Building hybrid multicast by combining IP and application layers
Aleksandre Lobzhanidze · 2007
Nowadays, Internet TV (IPTV) is becoming a hot topic and streaming media over the network remains one of the most challenging issues for Internet Service Providers (ISP).Due to the increased number of subscribers for IPTV and other Internet broadcast applications, efficient multicast protocols become more important than ever.Existing multicast protocols have their advantages and disadvantages.IP Multicast is very efficient for multimedia data distribution, but it has deployment issues; most of ISPs do not support IP Multicast.Application Layer Multicast (ALM) is an alternative for content owners, which aims to eliminate the dependency on IP-Multicast enabled routers, but has performance issues.The main drawbacks of ALM are degradation of efficiency (one-tomany delivery function is achieved with multiple unicast calls) and instability (due to the dependency of the distribution trees on end hosts).In this thesis, we propose a strategy that takes advantage of both existing techniques and maximizes the efficiency of resource usage.Our work explores how to build Hybrid Multicast (HM) by combining IP and Application layers.Our goal is to use available resources as much as possible, and provide a reliable solution for multicast applications.HM is a software solution that implements the integration between ALM and IP Multicast.The proposed solution always tries to use IP Multicast capability wherever available; each computer on the hybrid network acts as an agent and is ready to extend the network to those nodes that do not have access to IP Multicast.In Hybrid Multicast, the path from Server to End-Node is built with minimum delay algorithm; HM assigns stability coefficient to each node, and based on bandwidth, delay, processing speed and loss rate, gives priority to those nodes that represent themselves more stable on the hybrid network.Unlike most existing multicast protocols that do not consider node failure in advance, HM adopts a proactive approach in which each node on the network has alternate parents which allow it to switch to backup route quickly and smoothly.HM also provides backup routes for IP Multicast enabled nodes.In addition, HM takes advantage of passive members, which are nodes that run hybrid multicast software, but have not joined any group yet.Simulation results show, that HM performs much better than other multicast protocols.HM distributes the data with smaller delay than ALM, and the recovery time for backup routes in HM is smaller than other multicast protocols.The advantage is generally more significant when the multicast group size is large.