Category 5 cabling is required for 1000Base-T Gigabit Ethernet in order to provide full duplex operation. Full duplex 1000Base-T operation allows simultaneous transmission and reception, both at 1000Mbps, thus providing service potentially equal to 2000Mbps full-duplex service
To provide compatibility in traditional 100Mbps Fast Ethernet environments (where, for example DGE-528T adapters are installed anticipating upgrade of supporting switch equipment to Gigabit Ethernet), the DGE-528T also supports traditional 100Mbps Fast Ethernet operation, in full-duplex as well as half-duplex modes. Selection of the best operation mode in any given installation is automatically governed by auto-negotiation.
About Auto-Negotiation
You have probably had the experience of making a dialup connection through a modem, and have heard the sound exchange between your modem and the modem at the other end of the telephone line. As irritating as those few seconds of noise may be, they do let you know that your modem and the remote modem are on the job, preparing for your intended communication with the remote computer.
When the two modems have tested the phone-line quality and settled on the combination of shared options and parameters which will provide the best data communication over the connecting phone line, then you are given the “connect” message which signals the end of the intermodem negotiation and the beginning of your intended communication with the remote computer.
Auto-negotiation between devices within an Ethernet LAN is similar in concept, but much briefer. The two devices involved in the auto-negotiation will be the DGE-528T Adapter serving your station (installed in your computer), and the switch through which it is connected to the LAN. The options to be negotiated between the DGE-528T and its supporting switch includes Ethernet type (1000BASE-T Gigabit Ethernet or 100BASE-TX Fast Ethernet) and duplex mode (half-duplex, being one-way-at-a-time, or full duplex, being simultaneous transmit-and receive.)
Startup communication between the two devices occurs when both devices are powered up. Once the cable connection and the Network Operating System software is satisfied, the preparatory process of auto-negotiation between the DGE-528T and its supporting switch proceeds automatically. If the switch has auto-negotiation functionality, it and the DGE-528T exchange a series of messages, each device signals its capabilities and listens for corresponding information about the other. The auto-negotiation process requires only a few milliseconds, and the two devices select the best communication parameters supported by both.
If the switch does not support auto-negotiation, the (single capability) message will be recognized by the DGE-528T auto-negotiation facility, which will switch to those settings of its own capabilities, which match that of the switch.
Auto-negotiation reoccurs any time the linkage is restored, making the line ready again for optimal data communications.
About PCI Bus
Your DGE-528T Adapter delivers outstanding performance by fully exploiting the advance features of your computer’s PCI bus. DGE-528T Adapters utilize the Bus Master Mode of the PCI bus, allowing direct transfers of Ethernet packet content between computer memory and the adapter’s controller, thus minimizing network demands on the CPU. The adapter’s controller function provides the additional benefit of reduced command processing overhead.
