Tim Wauters, Koert Vlaeminck, Wim Van de Meerssche, Filip De Turck, Bart Dhoedt, Piet Demeester, Steven Van den Berghe,
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Developments in Access Technologies to Support New Services




Figure 1 Delivery mechanisms for IPTV

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Developments in Access Technologies to Support New Services




Figure 3 Evolution towards a converged, IP-aware, full ser...
Developments in Access Technologies to Support New Services




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Developments in Access Technologies to Support New Services




Figure 6 Basic principle of the tsTV caching algorithm at ...
Developments in Access Technologies to Support New Services




     Due to their significant bandwidth
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Developments in Access Technologies to Support New Services




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IPTV Deployment – Trigger for Advanced Network Services!

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IPTV Deployment – Trigger for Advanced Network Services!

  1. 1. Tim Wauters, Koert Vlaeminck, Wim Van de Meerssche, Filip De Turck, Bart Dhoedt, Piet Demeester, Steven Van den Berghe, Erwin Six and Tom Van Caenegem IPTV Deployment – Trigger for Advanced Network Services! The increasing popularity of multimedia broadband As a consequence, the architectural model of access networks has evolved applications, beyond basic triple-play, introduces new towards multi-service and multi-provider challenges in content distribution networks. These networks during the last few years. Ethernet next-generation services are not only very bandwidth- as well as full IP alternatives have been investigated as viable connectionless intensive and sensitive to the high delays and poor loss successors for the legacy ATM-based properties of today’s Internet, they also have to platforms. While the introduction of support interactivity from the end user. The current Ethernet up to the edge solves some of the existing access network problems, new ones trend is therefore to introduce IP-aware network are created. Per subscriber traffic elements in the aggregation networks to meet the segregation and the lack of QoS support are increasing QoS requirements, offering a smooth the main issues of standard Ethernet. While the introduction of VLANs could alleviate transition from legacy ATM-based platforms towards these shortcomings, it can be questioned more scalable, efficient and intelligent access whether this approach is sufficiently scalable for larger access network networks. One of the promising services triggering deployments. Therefore an IP-aware this evolution is IPTV. This article presents a large- network model1 is often considered a scale IPTV service deployment in an IP-aware multi- valuable alternative. Depending on the popularity of the service access network, supporting broadcast TV, content, different IPTV services can be time-shifted TV and pay-per-view services. distinguished (Figure 1). While traditional Transparent proxy caches collaborate providing live TV is broadcast from a central server deeper in the network, video-on-demand distributed network storage and user interactivity, (VoD) servers are typically located at the while offering an adequate end-to-end quality of edge of the core network. In order to experience. As a use case, a time-shifted TV solution support interactivity from the end user for live TV or to serve requests for other very is introduced in more detail. We discuss a distributed popular content, servers in the access caching model that makes use of a sliding window network can become beneficial. This approach, however, has important concept and calculates the optimal trade-off between implications for future access network bandwidth usage efficiency and storage cost. A architectures, as discussed further on in this prototype implementation of a diskless proxy cache is article. evaluated through performance measurements. Next-Generation Broadband This article was presented at the 45th FITCE Introduction Services Congress which took place in Athens 30 August – 2 September 2006. It is reproduced here by kind permission of FITCE. Although telecom operators continue to Next to IPTV services, a wide variety of build out their broadband access networks other value added (interactive) services, different services have to improve high-speed Internet access and such as managed home networking, home voice-over-IP (VoIP) services, IPTV services automation and security management, highly fluctuating band- are becoming the highest-priority residential telecom services, creating very promising multimedia multi-party conferencing and on-line gaming, can be offered by service market opportunities. These bandwidth- providers, each setting its own requirements width requirements intensive IPTV services have a significant for the underlying network. Different impact on the underlying transport network services have highly fluctuating bandwidth The Authors: Tim Wauters, Koert Vlaeminck, and require more intelligent access network requirements. Delay and jitter requirements Wim Van de Meerssche, Filip De Turck, Bart elements to meet the higher QoS also differ from service to service. Dhoedt and Piet Demeester are with Ghent requirements. For interactive services a low delay over University, and Steven Van den Berghe, Erwin IPTV is therefore considered as an the network is a critical success factor. Six and Tom Van Caenegem are with Alcatel important driver for other advanced When several parties exchange information Research and Innovation. network services. in an interactive way, the quality of the user The Journal of The Communications Network • Volume 5 Part 3 • July–September 2006 63
