packet-core

Core Network Fundamentals

High level functions Network Access Control Functions.

– Authentication and authorization, admission control, Policy and charging enforcement

Packet Routing and Transfer Functions: IP header compression function, packet screening.

Mobility Management Functions. – Reachability management for UE in ECM-IDLE state

Security Functions. Radio Resource Management Functions. Network Management Functions (O&M)

– GTP-C signaling based Load and Overload Control, Load balancing between MME, MME control of overload, PDN GW control of overload

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Core Network Fundamentals - Architecture

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Core Network Fundamentals – Access Networks

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WiMax, CDMA2000, WLAN,fixed networks

Core Network Fundamentals – schedule

12/12/2018 - - p 7

All IP network

IMS

eMBMS

Interworking with WiFi

ETWS PWS / CMAS

LTE Introduced

Enhanc. to LTE

LTE Advanced

Enhanc. to LTE Advan.

Further enhanc. to LTE Advanced

Meeting the growing throughput demand

The start of 5G standardiz.

Rel 1003/2011

Rel 1109/2012

Rel 1203/2015

Rel 1303/2016

Rel 1406/2017

Rel 1509/2018

Rel 912/2009

Rel 812/2008

KPAS EU‐ALERT

Enhancements to Wi-Fi interworking

Prose stage 1 Prose stage 2

Wifi integration with LTE

SIPTO

CUPS

Core Network Overload (GTP-c/DNS)

LIPA/SIPTO enhancements

EPC Signaling improv. For race scenarios

User Plane Congestion

Volte

D2D PS Relays, Priority V2X Multi-RAT Interworking

Outline

EPC fundamentals

OAI Core NetworkArchitecture overviewAvailable features

– MME– SPGW– HSS

CodeDeployment

Recent developments Testing Future plans Wish list

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OAI Core Network – Architecture overview

12/12/2018 - - p 9

S11S10

S1-U

S6aS1-MME

HSS

MME

ServingGateway

PDNGateway

SGi

OAI Core Network – MME Available features

12/12/2018 - - p 10

# interfaces Status Comments Protocols

1 S1-MME V Still rel 10 should be upgraded to rel 15 soon. S1AP/SCTP

2 S11 V GTPv2-C/UDP

3 S3 X To interface SGSN, not planned. GTPv2-C/UDP

4 S6a V Still rel 14 should be upgraded to rel 15. freeDiameter/TCP-SCTP

5 S10 V GTPv2-C/UDP

OAI Core Network – MME conformance functions 1/4 (3GPP TS 23.401 V15.5.0 §4.4.2)

12/12/2018 - - p 11

# Classification Status Comment

1 NAS signalling V2 NAS signalling security V3 Inter CN node signalling for mobility between 3GPP

access networks (terminating S3)X Intra LTE HO only

4 UE Reachability in ECM-IDLE state (including control, execution of paging retransmission and optionally Paging Policy Differentiation)

V We are working on this

5 Tracking Area list management V



6 Mapping from UE location (e.g. TAI) to time zone, and signalling a UE time zone change associated with mobility

X

7 PDN GW and Serving GW selection V spgw selection & neighboring MME selection via WRR

8 MME selection for handovers with MME change V S1 (inter (S10) and intra MME S1AP handover), X2 HO supported

9 SGSN selection for handovers to 2G or 3G 3GPP access networks

X

10 Roaming (S6a towards home HSS) X11 Authentication V Also NAS messages inside the S10 at

mobility

12 Authorization V HSS (UE-AMBR + defaults),PCRF (APN/Bearer Level QoS)

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13 Bearer management functions including dedicated bearer establishment

V Dedicated bearers are supported

14 Lawful Interception of signalling traffic X

15 Warning message transfer function (including selection of appropriate eNodeB)

X

16 UE Reachability procedures V

17 Support Relaying function (RN Attach/Detach) X

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18 Change of UE presence in Presence Reporting Area reporting upon PCC request

in the case of Change of UE presence in Presence Reporting Area reporting, management of Core Networkpre-configured Presence Reporting Areas.

X

19 For the Control Plane CIoT EPS Optimisationa) transport of user data (IP and Non-IP);b) local Mobility Anchor point;c) header compression (for IP user data);d) ciphering and integrity protection of user data;e) Lawful Interception of user traffic not transported via the Serving GW (e.g. traffic using T6a).

