CWSP Guide to Wireless Security
Chapter 6
Enterprise Wireless Hardware Security
Objectives
• List and describe the functions of the different types
of wireless LAN hardware used in an enterprise
• Tell how access control and protocol filtering can
protect a WLAN
• Describe the functions of Quality of Service,
handoffs, and power features of wireless networking
hardware
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Enterprise WLAN Hardware
• Wireless hardware
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Access points
Remote wireless bridges
Wireless routers
Wireless gateways
Wireless switches
Wireless mesh routers
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Access Point
• AP parts
– An antenna and a radio transmitter/receiver to send
and receive signals
– An RJ-45 wired network interface that allows it to
connect by cable to a standard wired network
– Special bridging software to interface wireless devices
to other devices
• Basic functions
– Acts as the base station for the wireless network
– Acts as a bridge between wireless and wired network
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Access Point (continued)
• Range of an access point depends on:
– Type of wireless network that is supported
– Walls, doors, and other solid objects can reduce the
distance the signal may travel
• Number of wireless clients supported varies
– Theoretical: 100 clients
– For light traffic: 50 clients
– For heavy traffic: 20 clients
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Remote Wireless Bridge
• Bridge
– Connects two network segments together
– Segments can use different types of physical media
– Software for transmitting and receiving signals
• Remote wireless bridge
– Wireless device designed to connect two or more
wired or wireless networks
– Transmits at higher power than APs
– Uses a highly directional or semi-directional antenna
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Remote Wireless Bridge (continued)
• Highly directional antennas
– Usually concave, dish-shaped devices used for long
distance, point-to-point wireless links
• Semi-directional antenna
– Focuses the energy in one direction
– Does not have the high power level of a highly
directional antenna
– Primarily used for short- and medium-range remote
wireless bridge networks
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Remote Wireless Bridge (continued)
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Remote Wireless Bridge (continued)
• Delay spread
– Minimizes the spread of the signal so that it can reach
farther distances
• Remote wireless bridges support two types of
connections
– Point-to-point connections
– Point-to-multipoint connections
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Remote Wireless Bridge (continued)
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Remote Wireless Bridge (continued)
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Remote Wireless Bridge (continued)
• Remote wireless bridge modes
– Access point mode
• Standard AP
– Root mode
• Acts as a root bridge and can communicate only with
other non-root bridges
– Non-root mode
• Can transmit only to a root bridge
– Repeater mode
• Extends the distance between LAN segments
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Remote Wireless Bridge (continued)
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Remote Wireless Bridge (continued)
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Remote Wireless Bridge (continued)
• Remote wireless bridges
– Cost-effective alternative to expensive leased wired
options for connecting remote buildings
– Distance can be up to 29 kilometers (18 miles)
transmitting at 11 Mbps
• Or up to 40 kilometers (25 miles) transmitting at 2 Mbps
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Wireless Router
• Router
– Transfers packets between networks
– Selects the best link (route) to send packets
• Wireless router
– Combines an access point with a router
– Typically with multiple ports
• Advantages
– Connects multiple networks
– Improves network performance
– Shares single IP address
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Wireless Router (continued)
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Wireless Router (continued)
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Wireless Gateway
• Gateway
– Acts as an entrance to another network
• Wireless gateway
– Combines an access point, router, network address
translation, and other networking features
• Enterprise wireless gateway functions
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Authentication
Encryption
Intrusion detection and malicious program protection
Bandwidth management
Centralized network management
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Wireless Switch
• Switch
– Joins multiple computers within one LAN
– Contains more “intelligence” than a hub
• Types of switches
– Unmanaged switch
• Provides no management capabilities of the switch
– Managed switch
• Provides all of the features of an unmanaged switch
along with enhanced management features
• Supports both control and monitoring of the network
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Wireless Switch (continued)
• One of the challenges of a wireless LAN in an
enterprise setting
– Integrates management of wired and wireless
networks
• Wireless switch
– Often a rack-mounted unit
– Performs user authentication and encryption
• Thin access point
– Simplified radios with a media converter for the wired
network
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Wireless Switch (continued)
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Wireless Switch (continued)
• Advantages
– Simplified wireless network management
– Eliminates handoff procedures
• Disadvantages
– All thin APs and wireless switches are proprietary
– Thin APs do not provide true convergence of the wired
and wireless networks
• IEEE 802.1v protocol
– Assists the management of WLAN devices
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Wireless Switch (continued)
• IEEE 802.1v protocol features
– Load balancing
– Automatic configuration
– Preserves battery life
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Wireless Mesh Routers
• Limitations of connecting APs to a router via the
wired network
– Placement of APs is limited
– APs have a limited range
• Mesh networks
– Solve these limitations
– Provide multiple paths through which data can travel
– Best example: the Internet
• Wireless mesh network
– Allows for multiple paths for wireless transmissions
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Wireless Mesh Routers (continued)
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Wireless Mesh Routers (continued)
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Wireless Mesh Routers (continued)
• Wireless mesh network types
– Ad hoc wireless mesh network
