USENIX HotEdge 2018

Department of Computer Science National Chiao Tung University, Taiwan

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Mobile Edge Computing Platform Deployment in 4G LTE Networks: A Middlebox Approach

Chi-Yu Li1, Hsueh-Yang Liu1, Po-Hao Huang1,Hsu-Tung Chien1, Guan-Hua Tu2, Pei-Yuan Hong1, Ying-Dar Lin1

1Department of Computer Science National Chiao Tung University

Taiwan

2Department of Computer Science and Engineering, Michigan State University

USENIX HotEdge 2018

Department of Computer Science National Chiao Tung University, Taiwan

l Introduction

l Background and Related Work

l Challenges and Design Ideas

l Prototype and Evaluation

l Conclusion

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Outline

USENIX HotEdge 2018

Department of Computer Science National Chiao Tung University, Taiwan

l Emerging low-latency apps in cellular networksp E.g., C-V2X (Cellular Vehicle-to-Everything), Virtual Reality (VR), etc.

l A key technology: Mobile Edge Computing (MEC) p Determined as a 5G feature by both ETSI and 3GPPp Providing a cloud computing platform at the network edge

l MEC: shortening latency with two major meritsp Short end-to-end distance

n Small propagation delayn No bottleneck/congestion from the Internet

p Offloading services from the cloud

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Introduction

C-V2X Apps

VR Apps

MEC Platform

. . .

USENIX HotEdge 2018

Department of Computer Science National Chiao Tung University, Taiwan

l Control plane: UE – RAN – MME/HSS p Functions: mobility, security, resource allocation

l User plane: UE – RAN – S-GW/P-GWp Routing data traffic between UE and Internetp Carried by GTP Tunnel

n One tunnel is built for each UE’s Internet traffic

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Background: 4G LTE Network

S1 Interface

UE (User Equipment)

eNB(evolved Node B)

Internet

MME

S-GW

HSS

P-GW

Core Network

GTP Tunnel

Control plane

User plane

MME: Mobility Management EntityHSS: Home Subscriber ServerS-GW: Serving GatewayP-GW: Packet Data Network GatewayGTP: GPRS Tunneling Protocol

USENIX HotEdge 2018

Department of Computer Science National Chiao Tung University, Taiwan

l ETSI standard[1]

p Several options in LTE networksn Various components at the Edge

p No concrete designs/implementations

l Other research studiesp Several Surveys [2] [3] [4] : No examination of the MEC deployment in 4G networksp Existing deployment solutions[5] [6]: Not standard-compliant

n Modifications on the eNB or/and the core network

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Related Work: MEC Deployment

UE eNBInternetCore

Network

MEC

.

.

S-GW MEC

S-GW MECP-GW MME

Our Solution

USENIX HotEdge 2018

Department of Computer Science National Chiao Tung University, Taiwan

l Goal: low costs, high deployment incentives

l Requirementsp Standard-compliant

p No modification requirements on eNB or/and core networks

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How to Deploy the MEC in LTE Networks?

eNBInternetCore

Network

MEC

.

.

S-GW MEC

S-GW MECP-GW MME

UE

USENIX HotEdge 2018

Department of Computer Science National Chiao Tung University, Taiwan

l MEC platform sits on the S1 interfacep Some traffic is routed to the MEC

p The others pass through the MEC to reach the Internet

l A middlebox approach: transparent to the network architecture

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Key Idea: MEC Deployment as a Middlebox

UE eNBInternetCore

Network

MEC

S1 Interface

USENIX HotEdge 2018

Department of Computer Science National Chiao Tung University, Taiwan

l I. How to intercept and forward GTP packets?l II. How to redirect data traffic to the MEC?l III. How to enable MEC apps to serve GTP packets?l IV. How to identify the GTP tunnel associated with each packet?

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Challenges

UE eNBInternetCore

Network

GTP TunnelGTP Packets

MEC

USENIX HotEdge 2018

Department of Computer Science National Chiao Tung University, Taiwan

l MEC divides S1 into two network segmentsl No ARP response: eNB/S-GW doesn’t know where to send packets

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I. How to intercept and forward GTP packets?

eNB172.17.1.1

S-GW172.17.100.254

No response No response

MEC platform172.17.1.2

ARP request ARP requestS1

Target IP =172.17.1.1Target MAC=?

