D-Link DWS-3024 [230/266] Packet bursting for better performance

D-Link Unified Access System Software User Manual

02/15/2011

Page 230 Document 34CS3000-SWUM104-D10

The random backoff used by the access point is a configurable parameter. To describe the random delay, a “Minimum

Contention Window” (MinCW) and a “Maximum Contention Window” (MaxCW) is defined.

• The value specified for the Minimum Contention Window is the upper limit of a range for the initial random backoff wait

time. The number used in the random backoff is initially a random number between 0 and the number defined for the

Minimum Contention Window.

• If the first random backoff time ends before successful transmission of the data frame, the access point increments a

retry counter, and doubles the value of the random backoff window. The value specified in the Maximum Contention

Window is the upper limit for this doubling of the random backoff. This doubling continues until either the data frame is

sent or the Maximum Contention Window size is reached.

PACKET BURSTING FOR BETTER PERFORMANCE

The D-Link Unified Access System includes 802.11e based packet bursting technology that increases data throughput and

speed of transmission over the wireless network. Packet bursting enables the transmission of multiple packets without the

extra overhead of header information. The effect of this is to increase network speed and data throughput. The size of packet

bursts allowed (maximum burst length) is a configurable parameter.

TXOP INTERVAL FOR CLIENT STATIONS

The Transmission Opportunity (TXOP) is an interval of time when a Wi-Fi Multimedia (WMM) client station has the right to

initiate transmissions onto the wireless medium (WM).

802.1P AND DSCP TAGS

IEEE 802.1p is an extension of the IEEE 802 standard and is responsible for QoS provision. One purpose of 802.1p is to

prioritize network traffic at the data link/ MAC layer.

The 802.1q tag includes a three-bit field for prioritization, which allows packets to be grouped into various traffic classes.

Eight priority levels are defined. The highest priority is seven, which might go to network critical traffic (voice). The lowest

priority level is zero, this is used as a best-effort default, it is invoked automatically when no other value has been set.

<Link>Figure 110 outlines the way in which tags are retrieved and traffic prioritized on a network.

Note: IEEE 802.1 prioritization will not work unless QoS and WMM are enabled. WMM must be enabled on both

the AP and on the client connecting to the AP.