vocabulary for protocol dataflows?

I'm having a mental block for the words describing data flow in a communications protocol + google isn't helping, due to information glut.

In the following scenarios A and B are communicating to each other.

• command or request: a packet of data going from A to B indicating that B should take some kind of action
• response: a packet of data going from B to A in response to a particular packet that A has previously sent to B.
• acknowledge or ACK: a specific kind of response that just indicates Yes I got that packet of data. (negative acknowledge or NAK indicates No there was some problem receiving data)
• {X}: unsolicited information either from A to B, or B t开发者_运维知识库o A, which is neither a response, nor a request for the recipient to take action. Examples: datalogging packets, notification packets, etc.

I can't think of what to call {X}, I'm having a brain cramp.

Also are there other common words in this category? Where would you look them up?

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Why not call your "X" just "Message" or "Signal" ?

For some inspiration regarding this subject, may I suggest the IETF or ITU-T standards bodies. These two bodies are dominating the communications scene.

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I would following the terminology in Steven's TCP/IP Illusrated

So you have a request, response, acknowledement, push and poll are used if I remember correctly