Target IP =172.17.100.254Target MAC=?

USENIX HotEdge 2018

Department of Computer Science National Chiao Tung University, Taiwan

l MEC replies ARP requestsp To eNB: MEC’s MAC address è S-GW’s IPp To S-GW: MEC’s MAC address è eNB’s IP

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Solution: Proxy ARP

eNB172.17.1.1

S-GW172.17.100.254

MEC platform172.17.1.2

ARP request ARP requestS1

Target IP =172.17.1.1Target MAC=?

Target IP =172.17.100.254Target MAC=?

Response:MAC+,- Response:MAC+,-

USENIX HotEdge 2018

Department of Computer Science National Chiao Tung University, Taiwan

l MEC needs to redirect UE’s data packets to its app serversp Instead of forwarding them to the Internet

l Keep both apps and their servers work as usual

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II. How to redirect data traffic to MEC?

UE eNBInternet

MEC platform

APPs

Core Network

USENIX HotEdge 2018

Department of Computer Science National Chiao Tung University, Taiwan

l Intercept all DNS packets from UEl Return local IP addresses in response to apps’ domain names

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Solution: Traffic Redirection via DNS

UE eNBInternet

MEC platform

APPs

Core NetworkDNS server

DNS query: “www.youtube.com”

DNS response: 10.0.0.2

IP: 10.0.0.2

USENIX HotEdge 2018

Department of Computer Science National Chiao Tung University, Taiwan

MEC platform

APPs

l IP packets are carried by GTP tunnelsl App servers don’t recognize GTP packets

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III. How to enable APPs to serve GTP packets?

GTPHDR IPHDR

UE

Payload

GTPHDR IPHDR Payload

Unrecognized Format

à Discarded

USENIX HotEdge 2018

Department of Computer Science National Chiao Tung University, Taiwan

l Strip off GTP headers before redirecting

l Maintain a dynamic table for each UE’s tunnel

l Encapsulate GTP headers back after app server respond

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Solution: GTP header repackaging

MEC platform

DNS server

GTPHDR IPHDR

Header Repackaging

uplink

IPHDR

UEIP: E

GTPHDR IPHDR

downlinkTEID: PQ

Uplink tunnel

Downlink tunnel

UE IP TEIDA XY

… …

E PQ

USENIX HotEdge 2018

Department of Computer Science National Chiao Tung University, Taiwan

l GTP tunnels are dynamically built for each UEl Encapsulating requires the correct mapping between IP and tunnel ID

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IV. How to identify tunnels for each UE

UE IP: A

UE IP: B

UE IP: EMEC platform

DNS server

Header Repackaging

TEID: MN

TEID: XY

TEID: PQ

USENIX HotEdge 2018

Department of Computer Science National Chiao Tung University, Taiwan

Stateful trackingmodule

l UE info are maintained in the MMEl Prevent changes to the CN: communication between MEC and MME

is prohibitedl Do stateful tracking when there is outgoing traffic instead

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Solution: Stateful tracking of GTP tunnels

MME HSS

SGW PGW

UE IP: EeNB Core Network

Interface?

Maintain mapping between UE IP & TEID

TEID: PQ

Internet

UE IP TEIDA XY… …E PQ

MEC platform

USENIX HotEdge 2018

Department of Computer Science National Chiao Tung University, Taiwan

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MEC Platform Architecture

MEC Platform

S1 Interface

APP1Server

…

eNB Core

APP2Server

DNSServer

GTP Unpacking and Repackaging

Platform Manager

StatefulTracking

New Data Path

Signaling Path

APPLayer

PacketsForwarding

Default GTP Tunnels

Proxy ARP

USENIX HotEdge 2018

Department of Computer Science National Chiao Tung University, Taiwan

l Prototype with OpenAirInterface (OAI) cellular platform

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Prototype

USENIX HotEdge 2018

Department of Computer Science National Chiao Tung University, Taiwan

l Compare webpage response (CNN news) between cloned web server on MEC platform and on Internetp Results in different percentile(5%, 50%, 95%)p Overall latency vs. radio-link-omitted latency

