With the advent of wireless networks come the challenges of making them work. As traditional wired networks evolved, so did the technologies that they were built upon. Both physically and logically, these "old school" networks began featuring more efficient, less expensive hardware and software for easier and more efficient physical and logical connections.

Since the early days, networking has come a long way. We are currently in the midst of a wireless revolution that has been highlighted by both office and home networks moving to wireless technologies. The reason for this transformation parallels the same reason for updating earlier networks from coax to cat 5 and cat 5 to fiber. Ultimately the profile of technology will reflect the new standards being developed. In the case of wireless networking there are several new areas to consider, including topologies. The following section will explain the newest wireless topologies that are being used as the foundation for wireless networking.

Infrastructure Mode vs. Ad Hoc Mode

Traditional wired networks can be implemented in one of two ways: either as a peer-to-peer network or as a client server network. Wireless networking features comparable profiles known as Infrastructure Mode and Ad-Hoc Mode.

• Ad-Hoc Mode
  
  Ad-Hoc Mode the simplest Wireless LAN (WLAN) topology. Unlike Infrastructure Mode, Ad-Hoc Mode is more common amongst home users.

Ad-Hoc Mode does not require an access point, therefore making it possible for two wireless devices to communicate directly with one another, essentially forming a wireless, peer-to-peer network. For an Ad-Hoc mode to function properly, all of the nodes must be within range of each other. If all nodes are not within range of each other, some nodes will be able to see other nodes but not all nodes.

• Infrastructure Mode
  
  Infrastructure Mode, also known as an Infrastructure Basic Service Set (BSS), requires a network infrastructure based around Wireless Access Points (WAP) to be in place in order for users to take advantage of file-sharing, network printers, and other network resources. In Infrastructure Mode, the wireless nodes must communicate through the Access Point. The nodes cannot communicate directly as in the Ad-Hoc mode. Infrastructure Mode WLANs are most often connected to a wired LAN via a WAP, but they can also function independent of a wired LAN.

An Extended Service Set (ESS) refers to multiple Basic Service Sets working together to form a single network. The multiple Basic Service Sets are connected via a wired network. The wired network is called a Distribution System (or DS) in an ESS.

Infrastructure Mode vs Ad-Hoc Mode

Generally speaking both Ad-Hoc and Infrastructure Mode wireless networks architectures have advantages and disadvantages.

	Infrastructure Mode	Ad-Hoc Mode
TCO		X
Security	X
Ease of Implementation		X
Performance	X
Access	X
Management	X

Bridged Mode

Bridged Mode refers to a wireless networking solution that is implemented when a company wants to extend a wired LAN using WAPs.

To best explain bridged mode it is necessary to understand why it was developed.

Problem:

Abc, Inc. has just moved into a new office complex in suburban Denver. The office complex consists of two buildings. Currently, each building is wired with its own LAN. Abc, Inc. wishes to join the two LANs into one, but unfortunately the size of their office complex makes running cables (whether copper or fiber optic) between the two buildings a costly proposition.

To solve this problem, Abc, Inc. has decided to use wireless bridging. The wired network in each building is connected to a WAP. The WAPs are positioned so they are in range of each other (for example, mounted outside the buildings). This mode is appropriately named because it is literally bridges the gap that exists between the two areas.

Repeater Mode

Repeater Mode is used to extend the range of a Wireless LAN.

Problem:

This wireless network is in a large warehouse. The management staff is situated on the east wing of the building and the sales staff is on the west wing. In between is a large manufacturing floor. The distance between the east wing and the west wing is too great and the WLANs cannot communicate with each other. WAPs, in repeater mode, can be used to fill this gap. In repeater mode, the WAP simply rebroadcasts the signal it receives, extending the range of the network.