rfc9550v2.txt		rfc9550.txt
	skipping to change at line 182 ¶		skipping to change at line 182 ¶
	* To add minimal or no delay to the forwarding process of packets.		* To add minimal or no delay to the forwarding process of packets.
	* To not require synchronization between PREOF nodes.		* To not require synchronization between PREOF nodes.
	Some aspects are explicitly out of scope for a POF:		Some aspects are explicitly out of scope for a POF:
	* To eliminate the delay variation caused by the packet ordering.		* To eliminate the delay variation caused by the packet ordering.
	Dealing with delay variation is a DetNet forwarding sub-layer		Dealing with delay variation is a DetNet forwarding sub-layer
	target, and it can be achieved, for example, by placing a de-		target, and it can be achieved, for example, by placing a de-
	jitter buffer or flow regulator (e.g., shaping) function after the		jitter buffer or flow regulator (e.g., shaping) function after the
	POF functionality.		POF.
	4. POF Algorithms		4. POF Algorithms
	4.1. Prerequisites and Assumptions		4.1. Prerequisites and Assumptions
	The POF algorithms discussed in this document make some assumptions		The POF algorithms discussed in this document make some assumptions
	and trade-offs regarding the characteristics of the sequence of		and trade-offs regarding the characteristics of the sequence of
	received packets. In particular, the algorithms assume that a PEF is		received packets. In particular, the algorithms assume that a PEF is
	performed on the incoming packets before they are handed to the POF.		performed on the incoming packets before they are handed to the POF.
	Hence, the sequence of incoming packets can be out-of-order or		Hence, the sequence of incoming packets can be out-of-order or
	skipping to change at line 422 ¶		skipping to change at line 422 ¶
	* When the first timer expires, the packet with lowest seq_num in		* When the first timer expires, the packet with lowest seq_num in
	the buffer is selected and forwarded, and "POFLastSent" is set		the buffer is selected and forwarded, and "POFLastSent" is set
	with its seq_num.		with its seq_num.
	* The basic or advanced POF rules are applied for the packet(s) in		* The basic or advanced POF rules are applied for the packet(s) in
	the buffer and the subsequently received packets.		the buffer and the subsequently received packets.
	4.6. Selecting and Using the POF Algorithms		4.6. Selecting and Using the POF Algorithms
	The selection of the POF algorithm depends on the network scenario		The selection of the POF algorithm depends on the network scenario
	and the remaining delay budget of a flow. Using the POF and		and the remaining delay budget of a flow. Using the POF algorithms
	calculating its parameters require proper design. Knowing the path		and calculating their parameters require proper design. Knowing the
	delay difference is essential for the POF algorithms described here.		path delay difference is essential for the POF algorithms described
	Failure scenarios breaking the design assumptions can impact the		here. Failure scenarios breaking the design assumptions can impact
	result of the POF (e.g., packet received out of the expected worst-		the result of the POF (e.g., packet received out of the expected
	case delay window -- calculated based on the path delay difference --		worst-case delay window -- calculated based on the path delay
	can result in unwanted out-of-order delivery).		difference -- can result in unwanted out-of-order delivery).
	In DetNet scenarios, there is always an elimination function before		In DetNet scenarios, there is always an elimination function before
	the POF (therefore, duplicates are not considered by the POF).		the POF (therefore, duplicates are not considered by the POF).
	Implementing them together in the same node allows the POF to		Implementing them together in the same node allows the POF to
	consider PEF events/states during the reordering. For example, under		consider PEF events/states during the reordering. For example, under
	normal circumstances, the difference between sequence numbers in		normal circumstances, the difference between sequence numbers in
	consecutive packets is bounded due to the history window of the PEF.		consecutive packets is bounded due to the history window of the PEF.
	However, in some scenarios (e.g., reset of sequence number), the		However, in some scenarios (e.g., reset of sequence number), the
	difference can be much larger than the size of the history window.		difference can be much larger than the size of the history window.
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