CCDA 640-864 Summary Notes – Chapter 5 – Day 9

Cisco Unified Wireless Network (UWN) architecture – combines wireless and wired network.

Exam Topic 1: Wireless LAN Technologies

WLAN Standards

IEEE 802.11 (Legacy) (1997)

• Speeds of 1 (typical) and 2 (max)  Mbps
• Used direct sequence spread spectrum (DSSS) and frequency-hopping spread spectrum (FHSS) in L1 
  • DSSS divides data into separate sections; each section travels over different frequencies at the same time
  • FHSS sends data in bursts and uses a frequency-hopping sequence  – first frequency 1 then 2 , eventually back to 1.
• Wireless Fidelity (WiFi) is the interoperability certification for 802.11 and is governed by Wireless Ethernet Compatibility Alliance (WECA)
• Uses ISM Frequency

802.11b (1999)

• Maximum Data rate of 11Mbps
• Speeds of 11 (max), 5.5, 2, 1
• Uses 11 channels of the Industrial, Scientific, and Medical (ISM) frequencies
• Uses DSSS
• Backward compartible with 802.11 DSSS  systems
• Uses 2.4 GHz bands
• Typical data rate = 6.5 Mbps
• Most commonly deployed

802.11a (1999) aka WiFi5

• Maximum Data rate of  54 Mbps
• Incompatible with 802.11b and 802.11g
• Speeds of 54 (max), 48,36,24,18,12,9,6 Mbps
• Uses 13 Channels of Unlicensed National Information Infrastructure (UNII) frequencies
• Uses the 5 GHz band
• Typical data rate = 25Mbps

802.11g (2003)

• Max Data rate of 54 Mbps
• Uses 2.4 GHz ISM Frequencies
• Backward compatible with 802.11b
• Typical data rate 25Mbps

802.11n (2009)

• Includes Multiple Input Multiple Output antennas
• Maximum data rate 600Mbps using 4 spatial streams each wik 40 MHz width. The signals are multiplexed by using different spaces within the same spectral channel. These spaces are known as spatial streams.
• Uses DSSS
• Uses orthogonal frequency-division multiplexing (OFDM) as a digital carrier modulation method
• Uses both 2.4GHz and 5GHz bands
• ISM or UNII
• Typical data rate 200 Mbps

ISM and UNII Frequencies

ISM Frequencies

• Set aside by the 5.138 and 5.150 ITU-R radio regulations
• Specified for unlicenced use
• Ranges:
  • 900 MHz to 928 MHz
  • 2.4 GHz to 2.5 GHz
    • 2.4GHz
      • Channels in 2.4 GHz range are used for 802.11b and 802.11g
      • Has 11 overlapping channels
      • Channels 1,6,11 are non overlapping (Pic source: http://wizbiz.co.nz/help/index.php?cat=14)

• 5.75 GHz to 5.875 GHz

Unlicensed National Information Infrastructure UNII Frequencies

• Specified for use with 802.11a
• Provides 12 non overlapping channels for 802.11a
• Ranges:
  • UNII 1: 5.15 GHz to 5.25 GHz and 5.25 GHz to 5.35 GHz
  • UNII 2: 5.47 GHz to 5.725 GHz
  • UNII 3: 5.725 GHz to 5.875 GHz (Overlaps with ISM)

Service Set Identifier (SSID)

• WLANs network name
• 2 to 32 Characters long
• To communicate, all devices must have same SSID
• Equivalent to VLANs in wired networks

WLAN Layer 2 Access Method

Access method used: carrier sense multiple access collision avoidance (CSMA/CA). Each station listens to see whether a station is transmitting or not. If no activity, the station transmits, If activity, station sets random countdown timer. Transmits when the timer expires

WLAN Security

Wired Equivalent Privacy (WEP) Protocol

• Used in 802.11b
• Vulnerable to numerous attacks
• Works at the Data link layer
• Shares the same key for all nodes to communicate

IEEE 802.11i – WiFi Protected Access 2 (WPA2) and Robust Security Network (RSN)

• Supercedes WEP
• Components:
  • 4-Way Handshake and Group Key Handshake
    • Use 802.1X for authentication
  • Robust Security Network (RSN)
    • Establishes security network associations
    • Tracks security network associations
  • Advanced Encryption Standard (AES)
    • Provides Confidentiality, Integrity and Origin authentication

Unauthorized Access

DSSS enables APs to identify WLAN cards via their MAC addresses and this may be a cause of security breach.

MAC addresses can be spoofed hence static assignments and access is unsecure

APs enhance security by:

• Implementing MAC address filtering

Not very scalable and can be hacked. Users can gather a list of the MAC addresses by listening then use the MAC to connect to AP

• Protocol filtering

WLAN Security Design Approach

• Use of EAP-Flexible Authentication via Secure Tunneling (EAP-FAST) to secure authentication
• Use VPN with IPSec to secure traffic from wireless to wired network
• WLANs with IPsec VPN software
• Use IEEE 802.1X-2001 port-based access control protocol
  • Standard for LAns
  • Authenticates users before allowing access to the network
    • Client requests access to services. Send EAP to switch
    • Switch verifies client with the authentication server
    • Server validates client and authorizes client. No encryption provided
• Use WPA

Dynamic WEP Keys

• Per user per session WEP keys for more security

LEAP

• Developed for centralized user-based authentication
• Uses mutual athentication between user and server
• uses IEEE 802.1X for 802.11 authentication
• Can be used with Temporal Key Integrity Protocol (TKIP)
• Uses RADIUS server to manage user info
• combination of 802.1X and EAP
• More scalable than MAC filtering
• Does not support one-time passwords (OTP)

Controlling WLAN Access to Servers

• RADIUS and DHCP servers should be secondary servers and not primary servers
  • Should be in a differentsement (VLAN) from the primary. This way, attacks will be confined to only thisVLAN
    • Access to the VLAn should be filtered
  • Network access to the servers should be controlled.
  • Protect against network attacks
  • Use IDS to detect attacks to these servers