xStack
®
DGS-3200 Series Layer 2 Gigabit Ethernet Managed Switch
53
Egress Filter Settings
Users can configure an egress filter on specific ports for unknown unicast and unregistered multicast packets.
The Switch drops all unknown unicast/multicast packets on egress ports when it detects unknown unicast/multicast packets for
egress ports. Therefore, a user can select which port is permitted or not permitted to receive unknown unicast/multicast packets.
To view the following window, click
Layer 2 Features
>
Egress Filter Settings
:
Figure 3 - 2. Egress Filter Settings window
The following fields can then be set:
Parameter Description
Unicast
Select ports to filter unknown unicast packets. These packets will not be forwarded to those
ports. Unselected ports will not filter unknown unicast packets and the packets may be forwarded
to those ports.
Multicast
Select ports to filter unregistered multicast packets. These packets will not be forwarded to those
ports. Unselected ports will not filter unregistered multicast packets and the packets may be
forwarded to those ports.
Click
Apply
to implement changes made.
802.1Q VLAN
Understanding IEEE 802.1p Priority
Priority tagging is a function defined by the IEEE 802.1p standard designed to provide a means of managing traffic on a network
where many different types of data may be transmitted simultaneously. It is intended to alleviate problems associated with the
delivery of time critical data over congested networks. The quality of applications that are dependent on such time critical data,
such as video conferencing, can be severely and adversely affected by even very small delays in transmission.
Network devices that are in compliance with the IEEE 802.1p standard have the ability to recognize the priority level of data
packets. These devices can also assign a priority label or tag to packets. Compliant devices can also strip priority tags from
packets. This priority tag determines the packet’s degree of expeditiousness and determines the queue to which it will be assigned.
Priority tags are given values from 0 to 7 with 0 being assigned to the lowest priority data and 7 assigned to the highest. The
highest priority tag 7 is generally only used for data associated with video or audio applications, which are sensitive to even slight
delays, or for data from specified end users whose data transmissions warrant special consideration.
The Switch allows you to further tailor how priority tagged data packets are handled on your network. Using queues to manage
priority tagged data allows you to specify its relative priority to suit the needs of your network. There may be circumstances where
it would be advantageous to group two or more differently tagged packets into the same queue. Generally, however, it is rec-
ommended that the highest priority queue, Queue 7, be reserved for data packets with a priority value of 7. Packets that have not
been given any priority value are placed in Queue 0 and thus given the lowest priority for delivery.
Strict mode and weighted round robin system are employed on the Switch to determine the rate at which the queues are emptied of
packets. The ratio used for clearing the queues is 4:1. This means that the highest priority queue, Queue 7, will clear 4 packets for
every 1 packet cleared from Queue 0.
Remember, the priority queue settings on the Switch are for all ports, and all devices connected to the Switch will be affected.
This priority queuing system will be especially beneficial if your network employs switches with the capability of assigning
priority tags.
