DGS-3024 Gigabit Ethernet Switch Manual
QoS
The DGS-3024 supports 802.1p priority queuing Quality of Service. The following section discusses the implementation of
QoS (Quality of Service) and benefits of using 802.1p priority queuing.
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 excessive bandwidth can be saved. The Switch has separate hardware queues on
every physical port to which packets from various applications can be mapped to, and, in turn prioritized. View the
following map to see how the DGS-3024 implements 802.1P priority queuing.
Figure 7- 38. 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.
For example, lets say a user wishes to have a video conference between two remotely set computers. The administrator can
add priority tags to the video packets being sent out, utilizing the Access Profile commands. Then, on the receiving end, the
administrator instructs the Switch to examine packets for this tag, acquires the tagged packets and maps them to a class
queue on the Switch. Then in turn, the administrator will set a priority for this queue so that will be emptied before any other
packet is forwarded. This results in the end user receiving all packets sent as quickly as possible, thus prioritizing the queue
and allowing for an uninterrupted stream of packets, which optimizes the use of bandwidth available for the video
conference.
Understanding QoS
The Switch has four priority queues. These priority queues are labeled as 3, the highest 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:
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