Internet Engineering Task Force (IETF) S. Gringeri
Request for Comments: 9801 J. Whittaker
Category: Standards Track Verizon
ISSN: 2070-1721 N. Leymann
Deutsche Telekom
C. Schmutzer, Ed.
Cisco Systems, Inc.
C. Brown
Ciena Corporation
June
July 2025
Private Line Emulation over Packet Switched Networks
Abstract
This document expands the applicability of Virtual Private Wire
Service (VPWS) bit-stream payloads beyond Time Division Multiplexing
(TDM) signals and provides pseudowire transport with complete signal
transparency over Packet Switched Networks (PSNs).
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc9801.
Copyright Notice
Copyright (c) 2025 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction and Motivation
2. Requirements Notation
3. Terminology and Reference Models
3.1. Terminology Abbreviations
3.2. Reference Models
4. Emulated Services
4.1. Generic PLE Service
4.2. Ethernet Services
4.2.1. 1000BASE-X
4.2.2. 10GBASE-R and 25GBASE-R
4.2.3. 40GBASE-R, 50GBASE-R, and 100GBASE-R
4.2.4. 200GBASE-R and 400GBASE-R
4.2.5. Energy Efficient Ethernet (EEE)
4.3. SONET/SDH Services
4.4. Fibre Channel Services
4.4.1. 1GFC, 2GFC, 4GFC, and 8GFC
4.4.2. 16GFC
4.4.3. 32GFC and 4-Lane 128GFC
4.4.4. 64GFC
4.5. OTN Services
5. PLE Encapsulation Layer
5.1. PSN and VPWS Demultiplexing Headers
5.1.1. New SRv6 Behaviors
5.2. PLE Header
5.2.1. PLE Control Word
5.2.2. RTP Header
6. PLE Payload Layer
6.1. Basic Payload
6.2. Byte-Aligned Payload
7. PLE Operation
7.1. Common Considerations
7.2. PLE IWF Operation
7.2.1. PSN-Bound Encapsulation Behavior
7.2.2. CE-Bound Decapsulation Behavior
7.3. PLE Performance Monitoring
7.4. PLE Fault Management
8. QoS and Congestion Control
9. Security Considerations
10. IANA Considerations
10.1. Bit-Stream Next Header Type
10.2. SRv6 Endpoint Behaviors
11. References
11.1. Normative References
11.2. Informative References
Acknowledgements
Contributors
Authors' Addresses
1. Introduction and Motivation
This document describes a method called Private Line Emulation (PLE)
for encapsulating not only Time Division Multiplexing (TDM) signals
as bit-stream Virtual Private Wire Service (VPWS) over Packet
Switched Networks (PSN). In this regard, it complements methods
described in [RFC4553].
This emulation suits applications, where carrying Protocol Data Units
(PDUs) as defined in [RFC4906] or [RFC4448] is not enough, physical
layer signal transparency is required and data or framing structure
interpretation of the Provider Edge (PE) would be counterproductive.
One example of such case is two Ethernet-connected Customer Edge (CE)
devices and the need for Synchronous Ethernet operation (see
[G.8261]) between them without the intermediate PE devices
interfering or addressing concerns about Ethernet control protocol
transparency for PDU-based carrier Ethernet services, beyond the
behavior definitions of MEF Forum (MEF) specifications.
Another example would be a Storage Area Networking (SAN) extension
between two data centers. Operating at a bit-stream level allows for
a connection between Fibre Channel switches without interfering with
any of the Fibre Channel protocol mechanisms defined by [T11].
Also, SONET/SDH (Synchronous Optical Network (SONET) / Synchronous
Digital Hierarchy (SDH)) add/drop multiplexers or cross-connects can
be interconnected without interfering with the multiplexing
structures and networks mechanisms. This is a key distinction to
Circuit Emulation over Packet (CEP) defined in [RFC4842] where
multiplexing and demultiplexing is desired in order to operate per
SONET Synchronous Payload Envelope (SPE) and Virtual Tributary (VT)
or SDH Virtual Container (VC). In other words, PLE provides an
independent layer network underneath the SONET/SDH layer network,
whereas CEP operates at the same level and peer with the SONET/SDH
layer network.
The mechanisms described in this document follow principles similar
to Structure-Agnostic TDM over Packet (SAToP) (defined in [RFC4553]).
