Installation guide

12 ProSwitch
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- Xtreme User’s Manual (Managed Models) Page 10
4.4 VLAN Configuration
4.4.1 Port-Based Virtual LANs (Static VLANs)
A VLAN is a group of ports designated by the switch as belonging to the same broadcast
domain. (That is, all ports carrying traffic for a particular subnet address would normally
belong to the same VLAN.)
The VLAN Configuration submenu allows configuration of up to four port based Virtual
LANs. When VLAN is enabled, a port can communicate with another port only if both are
members of the same VLAN.
The VLAN membership is entered as a port map as a string containing the port numbers.
The system will scan the string and create a port map using the numbers found in the string.
The map can be deleted by entering an empty string. For example, the string 13567, deletes
ports 2,4 and 8.
All ports will return to normal mode of operation when the VLAN operation is disabled. The
VLAN port maps are, however, remembered and can be brought to effect when the VLAN
operation is enabled later.
Note: Maximum four VLANs can be configured.
4.5 Quality of Service Configuration
The Xtreme switch offers Quality of Service (QoS) as specified in IEEE 802.1p standard.
Each port of the Xtreme has a packet buffer into which the packets destined for that port are
placed. The packets in the buffer are then transmitted in a first-in first-out basis. This can
create problems by ‘delaying critical’ traffic like audio and video streaming.
When QoS functionality is enabled, the packet buffer for the ports are divided into two. One
is treated as high priority and the other as low priority. Packets placed in the high priority
buffer will be given preference over those in the low priority buffer for transmission. The
switching engine prioritizes each packet and places it in the appropriate buffer.
The priority of a packet can be decided in two ways. The user can specify a particular port
to be of high/low priority or a particular packet can be marked as high/low priority using a
special tag field inserted into it. The Xtreme switch engine will identify the priority from
these and place the packet in the appropriate buffer.