Configuring WLAN optimization· 1

Overview·· 1

Rejecting wireless clients with a low RSSI 1

Ignoring weak signals 1

Configuring A-MPDU suppression· 2

Configuring channel sharing adjustment 2

Configuring channel reuse adjustment 3

Disabling multicast and broadcast buffering· 3

Configuring packet-based TPC·· 4

Triggering client reconnection· 4

Enabling the AP to receive all broadcast packets 4

Configuring roaming navigation· 5

Configuring client-type-based rate limiting· 5

Setting the maximum transmission times for probe responses 5

Setting the maximum interference threshold· 6

Enabling hidden node protection· 6

Setting the noise floor threshold· 6

WLAN optimization configuration examples 7

Optimizing an 802.11ac WLAN·· 7

Optimizing some APs in a WLAN·· 7

 

Overview

Channel planning and power control policies during WLAN deployment are important for good performance. However, in live WLANs, channel overlapping, collisions, and interference can easily occur because the non-overlapping channels are limited but the number of WLAN devices increases.

You can configure WLAN optimization features to improve the quality and stability of live WLANs.

A feature applied in different WLANs might have different effects because there are many factors impacting WLAN performance.

There is no fixed combination of features for optimizing a specific WLAN. Select the features that are most suitable for your WLAN.

WLAN optimization cannot significantly improve the performance of a WLAN. In practice, if the features can improve the WLAN performance by 3%, the optimization is determined to be successful.

Rejecting wireless clients with a low RSSI

Wireless clients with a low received signal strength indicator (RSSI) cannot get good service or performance but occupy wireless resources, especially when they are downloading a large amount of data. This might affect clients with a high RSSI.

Perform this task to configure the AP to reject clients whose RSSI is lower than the specified RSSI.

To reject wireless clients with a low RSSI:

 

Step	Command	Remarks
1.       Enter system view.	system-view	N/A
2.       Configure the AP to reject wireless clients whose RSSI is lower than the specified RSSI.	wlan option client-reject rssi [ 2g | 5g ]	By default, the AP does not reject wireless clients with a low RSSI.

 

Ignoring weak signals

When the AP detects weak signals from a remote client, it determines that the channel is occupied and does not forward other packets.

This feature can avoid the impact of weak signals by enabling the AP to ignore packets whose signal strength is lower than the specified RSSI.

This feature increases the forwarding rate of the AP but might cause interference or collisions with other devices working on the same channel.

To ignore weak signals:

 

Step	Command	Remarks
1.       Enter system view.	system-view	N/A
2.       Configure the AP to ignore signals weaker than the specified RSSI.	wlan option signal-ignore rssi [ 2g | 5g ]	By default, the AP does not ignore weak signals.

 

Configuring A-MPDU suppression

An A-MPDU can accommodate multiple MPDUs and use only one PHY header. This reduces the transmission overhead and the number of ACKs and improves network throughput. However, the MPDU aggregation capability of 802.11n and 802.11ac clients might affect the performance of 802.11gn, 802.11g, and 802.11b clients.

Perform this task to specify the threshold for the number of aggregated MPDUs and the threshold for the A-MPDU length. If either threshold is reached, the AP stops MPDU aggregation and sends the A-MPDU.

To configure A-MPDU suppression:

 

Step	Command	Remarks
1.       Enter system view.	system-view	N/A
2.       Configure A-MPDU suppression.	wlan option dot11n-restraint packet-number max-packets packet-length max-length [ 2g | 5g ]	By default, A-MPDU suppression is disabled.

 

Configuring channel sharing adjustment

The non-overlapping channels in a WLAN are limited. For example, 802.11g has only three non-overlapping channels. Therefore, the AP can easily detect other APs working on the same channel, especially in a high-density WLAN. Channel overlapping causes collisions and interference and reduces WLAN performance. Channel planning and power control policies during WLAN deployment are the major methods to avoid channel overlapping. In addition, you can perform this task in a live network to reduce the impacts of channel overlapping.

If the AP detects signals stronger than the specified power level, the AP determines that the channel is occupied and does not send packets. If the detected signals are weaker than the specified power level, the AP sends the packets. This mechanism avoids collisions and interference.

To enable channel sharing adjustment:

 

Step	Command	Remarks
1.       Enter system view.	system-view	N/A
2.       Enable channel sharing adjustment and set the power level.	wlan option channel-share power-level [ 2g | 5g ]	By default, channel sharing adjustment is disabled. Do not enable channel sharing adjustment and channel reuse adjustment at the same time.

 

Configuring channel reuse adjustment

 

	IMPORTANT: ·      Do not enable channel sharing adjustment and channel reuse adjustment at the same time. ·      Enabling channel reuse adjustment might result in increased hidden nodes.

 

WLAN devices within a space share the same media. They use collision avoidance and contention mechanisms to send frames over channels. When the number of devices working on a channel increases, the whole WLAN performance degrades. To solve the problem, make channel planning and power control policies before WLAN deployment. In addition, you can perform this task in a live network to improve the performance of APs that works on the same channel.

