ed in by the TCP/IP stack. This allows a host to monitor several multicast groups at once without receiving an entire general range of MAC addresses. Network adapters in this category use both hardware and software (drivers) to deliver their functionality. Dynamic Management of Group Membership IP multicasting works thanks to an extension of the IP service interface. This extension allows upper layer protocol modules to request that their hosts create, join, confirm ongoing participation in, or leave a multicast group. This process is known as dynamic registration. It is served within the IP module by the Internet Group Management Protocol (IGMP), which was defined by the IETF in RFC 1112. IGMP provides the mechanism by which users can dynamically subscribe and unsubscribe to multicasts. It ensures that multicast traffic is present only on those subnets where one or more hosts are actively requesting it. Using IGMP, hosts inform their network or subnet that they are members of a particular multicast group. Routers use this registration information to transmit, or abstain from transmitting, multicast packets that are associated with specific groups. There are three versions of IGMP. IGMPv2 lets a host tell a router that it no longer wants to receive traffic. The router will stop retransmission of traffic, based on a time- out parameter. This is not possible with IGMPv1. IGMPv3 adds source filtering ("only some" or "all but some" sources) to the host membership protocol. Routers merge requests from different hosts SO that everyone gets at least what they want (but maybe more). IGMP versions one and two attempted to reduce the group- membership protocol traffic by having hosts suppress group memberships that had already been reported. IGMPv3 transfers the burden of merging multiple requests from the hosts to the routers by eliminating the need for suppression by sending reports to the all-routers multicast group. There are three types of reports: current Standards for Conferencing over IP Networks state, filter mode