If every caller
on one switch tries to place a call to the same far-end switch at the same time, the IMT
would not have enough capacity. Therefore, the IMT can be said to be oversubscribed.
Things are similar in the packet world of Ethernet switches. Take, for example, a simple
Ethernet switch with five 10BaseT ports and one 100BaseT uplink. There is no way
for the 10BaseT ports to overfill the 100BaseT uplink because it always has enough
capacity. If instead the switch had fifteen 10BaseT ports and one 100BaseT uplink, it
would be possible for the client ports to send more data than the uplink could carry,
resulting in network congestion. With simple Ethernet, there is no management of the
traffic. The Ethernet switches essentially work on a first-come, first-served basis. With
the addition of IEEE 802.1q, Ethernet becomes capable of client prioritization. Although
this standard is primarily a definition of VLAN, it also includes 3 bits that can be used
to assign priority to individual Ethernet frames. An IEEE 802.1p-compliant switch uses
these three bits to manage traffic in congestion situations.
The circuit-bonding platform is also capable of oversubscription.
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