Cross-VLAN Multicast Support in GMRP Protocol
Original Publication Date: 2007-Mar-25
Included in the Prior Art Database: 2007-Mar-25
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As defined in IEEE standard 802.1Q, virtual LANs (VLAN-Virtual Local Area Network) offer a method of dividing one physical network into multiple broadcast domains. VLAN port assignments can be configured either of two ways: As static VLANs configured by an administrator or as dynamic VLANs using a standard protocol, e.g GARP (Generic Attribute Registration Protocol) VLAN Registration Protocol (GVRP). GARP Multicast Registration Protocol (GMRP) is a standard protocol application that provides a constrained multicast flooding facility. GMRP provides a mechanism that allows bridges and end stations to dynamically register group membership information with the MAC (Media Access Control) bridges attached to the same LAN segment and for that information to be disseminated across all bridges in the Bridged LAN that supports extended filtering services. The operation of GMRP relies upon the services provided by the GARP. When a host wants to join an IP (Internet Protocol) multicast group, it sends an IGMP (Internet Group Management Protocol) join message, which spawns a GMRP join message. Upon receipt of the GMRP join message, the switch adds the port through which the join message was received to the appropriate multicast group. The switch propagates the GMRP join message to all other hosts in the VLAN, one of which is typically the multicast source. When the source is multicasting to the group, the switch forwards the multicast only to the ports from which it received join messages for the group. The switch sends periodic GMRP queries. If a host wants to remain in a multicast group, it responds to the query. In this case, the switch does nothing. If a host does not want to remain in the multicast group, it can either send a leave message or not respond to the periodic queries from the switch. If the switch receives a leave message or receives no response from the host for the duration of the leave all timer, the switch removes the host from the multicast group.