X Future : NB-IoT, SMS

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OAI Core Network – SGW conformance Interfaces

12/12/2018 - - p 15

# Interface Status Comment Protocol

1 S5/S8 X SGW and PGW combined GTP-C/U

2 S1-U V GTP-U/UDP

3 S11 V S11-C only actually GTP-C/UDP

4 S4 X GTP-C/UDP

5 S12 X GTP-U/UDP

OAI Core Network – SGW conformance functions 1/2 (3GPP TS 23.401 V15.5.0 §4.4.3.2)

12/12/2018 - - p 16

# Classification Status Comments

1 the local Mobility Anchor point for inter-eNodeB handover (except when user data is transported using the Control Plane CIoT EPS Optimisation)

X Very soon, X2HO will be supported.

2 sending of one or more "end marker" to the source eNodeB, source SGSN or source RNC immediately after the Serving GW switches the path during inter-eNodeB and inter-RAT handover, especially to assist the reordering function in eNodeB

X Could be if requested by RAN team.

3 Mobility anchoring for inter-3GPP mobility (terminating S4 and relaying the traffic between 2G/3G system and PDN GW)

X No support of 2G and 3G systems.

4 ECM-IDLE mode downlink packet buffering and initiation of network triggered service request procedure and optionally Paging Policy Differentiation

X buffering is not supported for paging in idle mode.

5 Lawful Interception X

OAI Core Network – SGW conformance functions 2/2 (3GPP TS 23.401 V15.5.0 §4.4.3.2)

12/12/2018 - - p 17

# Classification Status Comments

6 Packet routing and forwarding V

7 Transport level packet marking in the uplink and the downlink, e.g. setting the DiffServ Code Point, based on the QCI, and optionally the ARP priority level, of the associated EPS bearer

X could be supported quickly

8 Accounting for inter-operator charging. For GTP-based S5/S8, the Serving GW generates accounting data per UE and bearer

X

9 Interfacing OFCS according to charging principles and through reference points specified in TS 32.240

X

10 Forwarding of "end marker" to the source eNodeB, source SGSN or source RNC when the "end marker" is received from PDN GW and the Serving GW has downlink user plane established. Upon reception of "end marker", the Serving GW shall not send Downlink Data Notification.

X

OAI Core Network – PGW conformance interfaces

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# Interface Status Comment

1 GTP-based S5/S8 X S-GW and P-GW combined.

2 Gx X Policy.

3 Gy interface X Charging.

4 SGi V

OAI Core Network – PGW conformance functions 1/4 (3GPP TS 23.401 V15.5.0 §4.4.3.3)

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# Classification Status

1 Per-user based packet filtering (by e.g. deep packet inspection) V

2 Lawful Interception X3 UE IP address allocation V Pools of IP addresses

4 Transport level packet marking in the uplink and downlink, e.g. setting the DiffServ Code Point, based on the QCI, and optionally the ARP priority level, of the associated EPS bearer

X Could be done

5 Accounting for inter-operator charging: for home routed roaming, the P-GW shall collect and report the uplink and downlink data volume (per EPS bearer) as received from and sent to the serving node

X


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6 UL and DL service level charging as defined in TS 23.203 (e.g. based on SDFs defined by the PCRF, or based on deep packet inspection defined by local policy)

X

7 Interfacing OFCS through according to charging principles and through reference points specified in TS 32.240

X

8 UL and DL service level gating control as defined in TS 23.203 X Gating control shall be applied by the PCEF on a per service data flow basis

9 UL and DL service level rate enforcement as defined in TS 23.203 (e.g. by rate policing/shaping per SDF); X

10 UL and DL rate enforcement based on APN-AMBR (e.g. by rate policing/shaping per aggregate of traffic of all SDFs of the same APN that are associated with Non-GBR QCIs);

X

11 DL rate enforcement based on the accumulated MBRs of the aggregate of SDFs with the same GBR QCI (e.g. by rate policing/shaping); X

12 DHCPv4 (server and client) and DHCPv6 (client and server) functions X Contributions welcome for server.


12/12/2018 - - p 21


13 The network does not support PPP bearer type in this version of the specification. Pre-Release 8 PPP functionality of a GGSN may be implemented in the PDN GW

X

14 The PDN GW may support Non-IP data transfer (e.g. with CIoT EPS Optimizations)

X

15 Packet screening X16 sending of one or more "end marker" to the source SGW immediately after

switching the path during SGW change; X

17 PCC related features (e.g. involving PCRF and OCS) as described in TS 23.203

X


12/12/2018 - - p 22


Additionally the PDN GW includes the following functions for the GTP-based S5/S8:

18 UL and DL bearer binding as defined in TS 23.203 X19 UL bearer binding verification as defined in TS 23.203 X20 Functionality as defined in RFC 4861 X21 Accounting per UE and bearer X

OAI Core Network – Source code

OAI Core network source code Download is free, no registration required.

