3Com 2916-SFP User Guide - Page 185

Electrical 185 Electrical Line Frequency Input Voltage Current Rating Switch 2916-SFP Plus Switch 2924-SFP Plus Maximum Power Consumption Switch 2916-SFP Plus Switch 2924-SFP Plus Max Heat Dissipation Switch 2916-SFP Plus Switch 2924-SFP Plus 50/60 Hz 100-240 Vac (auto range) 1 Amp (Max) 1.5 Amp (Max) 58 Watts 84 Watts 198 BTU/hr 286 BTU/hr Switch Features This section describes the device features. The system supports the following features: Table 11 Features of the Baseline Switch 2916-SFP Plus and Switch 2924-SFP Plus Feature Auto Negotiation Automatic MAC Addresses Aging Back Pressure Description The purpose of auto negotiation is to allow a device to advertise modes of operation. The auto negotiation function provides the means to exchange information between two devices that share a point-to-point link segment, and to automatically configure both devices to take maximum advantage of their abilities. Auto negotiation is performed totally within the physical layers during link initiation, without any additional overhead to either the MAC or higher protocol layers. Auto negotiation allows the ports to do the following: ■ Advertise their abilities ■ Acknowledge receipt and understanding of the common modes of operation that both devices share ■ Reject the use of operational modes that are not shared by both devices ■ Configure each port for the highest-level operational mode that both ports can support MAC addresses from which no traffic is received for a given period are aged out. This prevents the Bridging Table from overflowing. On half duplex links, the receiver may employ back pressure (i.e. occupy the link so it is unavailable for additional traffic), to temporarily prevent the sender from transmitting additional traffic. This is used to prevent buffer overflows.