Most of the traffic in a broadcast video cable network is directed downstream to the user. Conventional bidirectional links do not optimize bandwidth allocation to match the bandwidth requirements of this mostly one-way traffic flow. In addition, the bidirectional nature of ports requires a port to receive data from the same port that it transmits data to. This behavior quickly consumes port resources without using them effectively.
You can conserve port resources and address the bandwidth requirements by implementing unidirectional links in the network.
Physical interfaces operate in bidirectional mode by default, both transmitting and receiving traffic. When you configure unidirectional mode on the interface, two new physical interfaces are automatically created. One interface, designated by -tx in the interface name, can only transmit traffic. The other interface, designated by -rx in the interface name, can only receive traffic. The parent physical interface is still present, but you effectively see a port with two unidirectional links. Figure 9 illustrates the unidirectional nature of the new interfaces.
Figure 9: Unidirectional Link Behavior
You can configure unidirectional mode on a per-port basis on the 10-Gigabit Ethernet interfaces of the 4-port 10-Gigabit Ethernet DPC on the MX960 Ethernet Services Router only. You can configure both unidirectional and bidirectional ports on a single DPC.
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