Is TCP/IP encapsulation MSB or LSB?

Randomblue asked:

Application data sent over TCP experiences multiple encapsulations:

  1. The application data is encapsulated within one or many TCP fragments
  2. The TCP fragment is encapsulated within one or many IP datagrams
  3. The IP datagram is encapsulated within an Ethernet frame

It turns out Ethernet frames are sent most-significant byte first, and within each byte, most-significant bit first. What about the multiple encapsulations? Are they performed MSB first or LSB first?

My answer:

Virtually everything in IP and its related protocols is most significant byte first. In older documents, such as the RFCs you should be reading, you will see this referred to as “network byte order”.

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