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D-Link DGS-105/108 Gigabit Ethernet Switch
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If there is no link on a port, such as when there is no computer connected to the port or the connected computer is
powered off, D-Link’s Green Technology will enter a "sleep mode", drastically reducing power used for that port.
• Power saving by cable length: 0~20m, 21~50m.
D-Link’s Green Technology detects the length of connected Ethernet cable and adjusts power usage accordingly
without affecting performance. This way, a port connected to a less than 20m cable only uses as much power as it
needs, instead of using full power, which is only needed for 100m cables.
802.1p and QoS
The DGS-105/108 Switch supports 802.1p priority queuing Quality of Service. The implementation of QoS (Quality of
Service) and benefits of using 802.1p priority queuing are described here.
Advantages of QoS
QoS is an implementation of the IEEE 802.1p standard that allows network administrators a method of reserving
bandwidth for important functions that require a large bandwidth or have a high priority, such as VoIP (voice-over Internet
Protocol), web browsing applications, file server applications or video conferencing. Not only can a larger bandwidth be
created, but other less critical traffic can be limited, so bandwidth can be saved. The Switch has separate hardware queues
on every physical port to which packets from various applications are mapped to and assigned a priority. The illustration
below shows how 802.1P priority queuing is implemented on the Switch. The eight IEEE 802.1P priority levels defined by
the standard are mapped to the four class queues used in the Switch.
Mapping QoS on the Switch
The picture above shows the default priority setting for the Switch. Class-3 has the highest priority of the four priority
queues on the Switch. In order to implement QoS, the user is required to instruct the Switch to examine the header of a
packet to see if it has the proper identifying tag tagged. Then the user may forward these tagged packets to designated
queues on the Switch where they will be emptied, based on priority.
"The DUT support strict mode for 802.1p QoS. The untagged pkt will follow the priority 0 to work (i.e. class 1)."
Understanding QoS
The Switch has four priority queues. These priority queues are labeled as 3, the high queue to 0, the lowest queue. The
eight priority tags, specified in IEEE 802.1p are mapped to the Switch's priority tags as follows:
• Priority 0 is assigned to the Switch's Q1 queue.
• Priority 1 is assigned to the Switch's Q0 queue.
• Priority 2 is assigned to the Switch's Q0 queue.
• Priority 3 is assigned to the Switch's Q1 queue.
• Priority 4 is assigned to the Switch's Q2 queue.
• Priority 5 is assigned to the Switch's Q2 queue.
• Priority 6 is assigned to the Switch's Q3 queue.
• Priority 7 is assigned to the Switch's Q3 queue.
The Switch uses strict priority for Scheduling. Strict priority-based scheduling, any packets residing in the higher priority
queues are transmitted first.