ferret: fall-back to lte microservices for low latency
TRANSCRIPT
FERRET: Fall-back to LTE Microservices for Low Latency Data Access
Presenter: Muhammad Taqi Raza, Ph.D.The University of Arizona
June 25, 2020
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Background - LTE
– LTE Evolved Packet Core (EPC) functionality is divided into control-plane and user-plane.
– Control plane logic performs device registration/deregistration, mobility, location update, paging, and many more.
– User plane forwards traffic to the next hop along the path to the selected destination network according to control plane logic.
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Control-Plane
S1-AP MME HSS
Serving-Gateway
PDN-Gateway
User-Plane
LTE Core Network
Device Radio Network Internet
Background – IP Multimedia Subsystem (IMS) – Our Use Case Example
SGW PGW
LTE EPCRadio Network
IMS Core
Serving
Server
Media
Server
IMS Signaling (SIP)
IMS Service (RTP/RTCP)
Data Service
Telephony Network
Internet
IMS supports real-time multimedia services.
– Voice call request (control plane)
– Voice call speech packets flow (user plane)
– Regular user data traffic (user plane)
IMS Client
Proxy
Server
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Existing IMS over LTE– Purpose-built hardware platforms, such as Ericsson’s Blade Systems (EBS), Alcatel-Lucent’s Element Management
System (EMS), etc.
– Coupling between software and hardware, such as Ericsson’s ERLANG, Alcatel-Lucent’s NVP, etc.
– Dedicated network resources for each user.
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Device Radio Network
IMS
EPC
Internet
LTE-NFV Architecture
– LTE NFV virtualizes LTE core network functions over off-the-shelf boxes.– This reduces CAPEX and OPEX for operators.
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Device Radio Network
Operator Network
vEPC Data Center
InternetRadio Network
Mang.
vEPCNetwork
Mang.
Why LTE-NFV Architecture is bad for IMS?
– Control plane signaling messages are executed on the cloud– Good: Different vNFs coordinate with each other to facilitate an event (e.g. mobility)
– User plane traffic is forwarded to Internet through vEPC Gateways (i.e. Serving Gateway, PDN Gateway, IMS NFs).– Bad: Voice traffic unnecessarily goes through the data center.
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Device Radio Network
Operator Network
vEPC Data Center
InternetRadio Network
Mang.
vEPCNetwork
Mang.
Data Forwarding through Mobile Edge Compute NF
– Let’s decouple control-plane and user-plane– Control-plane traffic still goes to vEPC and vIMS– User-plane traffic is routed through mobile edge compute NFs.
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Device Radio Network
Operator NetworkInternetRadio
Network Mang.
vEPCNetwork
Mang.
Mobile Edge Compute
– We decompose SGW and PGW user plane functionalities and install them at the edge– We also install MGW of IMS at the edge.
Design Considerations
– Decouple LTE and IMS CP and UP and install them at core and edge, respectively.
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PGW – UResource management
IP address and TEID assignment
Packet forwarding
Forwarding of buffered packet
Accounting for Charging
Transport level packet marking
SGW – UResource management
IP address and TEID assignment
Packet forwarding
Transport level packet marking
UL/DL APN-AMBR enforcement
UL/DL bearer MBR enforcement
UL and DL service level gating
UL and DL service level MBR
PGW - C
IP address allocation
DHCPv4 / DHCPv6 client
Router advertisement
Mobility b/w 3GPP and non-3GPP
PGW pause of charging
Change of target GTP-U endpoint
SGW – C
Change of target GTP-U endpoint
Delay Downlink Data Notification
PGW pause of charging
Accounting for Charging
Bearer binding
Event reporting
Redirection
Mobile Edge
Forwarding of buffered packet
EPC and IMS CP
Proxy Server (of IMS)
Serving Server (of IMS)
Media Gateway (of IMS)
MEC Design
Design Considerations: Pure UP and CP Separation
– All UP functions are moved to edge, whereas all CP functions (including PCRF, LCS and others) are placed at the core.
Issue:– The UP traffic will steer to CP for charging. This adds latencies and bandwidth wastage for voice call operation.
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Device Radio Network
Operator Network vEPC Data Center
Internet
Radio Network
Mang.
vEPCNetwork
Mang.
Charging
Provide copy of all common CP NFs at the edge
MEC Design
Design Considerations: Share Common Functions between CP and UP
– Those functions (e.g. PCRF or charging function) which both CP and UP rely should be shared (i.e. copied).
– Let the CP, being central entity, handle the NF allocation.Issue:– Creates race conditions. Example, SGW-U requests SGW-C for relocating SGW-U, while the TAU procedure is ongoing at the core, e.g.
MME performs SGW relocation by sending same request to SGW-C.
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MMEDevice SGW-U
Relocation Req.(part of TAU)
SGW-C
Tracking Area Update Req.
Overload
Relocation Req.
Race Condition
Let UP manage its own resources based onpolicy provided by CP
MEC Design
Design Considerations: Share Common Functions between CP and UP
Those functions (e.g. PCRF or charging function) which both CP and UP rely should be shared (i.e. copied).
Issue:– Creates deadlocks. Example, when ModifyBearer request at CP and UP locks their respective PCRF copies.
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Tracking Area Update
OverloadModify Bearer Req.
Session Modification
LockModify Bearer Req.
Session Modification
Lock
Device PGW-U PCRF-U PGW-C PCRF-CMME
Reflect update to PCRF-C
Reflect update to PCRF-U
Deadlock
Use blocking mode operations
MEC Design
Realizing IMS Application over MEC through FERRET
FERRET Key Idea
– Let the CP perform all control-plane operations at the core.
– Once all operations are performed at CP, then replay them at the edge.
– Only transmit VoLTE call control plane packets once the call is established (before user-plane traffic starts).
– VoLTE call requires:
(1) Call establishment phase (control plane), and
(2) Speech data packets flow (user plane).
Core
NF1 NF2M1
M2
NF2
NF1
M1 M2
End
Edge
IMS Application over MEC
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Reducing User Plane Latencies through FERRET
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– VoLTE call packets are forwarded to the Internet without going to the core.
– Baseline results represent operational VoLTE network latencies. – This includes eNodeB <-> vEPC <-> IMS latencies for both caller and callee
Summary
–MEC is part of 5G agenda that requires important network components to be installed at the edge.
– Through IMS, we demonstrate MEC architecture that reduces upto 6X user-plane latencies.
– In the future work, we will measure MEC design from different system and networking aspects.– Bandwidth, Latency, Call Rate, Mobility and more.
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