– GitHub main page https://github.com/OPENAIRINTERFACE/openair-cn

– Git : https://github.com/OPENAIRINTERFACE/openair-cn.git Is open source

– all binaries can be generated from what is in the git repository, and on internet, for 3rd party software.

– If there is generated source code in the repository, you will find the code generator in it.

Contribution is opened to any people who signs the license agreement.

12/12/2018 - - p 23


License is Apache v2 (differ from RAN) Compatibility chart

12/12/2018 - - p 24

Source: https://en.wikipedia.org/wiki/License_compatibility


License Apache v2

12/12/2018 - - p 25

Source: https://tldrlegal.com/license/apache-license-2.0-(apache-2.0)

OAI Core Network – Deployment

Target OS Linux, interest is no proprietary stacks, open-source. The targets are Ubuntu 16.04 (Xenial), 18.04 (Bionic). May be plans for Fedora in 2019.

Hardware requirements CPU:

– Target is X86-64 (Intel, AMD).– No plans for ARM, we cannot guarantee the endianness-proof.

RAM – Some work is needed there, 4GB seems enough for hundreds of UEs.

Network interfaces– Better to have 3 network interfaces on the host were software switch of SPGW is deployed.

Linux Kernel Any kernel that comes along the OS for the MME, HSS. Let’s say above version 4.13 is fine. Kernel 4.9.x for the SPGW (Open vSwitch patch constraint).

Practically You can deploy any Network Function on a PC or server or VM.

12/12/2018 - - p 26

Outline

EPC fundamentals OAI Core Network

Recent developmentsMMESPGWHSS

Testing Future plans Wish list

12/12/2018 - - p 27

Recent developments – MME (Blackned)

Actualizing the code: Merging different branches for most actual version (develop

branch). Thereby rework on the whole code, reviewing the layers, contexts

and procedures.– Clear separation between EMM and rest of the layers.

Stabilisation Burst attaches with NG4T, Out of coverage scenarios with real

eNBs.

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Inter-MME S1 Handover & S1-TAU: Fallback methods and validations: VERY fault tolerant.

– Rejects, Missing Messages (TAC after HO, HO-Notify)– Failed Authorizations → Fallback to local security.– Return to local cell during handover.– Burst tests with NG4T.

Multi-APN is supported, Multi-Bearer in works.

12/12/2018 - - p 29

MME1HSS1SAE1

MME2HSS2SAE2

S1

S1

X2


Intra-MME S1 Handover & S1-TAU & X2: Up to 50 eNBs on a single node, same or different TAC. X2 : No SP-GW relocation considered.

12/12/2018 - - p 30

EPC1

S1

X2


12/12/2018 - - p 31


12/12/2018 - - p 32

Dynamic QoS: Multiple Dedicated Bearer Establishment, Modification and

Removal. Default Bearer QoS update based on PCRF authorized values. All TFT operations supported.

– Fault Detection: Verifying Packet Filters and Precedences.– Update of TFT & filter rules, precedence, QoS, IP-Filter

supported. Bearer QoS Update supported. Transaction based: Update of contexts only if success in access

network. Congestion support.

– Implicit Indicators : Handover/Service Request failures.– Explicit Indicator: Bearer Resource Command, Delete Bearer

Command.


12/12/2018 - - p 33

Further Functionalities Multi-APN Paging Restoration Procedures

EMM/ESM separation (in works) Independent processing to reduce errors, part of separation of EMM

from the rest (CN functions). No ESM context, only transactions (multiple simultanous).

Recent developments - SPGW

Facebook contributions: GTP-U patch on Open vSwitch contributed by Facebook for

handling GTPU encapsulation/decapsulation. Paging mechanism in OVS (table rules). There is an OpenFlow interface for Control/User Plane separation,

not 3GPP compliant, but a starting point (see next slides).

PGW NAT No more supported internally in the SPGW, you have to do your

own NAT on IP path behind SGi.

12/12/2018 - - p 34

Recent developments - HSS

A new HSS was contributed by Sprint. Rel14 compliant based on previous OAI HSS. Implements 3GPP interfaces:

– S6a: between HSS and MME– S6d: between HSS and SGSN, unused. – S6t: between the HSS and the Service Capability Exposure

Function (SCEF), unused actually.– S6c: interface between the HSS and the central SMS functions

(SMS-GMSC, SMS Router), unused actually. Implement Following messages: Contributed fork of freeDiameter allowing duplicate AVPs among

several dictionaries. Persistence of data done by Cassandra. Written in C++.

12/12/2018 - - p 35

Recent developments - HSS

Contributed HSS comes with modules. HSSGTW: Home Subscriber Server Provisioning Gateway, provides

a REST-ful interface for provisioning UE’s in the HSS database. Will be integrated soon.

