Product Documentation

Jumbo frames support for DNS to handle responses of large sizes

Starting with Citrix ADC 12.1 build 49.xx, DNS supports jumbo frames for handling UDP responses greater than 1,280 bytes. Previously, the Citrix ADC appliance only supported UDP packet size only up to 1,280 bytes.

You can set the maximum UDP packet size that the appliance can handle in proxy, ADNS, and forwarder modes by configuring the Maximum UDP Packet Size parameter value. For example, if the Maximum UDP Packet Size parameter value is set to 4096, the appliance can handle DNS response of size 4,096 bytes.

Important

  • In proxy mode, the least size between the client request OPT payload size and the Maximum UDP Packet Size value is considered for sending DNS queries to the backend. For example, if the client request OPT payload size is 3000, and the Maximum UDP Packet Size parameter value is set to 4096, DNS queries of size 3,000 bytes are sent to the backend.

    Also, from the backend, appliance can receive responses of large sizes and process responses of large sizes.

  • In forwarder mode, the appliance sets the OPT payload size equal to the UDP packet size parameter value.

  • If the DNS records are local to the appliance, then the appliance can compose response sizes as large as the Maximum UDP Packet Size parameter value. This is applicable for ADNS, proxy, and recursive resolvers.

To configure the maximum UDP packet size using the CLI

At the command prompt, type:

set dns parameter [-maxUDPPacketSize <positive_integer>]

Example:

set dns parameter -maxUDPPacketSize 10000

Note: The minimum and maximum value that you can set for the Maximum UDP Packet Size parameter is 512 and 16384 respectively. Default value is 1280.

To configure the maximum UDP packet size using the CLI

  1. Navigate to Traffic Management > DNS.
  2. In the details pane, click Change DNS settings.
  3. In Maximum UDP Packet Size, specify the maximum UDP packet size.
  4. Click OK.

Jumbo frames support for DNS to handle responses of large sizes