Information Technology Reference
In-Depth Information
Cisco has developed a strategy to address the increasing wireless demands placed on to-
day's networks. The Cisco Unified Wireless Network (UWN) architecture combines ele-
ments of wireless and wired networks to deliver scalable, manageable, and secure WLANs.
Lightweight Access Point Protocol (LWAPP) and Control and Provisioning for Wireless
Access Point (CAPWAP) allow the placement of lightweight access points (LWAP) that are
remotely configured and easily deployable versus them being manually configured on au-
tonomous APs. Cisco provides solutions for client roaming, radio frequency management,
and controller designs that make wireless networks scalable. This chapter covers the Cisco
UWN architecture and general WLAN technologies and design.
This section reviews the Institute of Electronics and Electrical Engineers (IEEE) 802.11
WLAN standards, WLAN frequencies, access methods, security, and authentication.
WLAN Standards
WLAN applications include inside-building access, LAN extension, outside building-to-
building communications, public access, and small office/home office (SOHO) communi-
cations. The first standard for WLANs was IEEE 802.11, approved by the IEEE in 1997.
The current specification is IEEE 802.11-1999, with many amendments thereafter.
Key
To p i c
IEEE 802.11 implemented WLANs at speeds of 1 Mbps and 2 Mbps using direct se-
quence spread spectrum (DSSS) and frequency-hopping spread spectrum (FHSS) at the
physical layer of the Open Systems Interconnection (OSI) model. DSSS divides data into
separate sections; each section travels over different frequencies at the same time. FHSS
uses a frequency-hopping sequence to send data in bursts. With FHSS, some data trans-
mits at Frequency 1, and then the system hops to Frequency 2 to send more data, and so
on, returning to transmit more data at Frequency 1. The interoperability certification for
IEEE 802.11 WLANs is wireless fidelity (WiFi). The Wireless Ethernet Compatibility
Alliance (WECA) governs the WiFi certification.
In 1999, the 802.11b amendment was introduced, providing an 11-Mbps data rate. It pro-
vides speeds of 11, 5.5, 2, and 1 Mbps and uses 11 channels of the Industrial, Scientific,
and Medical (ISM) frequencies. IEEE 802.11b uses DSSS and is backward compatible with
802.11 systems that use DSSS.
The IEEE approved a second standard in 1999. IEEE 802.11a provides a maximum 54-
Mbps data rate but is incompatible with 802.11b. It provides speeds of 54, 48, 36, 24, 18,
12, 9, and 6 Mbps. IEEE 802.11a uses 13 channels of the Unlicensed National Information
Infrastructure (UNII) frequencies and is incompatible with 802.11b and 802.11g. IEEE
802.11a is also known as WiFi5.
-
ible with 802.11b.