  2. 2. Developments in Access Technologies to Support New Services Figure 1 Delivery mechanisms for IPTV Implications for the Access Broadcast TV Time-shifted Video on Video on TV Demand Demand Network Architecture Broadcast Server Access Server Regional Server Central Server Network transformation The connection-oriented approach of current DSL (digital subscriber line) access Number of Requests networks (see Figure 2) has been identified as a limiting factor, both in terms of access network scalability – all PPP (point-to-point protocol) links are terminated in a single Start of 1 Hour 1 Day 1 Week device, the broadband access server (BAS), Live Broadcast and obstruct multicast support in the access Time network – and subscriber terminal autoconfiguration – PPP links cannot be autoconfigured as the link specification is experience (QoE) decreases with increasing network layer and could be deployed on a location dependent. Also, since PPP access delay. For instance, a telephone large scale inside the access network. Other networks are tailored to the connection of a conversation will become very difficult if services mainly focus on the application single device per subscriber, network the network delay exceeds a few 100 layer, but even these services could benefit address translation (NAT) is required on milliseconds. Multimedia services are very greatly from enabling technologies in the subscriber lines where multiple IP devices sensitive to jitter – variation in the delay will access network, e.g. a caching system in the are connected, breaking end-to-end IP drastically degrade audio and video quality access multiplexer supporting multimedia connectivity. – but, in non-interactive cases (e.g. video- content delivery. Furthermore, introducing new services, on-demand), some delay can be tolerated. However, several shortcomings of all imposing their own QoS (quality of Some services, such as firewalls and operational DSL access networks prevent service) requirements, is impossible over a intrusion detection systems for managed further generalisation of the Internet and the single best-effort access link as it exists home networking, interact directly with the introduction of such new services. today. To overcome all these issues, a converged IP access network architecture, Figure 2 Current access networks as depicted Figure 3, was introduced by Stevens et al2, showing how an IPv6 data- plane can be used as the cornerstone of a future service-oriented access network: • IP awareness close to the end user is IP Aware required for the deployment of new ADSL advanced services in the access network; Modem • a converged access network reduces the capital and operational expenses (CAPEX and OPEX) of maintaining per service separated networks – furthermore, DSLAM interaction between different services is IP Aware more flexible; • due to its connectionless nature, an IP Customer Premises PPP access network allows for multiple Network edges, greatly improving scalability and ATM Switch robustness in case of edge node failure; Aggregation • in light of the growing peer-to-peer traffic PSTN Network volume, the ability to process local traffic Broadband Access Server without edge involvement further increases the scalability of an IP access network. An overview of the most important Current network access implementations elements in the network transformation process is given in Table 13. For telephony, a switched path is set up over the PSTN (public switched telephone network) between the end-devices of the caller and the called party. For DSL (digital subscriber line) broadband Internet access, end users set up PPP (point-to-point protocol) connections inside Network processing power ATM VCs (asynchronous transfer mode/virtual circuits) from their customer premises network Because each service has its own (CPN) to a central aggregation node, the broadband access server (BAS). Only the tunnel end- requirements for the characteristics of the points are IP aware. When an end user wants to connect multiple IP devices to the Internet, a underlying network, advanced QoS support NAT (network address translation) router is used to terminate the PPP connection. Although geographically similar, PSTN and DSL networks are physically separate, except for the first mile. will be a critical success factor for such a Broadcast TV is distributed over yet another access network (e.g. cable, satellite). converged access network, requiring additional processing power to be present in 64 The Journal of The Communications Network • Volume 5 Part 3 • July–September 2006