CDF: Charging Data Functions, stub, not planned to be integrated. CTF: Charging Trigger Function, not planned to be integrated.

12/12/2018 - - p 36

Outline

EPC fundamentals

OAI Core Network

Recent developments

Testing (testers ng4T and 3 eNB connected to a box –attenuation/mobility scenarios ) NG4T Blackned Testing Environment

Future plans

Wish list

12/12/2018 - - p 37

Testing – MME

12/12/2018 - - p 38

Testing – MME

12/12/2018 - - p 39

Outline

EPC fundamentals

OAI Core Network

Recent developments

Testing mobility scenarios

Future plans MME Rel15 New SPGW

Wish list

12/12/2018 - - p 40

MME Future Plans

Multi Bearer S10 Handover For sake of completion (mesh-PCRF).

SMS/NB-IoT Functionalities will be added early next year.

Multicast M3 Interface Sm Interface MBMS Gateway (dummy).

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MME Future Plans

Rel15 S1AP will be upgraded to Rel15 (asn1c modification contributed by

Chiu Bi-Ruei https://github.com/brchiu)– Already started and visible on branch “prose”, except for HO

information elements.

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New SPGW - rewrite

Actual SPGW Written in C. GTPV2-C stack with clear design but with flaws in its implementation, not well

integrated (everything is uintptr*). SPGW split not envisioned at the beginning, missing procedures in regards of

recent MME developments, etc.

Recent interests for SPGW Need for supporting ProSe in Eurecom contracted project, partners expressing

the need for S/P-GW split, enabling the integration of a PCEF in the PGW. Internal request from Eurecom SDN researchers.

– To clearly separate Control and User Plane (CUPS). Actually done by Open-Flow, but not 3GPP compliant.

Recent Contributions From FB concerning the integration of a software switch. From Sprint concerning a PCEF, skeletons of TDF, tiny PCRF (still not

integrated). All recent contributions are provided in C++ (-std11).

12/12/2018 - - p 43

New SPGW - rewrite

Lead to the decision Rewrite SPGW

– In C++– C++ have pros and cons, but much more pros over C for writing

high level applications in regard of C IMHO (OO, memory management facilities, STL, Collections, etc).

– Python? And what about JAVA ? OO but interpreted, with changes this year in JAVA licensing conditions. (https://www.itassetmanagement.net/2018/05/01/oracle-to-charge-for-java-from-jan-2019/)

– Erlang would be a better competitor than all previous cited languages, but what about contributors (?)

Already started InterTask middleware (asynchronous message and timer facilities),

GTPV2-C stack and SPGW in C++ (OVS application controller was already contributed by FB in C++11).

Planned with same features as old SPGW end of January or before. More to come.

12/12/2018 - - p 44

New SPGW – Planned features

Multi-PDN PGW

– Will be able to manage several APNs of any type (IPv4, IPv6, IPv4andv6).

– Will manage several pools of IP addresses (IPv4, IPv6).

Dedicated bearers

ProSe SPGW will benefit from the ProSe work done inside a collaborative

project at Eurecom.

Rel 15 Is the targeted 3GPP compliance.

12/12/2018 - - p 45


SPGW split enabled Will not be finalized, but the new code will allow with some “not so big” extra-work to

split the SPGW if needed. Will have SGW_S5S8 and PGW_S5S8 tasks implemented exchanging S5/GTPV2-C

asynchronous messages over ITTI instead of UDP. Would allow to have a 3GPP compliant 5G/EPC interworking architecture (next

slide).

12/12/2018 - - p 46


12/12/2018 - - p 47

Outline

EPC fundamentals

OAI Core Network

Recent developments

Testing mobility scenarios

Future plans

Wish list CUPS, PFCP.

12/12/2018 - - p 48

Whish List CUPS

Packet Forwarding Control Protocol (PFCP) defined in TS 29.244 Interface between the Control Plane and User Plane of EPC Nodes.

In case of combined SPGW, Sxa and Sxb are also combined.

12/12/2018 - - p 49

Source: 3GPP TS 23.214 version 15.4.0 Release 15

Whish List

CUPS Important note: PFCP is also the protocol between SMF and UPF (5G

Core), interface N4.– A factorization of work is possible there.

PFCP is very similar to GTP-C, is over UDP port 8805, same retransmission strategy as GTP-C, identifier for transactions.

Only found 1 implementation of PFCP in erlang with a fork of the Cisco open source software switch.

12/12/2018 - - p 50

OAI Core Network – End

QUESTIONS ?

12/12/2018 - - p 51

OpenAirInterface Core Network: Recent enhancements in OAI ... · the DiffServ Code Point, based on...

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