Open Internet Challenges in Mobile Broadband Networks

Jennifer Rexford

Princeton University

http://www.cs.princeton.edu/~jrex

FCC and Open Internet

• Open Internet Order (2010)– Transparency– No blocking– No unreasonable discrimination

• Open Internet Advisory Committee (2012)– Track effects of the Open Internet Order– Provide recommendations to the FCC– Representatives from community organizations,

equipment manufacturers, application providers, venture capital firms, ISPs, Internet governance, and academia

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Mobile Broadband Working Group

• Mobile broadband– Increasingly crucial part of Internet access– Yet, still at an early stage of development

• Special treatment in Open Internet Order– Network practice transparency– Certain “no blocking” requirements– Wider latitude for differentiated service

• Three case studies– AT&T limiting the FaceTime application– Mobile apps overloading signaling resources– Carriers limiting use of Google Wallet

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Apple FaceTime

• High-quality video chat service

• Originally available only over WiFi

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AT&T and FaceTime: A Timeline

• Jun’12: Apple announces FaceTime over cellular– Carrier restrictions may apply

• Aug’12: AT&T limits use of FaceTime over cellular– Limited to customers with

the Mobile Share plan– Sprint and Verizon announce

support on all data plans

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AT&T and FaceTime: Timeline

• Aug’12: Some advocates and press denounce– AT&T is violating FCC’s Open Internet Order– FaceTime competes with AT&T’s voice/video telephony– Reasonable network management practices do not

include favoring one data plan over another

• Aug’12: AT&T responds in a blog posting– AT&T’s policy regarding FaceTime is fully transparent– AT&T does not have a competitive video chat app– FCC rules don’t regulate availability of preloaded apps

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AT&T and FaceTime: A Timeline

• Sep’12: Public interest groups respond– Announcing intent to file a formal FCC complaint

• Oct’12: AT&T customer files an FCC complaint– Blocking of FaceTime on his “unlimited” data plan

• Nov’12: AT&T relaxes limitations on FaceTime– Supporting FaceTime on tiered plans over LTE– … though other customers would not have access

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AT&T/FaceTime Issues

• Pre-loaded application– Available to all users of popular phone – Accessed via device’s core calling features

• High bandwidth requirements– Symmetric bandwidth usage, with asymmetric capacity– Limited adaptation in the face of congestion

• Staged deployment– Rapid adoption could lead to unpredictable load– Initially limit the number of users accessing an app

• Enforcement point– Usage limited on the device, not in the network

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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

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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

10http://web.eecs.umich.edu/~zmao/Papers/periodic_www2012.pdf

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

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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

• Complex optimizations– Cross-application and cross-device

• Joint management of bandwidth and signaling load

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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 today’s equipment–Best practices for network management

• Tension between competing goals–Managing limited cellular network resources–Encouraging innovation in applications 13