  3. 3. Developments in Access Technologies to Support New Services Figure 3 Evolution towards a converged, IP-aware, full service access Figure 4 Taxonomy network IP Aware Custom Silicon Performance/Watt (ASIC) NAP Edge Router Network Processor IP General Telephone Switch Purpose Processor Aggregation Network Flexibility technology for increasing application IP Aware awareness of IP access nodes. Gateway IP DSLAM IPTV Service Deployment Service Enablers IP Aware (e.g. Firewall, Time-shifted TV Customer Premises Caches) Due to the growing popularity of IPTV, a Network central server architecture has become insufficient to support these services. Recent deployments therefore introduce distributed IP access nodes. Furthermore, the As opposed to ASICs, general-purpose servers at the edge of the core network, deployment of service enablers or even full processors certainly meet the flexibility storing the more popular programmes. The services in the access network puts requirements for implementing modern time-shifted TV (tsTV) concept, however, as additional strain on the access nodes’ network services. explained in more detail in the next section, processing units. However, they often lack performance goes even one step further and introduces Traditionally, telecom equipment or consume too much power (generate too the storage of small sliding intervals of vendors have used fixed-function much heat) for integration in large telecom streaming content in the access network. application-specific integrated circuits systems. This way smaller, diskless streamers can be (ASICs) to cope with the huge performance For this reason, a hybrid device, called a deployed close to the end users, at the requirements of today’s network systems. network processor (NPU), has emerged over proxies. This is most beneficial, in terms of However, the ever-changing requirements of the last few years. Network processors are network bandwidth, for very popular content, a service oriented access network require highly parallel, programmable hardware, such as live TV shows on the major channels. flexible solutions with assured time to combining the low cost and flexibility of a Support of interactive commands (pause, market, while custom silicon provides little RISC processor with the speed and fast forward or rewind) on live TV then be- or no flexibility to introduce new protocols scalability of custom silicon4 (see Figure 4). comes possible at the proxies, at least within or services on existing hardware. NPUs are considered an important the time window of the stored interval. Table 1 Network Transformation Process for Triple Play Distributed storage Current ATM-based broadband Next-generation Ethernet/IP-based broad- End users have an increasing amount of aggregation band aggregation multimedia data (digital photo albums, ATM DSLAMs IP DSLAMS digital home videos, a digital music and • unintelligent layer 1 aggregation • intelligent aggregation with multicast support movie collection, etc). A major opportunity • low-speed ATM uplinks • mostly central office-based ⇒ • gigabit Ethernet uplinks • increasingly RT-based of multiservice access networks is allowing users to transparently store, access and Complex, fixed connections Simple, flexible connections share their digital media library from • DHCP-based anywhere. While hard disks are failure • PPP-based • bound to DSL, CPE in the house • provisioning cost high ⇒ • independent of device • user-based prone and recordable optical media only have limited archival lifespan5, having a • provisioning cost low high-speed network storage service, Centralised B-RAS Distributed routers enabling users to virtually take their data • optimised for best-effort Internet • optimised for QoS-sensitive services with them wherever they go and relieving • lack of scalable routing and QoS • typical OC-12 hand-off to IP core ⇒ • highly scalable • 10 GbE hand-off to IP/MPLS core them of the burden of meticulously backing up all data, would make life a lot easier. Lack of network resiliency High available network Guaranteeing fast access requires • outages tolerated • minimal financial repercussions ⇒ • little to no tolerance of service interruptions • risk of churn if reliability metrics are not met distributed servers and a pervasive replication mechanism, as introduced in Saito et al6, caching data wherever and Source: Yankee Group ‘Inside the Trends and Numbers of the Broadband Aggregation Market’, whenever it is accessed. Since multimedia June 2005 content is typically read-only data, no strong consistency is required between replicas. The Journal of The Communications Network • Volume 5 Part 3 • July–September 2006 65
