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Virtual LAN (VLAN)
A VLAN is a group of switch ports designated by the switch as belonging to the same broadcast domain. More specifically, VLANs can be seen as a group of end-stations, perhaps on multiple physical LAN segments, which are not constrained by the physical location and can communicate as if they were on a common LAN. This feature allows workgroups to be defined on the basis of their logical function instead of their physical location, and does not require re-cabling. VLAN helps isolate broadcast traffic and increase security, so as to increase bandwidth to each station.
There are four way to define VLAN membership: port grouping, MAC-layer grouping, network-layer grouping, and IP multicast grouping.
Port-Based VLAN (802.1q)
Port grouping is the most common method of defining VLAN membership, and its configuration is straightforward. But, when a user moves from one port to another, it takes a network manager to manually reconfigure VLAN membership. With manual VLAN configuration, the network administrator, enabling a high degree of control, controls both the initial setup and all subsequent moves or changes. Most of OvisLink VLAN switches are compliant with IEE802.1q Port-based VLAN standard.
Trunk (802.3ad)
Trunking is a very useful feature to multiply network bandwidth within your LAN. By establishing a connection that allows network devices to communicate using multiple links in parallel, data can be transferred at multiple bandwidths. For example, Ether-FSH24RS can set up 4-10/100Base ports as a trunking group thus link aggregate becoming 800Mbps.
Class of Service (CoS, 802.1p)
Class of Service applies to traffic prioritization and a small number of individual classes. 802.1p allows users or programs to put priorities (normally two levels: high or low) on a particular network transaction. When network traffic congestion occurs, the data tagged with
"high" priority will get through first. 802.1p also limits the extend of high bandwidth multicast traffic within a bridged LAN. It works in junction with 802.1q VLAN function for tagging and prioritization.
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