rfc9790v2.txt		rfc9790.txt
	skipping to change at line 89 ¶		skipping to change at line 89 ¶
	5. References		5. References
	5.1. Normative References		5.1. Normative References
	5.2. Informative References		5.2. Informative References
	Acknowledgements		Acknowledgements
	Authors' Addresses		Authors' Addresses
	1. Introduction		1. Introduction
	An MPLS packet consists of a label stack, an optional Post-Stack		An MPLS packet consists of a label stack, an optional Post-Stack
	Header (PSH), and an optional embedded packet (in that order).		Header (PSH), and an optional embedded packet (in that order).
	Examples of PSH include existing artifacts such as control words		Examples of PSHs include existing artifacts such as control words
	[RFC4385], BIER (Bit Index Explicit Replication) headers [RFC8296]		[RFC4385], BIER (Bit Index Explicit Replication) headers [RFC8296]
	and the like, as well as new types of PSH being discussed by the MPLS		and the like, as well as new types of PSH being discussed by the MPLS
	Working Group. However, in the data plane, there are very few clues		Working Group. However, in the data plane, there are very few clues
	regarding the PSH and no clue as to the type of embedded packet; this		regarding the PSH and no clue as to the type of embedded packet; this
	information is communicated via other means, such as the routing		information is communicated via other means, such as the routing
	protocols that signal the labels in the stack. Nonetheless, in order		protocols that signal the labels in the stack. Nonetheless, in order
	to better handle an MPLS packet in the data plane, it is common		to better handle an MPLS packet in the data plane, it is common
	practice for network equipment to "guess" the type of embedded		practice for network equipment to "guess" the type of embedded
	packet. Such equipment may also need to process the PSH. Both of		packet. Such equipment may also need to process the PSH. Both of
	these require parsing the data after the label stack. To do this,		these require parsing the data after the label stack. To do this,
	skipping to change at line 179 ¶		skipping to change at line 179 ¶
	MPLS Packet: A packet whose Layer 2 header declares the type to be		MPLS Packet: A packet whose Layer 2 header declares the type to be
	MPLS. For example, the Ethertype is 0x8847 or 0x8848 for		MPLS. For example, the Ethertype is 0x8847 or 0x8848 for
	Ethernet, and the Protocol field is 0x0281 or 0x0283 for PPP.		Ethernet, and the Protocol field is 0x0281 or 0x0283 for PPP.
	MPLS Payload: All data after the label stack, including the PFN, an		MPLS Payload: All data after the label stack, including the PFN, an
	optional post-stack header, and the embedded packet.		optional post-stack header, and the embedded packet.
	Post-stack First Nibble (PFN): The most significant four bits of the		Post-stack First Nibble (PFN): The most significant four bits of the
	first octet following the label stack.		first octet following the label stack.
	Post-Stack Header (PSH): Optional field of interest to the egress		Post-Stack Header (PSH): A field containing information that may be
	Label Switching Router (LSR) (and possibly to transit LSRs).		of interest to the egress Label Switching Router (LSR) or transit
	Examples include a control word [RFC4385] [RFC8964] or an		LSRs. Examples include a control word [RFC4385] [RFC8964] or an
	associated channel [RFC4385] [RFC5586] [RFC9546]. The PSH MUST		associated channel header [RFC4385] [RFC5586] [RFC9546]. A parser
	indicate its length, so that a parser knows where the embedded		needs to be able to determine where the PSH ends in order to find
	packet starts.		the embedded packet.
	1.3. Abbreviations		1.3. Abbreviations
	BIER: Bit Index Explicit Replication		BIER: Bit Index Explicit Replication
	FAT: Flow-Aware Transport		FAT: Flow-Aware Transport
	LSE: Label Stack Entry		LSE: Label Stack Entry
	LSR: Label Switching Router		LSR: Label Switching Router
	skipping to change at line 642 ¶		skipping to change at line 642 ¶
	Use the Ethernet Control Word", RFC 8469,		Use the Ethernet Control Word", RFC 8469,
	DOI 10.17487/RFC8469, November 2018,		DOI 10.17487/RFC8469, November 2018,
	<https://www.rfc-editor.org/info/rfc8469>.		<https://www.rfc-editor.org/info/rfc8469>.
	[RFC8964] Varga, B., Ed., Farkas, J., Berger, L., Malis, A., Bryant,		[RFC8964] Varga, B., Ed., Farkas, J., Berger, L., Malis, A., Bryant,
	S., and J. Korhonen, "Deterministic Networking (DetNet)		S., and J. Korhonen, "Deterministic Networking (DetNet)
	Data Plane: MPLS", RFC 8964, DOI 10.17487/RFC8964, January		Data Plane: MPLS", RFC 8964, DOI 10.17487/RFC8964, January
	2021, <https://www.rfc-editor.org/info/rfc8964>.		2021, <https://www.rfc-editor.org/info/rfc8964>.
	[RFC9789] Andersson, L., Bryant, S., Bocci, M., and T. Li, "MPLS		[RFC9789] Andersson, L., Bryant, S., Bocci, M., and T. Li, "MPLS
	Network Action (MNA) Framework", RFC 9789,		Network Actions (MNAs) Framework", RFC 9789,
	DOI 10.17487/RFC9789, May 2025,		DOI 10.17487/RFC9789, May 2025,
	<https://www.rfc-editor.org/info/rfc9789>.		<https://www.rfc-editor.org/info/rfc9789>.
	5.2. Informative References		5.2. Informative References
	[RFC4446] Martini, L., "IANA Allocations for Pseudowire Edge to Edge		[RFC4446] Martini, L., "IANA Allocations for Pseudowire Edge to Edge
	Emulation (PWE3)", BCP 116, RFC 4446,		Emulation (PWE3)", BCP 116, RFC 4446,
	DOI 10.17487/RFC4446, April 2006,		DOI 10.17487/RFC4446, April 2006,
	<https://www.rfc-editor.org/info/rfc4446>.		<https://www.rfc-editor.org/info/rfc4446>.
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