User's Manual

Figure 4:6 Ethernet Pow er I nserter
WARNI NG: Before connecting the LibraPlus to a power
source, ensure that you are using the correct power supply
for your radio.
4.4 QoS - Quality of Service
In the LibraPlus 5860, Quality of Service (QoS) is achieved through the provisioning of
the WMM (Wireless MultiMedia Extensions). WMM prioritizes traff ic according to four
Access Categories (AC) - voice, video, best effort, and background. WMM creates QoS
for traffic priority management to time-sensitive applications such as voice, video and
multimedia traffic. A WMM based QoS scheme can be further enhanced through the
use of VLAN customer separation.
4.5 VLAN
4.5.1 Overview
By using VLAN, one can logically group networks. Virtual LANs are essentially Layer 2
constructs, whereas IP subnets are Layer 3 constructs. VLANs are created to provide
the segmentation services traditionally provided by routers in LAN conf igurations.
Each VLAN is a logical network, and packets destined for stations that do not belong to
the same VLAN must be forwarded through a routing device like the LibraPlus.
The protocol used in configuring virtual LANs is IEEE 802.1Q. IEEE 802.1Q adds explicit
tagging to ethernet frames. The IEEE 802.1Q header contains a 4-byte tag header
containing a 2-byte tag protocol identif ier (TPI D) and a 2-byte tag control information
(TCI ). The TPI D has a f ixed value of 0x8100 that indicates that the frame carries the
802.1Q/ 802.1p tag information. The TCI contains the following elements:
• Three-bit user priority
• One-bit canonical format indicator (CFI)
• Twelve-bit VLAN identifier (VID) – Uniquely identifies the VLAN to which the
frame belongs
LibraPlus VLAN interfaces always transmit and receive tagged frames. Virtual LANs
operate at Layer 2 (the data link layer) of the OSI model. Each VLAN maps directly to
LibraPlus 5860 User Guide Product Description: QoS - Quality of Service Page 15 of 95