Abstract:                                                       CDNs have evolved to distribute and deliver media content ...
Table of ContentsIntroduction ............................................................... 2Distribution using P2P .......
IntroductionSimple CDNs have so far enjoyed wide-spread acceptance as channels to guarantee media contentdelivery over the...
While some ISPs have attempted to block P2P traffic completely, their attempts have been rebuked bygovernment authorities ...
servers. Hybrid CDN covers content distribution both on the core and the access networks. Some of thekey objectives of Hyb...
Other ConsiderationsNetwork OptimizationThe inherent unpredictability of content flow in a P4P network makes the quality o...
ConclusionTelcos need to introduce CDNs in their networks as demand for user generated as well as professionallyavailable ...
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Hybrid cd ns_leveragingthebestofbothworlds


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  1. 1. Abstract: CDNs have evolved to distribute and deliver media content to millions of users, across geographically disparate locations. However, the challenges on the networks toHybrid CDNs deliver quality content without succumbing to traffic loadsLeveraging the Best of Both Worlds and routing decisions, have only compounded. This paper investigates the dimension of a Hybrid CDN involving P2P/P4P schemes to improve the network health, and touches upon considerations that may be currently going unnoticed.Authors:Chitresh Markanda, Principal Consultant –IP networksGururaj Phadnis, Sr. Consultant- IP networksRaj Sahakari, Sr. Consultant- Customer Premise TechnologiesChirag Shinde, Consultant in Wireless Technologies © Tech Mahindra Limited 2010
  2. 2. Table of ContentsIntroduction ............................................................... 2Distribution using P2P ................................................... 2Disciplining using P4P .................................................... 3Architecture of a Hybrid CDN .......................................... 3Benefits to Telcos ........................................................ 4Other Considerations .................................................... 5Conclusion ................................................................. 6 © Tech Mahindra Limited 2010 1
  3. 3. IntroductionSimple CDNs have so far enjoyed wide-spread acceptance as channels to guarantee media contentdelivery over the internet to large numbers of users. However, these CDNs have reached somelimitations as per scale - Akamai’s CEO acknowledges that the load introduced by a million userswatching a typical internet TV multimedia clip streamed at 400 Kbps would result in traffic exceedingAkamai’s current peak capacity by about 30%. Simple CDNs function by copying media streams to alarge number of servers along a customer facing “edge”. User load is distributed over this edge.Limitations of this approach stem from the fact that a streamer can handle at most a few hundred userssimultaneously. For handling the typical viewership of popular content one would need hundreds ofthousands of streamers, a requirement that is simply not practical.This limitation of scale has created the need for other paradigms of media distribution. Prominentamong these approaches is Peer-To-Peer media sharing.Distribution using P2PPeer-To-Peer media distribution or media sharing as it is often called, achieves scalability by usingviewer numbers to its own advantage. It leverages viewer equipment itself to distribute andredistribute media.A consumer of media receives “pre-designated” fragments from other peers who already have thosefragments. This means consumers no longer load “edge streamers” as in the case of traditional CDNs.Media distribution load is evenly spread throughout the viewership. This system, in fact, performsbetter with an increasing number of users and easily scales to 100s of millions of users.Though P2P was only created with the ability to “download” media in mind, suitable modifications tothe mechanisms can enable streaming applications to view media on-the-fly. Just like traditional CDNsneed edge streamers, P2P needs to guarantee the existence of a “small” number of “seed” viewers tobegin the process of disseminating content among a larger user community and to guarantee itsavailability. P2P does this with the help of designated nodes which are “always on” and connected tomedia origin servers with high-speed links. In fact, minus actual viewers, P2P looks just like a simpleCDN and can “piggy-back” on existing Simple CDNs giving rise to the notion of “Hybrid CDNs”.One side-effect of P2P is that more users can share their own User Generated Content (UGC) leading toan explosion of content available in P2P communities. P2P was designed with this in mind andautomatically organizes and updates a content search database. The considerable computational powerrequired to update and search this vast database is derived again through distribution of both, thedatabase