H3C Technologies H3C WX3000E Series Wireless Switches - Manual (Page 186)

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• Link hold time—An active link remains up within the link hold time, even if the link switch margin is
reached. This mechanism is used to avoid frequent link switch.
• Link saturation RSSI—This is the upper limit of RSSI on the active link. If the value is reached, the
chipset is saturated and link switch will happen.
Formation of dormant links
A train MP performs active scanning to find neighboring rail MPs by sending probe requests at a very
high rate. Based on probe responses received, the train MP forms a neighbor table.
After that, the train MP creates dormant links with rail MPs that have an RSSI value greater than the link
formation RSSI.
Selection of active link
A train MP selects the active link from dormant links based on the following rules:
1. If no dormant link is available, the active link cannot be formed.
2. Active link switch will not happen within the link hold time, except the following two conditions:
{
Condition 1—The active link RSSI exceeds the link saturation RSSI.
{
Condition 2—The active link RSSI is below the link hold RSSI.
3. When the link hold timer expires, if no dormant link has RSSI greater than the active link RSSI by
the link switch margin, link switch will not happen.
4. In normal scenarios, active link switch will happen when all of these following conditions are met:
{
The link hold timer expires.
{
The dormant link's RSSI is higher than the current active link's RSSI by the link switch margin.
{
The dormant link RSSI is not greater than the link saturation RSSI.
{
The RSSI of the new link should be increasing.
5. Once the RSSI of the active and dormant links has gone below the link hold RSSI, links should be
broken. However, to ensure service availability in worse cases, if the active link RSSI has gone
below the link hold RSSI and no dormant links exist, the active link will not be broken.
Protocols and standards
• Draft P802.11s_D1.06
• ANSI/IEEE Std 802.11, 1999 Edition
• IEEE Std 802.11a
• IEEE Std 802.11b
• IEEE Std 802.11g
• IEEE Std 802.11i
• IEEE Std 802.11s
• IEEE Std 802.11-2004
• draft-ohara-capwap-lwapp-03
Introduction to WDS
Wireless distribution system (WDS) provides wireless bridging links between separate LAN segments to
provide connectivity between them.