A LAN is a high-speed data network that covers a relatively small geographic area. It typically connects workstations, personal computers, printers, servers, and other devices using Cat5e or Cat6 cabling. LAN speeds are 100 or 1000Mbps and offer computer users many advantages, including shared access to devices and applications, file exchange between connected users, and communication between users via electronic mail and other applications.

A W-LAN provides the same benefits as a LAN but without the cabling infrastructure. W-LAN can bu used as the entire basic for connectivity or in alliance with an existing LAN. Typically 802.11g is the standard used and this works at up to 54Mbps.
The primary reason for utilising a W-LAN is either:

• Most of your devices are mobile such as laptops and PDA’s and people may need to “hotdesk”.
  
• You cannot cable (i.e. the building is grade 1 listed or preserved)
   

• Client Devices: These connect desktop and mobile devices to the wireless LAN in 802.11b- or 802.11g-compliant networks. Most of today’s laptops are wireless-enabled, and many specialized wireless client devices are now available.
  
• Access Points: These help connect wireless devices to networks, providing ubiquitous network access for many wireless environments.
  
• Mobility Services: A comprehensive wireless network provides built-in support for leading-edge applications such as wireless voice over IP, location services, advanced security, and other emerging technologies.
  
• Security: This must be implemented to keep your LAN secure. The main methods are using encrypted passwords, hiding the SSID (Service Set Identifier) name and MAC address filters which only allow known devices to access the W-LAN

WANs are networks that span the distance between buildings, cities and even countries. WANs are LANs connected together using wide area network services from telecommunications carriers and typically use technologies such as standard phone lines (called POTS (Plain Old Telephone Service)), DSL services (ADSL and SDSL), PSTN (Public Switched Telephone Network)), ISDN (Integrated Services Digital Network), Frame Relay, ATM (Asynchronous Transfer Mode) or other high speed services.

The Self-Defending Network is Cisco's long-term strategy to protect an organization's business processes by identifying, preventing, and adapting to threats from both internal and external sources. This protection helps organizations take better advantage of the intelligence in their network resources, thus improving business processes and cutting costs.

There are three principal characteristics of the Cisco Self-Defending Network:

• The integration of security throughout all aspects of the network
  
• Collaborative processes between the various security and network elements
  
• The ability of the network to adapt to new threats as they arise

The Cisco networked-based strategy allows you to use your existing investment to solve your most pressing security concerns today, while providing an architectural platform that can evolve to proactive, automated, real-time management of threats.