The AP ignores packets with an RSSI that is lower than the specified reuse level to get more radio resources and higher speed.

To enable channel reuse adjustment:

 

Step	Command	Remarks
1.       Enter system view.	system-view	N/A
2.       Enable channel reuse adjustment and set the reuse level.	wlan option channel-reuse reuse-level [ 2g | 5g ]	By default, channel reuse adjustment is disabled.

 

Disabling multicast and broadcast buffering

If one of the clients associated with the AP is in sleep state, the AP buffers all broadcast and multicast packets before it sends the next beacon frame. This affects the performance of multicast applications.

Perform this task to disable multicast and broadcast buffering. The AP directly sends all broadcast and multicast packets regardless of whether an associated client is in sleep state.

You can set the power management parameter to the maximum value on wireless clients to prevent them from entering sleep state.

Disabling multicast and broadcast buffering improves multicast performance in specific scenarios such as multicast-based training, but clients in sleep state will lose some broadcast and multicast packets.

This feature is not applicable to 5 GHz radios of 802.11ac APs.

To disable multicast and broadcast buffering:

 

Step	Command	Remarks
1.       Enter system view.	system-view	N/A
2.       Disable multicast and broadcast buffering.	undo wlan option broadcast-buffer enable [ 2g | 5g ]	By default, multicast and broadcast buffering is disabled.

 

Configuring packet-based TPC

The AP typically uses a high and fixed transmit power to cover an area as large as possible. This is not energy saving.

Perform this task to enable the AP to dynamically perform transmit power control (TPC) on a per packet basis. For example, the AP reduces the transmit power when it sends packets to a client with a high RSSI. This reduces power consumption, radiation, and interference and improves user experience.

This feature is not applicable to 5 GHz radios of 802.11ac APs.

To configure packet-based TPC:

 

Step	Command	Remarks
1.       Enter system view.	system-view	N/A
2.       Enable per-packet TPC based on packet loss rate.	wlan option tpc enable [ 2g | 5g ]	Use either method. By default, packet-based TPC is disabled.
3.       Enable per-packet TPC based on signal strength of clients.	wlan option tpc [ rssithreshold rssithreshold | rssistep rssistep | powerstep powerstep | minpower minpower ] * enable [ 2g | 5g ]

 

Triggering client reconnection

This feature enables the AP to automatically send deauthentication frames to a client when the signal strength of the client is lower than the specified RSSI. Then the client can reconnect to the AP or roam to another AP.

To trigger client reconnection:

 

Step	Command	Remarks
1.       Enter system view.	system-view	N/A
2.       Enable the AP to trigger reconnection for clients whose signal strength is lower than the specified RSSI.	wlan option client-reconnect-trigger rssi signal-check [ 2g | 5g ]	By default, the AP does not trigger client reconnection.

 

Enabling the AP to receive all broadcast packets

This feature enables the AP to detect spoofing attacks for all BSSs.

Enable this feature only when necessary because receiving all broadcast packets affects the operation of the AP.

This feature is not applicable to 5 GHz radios of 802.11ac APs.

To enable the AP to receive all broadcast packets:

 

Step	Command	Remarks
1.       Enter system view.	system-view	N/A
2.       Enable the AP to receive all broadcast packets.	wlan option rx-broadcast-all enable [ 2g | 5g ]	By default, the AP does not receive all broadcast packets.

 

Configuring roaming navigation

802.11 protocols do not provide any client roaming control mechanisms. Roaming navigation enables clients to roam to the AP with better signal strength to enhance user experience.

To configure roaming navigation:

 

Step	Command	Remarks
1.       Enter system view.	system-view	N/A
2.       Configure roaming navigation.	wlan option roam-navigation level level [ rssi client-level ] [ 2g | 5g ]	Optional. By default, roaming navigation is disabled.

 

Configuring client-type-based rate limiting

Perform this task to limit the rate of the specified type of clients to avoid bandwidth consumption caused by low performance clients. For example, to ensure better experience of 802.11n clients, you can restrict the rate of 802.11g or 802.11a clients in the network.

To configure client-type-based rate limiting:

 

Step	Command	Remarks
1.       Enter system view.	system-view	N/A
2.       Configure rate limiting based on the client type.	wlan option client-rate-limit { dot11b | dot11ag | dot11n | dot11a | dot11g | dot11an | dot11gn | dot11ac } { inbound | outbound } cir kbps [ cbs byte ]	By default, client-type-based rate limiting is disabled.

 

Setting the maximum transmission times for probe responses

Perform this task to reduce the number of probe responses sent by a radio to improve network performance.

To set the maximum transmission times for probe responses:

 

Step	Command	Remarks
1.       Enter system view.	system-view	N/A
2.       Set the maximum transmission times for probe responses.	wlan option probe-response-try trynum [ 2g | 5g ]	By default, the maximum transmission times for probe responses is 2.

 

Setting the maximum interference threshold

This feature stops data forwarding on the channel where interference signal power reaches the threshold. This channel is unavailable until the interference signal power goes below the threshold again.

