Dell PowerConnect 55xx Systems User Guide 387FILE LOCATION: C:\Users\gina\Desktop\Checkout_new\Maintenance Projects\DellContax\sources\CxUGSwitching_Ports.fmD E L L C O N F I D E N T I A L – P R E L I M I N A R Y 1 0 / 3 0 / 1 3 - F O R P R O O F O N LYirrelevant. The standard wiring for end stations is known as MDI (MediaDependent Interface), and the standard wiring for hubs and switches is knownas MDIX.Flow ControlThe device supports 802.3x flow control for ports configured to Full Duplexmode. By default, this feature is enabled on all ports, and it can be disabledper port.Flow control creates a lossless link with no packet loss. The flow controlmechanism enables the receiving side to signal to the transmitting side thattransmission must temporarily be halted to prevent buffer overflow. Thissignaling is done by sending PAUSE frames. The ports that receives pauseframes stops transmitting traffic.Flow control on the device works in Receive-Only mode, meaning that theinterfaces with enabled flow control receive PAUSE frames, but do not sendthem.When flow control is enabled, the system buffers are allocated per port sothat if the buffers of one port are consumed, other ports will still have theirfree buffers.Back PressureThe device supports back pressure for ports configured to Half Duplex mode.By default, this feature is disabled, and it can be enabled per port. Theback-pressure mechanism prevents the sender from transmitting additionaltraffic temporarily. The receiver may occupy a link so it becomes unavailablefor additional traffic.Port Default SettingsTable 10-1 describes the port default settings.Table 10-1. Port Default SettingsFunction Default SettingPort speed and mode 10/100/1000 BaseT copper: auto-negotiationSFP+1000/10G Mbps full duplex, auto discoveryPort forwarding state Enabled