The applicability is expanded beyond the narrow set of Plesiochronous
Digital Hierarchy (PDH) interfaces (T1, E1, T3, and E3) to allow the
transport of signals from many different technologies such as
Ethernet, Fibre Channel, SONET/SDH ([GR253] / [G.707]), and OTN Optical
Transport Network (OTN) [G.709] at gigabit speeds. The signals are
treated as bit-stream payload, which was defined in the Pseudo Wire
Emulation Edge-to-Edge (PWE3) architecture in Sections 3.3.3 and
3.3.4 of [RFC3985].
2. Requirements Notation
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
3. Terminology and Reference Models
3.1. Terminology Abbreviations
ACH: Associated Channel Header [RFC7212]
AIS: Alarm Indication Signal
AIS-L: Line AIS
MS-AIS: Multiplex Section AIS
BITS: Building Integrated Timing Supply [ATIS-0900105.09.2013]
CBR: Constant Bit Rate
CE: Customer Edge
CEP: Circuit Emulation over Packet [RFC4842]
CSRC: Contributing Source [RFC3550]
DEG: Degradation
ES: Errored Second
FEC: Forward Error Correction
ICMP: Internet Control Message Protocol [RFC4443]
IEEE: Institute of Electrical and Electronics Engineers
INCITS: INternational Committee for Information Technology Standards
IWF: Interworking Function
LDP: Label Distribution Protocol [RFC5036], [RFC8077]
LF: Local Fault
LOF: Loss Of Frame
LOM: Loss Of Multiframe
LOS: Loss Of Signal
LPI: Low Power Idle
LSP: Label Switched Path
MEF: MEF Forum
MPLS: Multiprotocol Label Switching [RFC3031]
NOS: Not Operational
NSP: Native Service Processing [RFC3985]
ODUk: Optical Data Unit k
OOF: Out Of Frame
OTN: Optical Transport Network
OTUk: Optical Transport Unit k
PCS: Physical Coding Sublayer
PDV: Packet Delay Variation
PE: Provider Edge
PLE: Private Line Emulation
PLOS: Packet Loss Of Signal
PLR: Packet Loss Rate
PMA: Physical Medium Attachment
PMD: Physical Medium Dependent
PSN: Packet Switched Network
PTP: Precision Time Protocol
PW: Pseudowire [RFC3985] [RFC4664]
PWE3: Pseudo Wire Emulation Edge-to-Edge [RFC3985]
RDI: Remote Defect Indication
RSVP-TE: Resource Reservation Protocol Traffic Engineering [RFC4875]
RTCP: RTP Control Protocol [RFC3550]
RTP: Real-time Transport Protocol [RFC3550]
SD: Signal Degrade
SES: Severely Errored Seconds
SDH: Synchronous Digital Hierarchy
SID: Segment Identifier [RFC8402]
SR: Segment Routing [RFC8402]
SRH: Segment Routing Header [RFC8754]
SRTP: Secure Real-time Transport Protocol [RFC3711]
SRv6: Segment Routing over IPv6 [RFC8986]
SSRC: Synchronization Source [RFC3550]
SONET: Synchronous Optical Network
TCP: Transmission Control Protocol [RFC9293]
TDM: Time Division Multiplexing
TTS: Transmitter Training Signal
UAS: Unavailable Seconds
VPWS: Virtual Private Wire Service [RFC3985]
| Note: The term Interworking Function (IWF) is used to describe
| the functional block that encapsulates bit streams bit-streams into PLE
| packets and in the reverse direction decapsulates PLE packets
| and reconstructs
bit streams. bit-streams.
3.2. Reference Models
The reference model for PLE is illustrated in Figure 1 and is inline
with the reference model defined in Section 4.1 of [RFC3985]. PLE
relies on PWE3 preprocessing, in particular the concept of a Native
Service Processing (NSP) an NSP
function defined in Section 4.2.2 of [RFC3985].
|<--- p2p L2VPN service -->|
| |
| |<-PSN tunnel->| |
v v v v
+---------+ +---------+
| PE1 |==============| PE2 |
+---+-----+ +-----+---+
+-----+ | N | | | | N | +-----+
| CE1 |-----| S | IWF |.....VPWS.....| IWF | S |-----| CE2 |
+-----+ ^ | P | | | | P | ^ +-----+
| +---+-----+ +-----+---+ |
CE1 physical ^ ^ CE2 physical
interface | | interface
|<--- emulated service --->|
| |
attachment attachment
circuit circuit
Figure 1: PLE Reference Model
PLE embraces the minimum intervention principle outlined in
Section 3.3.5 of [RFC3985] whereas [RFC3985], which means the data is flowing through
the PLE encapsulation layer as received without modifications.