To set the maximum interference threshold:

 

Step	Command	Remarks
1.       Enter system view.	system-view	N/A
2.       Set the maximum interference threshold.	wlan option max-interfer-threshold value [ 2g | 5g ]	By default, the maximum interference threshold is 50.

 

Enabling hidden node protection

Perform this task to enable the AP to inform clients to use RTS and CTS to avoid collision between hidden nodes.

To enable hidden node protection:

 

Step	Command	Remarks
1.       Enter system view.	system-view	N/A
2.       Enable hidden node protection.	wlan option hide-node-protection enable [ 2g | 5g ]	By default, hidden node protection is disabled.

 

Setting the noise floor threshold

Perform this task to enable the AP to receive more signals and avoid interference.

To set the noise floor threshold:

 

Step	Command	Remarks
1.       Enter system view.	system-view	N/A
2.       Set the noise floor threshold.	wlan option cca { 2g | 5g } { max max-cca | min min-cca | normal normal-cca }	By default, the noise floor threshold is not set.

 

WLAN optimization configuration examples

Optimizing an 802.11ac WLAN

Network requirements

As shown in Figure 1, all the clients and APs get their IP addresses from the DHCP server. Client 1 (802.11n) is associated with AP 1 and Client 2 (802.11g) is associated with AP 2.

Configure A-MPDU suppression to ensure that Client 1 does not affect Client 2.

Figure 1 Network diagram

 

Configuration procedure

1.        Configure IP addresses and masks for devices as shown in Figure 1. (Details not shown.)

2.        Configure wireless services. For more information, see "Configuring WLAN access". This example configures a clear-type wireless service.

# Create clear-type service template 1, set its SSID to Service, and enable the template.

<AP> sysname

[AP] wlan service-template 1 clear

[AP-wlan-st-1] ssid Service

[AP-wlan-st-1] service-template enable

[AP-wlan-st-1] quit

# Bind service template 1 to the radio interface WLAN-Radio 1/0/1.

[AP] interface WLAN-Radio 1/0/1

[AP-WLAN-Radio1/0/1] service-template 1 interface WLAN-BSS 1

# Enable A-MPDU suppression, set the maximum number of MPDUs aggregated in an A-MPDU to six, and set the maximum A-MPDU length to 5000 bytes.

[AP] wlan option dot11n-restraint packet-number 6 packet-length 5000

Optimizing some APs in a WLAN

Network requirements

As shown in Figure 2, all the clients and APs get their IP addresses from the DHCP server. Client 1 is associated with AP 1 and Client 2 is associated with AP 2.

Configure the following optimization features on AP 1:

·          Reject wireless clients with a low RSSI.

·          Ignore weak signals.

Figure 2 Network diagram

 

Configuration procedure

1.        Configure IP addresses and masks for devices as shown in Figure 2. (Details not shown.)

2.        Configure wireless services. For more information, see "Configuring WLAN access". This example configures a clear-type wireless service.

a.    Configure AP 1.

# Create interface WLAN-BSS 1.

<AP1> system-view

[AP1] interface WLAN-BSS 1

[AP1-WLAN-BSS1] quit

# Create clear-type service template 1, set its SSID to Service1, and enable the template.

[AP1] wlan service-template 1 clear

[AP1-wlan-st-1] ssid Service1

[AP1-wlan-st-1] service-template enable

[AP1-wlan-st-1] quit

# Bind service template 1 to the radio interface WLAN-Radio 1/0/1, and enable the radio interface.

[AP1] interface WLAN-Radio 1/0/1

[AP1-WLAN-Radio1/0/1] service-template 1 interface WLAN-BSS 1

[AP1-WLAN-Radio1/0/1] quit

# Configure the AP to reject clients whose RSSI is lower than 15.

[AP1] wlan option client-reject 15

# Configure the AP to ignore signals whose RSSI is lower than 15.

[AP1] wlan option signal-ignore 15

b.    Configure AP 2.

# Create the interface WLAN-BSS 1.

<AP2> system-view

[AP2] interface WLAN-BSS 1

[AP2-WLAN-BSS1] quit

# Create clear-type service template 1, set its SSID to Service2, and enable the template.

[AP2] wlan service-template 1 clear

[AP2-wlan-st-1] ssid Service2

[AP2-wlan-st-1] service-template enable

[AP2-wlan-st-1] quit

# Bind service template 1 to the radio interface WLAN-Radio 1/0/1, and enable the radio interface.

[AP2] interface WLAN-Radio 1/0/1

[AP2-WLAN-Radio1/0/1] service-template 1 interface WLAN-BSS 1

[AP2-WLAN-Radio1/0/1] quit

Verifying the configuration

1.        Adjust the locations of the APs and clients to ensure that Client 1 and Client 2 can only establish a connection with AP 1 and AP 2, respectively.

2.        Move the two clients far from the APs. Use the display wlan client verbose command to verify that their RSSI is about 10.

3.        Disconnect and then reconnect the two clients.

4.        Verify that only Client 2 can access the WLAN.