Internet Protocol Television (IPTV) systems employ IP multicast to deliver television programs to end-users. To provide reliable IPTV services over the error-prone DSL access networks, a combination of multicast forward error correction (FEC) and unicast retransmissions is employed to mitigate the impulse noise in DSL links. In current systems, the error control function is provided by special retransmission servers. In this work, we propose an alternative distributed solution where the burden

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... f packet loss repair is partially shifted to end-user set-top boxes (STBs). Using a Peer-Assisted Repair (PAR) protocol, we demonstrate how packet repairs can be delivered in a timely, reliable and decentralized manner using the combination of server-peer coordination and redundant repairs. We also show that this distributed protocol can be seamlessly integrated with an application-layer source-aware error protection mechanism called forward and retransmitted Systematic Lossy Error Protection (SLEP/SLEPr). Analysis and simulations show that this joint PAR-SLEP/SLEPr framework not only efficiently improves the resistance to the impulse noise, but also effectively mitigates the bottleneck experienced by the Retransmission Servers, thus greatly enhancing system scalability. Index Terms-IPTV, error-resilient video, impulse noise, peerto-peer, reliable multicast, scalability.