14-WLAN Configuration Guide (Fat AP)

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09-WLAN multicast optimization configuration
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Configuring WLAN multicast optimization

About WLAN multicast optimization

Multicast transmission in a wireless network has the following limitations:

·     Great packet loss upon poor link quality—Multicast packets do not require acknowledgments and lost packets are not retransmitted.

·     Low transmission efficiency—The device sends multicast packets at the lowest mandatory rate.

With these limitations, multicast transmission cannot meet the requirements for applications that are not sensitive to time delay but sensitive to data integrity. To address this issue, you can configure WLAN multicast optimization.

 

 

NOTE:

The term "AP" in this document refers to MSR routers that offer WLAN services as fat APs. For more information, see "Compatibility of hardware and AP functionality."

WLAN multicast optimization mechanism

WLAN multicast optimization enables an AP to convert multicast packets to unicast packets.

Figure 1 Data transmission with WLAN multicast optimization enabled

WLAN multicast optimization entries

WLAN multicast optimization uses multicast optimization entries to manage traffic forwarding. The multicast optimization entries use the clients' MAC addresses as indexes. A multicast optimization entry records information about multicast groups that clients join, multicast sources from which clients receive traffic, multicast group version, and multicast optimization mode.

After you enable WLAN multicast optimization, an AP creates or updates multicast optimization entries for a client according to the IGMP reports received from the client. If IGMPv3 or MLDv2 is used, the AP can also update the multicast sources allowed by the client. The AP removes a multicast optimization entry if it receives a leave message from the client or when the aging time for the entry expires. If you disable WLAN multicast optimization for the service template that an AP uses, the AP removes all multicast optimization entries.

When an AP receives a non-IGMP or non-MLD packet from a multicast source, the AP matches the multicast group address in the packet against the multicast optimization entries. If a match is found, the AP converts the multicast packet to unicast packets and sends the unicast packets to all clients in the multicast group. If no match is found, the AP discards the packet.

WLAN multicast optimization tasks at a glance

To configure WLAN multicast optimization, perform the following tasks:

1.     Enabling WLAN multicast optimization

2.     (Optional.) Configuring a multicast optimization policy

3.     (Optional.) Setting rate limits for IGMP/MLD packets from clients

4.     (Optional.) Setting the limit for multicast optimization entries

5.     (Optional.) Setting the limit for multicast optimization entries per client

6.     (Optional.) Setting the aging time for multicast optimization entries

Enabling WLAN multicast optimization

1.     Enter system view.

system-view

2.     Enter service template view.

wlan service-template service-template-name

3.     Enable WLAN multicast optimization.

IPv4:

multicast-optimization enable

IPv6:

ipv6 multicast-optimization enable

By default, WLAN multicast optimization is disabled.

Configuring a multicast optimization policy

About multicast optimization policies

A multicast optimization policy defines the maximum number of clients that WLAN multicast optimization supports and defines the following actions an AP takes when the limit is reached:

·     Unicast forwarding—Sends unicast packets converted from a multicast packet to only n (n equal to the specified threshold) clients that are randomly selected.

·     Multicast forwarding—Forwards the multicast packet to all clients.

·     Packet dropping—Drops the multicast packet.

Procedure

1.     Enter system view.

system-view

2.     Configure a WLAN multicast optimization policy.

IPv4:

wlan multicast-optimization entry client-limit [ limit-value ] [ drop | multicast | unicast ]

IPv6:

wlan ipv6 multicast-optimization entry client-limit [ limit-value ] [ drop | multicast | unicast ]

By default, no multicast optimization policies exist and an AP performs multicast optimization for all clients.

If you do not specify an action, an AP performs unicast forwarding.

Setting rate limits for IGMP/MLD packets from clients

About rate limits for IGMP/MLD packets from clients

Perform this task to configure the maximum number of IGMP or MLD packets that an AP can receive from clients within the specified interval. The AP discards the excessive IGMP or MLD packets. For more information about IGMP or MLD, see IP Multicast Configuration Guide.

Procedure

1.     Enter system view.

system-view

2.     Set the rate limit for IGMP packets from clients. (IPv4)

wlan multicast-optimization packet-rate-limit [ interval interval-value | threshold threshold-value ] *

By default, no rate limit is set for IGMP packets from clients.

3.     Set the rate limit for MLD packets from clients. (IPv6)

wlan ipv6 multicast-optimization packet-rate-limit [ interval interval-value | threshold threshold-value ] *

By default, no rate limit is set for MLD packets from clients.

Setting the limit for multicast optimization entries

About the limit for multicast optimization entries

Each time a client joins a multicast group, the AP creates a multicast optimization entry for the multicast group. If multicast sources have been specified for a client when the client joins the multicast group, the AP also creates a multicast optimization entry for each multicast source. When a client leaves a multicast group or rejects a multicast source, the AP deletes the relevant multicast optimization entry for the client. These might consume system resources.

Perform this task to limit the number of multicast optimization entries to save system resources.

When the number of multicast optimization entries reaches the limit, the AP stops creating new entries until the number falls below the limit.

Procedure

1.     Enter system view.

system-view

2.     Set the limit for multicast optimization entries.

IPv4:

wlan multicast-optimization global entry-limit [ limit-value ]

IPv6:

wlan ipv6 multicast-optimization global entry-limit [ limit-value ]

By default, no limit is set for multicast optimization entries.