• Allows greater distances away from the access point
• Each client device can act as a relay station for signals
• Advantages
– Decentralized network
– Can decrease costs
– Can also be reliable
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Wireless Mesh Routers (continued)
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Wireless Mesh Routers (continued)
• Wireless mesh network types (continued)
– Backhaul wireless mesh network
• Connects special access points, known as wireless
mesh routers
– In a mesh configuration
• Provides alternative data paths for the “backside”
connection to the Internet
• Backhaul
– Connection from the routers to the Internet
• Used extensively in outdoor municipal WLANs
• Can be quickly deployed in an emergency
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Wireless Mesh Routers (continued)
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Wireless Mesh Routers (continued)
• No standards exist for wireless mesh networks
– IEEE 802.11s task group is working on standards
• Over 70 different wireless mesh routing protocols
– Differ in the following features:
• Algorithm
• Management data versus transmit data
• Number of radios
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Hardware Security Features
• Features include:
– Controlling access to hardware
– Protocol filtering
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Controlling Access to Hardware
• Access control
– Restricts the user to accessing only the resources
essential for the user to do his or her job
– Limits access to resources based on the users’
identities and their membership in various groups
• Mandatory access control (MAC)
– Most restrictive model
– User is not allowed to give access to another user to
use or access anything on the network
– All controls are fixed in place and there is no flexibility
– Typically used in military environments
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Controlling Access to Hardware
(continued)
• Role based access control (RBAC)
– Administrator assigns permissions to a position (role)
• Assign users and other objects to that role
• Discretionary access control (DAC)
– Least restrictive model
– User can adjust the permissions for other users over
network devices
– Poses risks in that incorrect permissions may be
granted or given
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Controlling Access to Hardware
(continued)
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Protocol Filtering
• Filtering restricts the traffic on a network based on
specific criteria
• Types of filtering
– Address filtering
– Data filtering
– Protocol filtering
• Some access points can be configured to filter
unwanted protocols
– From either entering or leaving the wireless network
• Can only be used in a few specific situations
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Protocol Filtering (continued)
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Other Hardware Features
• Features include:
– Quality of service
– Fast handoff
– Power features
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Quality of Service (IEEE 802.11e)
• IEEE 802.11 standard was intended to be “fair”
– Not appropriate for real-time traffic
• Quality of Service (QoS)
– Capability to prioritize different types of frames
• IEEE 802.11e task group has two new modes of
operation for the 802.11 MAC layer
– Enhanced Distributed Channel Access (EDCA)
– Hybrid Coordination Function Controlled Channel
Access (HCCA)
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Quality of Service (IEEE 802.11e)
(continued)
• Enhanced Distributed Channel Access (EDCA)
– Contention-based
– Supports four different “streams” (types) of traffic
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Voice
Video
Best effort
Background
– Provides relative QoS but cannot guarantee its service
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Quality of Service (IEEE 802.11e)
(continued)
• Hybrid Coordination Function Controlled Channel
Access (HCCA)
– Based upon polling
– Serves as a centralized scheduling mechanism
• Wi-Fi Multimedia (WMM)
– Wi-Fi Alliance’s own QoS specification
– Modeled after a wired network QoS prioritization
scheme
– Subset of IEEE 802.11e
– Defines new Arbitrary Inter-frame Space Number
(AIFSN) and contention window values
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Quality of Service (IEEE 802.11e)
(continued)
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Handoffs
• Inter-Access Point Protocol (IAPP) (IEEE 802.11F)
– 802.11 standard did not specify how communications
were to take place between access points
– 802.11F specified information that access points need
to exchange to support WLAN roaming
• Fast Handoff (IEEE 802.11r)
– VoWLAN mobile phones need fast handoff
– Allows a wireless client to determine the QoS (and
security) being used at a different AP
• Before making the transition
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Power Features
• Dynamic Frequency and Power Control (IEEE
802.11h)
– 802.11h is designed to enable WLAN devices to share
the 5 GHz spectrum
– Mechanisms
• Dynamic frequency selection (DFS)
– Switches the WLAN to another channel if necessary
• Transmit power control (TPC)
– Designed to reduce interference
– Reduces radio transmit power used by devices
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Power Features (continued)
• Power over Ethernet (IEEE 802.3af)
– APs are typically mounted high off the ground
• To reduce interference from surrounding objects
– Electrical power outlets are generally not found in
these locations
– Power over Ethernet (PoE)
• Delivers direct current (DC) to the AP through the
unused wires in a standard UTP Ethernet cable
– End-span
• Ethernet switch that has embedded PoE technology
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Power Features (continued)
• Power over Ethernet (IEEE 802.3af) (continued)
– Failover support
• Has duplicate equipment alongside the main equipment
– Hot standby
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Summary
• Wireless hardware
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Access points
Remote wireless bridges
Wireless routers
Wireless gateways
Wireless switches
Wireless mesh routers
• Access control limits access to resources
– Based on the users’ identities and membership
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Summary (continued)
• Some access points can be configured to filter
unwanted protocols
• The capability to prioritize different types of frames is
known as Quality of Service
• Inter-Access Point Protocol (used in IEEE 802.11F)
sets standards for handoffs between access points
– Fast handoff is based on the IEEE 802.11r standard
• Power management types
– IEEE 802.11h standard
– Power over Ethernet (IEEE 802.3af)
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