L2 Features; Vlan - D-Link DGS-3600 Series User Manual

L2 Features

VLAN

Trunking
IGMP Snooping
MLD Snooping
Spanning Tree
Forwarding & Filtering
LLDP
The following section will aid the user in configuring security functions for the Switch. The Switch includes various functions for
VLAN, Trunking, IGMP Snooping, Spanning Tree, and Forwarding & Filtering, and LLDP, all discussed in detail in the
following section.
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 also allows further tailoring of how priority tagged data packets are handled on your network. Using queues to
manage priority tagged data allows users 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 recommended 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.
VLAN Description
A Virtual Local Area Network (VLAN) is a network topology configured according to a logical scheme rather than the physical
layout. VLANs can be used to combine any collection of LAN segments into an autonomous user group that appears as a single
LAN. VLANs also logically segment the network into different broadcast domains so that packets are forwarded only between
ports within the VLAN. Typically, a VLAN corresponds to a particular subnet, although not necessarily.
VLANs can enhance performance by conserving bandwidth, and improve security by limiting traffic to specific domains.
A VLAN is a collection of end nodes grouped by logic instead of physical location. End nodes that frequently communicate with
each other are assigned to the same VLAN, regardless of where they are physically on the network. Logically, a VLAN can be
equated to a broadcast domain, because broadcast packets are forwarded to only members of the VLAN on which the broadcast
was initiated.
xStack DGS-3600 Series Layer 3 Gigabit Ethernet Managed Switch
Section 7
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