5
Category 5 cabling is required for
1000
Base-T
Gigabit
Ethernet in order to provide full duplex
operation
. Full duplex 10
0
0Base-T operation allows simultaneous transmission and reception,
both at
1
0
00Mbps, thus providing service potentially equal to 2
0
00Mbps full-duplex service
To provide compatibility in traditional
100
Mbps
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
100
Mbps
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
(100
0
BASE-T
Gigabit
Ethernet or 10
0
BASE-T
X
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.
