Distribute what you can, centralize what you must! Narseo Vallina-Rodriguez Supervisor: Jon Crowcroft Qualcomm – Cambridge 22nd May 2013 Apologize Jon; 2 day project meeting in London Idea: current centralised model: cloud-phone does not really work

Motivation The web is becoming mobile Apps rely on multiple online/cloud services (mobile mashup): CDNs (Akamai) Cloud services (Amazon WS) Authentication APIs (Oauth) Assisting sensors (A-GPS) Advertisement (AdMob, Burstly, Millennial Media, …) Push notifications (Google’s GCM) NAT punching for P2P (Skype)

Research question How do mobile apps’ cloud dependency impact on cellular network and battery life of mobile handsets?

2012-2013 outcome When Assistance becomes Dependence: characterizing the costs and inefficiencies of A-GPS. Vallina-Rodriguez, Finamore, Grunenberger, Papagiannaki and Crowcroft. ACM SIGMOBILE MC2R (under review) Breaking for Commercials: Characterizing Mobile Advertising. Vallina-Rodriguez, Finamore, Shah, Grunenberger, Haddadi, Papagiannaki and Crowcroft. In ACM Internet Measurement Conference 2012(IMC'12) Energy Management Techniques in Modern Mobile Devices. Vallina-Rodriguez and Crowcroft. In IEEE Communications Tutorials and Surveys, 2012. When David can help Goliath: the case for cellular augmentation of wired networks. Vallina-Rodriguez, Erramilli, Grunenberger, Gyarmati, Laoutaris, Stanojevic, Papagiannaki, In ACM HotNets'12 Signposts: End-to-End Networking in a World of Middleboxes. Aucinas, Chaudhry, Crowcroft, Probst Eide, Hand, Madhavapeddy, Moore, Mortier, Rotsos and Vallina-Rodriguez. In ACM SIGCOMM 2012. DEMO

Take away: moving to the edge! Mobile applications may abuse cellular networks: they cause network (signaling/channels/operational) and energy costs! Fetching content in a centralized fashion is not the only way Apps and OS must exploit locality and neighboring devices when possible!

Distribute as much as you can!

Flashlinq/LTE-direct P2P wireless technology Perfect candidate for transparent communication in the edge! Peer discovery (energy efficient) Expression-based discovery (service) Always-on background service with low duty-cycle Similar to powering up a paging channel every X seconds Current prototype performance: Low-latency (<10 ms) Good throughput (~ 20 Mbps) Discovery (1~2 seconds)

… but what can be distributed?

1. Localized data

Use case 1: Localized data A large fraction of mobile data is local Weather Notifications Ads Apps use cellular networks and push notifications to fetch this content High latency No delivery guarantees [Cellular data network infrastructure characterization and implication on mobile content placement, Xu et al. SIGMETRICS’2011]

Use case 1: Airport notifications SERVER (UK) NODE B Google GCM (Ir) RNC SGSN GGSN INTERNET

Use case 1: Airport notifications Traffic Pattern Heathrow App For Android (Flight Update) Energy Signaling Spectrum (HSPA) TCP/IP Push notification model is broken for local data: Frequent RNC promotions (some caused by TCP Heartbeats) Waste of energy, middleboxes/proxies memory and radio channels (+200K users/day, a lot of signaling traffic!)

Use case 1: Airport notifications PubSub model Low latency No net overhead Energy efficient No Middleboxes! SERVER (UK) Flashlinq NODE B Google GCM (Ir) RNC SGSN GGSN INTERNET

2. Collaborative sensing

Use case 2: Collaborative A-GPS Assisting data (time, ephemeris, almanac, coarse location) downloaded from network: Reduces TTFF (usability) Temporal validity up to 2 weeks for ephemeris Problem: use of cellular network may impair performance and increase energy costs!

Use case 2: Collaborative A-GPS 2x current! Control-plane latency

Use case 2: Collaborative A-GPS Collaboration between devices in a P2P fashion: Context-awareness (sense environment so do not turn on AGPS indoors!) Share/pre-fetch assisting data (reduces latency to fetch data) Prototype for Nexus One: Pre-fetch and cache of assisting data Devices can detect if they’re indoors in less than 10 seconds Blackbox. Hard to inject assisting data on chipsets (A-GPS is controlled by binary/proprietary files/drivers  )

3. Wired-wireless integration Thinking beyond app-level use cases, Flashlinq is a perfect candidate for wired-wireless integration.

Use case 3: Wired-wireless integration 3G offloading to WiFi and femtocells: Reduce network traffic No real benefit for users (unless volume cap in data-plan) Wired network can be constrained! Can cellular networks augment wired networks? Wired nets deployment is $$$ Cellular nets have good coverage

Use case 3: Wired-wireless integration Cellular network can provide more capacity than wired ones (DSL) Spare capacity on cellular network Powerboost for video- streaming apps Use-and-release Does NOT work everywhere anytime! 4.7 Mbps DSLAM DSL in rural/suburbs: far from DSLAM Spare capacity for small periods of time (HSPA) Powerboost (use and release) A 2 Km 2.8 Mbps Google Maps

Use case 3: Wired-wireless integration 2x downlink/5x uplink for most locations with 1 mobile device Simulation: 50% of the videos have a speed up factor of 10x 2x downlink 5x uplink Some locations are congested Nevertheless, worst case shows that 50% apps can reduce by 10x the buffering time

Conclusions Current cloud-mobile model is not efficient Hyper-centralized: push notifications Lack of connectivity between handsets: missing opportunities Cellular and wired networks are fully decoupled Flashlinq/LTE-direct can bring a new mobile paradigm! Energy and network efficient Distributed Flexible

Flashlinq limitations and extensions Transparent security/authentication mechanisms Lessons to be learnt from the past: Bluetooth and WiFi-direct failed! Source of DoS/Privacy/Energy attacks Global Signpost-ish naming (OpenSource, DNSSEC based) Low-level radio details must be exposed to OS! Too much layering hides inefficiencies: e.g. A-GPS and 3G Cross-layer optimizations are key (e.g. iPhone vs. Android) Incentives for operators? Reduce operational costs: better use of limited capacity Licensed frequency .. But there are few missing bits from my perspective as a developer that are being missing

Thank you for your attention! http://www.cl.cam.ac.uk/~nv240 nv240@cam.ac.uk