3Com 3CBLSG48 User Guide - Page 223

212 appendix F: gLOSSARY IEEE 802.1X Port Authentication controls access to the switch ports by requiring users to first enter a user ID and password for authentication. IEEE 802.3ac Defines frame extensions for VLAN tagging. IEEE 802.3x Defines Ethernet frame start/stop requests and timers used for flow control on full-duplex links. IGMP Snooping Listening to IGMP Query and IGMP Report packets transferred between IP Multicast Routers and IP Multicast host groups to identify IP Multicast group members. IGMP Query On each subnetwork, one IGMP-capable device can act as the querier - that is, the device that asks all hosts to report on the IP multicast groups they wish to join or to which they already belong. The elected querier is the device with the lowest IP address in the subnetwork. Internet Control A network layer protocol that reports errors in processing IP packets. Message Protocol ICMP is also used by routers to feed back information about better (ICMP) routing choices. Internet Group A protocol through which hosts can register with their local router for Management multicast services. If there is more than one multicast switch/router on Protocol (IGMP) a given subnetwork, one of the devices is made the "querier" and assumes responsibility for keeping track of group membership. In-Band Management Management of the network from a station attached directly to the network. IP Multicast Filtering A process whereby this switch can pass multicast traffic along to participating hosts. IP Precedence The Type of Service (ToS) octet in the IPv4 header includes three precedence bits defining eight different priority levels ranging from highest priority for network control packets to lowest priority for routine traffic. The eight values are mapped one-to-one to the Class of Service categories by default, but may be configured differently to suit the requirements for specific network applications. Layer 2 Data Link layer in the ISO 7-Layer Data Communications Protocol. This is related directly to the hardware interface for network devices and passes on traffic based on MAC addresses.