1ad Q-in-Q
Provider bridge
cloud
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802.1ad Q-in-Q
Provider bridge
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Ethernet Bridging 377
Every station had a globally unique 48-bit Media Access Control (MAC) address. It
was up to each station to filter the frames whose destination addresses were of no
interest, i.e., those whose destination address fields contained another station??™s address
or a multicast address that the station was not interested in receiving. Thus,
since Ethernet??™s beginnings, both unicast (the destination address corresponds to a
particular station) and multicast (the destination address corresponds to some subset
of stations or to all stations) frames have been an essential part of the service offered
by a LAN. So has the notion that the service offered by an Ethernet LAN (the ???MAC
service???) is one of getting a message to at least the station(s) to whom it is addressed,
not necessarily to just those stations.
The need to concatenate two or more coaxial trunk cables economically into what,
to the connected stations, appeared to be a single trunk cable, arose almost instantly.
The bridge, standardized by IEEE Std 802.1D, was one result1.
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