This can ease congestion
and help a roaming STA transition from one access point in the system to another without
losing network connectivity.
An ESS introduces the possibility of forwarding traffic from one BSS to another over
the wired network. This combination of APs and the wired network connecting them is
referred to as the distribution system (DS). Messages sent from a wireless device in one
BSS to a device in a different BSS by way of the wired network are said to be sent by way
of the DS.
The 802.11 WLAN standards attempt to ensure minimum disruption to data delivery,
and provide some features for caching and forwarding messages between BSSs. The
802.11i revision provides some support for optional fast transitions for stations moving
between BSSs within a single ESS. Particular implementations of some higher layer
protocols such as TCP/IP may be intolerant of dropped and restored connections. For
example, in a network where DHCP is used to assign IP addresses, a roaming node may
lose its connection when it moves across cell boundaries and have to reestablish it when it
enters the next BSS or cell.
Additional specifications are also being developed, including 802.
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