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Transcript of Heikki Lindholm , Lirim Osmani , Sasu Tarkoma , Hannu Flinck*, Ashwin Rao State Space Analysis to...
Heikki Lindholm, Lirim Osmani,Sasu Tarkoma, Hannu Flinck*,
Ashwin Rao
State Space Analysis to Refactor the Mobile Core
University of Helsinki *Nokia Networks
HomeSubscriber
Server(HSS)
ServingGateway(SGW)
EvolvedNode B
(eNodeB)
Network Functions in LTE Networks
Policy Control &ChargingFunction(PCRF)
MobilityManagement
Entity(MME)
UserEquipment
(UE) Inte
rnet
Mob
ile N
etw
ork
Radi
o Ac
cess
Net
wor
k
Mob
ile C
ore
PacketData
NetworkGateway(PGW)
2 / 12
• Shortcomings of current architecture– Signaling Storm– Stateful gateways
• Demands from network operators– Reduce costs– Move functionality close to radio access network
Motivation for Refactoring
ServingGateway(SGW)
EvolvedNode B
(eNodeB)
PacketData
NetworkGateway(PGW)
3 / 12
With virtualization at our disposal, can we simplify the architecture?
ForwardingElement
ForwardingElement
A Desirable Architecture
Policy Manager
UserEquipment
(UE) Inte
rnet
Mob
ile N
etw
ork Radio Access
NetworkMobile Core
ForwardingElement
Control PlaneUser Plane Logically Centralized Controller
Forwarding rules govern where packets are forwarded
Program forwarding elements to comply with the policy
4 / 12
How do we refactor the mobile core?
• Device ID• Radio State • Location• Control-plane State• User-plane State
Grouping of State Variables
Abstracting usage of state variables
5 / 12
• Initial Attach• Idle • Wake-up• Mobility• Service Request• … many more
Procedures using State Variables
Paper
6 / 12
Network Function Device ID Location Radio State
Control-plane State
User-plane State
eNodeB ✔ ✔ ✔ ✔ ✔
MME ✔ ✔ ✗ ✔ ✔
SGW ✔ ✔ ✗ ✔ ✔
PGW ✔ ✔ ✗ ✔ ✔
HSS ✔ ✗ ✗ ✔ ✔
PCRF ✔ ✔ ✗ ✗ ✔
State Variables after Attach
Network Functions replicate state variables
7 / 12
Network Function Location Control-plane State User-plane State
eNodeB P - P C P C
MME P C P C P C
SGW - C P C P C
PGW - C P C P C
HSS - - - C P -
PCRF - C - - P C
How are State Variables Replicated?
P : ProducerC : Consumer
• Can we group the Producers?• Can we move Consumers close to the Producers?
Take decisions at Producers?
8 / 12
• Module for managing each variable group– Multiple variable groups modified in each
procedure– Incurs additional signaling between modules
• Module to serve each procedure– Merge modules from network functions that serve
the same procedure– Flexibility to determine physical location of
modules
Approaches to Refactor
9 / 12
ForwardingElement
ForwardingElement
Proposed Architecture
Policy Manager
UserEquipment
(UE) Inte
rnet
Mob
ile N
etw
ork Radio Access
NetworkMobile Core
ForwardingElement
Control PlaneUser Plane
Mobile CoreControl Agent
Logically Centralized Mobile Core Controller
Attac
h
Idle
Wak
e
Mob
ility
Attac
h
Idle
… …
10 / 12
Publish SubscribeSHIM for backward compatibility
• Formal Analysis – Analyze dependency network of Procedures and
State Variables– Essential to gather insights on the requirements
from the mobile core• Simulations/Emulations– Modifying LTE simulator/emulator
Next Step
11 / 12
• Can we leverage virtualization technologies to simplify the architecture of the mobile core?
• Abstract the state variables• Producer/Consumer relationship between
network functions• Pub-sub architecture to serve the mobile core
Conclusion
12 / 12
Thank You!
State Space Analysis to Refactor the Mobile Core
University of Helsinki Nokia Networks
Backups
• Route packets• Control network access• Support client mobility• Provide network security• Manage network functions
Main Functions of the LTE Core
Modularity based on Abstraction
16 / 12
Why should future network functions be based on the existing protocol interactions?
17 / 12
What do we gain from a refactored
centralized control plane?
18 / 12
Could you have reached the same architecture by considering the
generic functions that any mobile network will need?
19 / 12
• Network Access Control• Packet Routing and Transfer• Mobility Management• Security• Network Management
Main Functions of the Core
Complete List of Procedures
1) Device ID Primary keys in device/subscription lookupsIMSI, GUTI, …
2) Location Cell level location informationTAI, Tracking area list, ECGI, …
3) Radio Session State Radio link related informationC-RNTI, DRB, AS security context, …
4) Control-plane State Identifiers for control plane connectionsS5/S8/… IPs and TEIDs, NAS security context, …
5) User-plane State User-plane state identifiersS1u/S5u/…, QoS, bearer info, …
Grouping of State Variables
– Is this the best grouping?– Why not consider events first?– Backward compatibility issues?– What about other procedures?
TODO: Backups
ServingGateway(SGW)
EvolvedNode B
(eNodeB)
Network Functions in LTE Networks
Policy Control &ChargingFunction(PCRF)
MobilityManagement
Entity(MME)
HomeSubscriber
Server(HSS)
UserEquipment
(UE) Inte
rnet
Mob
ile N
etw
ork
Radi
o Ac
cess
Net
wor
k
Mob
ile C
ore
PacketData
NetworkGateway(PGW)
Control PlaneUser Plane