201 Certified Wireless Network Professional :: CWNA-109 Interframe Space Delay Extended interframe space (EIFS) – used with frame corruption Arbitration interframe space (AIFS) – used by QoS stations DCF interframe space (DIFS) – lowest priority Short interframe space (SIFS) – second highest priority Reduced interframe space (RIFS) – highest priority DIFS – before data frames AIFS – before QoS data frames SIFS – before ACK frames and other rapid delivery frames EIFS – used for frames transmitted after receiving a corrupted frame
202 Certified Wireless Network Professional :: CWNA-109 Backoff Timer Contention Window (CW) – A range of numbers from which stations randomly select a back off value in the range of 0 to CWmin on initial frame transmission. Random Backoff – The number randomly chosen from the CW. This number determines how long (in slots) the wireless medium (WM) must be idle before a STA can transmit. 0 15 CW 0 31 CW 802.11a/g/n/ac 802.11b and DSSS
203 Certified Wireless Network Professional :: CWNA-109 DCF Overview • Time required to transmit a frame • Listen before you talk • Time between transmissions • Variableness for relatively fair access to the medium Random Back-off Interframe Space Duration/ID Carrier Sense Data Ack Time SIFS Duration
204 Certified Wireless Network Professional :: CWNA-109 RTS/CTS RTS CTS
205 Certified Wireless Network Professional :: CWNA-109 Channel Width Operations 20 MHz Channel Primary Channel Secondary Channel HT (802.11n) Channel Widths Single Channel Bonded Channel 20 MHz Channel Primary Channel Primary Channel 40 MHz Channel 80 MHz Channel VHT (802.11ac) Channel Widths
206 Certified Wireless Network Professional :: CWNA-109 Legacy Power Management Active mode • Radio is on all the time Power Save mode • Radio sleeps • Client notifies AP of sleep state
207 Certified Wireless Network Professional :: CWNA-109 Automatic Power Save Delivery (APSD) Scheduled (S-APSD) • Not commonly implemented Unscheduled (U-APSD) • The basis of WMM-Power Save (WMM-PS)
208 Certified Wireless Network Professional :: CWNA-109 Chapter 9: WLAN Network Architectures Objectives Covered: 4.3 Define and describe controller-based, distributed, cloud-based, and controller-less WLAN architectures 4.4 Define and describe multiple channel architecture (MCA) network model and contrast it with a single channel architecture (SCA) model
209 Certified Wireless Network Professional :: CWNA-109 Control, Management and Data Planes Control – operations and infrastructure Management – configuration and monitoring Data – user data
210 Certified Wireless Network Professional :: CWNA-109 Centralized Data Forwarding
211 Certified Wireless Network Professional :: CWNA-109 Core, Distribution and Access Layer Forwarding Core – all data goes to the network core and is forwarded out from there Distribution – all data goes to the network distribution layer and is forwarded out from there Access layer – also called edge forwarding – all data goes to the access/layer or edge controller and is forwarded out from there
212 Certified Wireless Network Professional :: CWNA-109 Distributed Data Forwarding
213 Certified Wireless Network Professional :: CWNA-109 WLAN Controller Solutions MAC Functions (Controller) MAC Functions (AP) 802.11 authentication Beacons 802.11 association Probe Responses 802.11 reassociation Ack and Block Ack 802.1X/EAP MAC encryption/decryption (may be performed in the controller to prevent exploits at the AP) WLAN controller-based APs typically implement a split-MAC model. Part of the MAC is in the controller and part of it is in the AP
214 Certified Wireless Network Professional :: CWNA-109 +1 N Scalability and Availability Solutions Primary Controller Primary Controller Primary Controller Secondary or Backup Controller
215 Certified Wireless Network Professional :: CWNA-109 GRE/CAPWAP Tunnel Tunneling 802.11 Frames 802.11 Frames Vendors use different tunneling methods: CAPWAP LWAPP GRE
216 Certified Wireless Network Professional :: CWNA-109 Virtual Local Area Networks (VLANs) SSID: CORP01 VLAN: 40 SSID: GUEST VLAN: 60 SSID: CORP02 VLAN: 80 SSID: CORP01 VLAN: 40 SSID: GUEST VLAN: 60 SSID: CORP02 VLAN: 80 5 GHz Radio 2.4 GHz Radio
217 Certified Wireless Network Professional :: CWNA-109 Intra- and Inter-Controller STA Roaming IntraController InterController
218 Certified Wireless Network Professional :: CWNA-109 Cloud-Based Model AP management and control in the cloud Local GRE tunnel servers for centralized data may be available Initial cloud connection required for setup Cloud failure does not equal WLAN failure Monitoring and statistics available in the cloud
219 Certified Wireless Network Professional :: CWNA-109 Distributed Model Aerohive is a well-known distributed model WLAN vendor They call it cooperative control APs cooperate with each other in the control plane Hive Manager administers the management plane Data plane is distributed forwarding
220 Certified Wireless Network Professional :: CWNA-109 Controller-Less (Autonomous) Model Direct configuration or through a WNMS Control/data planes in the AP Management plane in the AP or WNMS