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Evaluation – Experiment #1

69.86%

98.46%

DNS query Webpage service

95%

50%

5%66.18%

13.36%

USENIX HotEdge 2018

Department of Computer Science National Chiao Tung University, Taiwan

l Video streaming from MEC and from Google Cloud Platform(GCP)p Using VLC media player

l Experiment settings:p RTP protocolp Streaming settings

n Video: H264 codec, 24fps, 720p qualityn Audio: MPEG codec, 128K bitrate

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Evaluation - Experiment #2 (1/2)

USENIX HotEdge 2018

Department of Computer Science National Chiao Tung University, Taiwan

l Results: pStream 1: 512K video bitrate; Stream 2: 1M video bitrate pPacket jitter in different percentile

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Evaluation - Experiment #2 (2/2)

Video stream Audio stream

60.34%67.85%

Stream1 Stream2 Stream1 Stream2

46.40% 57.71%

USENIX HotEdge 2018

Department of Computer Science National Chiao Tung University, Taiwan

l Scalability Challengesp Computing power demand for GTP packetsp Context management for different eNBs

l Security and Billingp Third party content provider could imply malicious applicationsp Traffic does not travel through CN so billing and access control is necessary

l Mobility ManagementpMigrate application states and UE context during handover

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Discussion

USENIX HotEdge 2018

Department of Computer Science National Chiao Tung University, Taiwan

ü Enabled MEC with a middlebox approach in Cellular NetworksØ A Standard compliant solution

ü Effectiveness of latency reductionü Can be a reference design of the 5G MEC

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Conclusion

USENIX HotEdge 2018

Department of Computer Science National Chiao Tung University, Taiwan

l A middlebox approach of MEC deployment in Cellular Networksp Standard-compliant, low costs, high deployment incentives

l Open issuesp Scalability challenges

p Multiple MEC apps and their state transfers

p Mobility management

p Security and billing

p Fault tolerance

l Limitation: S1 interface cannot be confidentially protectedp 3GPP standard: this confidentiality protection is vendor-specificp It is usually disabled by default

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Concluding Remarks

USENIX HotEdge 2018

Department of Computer Science National Chiao Tung University, Taiwan

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Thank you for your attentionQuestions?

USENIX HotEdge 2018

Department of Computer Science National Chiao Tung University, Taiwan

l Enabling confidentiality protection on S1 interface is based on the operator’s choice

l In practice, S-GW and eNB are usually placed in physically secured environmentl If ciphering function is enabled, operators need to allow MEC to acquire the

security context of the S1 interface

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What if confidentiality protection is enabled on S1 interface?

USENIX HotEdge 2018

Department of Computer Science National Chiao Tung University, Taiwan

[1] ETSI white paper 24: MEC deployment in 4G, 5G networks[2] AHMED, A., AND AHMED, E. A Survey on Mobile Edge Computing. In International Conference on Intelligent Systems and Control (ISCO) (2016), IEEE.[3] TALEB, T., SAMDANIS, K., AND MADA, B. On Multi-Access Edge Computing: A Survey of the Emerging 5G Network Edge Cloud Architecture and Orchestration. IEEE Communications Surveys and Tutorials 19, 3 (2017), 1657–1681.[4] MACH, P.,AND BECVAR, Z. Mobile Edge Computing: A Survey on Architecture and Computation Offloading. IEEE Communications Surveys and Tutorials 19, 3 (2017), 1628–1656. [5] CHANG, C.-Y., ALEXANDRIS, K., NIKAEIN, N., KATSALIS, K., AND SPYROPOULOS, T. MEC Architectural Implications for LTE/LTE-A Networks. In Proceedings of the Workshop on Mobility in the Evolving Internet Architecture(MobiArch)(2016), ACM. [6] HUANG, S.-C., CHEN, B.-L., LUO, Y.-C., CHUNG, Y.-C., AND CHOU, J. Application-aware Traffic Redirection: A Mobile Edge Computing Implementation toward Future 5G Networks. In International Symposium on Cloud and Service Computing(SC2) (2017), IEEE.

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Reference