For some service types, the NSP function is responsible for
performing operations on the native data received from the CE. Examples are
terminating Forward Error Correction (FEC), FEC, terminating the OTUk layer for OTN, or dealing with
multi-lane processing. After the NSP, the IWF is generating the
payload of the VPWS, which is carried via a PSN tunnel.
To allow the clock of the transported signal to be carried across the
PLE domain in a transparent way, the relative network synchronization
reference model and deployment scenario outlined in Section 4.3.2 of
[RFC4197] are applicable and are shown in Figure 2.
J
| G
| |
| +-----+ +-----+ v
+-----+ v |- - -|=================|- - -| +-----+
| |<---------|.............................|<---------| |
| CE1 | | PE1 | VPWS | PE2 | | CE2 |
| |--------->|.............................|--------->| |
+-----+ |- - -|=================|- - -| ^ +-----+
^ +-----+ +-----+ |
| ^ C D ^ |
A | | |
+-----------+-----------+ E
|
+-+
|I|
+-+
Figure 2: Relative Network Scenario Timing
The local oscillators C of PE1 and D of PE2 are locked to a common
clock I.
The attachment circuit clock E is generated by PE2 via a differential
clock recovery method in reference to the common clock I. For this
to work, the difference between clock A and clock C (locked to I)
MUST be explicitly transferred from PE1 to PE2 using the timestamp
inside the RTP header.
For the reverse direction, PE1 generates the attachment circuit clock
J and the clock difference between G and D (locked to I) is
transferred from PE2 to PE1.
The method used to lock clocks C and D to the common clock I is out
of scope of this document; however, there are already several well-
established concepts for achieving clock synchronization (commonly
also referred to as "frequency synchronization") available.
While using external timing inputs (aka BITS [ATIS-0900105.09.2013])
or synchronous Ethernet (as defined in [G.8261]), the characteristics
and limits defined in [G.8262] have to be considered.
While relying on precision time protocol (PTP) PTP (as defined in [G.8265.1]), the network limits
defined in [G.8261.1] have to be considered.
4. Emulated Services
This specification describes the emulation of services from a wide
range of technologies, such as TDM, Ethernet, Fibre Channel, or OTN,
as bit streams bit-streams or structured bit streams, bit-streams, as defined in Sections
3.3.3 and 3.3.4 of [RFC3985].
4.1. Generic PLE Service
The generic PLE service is an example of the bit stream bit-stream defined in
Section 3.3.3 of [RFC3985].
Under the assumption that the CE-bound IWF is not responsible for any
service-specific operation, a bit stream bit-stream of any rate can be carried
using the generic PLE payload.
There is no NSP function present for this service.
4.2. Ethernet Services
Ethernet services are special cases of the structured bit stream bit-stream
defined in Section 3.3.4 of [RFC3985].
The IEEE has defined several layers for Ethernet in [IEEE802.3].
Emulation is operating at the physical (PHY) layer, more precisely at
the Physical Coding Sublayer (PCS). PCS.
Over time, many different Ethernet interface types have been
specified in [IEEE802.3] with a varying set of characteristics, such
as optional versus mandatory FEC and single-lane versus multi-lane
transmission.
Ethernet interface types with backplane physical media dependent
(PMD) PMD variants and Ethernet
interface types mandating auto-
negotiation auto-negotiation (except 1000Base-X) are
out of scope for this document.
All Ethernet services are leveraging the basic PLE payload and
interface-specific mechanisms are confined to the respective service
specific NSP functions.
4.2.1. 1000BASE-X
The PCS layer of 1000BASE-X (defined in Section 36 of [IEEE802.3]) is
based on 8B/10B code.
The PSN-bound NSP function does not modify the received data and is
transparent to auto-negotiation; however, it is responsible for
detecting attachment circuit faults specific to 1000BASE-X such as
LOS and sync loss.