221 Certified Wireless Network Professional :: CWNA-109 RF Channel Planning Multiple Channel Architecture (MCA) • Most common model • Staggered channels throughput • Channel selection and AP placement important Single Channel Architecture (SCA) • Single channel throughout • Centralized control of AP transmissions • Multiple channel layers may be used
222 Certified Wireless Network Professional :: CWNA-109 BSSID and ESS Configuration MCA • One BSSID per SSID on the radio • ESS is formed when multiple APs share: SSID Security configuration Distribution system media SCA • Virtual BSSID spans multiple APs • ESS is handled through perception of a single BSS by clients
223 Certified Wireless Network Professional :: CWNA-109 AP Placement
224 Certified Wireless Network Professional :: CWNA-109 Channel Selection
225 Certified Wireless Network Professional :: CWNA-109 Cell Sizing Output power AP placement Attenuation factors
226 Certified Wireless Network Professional :: CWNA-109 Co-Channel Interference 100 mW Output Power 20 mW Output Power 5 APs
227 Certified Wireless Network Professional :: CWNA-109 Chapter 10: WLAN Requirements and Solutions Objectives Covered: 4.1 Identify technology roles for which WLAN solutions are appropriate and describe the typical use of WLAN solutions in those roles 4.5 Match WLAN deployment requirements commonly specified to technology solutions 4.6 Determine and document required network services supporting the WLAN
228 Certified Wireless Network Professional :: CWNA-109 Corporate Data Access Ensure sufficient coverage in needed areas Ensure sufficient throughput Ensure proper security Ensure availability Ensure end-user mobility
229 Certified Wireless Network Professional :: CWNA-109 Enterprise Network Extension Ensure efficient spectrum utilization Ensure sufficient throughput for the link Ensure proper security for the link Utilize mesh networking when available
230 Certified Wireless Network Professional :: CWNA-109 Small Office/Home Office (SOHO) Ensure cooperative frequency usage Ensure proper security Ensure proper selection and placement of potential interferers Cordless phones Microwave ovens Video camera systems HP printers SONOS with hidden SSIDs
231 Certified Wireless Network Professional :: CWNA-109 Mobile Offices
232 Certified Wireless Network Professional :: CWNA-109 Educational/Classroom Ensure proper filtering technology is used Ensure proper security is used
233 Certified Wireless Network Professional :: CWNA-109 Industrial
234 Certified Wireless Network Professional :: CWNA-109 Healthcare Building materials Specialty devices Security regulations
235 Certified Wireless Network Professional :: CWNA-109 Hospitality
236 Certified Wireless Network Professional :: CWNA-109 High Density Scenarios High density in corporate spaces Large public venues (LPV) • Conference and convention facilities • Arenas and stadiums
237 Certified Wireless Network Professional :: CWNA-109 Transportation Networks Uplink connections Coverage Capacity User bandwidth throttling
238 Certified Wireless Network Professional :: CWNA-109 Law Enforcement Networks
239 Certified Wireless Network Professional :: CWNA-109 Last-Mile Data Delivery Wireless ISP (WISP) • Ensure sufficient throughput • Ensure proper installation location • Ensure the proper service-level agreement is in place
240 Certified Wireless Network Professional :: CWNA-109 WLAN Bridging Ensure proper antenna alignment Ensure proper line of sight Ensure protected installations are used
241 Certified Wireless Network Professional :: CWNA-109 Hotspots Ensure proper separation from the internal network Ensure payment processing is confidential Ensure the user understand the terms of service
242 Certified Wireless Network Professional :: CWNA-109 Application Demands Data Voice Video Real-Time Location Services (RTLS)
243 Certified Wireless Network Professional :: CWNA-109 Highly Mobile Devices Tablets and smartphones Push-to-talk VoIP handsets
244 Certified Wireless Network Professional :: CWNA-109 BYOD and Guest Access BYOD considerations • Security • Applications Guest access considerations • Network segregations • VLANs • Captive portals
245 Certified Wireless Network Professional :: CWNA-109 Mobile Device Management (MDM) Functional for enterprise and BYOD devices Centralized management • Devices • Applications • Configurations • Functionality May be provided by WLAN vendors May function as an overlay
246 Certified Wireless Network Professional :: CWNA-109 Network Access Control (NAC)
247 Certified Wireless Network Professional :: CWNA-109 Radio Resource Management (RRM) and Adaptive Radio Management (ARM) Automatic channel selection Automatic output power selection Based on neighbor feedback Centrally gathered for decision analysis
248 Certified Wireless Network Professional :: CWNA-109 Band Steering 2.4 GHz Probe Request 5 GHz Probe Request 5 GHz Probe Response No Response
249 Certified Wireless Network Professional :: CWNA-109 Fundamental Network Services Dynamic Host Configuration Protocol (DHCP) Domain Name System (DNS) Network Time Protocol (NTP)
250 Certified Wireless Network Professional :: CWNA-109 Security-Related Network Services RADIUS VLANs Access Control Lists (ACLs)