The Effect of Caches for Mobile Broadband Internet Access

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1 The Effect of s for Mobile Jochen Eisl, Nokia Siemens Networks, Munich, Germany Haßlinger, Deutsche Telekom Technik,, Darmstadt, Germany IP-based content delivery: CDN & cache architecture Impact of access pattern application mix content provider preferences & standardization on efficiency of caching Conclusions on cache efficiency in fixed/mobile networks

2 Overview: Locations in Mobile Networks Source: Thomas M. Knoll

3 Content Distribution: CDN Peer-to-peer overlays P2P Long paths for P2P data exchange CDN P2P Short CDN paths Users Users Access Network PoPs ISP Backbone Peering Other ISPs Global Internet Points of Presence Access Control

4 Content Delivery Overlays (CDN, Akamai, Limelight...) Main WWW Server of a CDN Customer e.g. Yahoo DNS Redirect Source: A. Su et al., Drafting behind Akamai, IEEE/ACM Trans. on Networking Hierarchical server farm on thousands of edge nodes Path Performance Measurement & Update Process Backup Path Internet Access User Best Path

5 Link Measurement of RTT-Delays for CDN and P2P Method based on Round Trip Time (RTT) in TCP-Handshake 1 0,8 0,6 0,4 0,2 Content delivery networks: CDF Content delivery networks: frequencies Peer-to-peer: CDF Peer-to-peer: frequencies 0 0,0 0,5 Time [s] 1,0 Cumul. Distrib. Fcts. of Round Trip Times: Longer RTTs & paths for P2P than via CDN Mean RTT: 0.125s for CDN; 0.33s for P2P

6 Peering Points of Presence Effect of Caching for Mobile Users, Terminals Overview: Caching & CDN in broadband access Content and Service Platforms IP/MPLS- Backbone Aggregation Network Caching is applied in global content delivery networks and in network provider platforms of large ISPs but usually without cooperation between them! Working group on CDN interconnection at the IETF <datatracker.ietf.org/wg/cdni/charter>

7 Zipf Laws Determine Access to Popular Content Zipf laws A(R) = a R b (a > 0; 0 < b < 1) are observed for access to videos on IP platforms, books, DVD sellings etc. (YouTube, America Free TV, BBC iplayer, Amazon ) L. Breslau et al. (1999): many cases where 0.64 < b < 0.85; P. Gill (2008); M. Eubanks (IETF Plenary 2008) s of small size are efficient for Zipf law accesses! for file sizes, transfer times Crovella & Bestavros (1997) for IP connectivity (web links, BGP routes between AS nodes) A. Barabási and R. Albert (1999): Scale-free networks build randomly; small world effect for traffic volume per session and per broadband access users

8 Hit Rate Effect of Caching for Mobile Efficiency e.g. for YouTube Videos 60% 50% Optimal Strategy: Most Popular Data in LRU Strategie: Least Recently Used 40% 30% 20% 10% 0% 0.008% 0.03% 0.12% 0.5% 2% Size: Fraction of videos in the cache Evaluation of statistics on YouTube accesses in Dec. 2006: 3.7 billion accesses included on 1.65 million files Source: M. Cha et al., I tube, you tube, everybody tubes: Analyzing the world s largest user generated content video system, Internet measurement conference IMC, San Diego, USA (2007) Basically confirmed in recent YouTube evaluation at TU Munich (L. Braun et al. 2012)

9 ability of popular Internet data An essential portion of IP traffic uses HTTP protocol, most of which is marked as being cacheable, often with expiry date Requests focus on most popular content small caches are efficient Zipf law rule: 90% of requests address only 10% of content Some content providers/cdns support caching, e.g. software updates others don t: Personalised communication with user makes content identification difficult for cache manager; no standard feedback & control between cache content provider Some content providers/cdns have business relations with content owners and/or users but often without involving network providers

10 Conclusions on Caching Efficiency s reduce traffic and delays Improved QoS Popular websites are supported by global CDNs, with limited cooperation to CDNs of large network providers s on user devices can avoid 20% of traffic Zipf law popularity of content small caches are efficient Dynamic data, business models of content providers and lack of standardized cache communication as main drawbacks Combined CDN / P2P networks to achieve highest throughput

11 Conclusions on Caching in Fixed Mobile Networks Traffic via mobile platforms makes only a few % of fixed network IP traffic Separated fixed / mobile caching but mobile network traffic is catching up with high growth Transmission capacity over air interfaces is most expensive Caching on end devices should be fully exploited User driven prefetching strategy seems useful Locally relevant content in mobile networks, e.g. augmented reality applications and specific mobile content (apps, software downloads etc.)

DATA COMMUNICATOIN NETWORKING

DATA COMMUNICATOIN NETWORKING Instructor: Ouldooz Baghban Karimi Course Book: Computer Networking, A Top-Down Approach, Kurose, Ross Slides: - Course book Slides - Slides from Princeton University COS461