and the search functions, among certain available P2P nodes called DHT (Distributed HashTable) nodes. Some DHT nodes are designated by Hybrid CDN creators to guarantee functioning of theirnetworks, while some are P2P nodes volunteering to serve these functions. P2P networks locate andquery DHT nodes with keywords to find available content and the corresponding peers willing to shareit.Though P2P presents a very powerful paradigm for media distribution it creates significant challengesfor ISPs. P2P nodes essentially connect with each other in an undisciplined manner. In particular, a P2Pnode regards any node from which it can obtain content as a “neighbor”. Such neighbors can lie overlarge geographical distances translating to a high amount of traffic between “neighbors” going overOPEX-intensive long distance ISP backbone links. The problem is further compounded by the popularityof P2P for publishing User Generated Content. The ISPs typically end up playing for this additionaltraffic with no compensatory arrangement with content providers and consumers. © Tech Mahindra Limited 20102
  4. 4. While some ISPs have attempted to block P2P traffic completely, their attempts have been rebuked bygovernment authorities that tend to encourage openness of communication and user empowerment.The need to discipline P2P traffic however, can be addressed by extending the role of content locatorswithin peer communities. Some ISPs have been researching the notion of P4P to deal with this aspect.Disciplining using P4PP4P disciplines P2P traffic by making DHT nodes aware of network topology, altering the notion of the“neighbor” to be cost-sensitive. DHT nodes are made to query ISP provided portals providing networkpath costs to be incorporated when advising P2P peers searching for content. This way, P2P nodeslocate and download content fragments from peers to which they can talk over local links.Content that is not locally available continues to be obtained over long distance links. However, apopulation of a few hundred users effectively downloads content once over long distance links andshares it locally. Without P4P, most of these users would end up repeatedly downloading the same“remote” content, thus increasing the ISPs long distance bills. P4P has been observed to be veryeffective in practice, limiting long distance P2P traffic by over 80%.P4P was not designed with streaming in mind. Peers attempt to download “rarer” content fragmentswith higher priority. This is to mitigate the risk of peers dropping off the network. The result is thatcontent fragments arrive in no particular order making it harder to watch a multi-media clip on-the-fly.This can be addressed without fundamentally modifying P2P mechanisms. Re-prioritization of contentfragments based on sequence, rather than on “rarity” has been successfully employed for streamingapplications.Architecture of a Hybrid CDN Figure 1: Telco CDN 2.0 – Hybrid CDNFigure 1, presents various CDNs which are needed to deliver content effectively. Typically, the Edge(between Core and Access network) is the “middle mile” or peering point for a CDN. CDNs traditionallyare overlaid beyond the Edge (into the Core) via small number of dedicated content distribution © Tech Mahindra Limited 2010 3
  5. 5. servers. Hybrid CDN covers content distribution both on the core and the access networks. Some of thekey objectives of Hybrid CDNs include: Ability to deliver HD (High Definition) Content over the CDN Ability to stream live content Ability to monetize the content at the Edge – via Byte billing or advert insertion Ability to localize traffic - especially P2P and UGC trafficFor end to end content delivery SLAs – Service management, Rights management, Reliability and Priceare important considerations. Another important consideration is the QoS guarantee across CDNnetworks.P2P traffic management within the access network is important for a Telco in order to ensuredemocratic utilization of available network capacities. Localization of P2P would ensure that edgerouting is reduced and hence lower cost of peering. Implementation of P4P makes P2P location aware.Also, data centre/hosting costs are dramatically reduced by implementation of P2P/P4P basedtechnologies in the access network.Edge caching is done for reasons of content caching and monetizing CDN traffic. Cloud technologiestoday offer the edge caching capabilities and hence are being increasingly used. Ad-insertion via Ad-splicing and other content adaptations at the Edge can further help monetize the assets. In case of P2Ptraffic, if the edges are being used, Ad-funded schemes can be developed to enable such “add-ons”.Benefits to TelcosSome of the advantages of the proposed architecture arise from better management of user generatedtraffic. They principally include: Being able to launch multi-tenant services and being able to guarantee reliable, optimized service delivery Help telcos launch HD content over their networks – for video streaming, download, P2P traffic Effectively enable UGC over telco networks and monetize it Launch live-streaming services, both events and user generated, over telco networks Being able to launch Ad-funded revenue models for P2P and user generated traffic Finally, deliver good user experience via better management and traffic shapingWith this strong infrastructure backup, telcos are in a position to launch a wide range of applications,such as: Broadcast and Stagger cast TV HDTV EPG and Interactive TV User Generated Broadcast Video Conferences Video on Demand Application/Web Hosting and Edge caching services © Tech Mahindra Limited 20104
