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dns_flag_day_2020
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| Both sides previous revisionPrevious revision | Next revisionBoth sides next revision | ||
| dns_flag_day_2020 [2023/05/24 04:10] – [Problem with DNS transport over UDP] -changed to subhead1 hogwild | dns_flag_day_2020 [2023/05/24 04:11] – [DNS message fragmentation] -changed head to subhead1 hogwild | ||
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| Even the earliest DNS standards (RFC 1035) specified the use of sending DNS messages over TCP as well as over UDP. Unfortunately, | Even the earliest DNS standards (RFC 1035) specified the use of sending DNS messages over TCP as well as over UDP. Unfortunately, | ||
| - | ====== DNS message fragmentation | + | ===== DNS message fragmentation ===== |
| Sending data over networks and the Internet is restricted to the limitation of how large each packet can be. Data is chopped up into a stream of packets, and sized to adhere to the Maximum Transmission Unit (MTU) of the network. MTU is typically 1500 bytes for IPv4 and, in the case of IPv6, the minimum is 1280 bytes. Subtracting both the IP header size (IPv4 20 bytes/IPv6 40 bytes) and the UDP protocol header size (8 bytes) from the MTU, we end up with a maximum DNS message size of 1472 bytes for IPv4 and 1232 bytes in order for a message to fit within a single packet. If the message is any larger than that, it will have to be fragmented into more packets. | Sending data over networks and the Internet is restricted to the limitation of how large each packet can be. Data is chopped up into a stream of packets, and sized to adhere to the Maximum Transmission Unit (MTU) of the network. MTU is typically 1500 bytes for IPv4 and, in the case of IPv6, the minimum is 1280 bytes. Subtracting both the IP header size (IPv4 20 bytes/IPv6 40 bytes) and the UDP protocol header size (8 bytes) from the MTU, we end up with a maximum DNS message size of 1472 bytes for IPv4 and 1232 bytes in order for a message to fit within a single packet. If the message is any larger than that, it will have to be fragmented into more packets. | ||
dns_flag_day_2020.txt · Last modified: 2023/05/24 04:17 by hogwild
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