DNS: Difference between revisions

DNS (view source)

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Line 30: Therefore DNS ALG is used to close the DNS session on getting a reply message. If DNS ALG is disabled, the session table may fill in a short time. ; DNS Flow {{UC}} = DNS Headers = Line 77 ⟶ 80: * TC - Truncation Flag When set to 1, indicates that the message was truncated due to its length being longer than the maximum permitted for the type of transport mechanism used. TCP doesn't have a length limit for messages, while UDP messages are limited to 512 bytes~~, so this bit being sent usually is an indication that the message was sent using UDP and was too long to fit~~. So this bit being sent usually is an indication that the message was sent using UDP and was too long to fit. The client may need to establish a TCP session to get the full message. On the other hand, if the portion truncated was part of the Additional section, it may choose not to bother.