Immediate IPTV channel leave by explicit user tracking in PON

Abstract

ABSTRACT In this paper, we propose a novel IPTV channel leave mechanism for Passive Optical Network (PON). By explicit user tracking and automatic differentiation of IGMP v2 and v3 us ers, the proposed mechanism can realize immediate channel leave in both Optical Line Terminal (OLT) and Optical Network Unit (ONU) while avoiding removing the channel which still has users. Simulation results show that the proposed mechanism can significantly save the bandwidth consumption during “channel surf” by users, compared to the standard IGMP timeout mechanism. Keywords: IPTV, IGMP, PON, channel leave 1. INTRODUCTION Internet Protocol Television (IPTV) is a rapidly developing technology for the delivery of broadcast TV and multimedia services over a secure, managed broadband IP network. The advantage of IPTV over traditional cable TV is that it can provide totally different user experience and integrated services of video, data and voice, which can include broadcast TV, video on demand (VOD), interactive multimedia applica tion (e.g. video conference), an d Internet access, etc. IPTV provides telecom operators an opportunity of providing new services through their network and increasing the revenue. Several famous international telecom operators have begun to deploy IPTV services. To guarantee satisfied user experience is crucial for the success of IPTV business. Of the metrics of user experience, channel switch performance is one of the critical issues. Users have been familia r with fast channel switch in cable TV, where channel switch delay could be within 200ms. However in IPTV, if the technology is not properly chosen, the delay could be up to several seconds, which will be very annoying for users. To realize fast channel switch, both fast change to the new channel and fast leave from the original ch annel are important. Currently, the leave latency of one channel in IPTV depends on the timeout mechanism of IGMP (Internet Group Management Protocol). This delay may be long (usually 2~3s), which may lead to concurrent existing of the new requested channel and the slow leaving channel when users are performing “channel surf”, which will lead to bandwidth wasting. Furthermore, if there is some bandwidth constraint for the user, the slow leaving channel might block the joining of the new requested channel, whic h may enlarge the channel change delay. To reduce the leave latency, several fast leave mechanisms have been proposed. In IGMP v2 [1] and v3 [2], one can reduce the timeout value in IGMP to speed up the leaving process. When receiving one IGMP leave message, the router/IGMP proxy can set [Max Response Time] in the query message to a small value (even 0) to force users to send membership reports immediately after the receipt of the query message. Thus the timeout value can be reduced. However, this value can not be set too small considering th e Round Trip Time between the router/ proxy and users, and possible loss of membership reports. All users’ sending report s simultaneously will lead to burst traffic, and high burden of IGMP processing in router/IGMP proxy especially in a large IPTV multicast session. In [3], the improved version of IGMP is proposed. When th e router detects that the network will become congested, it will intelligently select one pending leave group to drop. The prin ciple behind is to make sure the playback of the groups which still have uses by dropping the channel which is the most probable to have no users. But certainly there exists the possibility that some channel having users is incorrectly removed. To realize immediate leave, in [4] and [5], explicit user tracking is used by routers/IGMP proxy or snooping devices to record the user subscription information in every port according to the received IGMP messages. If there is no user for some group in one port according to the user table, that group can be immediat ely removed in that port when necessary without waiting for the expiration of the IGMP timer.