Abstract: File sharing systems cause a huge portion of trafﬁc in the Internet. With respect to the peer-to-peer approach, unicast delivery of content is the common case. Unfortunately, an inherent characteristic of ﬁlesharing systems employing unicast communication is that the sum of all download rates cannot exceed the sum of all upload rates. As asymmetric internet connections become increasingly popular, this restriction is clearly noticeable in form of low download rates. Together with the observation that popular ﬁles are requested by many users within a short time frame, this motivates the usage of multicast communication. This paper analyzes the effects of using IP multicast in a ﬁlesharing system.