本文說明排除無線吞吐量問題時需要考慮的常見問題。本文包括使用工具來測量無線網路的效能和吞吐量,其中包括在類似測試條件下與Cisco 1252 AP進行比較的不同供應商802.11n接入點(AP)。
思科建議您瞭解以下要求:
工具(如iPerf)和網路分析器(如OmniPeek和Cisco Spectrum Analysis)
支援802.11n的1140、1250、3500和1260系列AP
本文中的資訊係根據以下軟體和硬體版本:
運行軟體版本6.0.182的WS-SVC-WiSM控制器
AIR-LAP1142-A-K9 AP
如需文件慣例的詳細資訊,請參閱思科技術提示慣例。
802.11n產生的原因是對接入點幀聚合進行了大量更改:A-MPDU和A-MSDU。
塊確認大小
MCS和通道繫結
MIMO
在2.4 GHz上使用5 GHz:另外還提到Wi-Fi在5GHz上認證通道繫結
請完成以下步驟:
驗證控制器上是否已啟用802.11n支援。
(WiSM-slot3-2) >show 802.11a 802.11a Network.................................. Enabled 11nSupport....................................... Enabled 802.11a Low Band........................... Enabled 802.11a Mid Band........................... Enabled 802.11a High Band.......................... Enabled 802.11a Operational Rates 802.11a 6M Rate.............................. Mandatory 802.11a 9M Rate.............................. Supported 802.11a 12M Rate............................. Disabled 802.11a 18M Rate............................. Supported 802.11a 24M Rate............................. Mandatory 802.11a 36M Rate............................. Supported 802.11a 48M Rate............................. Supported 802.11a 54M Rate............................. Supported 802.11n MCS Settings: MCS 0........................................ Supported MCS 1........................................ Supported MCS 2........................................ Supported MCS 3........................................ Supported MCS 4........................................ Supported MCS 5........................................ Supported
N速率有兩種方式。無需使用通道繫結即可達到調制編碼方案(MCS)7的速度。對於高於7且高達15的MCS速率,需要啟用通道繫結。您可以在控制器上使用以下show指令驗證是否已啟用通道粘合:
(WiSM-slot3-2) >show advanced 802.11a channel Automatic Channel Assignment Channel Assignment Mode........................ AUTO Channel Update Interval........................ 600 seconds [startup] Anchor time (Hour of the day).................. 0 Channel Update Contribution.................... SNI. Channel Assignment Leader...................... 00:1d:45:f0:d2:c0 Last Run....................................... 371 seconds ago DCA Sensitivity Level.......................... STARTUP (5 dB) DCA 802.11n Channel Width...................... 40 MHz Channel Energy Levels Minimum...................................... unknown Average...................................... unknown Maximum...................................... unknown Channel Dwell Times Minimum...................................... unknown Average...................................... unknown Maximum...................................... unknown 802.11a 5 GHz Auto-RF Channel List Allowed Channel List......................... 36,40,44,48,52,56,60,64,149, 153,157,161 Unused Channel List.......................... 100,104,108,112,116,132,136,
您也可以使用以下命令配置每個AP的通道寬度:
(WiSM-slot2-2) >config 802.11a disable AP0022.9090.8e97 (WiSM-slot2-2) >config 802.11a chan_width AP0022.9090.8e97 40 Set 802.11a channel width to 40 on AP AP0022.9090.8e97
Guard間隔和相應的MCS速率有助於確定802.11n客戶端上顯示的資料速率。以下是驗證此組態的命令:
(WiSM-slot3-2) >show 802.11a 802.11a Network.................................. Enabled 11nSupport....................................... Enabled 802.11a Low Band........................... Enabled 802.11a Mid Band........................... Enabled 802.11a High Band.......................... Enabled 802.11a Operational Rates 802.11a 6M Rate.............................. Mandatory 802.11a 9M Rate.............................. Supported 802.11a 12M Rate............................. Disabled 802.11a 18M Rate............................. Supported 802.11a 24M Rate............................. Mandatory 802.11a 36M Rate............................. Supported 802.11a 48M Rate............................. Supported 802.11a 54M Rate............................. Supported 802.11n MCS Settings: MCS 0........................................ Supported MCS 1........................................ Supported MCS 2........................................ Supported MCS 3........................................ Supported MCS 4........................................ Supported MCS 5........................................ Supported MCS 6........................................ Supported MCS 7........................................ Supported MCS 8........................................ Supported MCS 9........................................ Supported MCS 10....................................... Supported MCS 11....................................... Supported MCS 12....................................... Supported MCS 13....................................... Supported MCS 14....................................... Supported MCS 15....................................... Supported 802.11n Status: A-MPDU Tx: Priority 0............................... Enabled Priority 1............................... Disabled Priority 2............................... Disabled Priority 3............................... Disabled Priority 4............................... Disabled Priority 5............................... Disabled Priority 6............................... Disabled Priority 7............................... Disabled Beacon Interval.................................. 100 CF Pollable mandatory............................ Disabled CF Poll Request mandatory........................ Disabled --More-- or (q)uit CFP Period....................................... 4 CFP Maximum Duration............................. 60 Default Channel.................................. 36 Default Tx Power Level........................... 1 DTPC Status..................................... Enabled Fragmentation Threshold.......................... 2346 Pico-Cell Status................................. Disabled Pico-Cell-V2 Status.............................. Disabled TI Threshold..................................... -50 Traffic Stream Metrics Status.................... Disabled Expedited BW Request Status...................... Disabled World Mode....................................... Enabled EDCA profile type................................ default-wmm Voice MAC optimization status.................... Disabled Call Admission Control (CAC) configuration Voice AC - Admission control (ACM)............ Enabled Voice max RF bandwidth........................ 75 Voice reserved roaming bandwidth.............. 6 Voice load-based CAC mode..................... Enabled Voice tspec inactivity timeout................ Disabled Video AC - Admission control (ACM)............ Disabled Voice Stream-Size............................. 84000 Voice Max-Streams............................. 2 Video max RF bandwidth........................ Infinite Video reserved roaming bandwidth.............. 0
確保A-MPDU資料包聚合。為盡最大努力,可通過以下命令啟用QoS級別:
config 802.11a 11n支援a-mpdu tx priority 0 enable
config 802.11b 11n支援a-mpdu tx priority 0 enable
必須使用A無線電上的所有三個天線。確保天線型號相同。
在為客戶端連線配置的WLAN上,應該允許或需要WMM,且只能使用AES或開放加密。可以使用以下命令輸出驗證這一點:
(WiSM-slot2-2) >show wlan 1 WLAN Identifier.................................. 1 Profile Name..................................... wlab5WISMip22 Network Name (SSID).............................. wlab5WISMip22 Status........................................... Enabled MAC Filtering.................................... Disabled Broadcast SSID................................... Enabled AAA Policy Override.............................. Disabled Network Admission Control NAC-State...................................... Disabled Quarantine VLAN................................ 0 Number of Active Clients......................... 0 Exclusionlist Timeout............................ 60 seconds Session Timeout.................................. 1800 seconds CHD per WLAN..................................... Enabled Webauth DHCP exclusion........................... Disabled Interface........................................ management WLAN ACL......................................... unconfigured DHCP Server...................................... Default DHCP Address Assignment Required................. Disabled Quality of Service............................... Silver (best effort) WMM.............................................. Allowed CCX - AironetIe Support.......................... Enabled CCX - Gratuitous ProbeResponse (GPR)............. Disabled CCX - Diagnostics Channel Capability............. Disabled Dot11-Phone Mode (7920).......................... Disabled Wired Protocol................................... None IPv6 Support..................................... Disabled Peer-to-Peer Blocking Action..................... Disabled Radio Policy..................................... All DTIM period for 802.11a radio.................... 1 DTIM period for 802.11b radio.................... 1 Radius Servers Authentication................................ Global Servers Accounting.................................... Disabled Local EAP Authentication......................... Disabled Security 802.11 Authentication:........................ Open System Static WEP Keys............................... Disabled 802.1X........................................ Disabled Wi-Fi Protected Access (WPA/WPA2)............. Enabled WPA (SSN IE)............................... Disabled WPA2 (RSN IE).............................. Enabled TKIP Cipher............................. Disabled AES Cipher.............................. Enabled Auth Key Management 802.1x.................................. Enabled PSK..................................... Disabled CCKM.................................... Disabled FT(802.11r)............................. Disabled FT-PSK(802.11r)......................... Disabled FT Reassociation Timeout......................... 20 FT Over-The-Air mode............................. Enabled FT Over-The-Ds mode.............................. Enabled CKIP ......................................... Disabled IP Security................................... Disabled IP Security Passthru.......................... Disabled Web Based Authentication...................... Disabled Web-Passthrough............................... Disabled Conditional Web Redirect...................... Disabled Splash-Page Web Redirect...................... Disabled Auto Anchor................................... Disabled H-REAP Local Switching........................ Enabled H-REAP Learn IP Address....................... Enabled Infrastructure MFP protection................. Enabled (Global Infrastructure MFP Disabled) Client MFP.................................... Optional Tkip MIC Countermeasure Hold-down Timer....... 60 Call Snooping.................................... Disabled Band Select...................................... Enabled Load Balancing................................... Enabled
天線分集:如果由於任何原因僅使用兩個天線,則需要對發射器/接收器埠使用天線A和B。
在客戶端:
用於控制無線卡的請求方,首選將請求方的供應商與無線卡匹配。
客戶端驅動程式:您需要確保無線卡上運行最新的客戶端驅動程式。
請與無線介面卡供應商聯絡。
確保使用11n認證介面卡來獲得11n資料速率。
Wi-Fi認證產品:
http://www.wi-fi.org/certified_products.php
如何提高效能:
通道利用率 — 網路分析器報告通道利用率,以傳送和接收幀所花費時間的百分比表示。這有助於測量由於距離接入點距離而產生的潛在速度差異。這將有助於監控和檢視通道是否完全被佔用,例如,在理想條件下以1Mbps的速率傳輸,在100%的利用率下將以0.94Mbps的速度執行。
無線中使用的物理介質也決定了效能。使用802.11g或802.11a over 802.11b可提供高得多的吞吐量,通常在802.11b上最高可達30 mbps,其中6mpbs的無線電容量被分配給所有相關的站點。
單元格大小 — 建議縮小單元格大小,以使客戶端儘可能靠近AP。這將有利於客戶端連線到AP的資料速率。這可以通過將AP上的電源級別降至最低來實現。
縮小信元大小也能減少同通道干擾。如果使用RRM,AP應該根據部署動態選擇通道。但是,如果實施動態通道分配,請確保同一通道上不存在兩個功率級別較高的AP,並且這兩個接入點彼此緊鄰在一起。
保護也會導致吞吐量命中。
對於不擁有Chariot的客戶或測試者,可以使用Iperf。可從http://www.macalester.edu/crash/software/pc/iperf/kperf_setup.exe獲取該資訊。
在伺服器端運行此命令:
Iperf –s -w 256k
在客戶端運行此命令:
Iperf –c-P 6 –w 256k -r –t 60
此影象中的第一個圈數字表示上游吞吐量,第二個圈數字表示下游(AP到客戶端)吞吐量。
關閉伺服器和客戶端上先前的Iperf應用程式。兩者都需要重新設定,但這次是為了進行UDP效能測試。
在伺服器端運行此命令:
Iperf –s -u –l 56k
在客戶端運行此命令:
Iperf –c-u –b 50M –l 56k –P
以下是Omnipeek捕獲分析聚合MAC服務資料單元的示例:
A-MSDU跟蹤顯示一個資料包
僅顯示第一個子幀。
需要檢查十六進位制轉儲以檢視其他子幀。
A-MPDU是一種包含多個MPDU的結構,由PHY作為單個PSDU傳輸。
在物理層融合過程(PLCP)中指示資料包為資料A-MPDU。
以下是Omnipeek捕獲分析聚合MAC協議資料單元的示例:
A-MPDU設定
ADDBA — 新增塊確認
ADDBA Request — 包含識別符號、塊確認策略、緩衝區大小等。
ADDBA Response — 可以更改策略和緩衝區大小。
A-MPDU設定
ADDBA請求
AP1250使用零超時來指示無超時。
A-MPDU設定
ADDBA響應
接收方需要指示已成功建立塊確認協定。
A-MPDU資料傳輸
塊確認包含壓縮點陣圖,指示已接收的MPDU。
有關傳送塊確認的資訊,請參閱IEEE 802.11n第9.10.7節「HT-immediate Block Ack extensions」。
信標中通告的功能:
信標中通告的功能:
與為A-MPDU新增塊確認設定的關聯相似:
修訂 | 發佈日期 | 意見 |
---|---|---|
1.0 |
10-Dec-2013 |
初始版本 |