What is the Distribution System?
A key logical and architectural component of IEEE 802.11 (Wi-Fi) wireless networks is the Distribution System (DS). Large, intricate, and flawless wireless networks require it.
Definition of Distribution System
The DS is the logical component that acts as the backbone of the IEEE 802.11 standard, connecting several Basic Service Sets (BSSs) to create an Extended Service Set (ESS). All communication between the different wireless architecture components that do not share the same BSS is handled by the DS.
The DS serves as a Wireless Local Area Network’s (WLAN) backbone or wired backbone architecture. Among its principal functions are:
- Connecting Access Points (APs): The DS serves as a logical and physical link between several APs.
- Interconnecting BSSs: It makes it possible for several Basic Service Sets (BSSs), which are the distinct wireless cells that each AP creates, to communicate with one another.
- Forming an ESS: An Extended Service Set (ESS) is created when two or more BSSs are connected via a common DS.
Essentially, the DS is in charge of moving data across wired and wireless networks. It serves as the central connection between these two network components.
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Key Functions and Capabilities
Important functions required for growing and overseeing a sizable Wi-Fi network are offered by the DS:
- Uplink and Connectivity: To uplink into an Ethernet network, an AP employs the DS. The complete wireless network (the ESS) is connected to the internet and other wired corporate networks via the DS.
- Data Movement and Translation: Data can travel between APs or between APs and the wired network, the DS. The task of converting frames between 802.3 Ethernet and 802.11 wireless protocols falls to an AP that is connected to the DS.
- Roaming and Mobility Support: By offering the services required to manage address mapping and the smooth integration of several BSSs, the DS facilitates mobility. As a result, client devices (stations) can move freely across AP coverage zones without losing their IP address or connection. The APs must be connected by the DS and often have the same Service Set Identifier (SSID) in order for this roaming capability to function.
- AP Communication: Access Points communicate with one another about hosts in their respective coverage areas via the DS.
Implementation of the Distribution System
The physical attributes of the DS have no bearing on the architecture of the IEEE 802.11 WLAN:
- Typical Implementation (Wired): The DS is usually implemented as a wired network, like an Ethernet LAN, which provides high speed and dependability. The DS is already installed in the majority of commercial APs, allowing for a direct connection to a wired network like Ethernet.
- Wireless Implementation: Although this frequently leads to decreased throughput, the DS can also be implemented as a Wireless Distribution System (WDS), connecting the APs over wireless links. The DS can be LAN or WAN, wired or wireless.
Distribution System in Centralized Architectures (WLCs)
The idea of the DS is expanded to particular ports on the Wireless LAN Controller (WLC) in centralized wireless systems that make use of one:
- Distribution System Ports: WLCs have a number of Distribution System Ports that need to be connected to the network. The point where APs theoretically touch the DS is shifted upstream to the WLC in a split-MAC design.
- Traffic Handled: The majority of standard AP traffic, management traffic (SSH, SNMP, TFTP), and client data are carried via these ports. Additionally, they carry the control and data CAPWAP tunnels that reach every AP.
- Configuration: Distribution System Ports always function in 802.1Q trunking mode since they transport data linked to numerous Virtual LANs (VLANs). For load-balancing, they can be set up in redundant pairs or combined into a single logical entity, like a Link Aggregation Group (LAG).
Distinction from the Distribution Layer
It is important to distinguish the Distribution System (DS) used in wireless (802.11) networking from the Distribution Layer used in wired LAN/WAN architectural models:
| Term | Context | Primary Function |
|---|---|---|
| Distribution System (DS) | Wireless (802.11) | The wired Ethernet backbone used to connect Access Points (APs) and move traffic between the wireless and wired portions of the network. |
| Distribution Layer | Wired Campus LAN Design | The layer that aggregates access switches, provides connectivity, handles routing and policy, but does not connect directly to end-user devices. |
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