| Epidemic and its variants are one main category of routing protocols in Delay Tolerant Networks (DTNs). They are known to be simple, have low latency and high delivery ratio. However, to date, virtually no work has investigated their suitability in delivering multicast bundles. To this end, we have conducted extensive and comprehensive simulation studies to answer this question. Specifically, we compare their delivery ratio, delay and buffer occupancy level in various multicast scenarios where nodes move according to both Random WayPoint (RWP) model and a trace file containing records of student movements on a campus. Moreover, we tested the influence of key factors such as anti-entropy session, multicast group size, the number of groups and subscribers forwarding policies. We found that, achieving a high delivery ratio is dependent on nodes using anti-entropy session, relay/subscriber ratio and subscribers working as relays. Additionally, we also observed that relay nodes that use epidemic variants experience high buffer occupancy level. In particular, protocols such as epidemic with Encounter Count (EC) result in 100\% buffer utilization. To solve this problem, we propose EC quota, in which bundles can only be transmitted to $k$ relay nodes. Our experiments prove that EC quota is capable of reducing the buffer occupancy level of relay nodes by 15\% to 100\% whilst maintaining high delivery ratios. |