Title: 3.2 Wireless Network Architecture
Course: Information and Communication Technology: Module B > Section: Section 3 - Wireless Technology Basics

3.2.1 Network Architecture

Core, Distribution, and Access are part of a network architecture model for both wired and wireless networks:

- The Core Layer is the high-speed backbone of the network that connects to the Internet. It does not perform complex routing of traffic or manipulate packets. It is responsible for carrying large amounts of data between distribution areas and performing high-speed switching.
- The Distribution Layer provides routing, filtering, and WAN access. It also determines how packets can access the core. Access lists are implemented at this layer. It routes traffic to smaller groups of networks such as VLANs or subnets. Wireless bridging occurs at the Distribution Layer. With lightweight or thin client access points, WLAN controllers may be implemented at the Core or Distribution Layers.

- The Access Layer is responsible for delivery of data to the end user or node. Wireless networking is most often implemented at this layer.

3.2.2 Wireless Network Architecture

This section concentrates on the Access layer and how users connect. There are two wireless modes that devices use to connect: through Infrastructure mode and Ad hoc mode.

Infrastructure mode requires an Access Point (AP), acting as a central control point. An Access Point (AP) is a stand-alone device or part of an integrated service device that controls access between a wired and a wireless network. The AP controls all communications and ensures that all stations have equal access to the medium. Wireless clients, sometimes referred to as hosts or nodes, are commonly referred to as a Station (STA). There are two general architectures used:

- Basic Service Set (BSS)—a set of stations connected to a single access point.
- Extended Service Set (ESS)—a set of interconnected BSSs. This architecture uses multiple APs, each of which is a separate BSS. As stations move out of one BSS and into another, they seamlessly transfer their connections to the new AP. All APs and STAs share the same Service Set Identifier (SSID).

Ad hoc mode is created by connecting clients in a peer-to-peer network. It does not use an AP. Instead, clients connect directly to each other. This architecture is known as an Independent Basic Service Set (IBSS).

A Service Set Identifier (SSID) is an identifier for a single wireless lan (WLAN).  All wireless devices on a single WLAN use the same SSID, and the SSID is in the header of all frames a device transmits.  The SSID is 32 characters long, alphanumeric, and case-sensitive.