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(Revised 2010-9-27) Page 19 of 159
Overview of Advanced Features
Mode of Operation
Each port on the switch can be configured into different modes of operation as shown below:
Copper Ports: 100Base Fiber Ports: 1000Base Copper/Fiber Ports:
- Half Duplex - Full Duplex - Full Duplex
- Full Duplex
- Auto Negotiation
Half Duplex
In half duplex mode, the CSMA/CD media access method is the means by which two or more stations share
a common transmission medium. To transmit, a station waits (defers) for a quiet period on the medium (that
is, no other station is transmitting) and then sends the intended message in bit-serial form. If, after initiating
a transmission, the message collides with that of another station, then each transmitting station intentionally
transmits for an additional predefined period to ensure propagation of the collision throughout the system.
The station remains silent for a random amount of time (back-off) before attempting to transmit again.
Full Duplex
Full duplex operation allows simultaneous communication between a pair of stations using point-to-point
media (dedicated channel). Full duplex operation does not require that transmitters defer, nor do they
monitor or react to receive activity, as there is no contention for a shared medium in this mode.
Auto Negotiation
In Auto Negotiation mode, the port / hardware detects the mode of operation of the station that is connected
to this port and sets its mode to match the mode of the station.
Port Mirroring
A Mirroring Port is a dedicated port that is configured to receive the copies of Ethernet frames that are being
transmitted out and also being received in from any other port that is being monitored.
Port Trunking
Port Trunking is the ability to group two network ports to increase the bandwidth between two machines
(switch or any work station). This feature allows grouping of high-speed connectivity and provides
redundant connection between switches, so that a trunk can act as a single link between the switches.
Quality of Service (QoS)
Quality of service (QoS) refers to resource reservation control mechanisms. Quality of service is the ability
to provide different priority to different applications, users, or data flows. Quality of service guarantees are
important if the network capacity is insufficient, especially for real-time streaming multimedia applications
such as voice over IP, online games and IP-TV, since these often require fixed bit rate and are delay
sensitive, and in networks where the capacity is a limited resource, for example in cellular data
communication. In the absence of network congestion, QoS mechanisms are not required.