Juniper Networks 10.4

•bridge—Anetworkcomponent defined by the IEEE that forwards framesfrom one LAN

segmentor VLAN to another. The bridging function can be containedin a router, LAN

switch,or other specialized device. See also switch.

•bridgedomain—A set of logical ports that share the same floodingor broadcast

characteristics.Asin a virtual LAN, a bridge domain spans one or more ports of multiple

devices.By default, each bridge domain maintains its ownforwarding database of

MACaddresseslearned from packets receivedon ports belonging to that bridge domain.

Seealsobroadcast domain and VLAN.

•B-TAG—Afielddefined in the IEEE 802.1ah provider MAC encapsulation header that

carriesthe backbone VLAN identifier information. The format of the B-TAGfield is the

sameas that of the IEEE 802.1ad S-TAGfield. See also S-TAG.

•B-VID—Thespecific VLAN identifier carried in a B-TAG.

•CFM—Connectivity-faultmanagement.The part of Ethernet OAM thatmonitors events

atlevels above the physicallevel, as does LFM. See also OAM,LFM, and ETH-DM.

•CIST—Commonand Internal Spanning Tree.The single spanning tree calculatedby

thespanning tree protocol (STP) and the rapid spanning tree protocol(RSTP) and

thelogical continuation of that connectivity throughmultiple spanning tree (MST)

bridgesand regions, calculatedto ensure that all LANs in the bridged LAN are simply

andfully connected. See also MSTI.

•ETH-DM—EthernetFrame Delay Measurements. See alsoOAM,CFM, and Y.1731.

•Ethernet—Aterm loosely applied toa family of LAN standards based on the original

proprietaryEthernet from DEC, Intel, and Xerox(DIX Ethernet), and the open

specificationsdeveloped by the IEEE 802.3 committee(IEEE 802.3 LANs). In practice,

fewLANs comply completelywith DIX Ethernet or IEEE 802.3.

•IRB��Integratedbridging and routing. IRB provides simultaneoussupport for Layer 2

bridgingand Layer 3 routing within the same bridge domain. Packetsarriving on an

interfaceof the bridge domain are Layer 2 switchedor Layer 3 routed based on the

destinationMAC address. Packetsaddressed to the router's MAC address are routed

toother Layer 3 interfaces.

•I-SID—The24–bit service instance identifier fieldcarried inside an I-TAG. The I-SID

definesthe service instance to which the frame is mapped.

•I-TAG—Afielddefined in the IEEE 802.1ah provider MAC encapsulation header that

carriesthe service instance information (I-SID) associatedwith the frame.

•learningdomain—AMAC address databasewhere the MAC addresses are added based

onthe normalized VLAN tags.

•LFM—Linkfault management. A method used to detectproblems on links and spans

onan Ethernet network defined in IEEE 802.3ah. See also OAM.

•MSTI—MultipleSpanningTree Instance. One of a number of spanning trees calculated

byMSTP within an MST region. TheMSTI provides a simple and fully connectedactive

topologyfor frames classified asbelonging to a VLAN that is mapped to the MSTI by

theMST configuration table used bythe MST bridges of that MST region. See also

CIST.

Junos10.4 MX Series Ethernet ServicesRouters Solutions Guide