Wireless LAN

Foundation Concepts and Design

Types of Wireless Networks

• Personal Area Network (PAN)
• Local Area Network (LAN)
• Metropolitan Area Network (MAN)
• Wide Area Network (MAN)

Wireless LAN Facts

• A Wireless Access Point (WAP) communicates like a hub
  • Shared signal
  • Half duplex
• Uses unlicensed bands of radio frequency (RF)
• Wireless is a physicall and data link standard
• Uses CSMA/CA instead of CSMA/CD
• Faces connectivity issues because of interference

Understanding the SSID

• The Service Set Identifier (SSID) uniquely identifies and seperates wireless networks
• When a wireless client is enabled:
  1. Client issues a proble
  2. Access Point(s) respond with a beacon
  3. Client associates with chosen SSID
  4. Access Point adds client MAC to association table

Correct Design of a WLAN

• RF service areas should have 10-15% overlap
• Repeaters should have 50% overlap
• Bordering access points should use different channels

Client Roaming

• As more mobile devices are released, client roaming becomes a big deal
• True roaming allows seamless movement between access points
• Not a feature 'Joe-Shmo' access points can support
• Provides solid coverage and better battery life
• Can be costly

Two Flavors or Roaming

Layer 2 Roaming

Requirement: same SSID, same VLAN, same Subnet

Layer 3 Roaming (AKA Mobile IP)

Requirement: same SSID

How a Client Roams

• Beacons are missed
• Data reaches maximum retry count
• Data rate shifts down
• Periodic intervals

Wireless VLAN Support

Multiple VLANs provide support for:

• Multiple security levels
• Multiple subnets
• Multiple access privileges

Frequencies and 802.11 Standards

Unlicensed Frequencies

• 900MHz Range: 902 - 928
• 2.4GHz Range: 2.400 - 2.483
• 5GhZ Range: 5.150 to 5.350

Understanding RF

• RF waves are absorbed (passing through walls) or reflected (by metal)
• Higher data rates have shorter ranges
• Higher frequencies of RF have higher data rates
• Higher frequencies of RF have shorter ranges

The 802.11 Lineup

• 802.11b
  • Official as of september 1999
  • up to 11 mbps (1, 2, 5.5, 11 data rates)
  • most popular standard
  • three 'clean' channels
• 802.11g
  • Official as of june 2003
  • Backwards compatible with 802.11b
  • Up to 54 Mbps (12 data rates)
  • Three 'clean' channels
• 802.11a
  • Official as of september 1999
  • Up to 54 Mbps
  • Not cross-compatible with 802.11b/g
  • 12 to 23 'clean' channels

Wireless Range

• The further you go, the lower your speed
• Example: 802.11g does 54Mbps if you're 40ft from the AP
• Example: 802.11a does 54Mbps if you're 20 from the AP
• Example: 802.11b does 11Mbps if you're 110ft from the AP

Wireless LAN Security

• Wireless has added a whole new paradigm to security
• The wireless security evolution:
  • 1997 - Wired Equivalent Privacy (WEP)
  • 2001 - 802.1x EAP
  • 2003 - Wi-Fi protected Access (WPA)
  • 2004 - IEEE 802.11i (WPA2)

Understanding the Hardware

Understanding the AP Categories

• Autonomous APs
  • Stand alone system
  • Cisco IoS-based
  • Can be centrally controlled using Wireless Domain Services (WDS)
  • Managed using Ciscoworks WLAN Solution Engine (WLSE)
• Lightweight APs
  • Server-dependant system
  • Zero-configuration access points
  • Can be centrally controlled using Wireless LAN Controller (WLC)
  • Managed using Cisco Wireless Control System (WCS) - optional

Understanding Lightweight Access Points

• Lightweight Access Point Protocol (LWAPP) used between controller and WAPs
• Controller has all the intellegence for communication
• Access point acts as "dumb terminal" that processes packets
• Referred to as "split mac" design

Wireless LAN Controllers

• 2100 series controller
  • Designed for SMB
  • Currently supports up to 6 access points
• 4400 series controller
• 4402 supports 12, 25, or 50 access points
• 4404 supports 100 access points

Cisco Wireless Indoor Access Points

• 1130AG
  • Indoor design
  • Slick, glowing plastic enclosure
  • Designed for cubicle/office environment
• 1240AG
  • Indoor design
  • Durable metal enclosure
  • Handle larger temperature swings
  • Manufacturing, warehouses, etc
• 1300 series
  • Outdoor design
  • your typical "put it there, get wireless" sort of AP
  • Handles outdoor temperatures (-22 to 131)
  • Can be configured as a bridge
• 1400 series
  • Outdoor design
  • Point-to-point or multipoint bridging
  • Handles outdoor temperatures
  • 8.5 mile (p2p) pr 2.75 mile (p2m) range

Power Over Ethernet

• Two Standards:
  • 802.3af
  • Cisco proprietary PoE
• Comes in many forms
  • Cisco PoE switches
  • Switch router cards
  • SOHO firewalls and routers
  • Power patch panel
  • Inline power injector

Understanding Antennas

• Omni-Directional Antenna: Provides even spread of wireless signal in a radius around the access point
• Directional Antenna: Allows you to point antennas to get more radius and range in a specific direction
• Yagi Antenna: Provides dual adjustments of direction and focus. The more streamlined focus gets intense reach/range.