  4. 4. Developments in Access Technologies to Support New Services the popularity of a television programme typically Updates can be propagated periodically, at reaches its peak within several minutes after the initial the same time deciding whether a replica should be retained or deleted (e.g. based on broadcast of the programme and exponentially last access time, access frequency). A minimum set of replicas should be decreases afterwards maintained at all times in order to ensure reliability. A further speed-up of data access exponentially decreases afterwards. This supported within the segment window, as and sharing could be achieved by deploying means that caching a segment with a sliding well as fast forward or rewind (parallel to small caches close to the end user, operating window of several minutes for each current the vertical axis). in a manner analogous to the tsTV proxies. programme can serve a considerable part of all user requests for that programme, from Caching algorithm start to finish, hence the benefit of using Our caching algorithm for tsTV services is distributed streamers with limited storage Use Case: Time-shifted presented in this section. Since we assume capacity. In Figure 5(a) and Figure 5(b) for Television example, user 1 is the first to request a that in general only segments of pro- grammes will be stored, cache sizes can be certain television programme and gets limited to a few gigabytes in stand-alone Concept served from the central server. Afterwards, mode or even less in case of co-operative Time-shifted TV enables the end user to other requesting users (e.g. user 2) can be caching. This way smaller streaming servers watch a broadcast TV programme with a served by the proxy, as long as the window can be deployed closer to the users, without time shift, i.e. the end user can start of the requested programme is still growing. increasing the installation cost excessively. watching the TV programme from the After several minutes, the window stops We virtually split the cache into two beginning although the broadcasting of that growing and begins sliding, so that user 3 parts – a small part S and a main part L. Part programme has started or is even already cannot be served anymore and will be S will be used to cache the first few (e.g. 5) finished. redirected to the (central or regional) server minutes of every newly requested (or As shown in Figure 1, the popularity of or, in case of co-operative caching, to a broadcast) programme, mainly to learn a television programme typically reaches its neighbour proxy with the appropriate about its initial popularity. Its size is peak within several minutes after the initial segment, if present. Pausing (parallel to the generally smaller than 1 GB (typically 1 broadcast of the programme and horizontal axis, Figure 5(b)) can also be hour of streaming content). Part L will be used to actually store the Figure 5 Time-shifted television appropriate segments (with growing or sliding windows). These segments and their Core Network Regional Network Access Network window size are chosen based on local User 1 popularity (especially useful in cases of stand-alone caching), distance from the end Access user (important in cases of co-operative Multiplexer caching) or a combination of both metrics. User 2 Figure 6 shows the basic principle of the tsTV caching algorithm. We assume that all caches know which Access Router segments are stored on the other caches, Central User 3 through a cache state exchange (CSE) Server protocol. Deployment options To demonstrate both deployment options, Edge stand-alone or co-operative caching, Router simulations were performed on the typical (a) Typical Access Network Topology access network topology shown in Figure 5(a). The server offers five popular channels through the tsTV service, each with six programmes of 45 minutes per storage pause evening. User 1 Real-time t_program t_pause The popularity of each programme User 2 Delayed t1 reaches a peak during the first interval (= 5 User 3 Delayed t2 min) after the start, and is halved after each play subsequent interval (similar to Figure 1), so that all requests for each programme are t0 t1 t w t2 made before the programme has ended. t_storage Figure 7 shows the load on the different links between the edge server (ER), the t_viewing access routers (ARs) and the access (b) tsTV Streaming Diagram multiplexers (AMs) from Figure 5(a). In stand-alone mode, requests that cannot be 66 The Journal of The Communications Network • Volume 5 Part 3 • July–September 2006
  5. 5. Developments in Access Technologies to Support New Services Figure 6 Basic principle of the tsTV caching algorithm at each proxy Request for Programme p served by the cache at an AM are forwarded to its AR cache and, if necessary, forwarded to the ER (hierarchical). In co-operative Programme Stored mode, caches are present at the AMs only Locally? (no hierarchical caching), forwarding requests among each other effectively, using No Yes real-time streaming protocol (RTSP) messages7. In co-operative mode, the server load Is it New? Window Appropriate? decreases n times faster than in stand-alone mode without hierarchical caching, where n No Yes No Yes is the number of AM caches (6 in Figure 7). At low cache sizes (<1 GB), the access – Stream from – Stream from – Stream from – Stream Locally network traffic due to the cache co- Other Cache Server Other Cache – Set to ‘Occupied’ operation is relatively high. When using – Update Metric – Cache in S – Update Metric larger caches, this load is reduced as well, since most requests can be served locally. Figure 7 Relative load on the links between ER, AR and AM RTSP proxy A transparent RTSP proxy for time-shifted (upstream and downstream) for hierarchical and TV has been implemented for evaluation co-operative caching purposes. An overview of the performance measurements on an AMD AthlonTM 64 100 processor 3000+ (512 MB RAM) is presented in Wauters et al7. Figure 8 shows ER → AR (Hierarchical) the delay between a PLAY request sent by a 80 PC client and the arrival of the first RTP ER → AR (Co-operative) packet at the PC client, for different AR → AM (Co-operative) configurations (server-proxy-client). Even 60 Requests, % AM → AR (Co-operative) when the proxy has to fetch the content from the server, the delay is never higher 40 than 35 ms (1000 measurements per configuration). When the proxy acts as a mere router, the delay caused by the server 20 is less than 1 ms. The delay on the network links between server, proxy and client is negligible. 0 0 1 2 3 4 Cache Size, GB Conclusions In this article, the necessary transformations in access network architectures for next- Figure 8 Delay between a client request and the actual start of the generation broadband services have been RTP stream on a client PC described. Improved scalability, flexibility and availability can be achieved through the 40 introduction of IP-aware network elements. 30 Minimum Delay when the proxy acts as a Average Delay mere router, the delay Delay, ms Maximum Delay 20 caused by the server is less 10 than 1 ms – the delay on the network links between 0 Content Not Cached at Proxy Content Cached at Proxy Server Only (Proxy Disabled) server, proxy and client is negligible The Journal of The Communications Network • Volume 5 Part 3 • July–September 2006 67
  6. 6. Developments in Access Technologies to Support New Services Due to their significant bandwidth Biographies requirements and steadily rising popularity, IPTV services have been identified as the main trigger for this evolution, offering opportunities for service providers to introduce other value added (interactive) services. One of the most promising IPTV services is time-shifted TV, which can be deployed using diskless distributed caches, effectively offloading the server and Wim Van de transport network. Tim Wauters Meerssche Ghent University Ghent University Acknowledgements Tim Wauters received his MSc degree in Wim van de Meerssche received his MSc This work is partly funded by the IST FP6 electrotechnical engineering (communication degree in software development in 2004 MUSE project. MUSE contributes to the techniques option) in 2001 from the from the University of Ghent, Belgium. In strategic objective ‘Broadband for All’ of IST University of Ghent, Belgium. Since August 2004, he started working on software (Information Society Technologies) and it is September 2001, he has been working on the technologies for access networks in the partially funded by the European Com- design of content distribution and peer-to- Department of Information Technology mission. peer networks in the Department of (INTEC), at the same university. His work Information Technology (INTEC), at the has been published in several scientific same university. His work has been published publications in international conferences. in several scientific publications in wim.vandemeerssche@intec.ugent.be References international conferences and journals. 1 Gilon, E., Van de Meerssche W. et al. tim.wauters@intec.ugent.be Demonstration of an IP Aware Multi-service Access Network. BroadBand Europe 2005, December 2005, Bordeaux, France. 2 Stevens, T., Vlaeminck, K., Van de Meerssche, W., De Turck, F., Dhoedt, B. and Demeester, P. Deployment of service aware access networks through IPv6. 8th International Conference on Telecommunications, ConTEL 2005, Zagreb, Filip de Turck Croatia, June 2005, 1, pp 7–14. Koert Vlaeminck Ghent University Ghent University 3 Mestric, R., Mehdi, S. and Festraets, E. Filip de Turck received his MSc degree in Optimizing the network architecture for triple Electronic Engineering from Ghent Koert Vlaeminck is working as a PhD student play. Alcatel Strategy White Paper, 2005 – http://www.alcatel.com/doctypes/opgrelated in the Broadband Communication Networks University, Belgium, in June 1997. In May information/TriplePlay_wp.pdf lab of the Dept of Information Technology at 2002, he obtained a PhD in Electronic Ghent University, Belgium, from where he Engineering from the same university. From received the MSc degree in Computer October 1997 to September 2001, he was a 4 Comer, D. E. Network System Design using Science Engineering in June 2002. The main research assistant with the Fund for Scientific Network Processors. Pearson Education Inc, focus of his research is on next-generation Research, Flanders, Belgium (FWO-V). At New Jersey, 2004. multi-service access networks. Topics of the moment, he is a part-time professor and interest include the deployment of network a post-doctoral fellow of the FWO-V, processors to increase functional intelligence affiliated to the Department of Information 5 Vitale, T. Digital Imaging in Conservation: File of access nodes and the migration towards Technology of Ghent University. He is author Storage. AIC News, January 2006, 31(1). IPv6. In this respect he has been active in the or co-author of approximately 80 papers EU IST-FP6 project MUSE. He is currently published in international journals or in the working on distributed file systems and data proceedings of international conferences. 