ack Box Modular Switches | Installation and User Guide (8/99) |
∙NOTE – some NIC cards only auto-negotiate when the computer system that they are in is powered up. These are exceptions to the “negotiate at LINK – enabled” rule above, but may be occasionally encountered.
When operating in 100Mb half-duplex mode, cable distances and hop-counts may be mited within that collision domain. The Path Delay Value (PDV) bit-times must account for all vices and cable lengths within that domain. For Black Box LE14XXA-Series Fast Ethernet witched ports operating at 100Mb half-duplex, the bit time delay is 50BT.
5 Auto-negotiation for 10 Mb ports, half- or full-duplex mode
Full-duplex Ethernet provides separate Transmit and Receive data paths, enabling multaneous bi-directional collision-free data movements on a port. The network topology must a “star” type, not a “bus” type. With full-duplex mode, the cable distance is only limited by e physical layer line driver and cable attenuation. There are no collision-domain restrictions or mitations.
The LE14XXA-Series Switches perform half- or full-duplex mode auto-negotiation dependently on all switched ports. If the device or node on the other end of a port’s attached ble supports F/H mode auto-negotiation or is set to operate as full-duplex, the 4-Port Switch ill negotiate to run full-duplex. If the attached device or node doesn’t support F/H mode auto- gotiation (for example, if it is a 10 Mb repeater or a standard 10 Mb hub), the 4-Port -Switch’s J-45 ports will default to operate at half-duplex.
6 Flow-control, IEEE 802.3x standard
Black-Box LE14XXA- Series Switches incorporate a flow-control mechanism for Full- uplex mode. The purpose of flow-control is to reduce the risk of data loss if a long burst of tivity causes the switch to save frames until its buffer memory is full. This is most likely to cur when data is moving from a 100Mb port to a 10 Mb port, and the speed difference makes e 10Mb port unable to keep up. It can also occur when multiple 100Mb ports are attempting transmit to one 100Mb port, and in other protracted heavy traffic situations.
LE14XXA-Series Fiber Switches implement the 802.3x flow control (non-blocking) on ull-Duplex ports, which provides for a “PAUSE” packet to be transmitted to the sender when e packet buffer is nearly filled and there is danger of lost packets. The transmitting device is mmanded to stop transmitting into the 4-switch port for sufficient time to let the Switch