Setting the limit for multicast optimization entries per client

About the limit for multicast optimization entries per client

Perform this task to limit the number of multicast optimization entries that an AP maintains for each client to prevent a client from occupying excessive system resources.

Procedure

1.     Enter system view.

system-view

2.     Set the limit for multicast optimization entries per client.

IPv4:

wlan multicast-optimization client entry-limit [ limit-value ]

IPv6:

wlan ipv6 multicast-optimization client entry-limit [ limit-value ]

By default, no limit is set for multicast optimization entries per client.

Setting the aging time for multicast optimization entries

1.     Enter system view.

system-view

2.     Set the aging time for multicast optimization entries.

IPv4:

wlan multicast-optimization aging-time aging-value

IPv6:

wlan ipv6 multicast-optimization aging-time aging-value

By default, the aging time is 260 seconds for multicast optimization entries.

Display and maintenance commands for WLAN multicast optimization

Execute display commands in any view and reset commands in user view.

 

Tasks

Command

Display IPv6 multicast optimization entry information.

display wlan ipv6 multicast-optimization entry [ client mac-address [ group group-ip [ source source-ip ] ] ]

Display IPv4 multicast optimization entry information.

display wlan multicast-optimization entry [ client mac-address [ group group-ip [ source source-ip ] ] ]

Clear IPv6 multicast optimization entries.

reset wlan ipv6 multicast-optimization entry { all | client mac-address [ group group-ip [ source source-ip ] ] }

Clear IPv6 multicast optimization entries for the specified multicast group.

reset wlan ipv6 multicast-optimization entry group group-ip [ source source-ip ]

Clear IPv4 multicast optimization entries.

reset wlan multicast-optimization entry { all | client mac-address [ group group-ip [ source source-ip ] ] }

Clear IPv4 multicast optimization entries for the specified multicast group.

reset wlan multicast-optimization entry group group-ip [ source source-ip ]

 

WLAN multicast optimization configuration examples

Example: Configuring basic WLAN multicast optimization

Network configuration

As shown in Figure 2, the switch acts as the DHCP server to assign IP addresses to the AP and clients. The AP provides wireless services to the clients through the SSID service. Configure WLAN multicast optimization to manage multicast packet forwarding.

Figure 2 Network diagram

 

Procedure

# Enable IGMP snooping both globally and for VLAN 1.

<AP> system-view

[AP] igmp-snooping

[AP-igmp-snooping] quit

[AP] vlan 1

[AP-vlan1] igmp-snooping enable

[AP-vlan1] quit

# Create service template 1, set its SSID to service, and enable WLAN multicast optimization for it.

[AP] wlan service-template 1

[AP-wlan-st-1] ssid service

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

[AP-wlan-st-1] multicast-optimization enable

[AP-wlan-st-1] quit

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

[AP] interface wlan-radio 0/0

[AP-WLAN-Radio0/0] undo shutdown

[AP-WLAN-Radio0/0] service-template 1

[AP-WLAN-Radio0/0] quit

# Set the aging time to 300 seconds for IPv4 multicast optimization entries.

[AP] wlan multicast-optimization aging-time 300

# Configure the AP to receive a maximum of 100 IGMP packets from clients every 60 seconds.

[AP] wlan multicast-optimization packet-rate-limit interval 60 threshold 100

# Set the limit for IPv4 multicast optimization entries to 100.

[AP] wlan multicast-optimization global entry-limit 100

# Set the limit for multicast optimization entries per client to 10.

[AP] wlan multicast-optimization client entry-limit 10

# Set the maximum number of clients that WLAN multicast optimization supports to 2, and configure the AP to drop multicast packets when the number of clients reaches the threshold.

[AP] wlan multicast-optimization entry client-limit 2 drop

Verifying the configuration

# Verify the following information after Client 1 and Client 2 join the multicast group with the address 230.1.1.1 and the multicast source address 1.1.1.1 has been specified. (Details not shown.):

·     The AP has created multicast optimization entries for Client 1 and Client 2.

·     Client 1 and Client 2 can receive traffic from the multicast source.

# Display information about multicast optimization entries after Client 3 joins the multicast group with the address 230.1.1.1 and the multicast source address 1.1.1.1 has been specified.

[AP] display wlan multicast-optimization entry

Total 3 clients reported

 Client: 0001-0001-0001

  Reported from AP 1 on radio 1

  Total number of groups: 1

 

  Group: 230.1.1.1

    Version: IGMPv3

    Mode: Include

    Duration: 00h 00m 30s

    Sources: 1

      Source: 1.1.1.1

      Duration: 00h 00m 30s

 

 Client: 0001-0001-0002

  Reported from AP 1 on radio 1

  Total number of groups: 1

 

  Group: 230.1.1.1

    Version: IGMPv3

    Mode: Include

    Duration: 00h 00m 15s

    Sources: 1

      Source: 1.1.1.1

      Duration: 00h 00m 15s

 

 Client: 0001-0001-0003

  Reported from AP 1 on radio 1

  Total number of groups: 1

 

  Group: 230.1.1.1

    Version: IGMPv3

    Mode: Include

    Duration: 00h 00m 10s

    Sources: 1

      Source: 1.1.1.1

      Duration: 00h 00m 10s

The output shows that the AP has created multicast optimization entries for Client 3.

# Verify that Client 1, Client 2, and Client 3 cannot receive traffic from the multicast source because the number of clients that WLAN multicast optimization supports exceeds the limit. (Details not shown.)