6 Saito, Y., Karamanolis, C., Karlsson, M. and replication. His main research interests include scalable Mahalingam, M. Taming aggressive replication in the Pangaea wide-area file system. 5th koert.vlaeminck@intec.ugent.be software architectures for telecommuni- Symposium on Operating System Design and cations network and service management, Implementation (OSDI 2002), December 2002, performance evaluation and optimisation of pp. 15–30. routing, admission control and traffic management in telecommunications systems. filip.deturck@intec.ugent.be 7 Wauters, T. et al. Co-operative Proxy Caching Algorithms for Time-Shifted IPTV Services. 32nd Euromicro Conference, Cavtat/ Dubrovnik, Croatia, August–September 2006. 68 The Journal of The Communications Network • Volume 5 Part 3 • July–September 2006
  7. 7. Developments in Access Technologies to Support New Services Biographies Piet Steven Van Bart Dhoedt Demeester den Berghe Ghent University Ghent University Alcatel R &I Bart Dhoedt received a degree in En- Piet Demeester received a Masters degree in Steven Van den Berghe graduated in gineering from Ghent University in 1990. In electro-technical engineering and a PhD from Computer Science at Ghent University in September 1990, he joined the Department Ghent University, Belgium in 1984 and 1988, 1999. In July of that year he joined the of Information Technology of the Faculty of respectively. In 1992 he started a new Broadband Communication Network Group Applied Sciences, University of Ghent. His research activity on broadband communi- of the Faculty of Engineering at Ghent research, addressing the use of micro-optics cation networks resulting in the IBCN-group University. In 2001 he was granted an IWT to realise parallel free space optical inter- (INTEC Broadband Communications Net- scholarship. He performed research in the connects, resulted in a PhD degree in 1995. work research group). Since 1993 he has area of quality of service, traffic engineering After a 2 year post-doctoral post in opto- been a professor at Ghent University where and monitoring in IP networks, which electronics, he became a professor at the he is responsible for research and education resulted in the award of his PhD on Adaptive Faculty of Applied Sciences, Department of on communication networks. The research Traffic Engineering in 2005. Since 2005 he has Information Technology. Since then, he has activities cover various communication been active in the IBCN research laboratory been responsible for several courses on networks (IP, ATM, SDH, WDM, access, and the IBBT research institute. His main algorithms, programming and software devel- active, mobile), including network planning, topics of interest include design, control and opment. His research interests are software network and service management, telecom management of multimedia networks, and engineering, and mobile and wireless com- software, internetworking, network proto- the application of Internet technologies in munications. His current research addresses cols for QoS support, etc. He is author of niche markets. He has been involved in software technologies for communication more than 400 publications in the area of several European and national research networks, peer-to-peer net-works, mobile network design, optimisation and manage- projects, standardisation bodies and has (co-) networks and active networks. ment. He is member of the editorial board of authored several scientific publications. bart.dhoedt@intc.ugent.be several international journals and has been Steven.Van_Den_Berghe@alcatel.be member of several technical programme com- mittees (ECOC, OFC, DRCN, ICCCN, IZS). piet.demeester@intec.ugent.be Erwin Six Alcatel R&I Tom Van Caenegem Alcatel R&I Erwin Six received his master’s degree in electronic engineering, specialising in telecommunication, from the University of Tom Van Caenegem received an MSc in Ghent, Belgium in 2001. He joined the physical engineering in 1995 and a PhD in Alcatel Research & Innovation (R&I) Center electrotechnical engineering in 2001 from in Antwerp, working as a systems engineer in Ghent University. In 2001 he joined the the access technology group on Passive Optical Access networks group in the Alcatel Optical Networks (PON). Afterwards, as a R&I Center in Antwerp, Belgium. Since 2002, member of the network architecture team, he has been active in systems engineering he helped with the definition of Alcatel's IP specialising in PON access and was involved DSLAM and Home Device Manager product. in the G-PON standardisation. In 2005 he Presently, his research is focused on joined the Network and Services Architecture advanced broadband access equipment subgroup of the R&I Wired Access division, features, for next generation service delivery. where he is involved in IPTV related studies. Erwin.Six@alcatel.be Tom.Van_Caenegem@alcatel.be The Journal of The Communications Network • Volume 5 Part 3 • July–September 2006 69

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