Mobile Broadband Working Group Open Internet Advisory Committee Jennifer Rexford Princeton University

Mobile Broadband Working Group Harvey Anderson, Mozilla Brad Burnham, Union Square Ventures Alissa Cooper, Center for Democracy & Technology Jessica Gonzalez, National Hispanic Media Coalition Charles Kalmanek, AT&T Matthew Larsen, Vistabeam Dennis Roberson, IIT and representing T-Mobile Marcus Weldon, Alcatel-Lucent 2

Mobile Broadband Mobile broadband –Increasingly crucial part of Internet access –Yet, still at an early stage of development Open Internet Order –Network practice transparency –Certain no blocking requirements –Wider latitude for differentiated service Working group –Review state of mobile broadband –Assess how Open Internet principles are working 3

Our Initial Approach Discuss several case studies –Focus on concrete, real-life scenarios –Capture the relevant facts, issues, and viewpoints –Identify trade-offs, principles, and areas needing study –Not articulating specific policy recommendations Three specific examples –AT&T limiting the FaceTime application –Mobile apps overloading signaling resources –Carriers limiting use of Google Wallet 4

AT&T and FaceTime Apple FaceTime –High-quality video chat service on iPhone/iPad/Mac –Originally available only over WiFi on iPhone and iPad –Phone call upgraded to FaceTime by tapping a button FaceTime over 3G networks –Jun12: Apple announced FaceTime over 3G in iOS 6 … though carrier restrictions may apply –Aug12: AT&T limits 3G FaceTime to MobileShare users … with data cap shared across multiple devices Other mobile providers –Sprint and Verizon confirm that FT works on all plans –Verizon requires iOS 6 users to have mobile share plan 5

Arguments in the AT&T/FT Debate Some advocates and press denounce the decision –AT&T is violating FCCs Open Internet Order –AT&T is blocking an application competing with its own voice or video telephony services –Reasonable network management practices do not include favoring one data plan over another –Suspicion that Apple is cooperating with the scheme AT&T responds in a blog posting –AT&Ts policy regarding FaceTime is fully transparent –AT&T does not have a competitive video chat app –FCC rules dont regulate availability of preloaded apps –All users can continue to run FaceTime over WiFi 6

AT&T/FaceTime Issues Pre-loaded application, tightly integrated with OS –Available to all users of popular phone w/o downloading –Accessed via the core calling functions of the device Symmetric bandwidth usage –Access network capacity is asymmetric –Single FaceTime user consumes 33-50% of sector uplink Limited adaptation to congestion –Many multimedia apps reduce rate during congestion –… but, FT doesnt seem to adapt as much as other apps Staged deployment to understand the effects –Initially limit number of users accessing an app 7

Apps With High Signaling Traffic Signaling channel –Keeps track of mobile devices and their locations –Notifies network when a device wants to send traffic Overloaded signaling channel –Prevents new requests from reaching the network –Can become congested before the network bandwidth Unique issue in cellular networks –Due to Radio Resource Control function –… and the shared, constrained resources 8

Chatty Applications Periodic transfers –Keep-alive messages (e.g., push services, NATs) –Polling (i.e., has something happened?) –Ad updates –Measuring user behavior Skewed usage of signaling resources –Up to 30% resource usage for <2% traffic volume –In some cases, 90% signaling usage by one application –Also drains the battery on the phone Machine-to-machine traffic could make this worse 9

Managing Signaling Load is Hard End device –Strong incentives, and (some) app-level knowledge –But, incomplete control over application behavior Application developer –Complete knowledge of own application, but not others –But, limited knowledge of the network state Network –Sees all traffic and controls resource scheduling –But, incomplete knowledge of applications, or ability to infer app before harm has been caused 10

Signaling Management Challenges Application-specific management –Adjusting timers for periodic polling –Piggybacking of requests on data traffic –Application-level signaling control Huge number of applications –Average lifetime of 30 days and revenue of $700 –E.g., AT&T has worked with ~100 app developers to better optimize their applications Complex optimizations –Cross-application and cross-device Joint management of bandwidth and signaling load 11

Going Forward… Network management is challenging –Large mix of rapidly evolving applications –Growing number of mobile devices –Limited bandwidth and signaling capacity The technical details matter –Capabilities of todays equipment –Best-common practices for network management Perhaps enlist help from other groups –To capture the relevant technical context –E.g., Broadband Internet Technical Advisory Group Review ongoing standards work (e.g., 3GPP) 12