  6. 6. Other ConsiderationsNetwork OptimizationThe inherent unpredictability of content flow in a P4P network makes the quality of service particularlydifficult to guarantee. There is a need for mechanisms within or complementary to P4P to address QoSprovisioning in peer networks. This provisioning mechanism must be robust enough to handle the largenumbers of peers joining and dropping off the network, while maintaining the desired QoS. Statisticaltechniques analogous to those used in high capacity web content delivery setups could be combinedwith peer “reservation” mechanisms to achieve guaranteed content flow in peer networks.Need for StandardizationThe ability of a CDN to interact with other CDNs plays an important role, especially when telcos wish toextend their content services beyond their current subscriber base. Also, telco CDNs could get loadedand would need the assistance of other CDNs to offload traffic. Thus, the need to standardize CDNinterworking is greatly felt.However, most of the current day CDNs are proprietary and IP protected, thus causing challenges inintegration. Standards bodies such as the Open IPTV Forum and ETSI have initiated the standardizationprocess, but have primarily focused on the internal CDN functional entities and the associatedreference points. Interfaces for inter-CDN communication, which typically cater to ingest, redirection,access requests, network statistics, etc., are required to be defined.Need for DRMIllegal content distribution is the prime concern that content providers are attempting to tackle. Thisincludes both, downloadable as well as streaming content. Introduction of P2P/P4P distributionschemes exacerbates the issues as it introduces an expensive tradeoff with DRM enforcement.DRM policies for professionally available content and UGC, especially for P2P/P4P networks, arerequired to be defined for controlling the usage and redistribution of the content, thus preventingcopyright breaching. Run-time encryption coupled with efficient key management could help addressDRM needs in a P2P/P4P environment. Also, as content flows across diverse CDNs, aspects related toDRM interoperability need to be considered.Strategies for Home NetworksThe interconnection of devices in the home to watch multimedia is scaling by the day and is creating anetwork that needs efficient management. P2P-based CDNs, in a modified and adapted form, are agood candidate to fit the bill.Such CDNs could typically overlay existing home networks – DLNA (Digital Living Network Alliance),G.hn, HPNA (Home Phone line Networking Alliance), HANA (High-Definition Audio-Video NetworkAlliance), MoCA (Multimedia over Coax Alliance), etc. – to host, distribute and deliverservices/applications, integrate with the physical networks, as well as manage the load and usage ofthe home networks. © Tech Mahindra Limited 2010 5
  7. 7. ConclusionTelcos need to introduce CDNs in their networks as demand for user generated as well as professionallyavailable content is becoming more and more profound. Telcos can adopt various strategies includingupgrade of network equipment, service management equipment; create/lease overlay networks for thecore network. For the access network, telcos need to focus on user generated traffic (UGC, semi,professional content) and optimize both the cost of transmission and storage of these contents. Byusing a hybrid CDN approach involving a simple CDN coupled with a P2P/P4P scheme, telcos canleverage the best of both worlds.ABOUT TECH MAHINDRA:Tech Mahindra is a global systems integrator and business transformation consulting organizationfocused on the communications industry. With the convergence of media and telecom, the changinglandscape of the telecom industry is becoming extremely competitive. As companies rapidly strive togain a competitive advantage, Tech Mahindra helps them innovate and transform by leveraging itsunique insights, differentiated services and flexible partnering models. This has helped our customersreduce operating costs and generate new revenue streams. Margins from connectivity are rapidly fallingand future growth in revenues will only come from new applications, content and services. Hence,operators today are busy addressing business opportunities revolving around commerce, content,convergence and customer experience to gain a sustainable competitive advantage. At Tech Mahindra,we understand this and we offer solutions that help our customers achieve their business goals. © Tech Mahindra Limited 20106