Size of empty UDP and TCP packet?

Question

Hi,

what is the size of an empty UDP datagram? And that of an empty TCP packet?

I can only find infos about the MTU, but I want to know what is the "base" size of these, in order to estimate bandwidth consumption for protocols on top of them.

Thanks in advance for infos.

Answer 1

See User Datagram Protocol. The UDP Header is 8 Bytes (64 bits) long.

The mimimum size of the bare TCP header is 5 words (32bit word), while the maximum size of a TCP header is 15 words.

Best wishes, Fabian

Answer 2

Artelius and halfdan are correct, but you're missing something: UDP and TCP both run on top of some physical transport. For example, if you're using UDP over ethernet, you should also include the size of the ethernet frame

Answer 3

Size of Ethernet frame - 24 Bytes Size of IPv4 Header (without any options) - 20 bytes Size of TCP Header (without any options) - 20 Bytes So total size of empty TCP datagram - 24 + 20 + 20 = 64 bytes

Size of UDP header - 8 bytes So total size of empty UDP datagram - 24 + 20 + 8 = 52 bytes