When the CE-bound IWF is in PLOS state or when PLE packets are
received with the L bit set, the CE-bound NSP function MAY disable
its transmitter as no appropriate maintenance signal was defined for
1000BASE-X by the IEEE.
4.2.2. 10GBASE-R and 25GBASE-R
The PCS layers of 10GBASE-R (defined in Section 49 and 25GBASE-R
defined in Section 107 of [IEEE802.3]) are based on a 64B/66B code.
Sections 74 and 108 of [IEEE802.3] define an optional FEC layer; if
present, the PSN-bound NSP function MUST terminate the FEC and the
CE-bound NSP function MUST generate the FEC.
The PSN-bound NSP function is also responsible for detecting
attachment circuit faults specific to 10GBASE-R and 25GBASE-R such as
LOS and sync loss.
The PSN-bound IWF maps the scrambled 64B/66B code stream into the
basic PLE payload.
The CE-bound NSP function MUST perform:
* PCS code sync (Section 49.2.9 of [IEEE802.3]) and
* descrambling (Section 49.2.10 of [IEEE802.3])
in order to properly:
* transform invalid 66B code blocks into proper error control
characters /E/ (Section 49.2.4.11 of [IEEE802.3]) and
* insert Local Fault (LF) LF ordered sets (Section 46.3.4 of [IEEE802.3]) when the
CE-bound IWF is in PLOS state or when PLE packets are received
with the L bit set.
| Note: Invalid 66B code blocks typically are a consequence of
| the CE-
bound CE-bound IWF inserting replacement data in case of lost PLE
| packets or the far-end PSN-bound NSP function setting sync
| headers to 11 due to uncorrectable FEC errors.
Before sending the bit stream bit-stream to the CE, the CE-bound NSP function
MUST also scramble the 64B/66B code stream (Section 49.2.6
[IEEE802.3]).
4.2.3. 40GBASE-R, 50GBASE-R, and 100GBASE-R
The PCS layers of 40GBASE-R and 100GBASE-R (defined in Section 82 of
[IEEE802.3]) and of 50GBASE-R (defined in Section 133 of [IEEE802.3])
are based on a 64B/66B code transmitted over multiple lanes.
Sections 74 and 91 of [IEEE802.3] define an optional FEC layer; if
present, the PSN-bound NSP function MUST terminate the FEC and the
CE-bound NSP function MUST generate the FEC.
To gain access to the scrambled 64B/66B code stream, the PSN-bound
NSP further MUST perform:
* block synchronization (Section 82.2.12 of [IEEE802.3]) [IEEE802.3]),
* PCS lane de-skew (Section 82.2.13 of [IEEE802.3]) [IEEE802.3]), and
* PCS lane reordering (Section 82.2.14 of [IEEE802.3]) [IEEE802.3]).
The PSN-bound NSP function is also responsible for detecting
attachment circuit faults specific to 40GBASE-R, 50GBASE-R, and
100GBASE-R such as LOS and loss of alignment.
The PSN-bound IWF maps the serialized and scrambled 64B/66B code
stream including the alignment markers into the basic PLE payload.
The CE-bound NSP function MUST perform:
* PCS code sync (Section 82.2.12 of [IEEE802.3]) [IEEE802.3]),
* alignment-marker removal (Section 82.2.15 of [IEEE802.3]) [IEEE802.3]), and
* descrambling (Section 49.2.10 of [IEEE802.3])
in order to properly:
* transform invalid 66B code blocks into proper error control
characters /E/ (Section 82.2.3.10 of [IEEE802.3]) and
* insert Local Fault (LF) LF ordered sets (Section 81.3.4 of [IEEE802.3]) when the
CE-bound IWF is in PLOS state or when PLE packets are received
with the L bit set set.
| Note: Invalid 66B code blocks typically are a consequence of
| the CE-
bound CE-bound IWF inserting replacement data in case of lost PLE
| packets or the far-end PSN-bound NSP function not setting sync
| headers to 11 due to uncorrectable FEC errors.
When sending the bit stream bit-stream to the CE, the CE-bound NSP function MUST
also perform:
* scrambling of the 64B/66B code (Section 49.2.6 of [IEEE802.3]) [IEEE802.3]),
* block distribution (Section 82.2.6 of [IEEE802.3]) [IEEE802.3]), and
* alignment-marker insertion (Sections 82.2.7 and 133.2.2 of
[IEEE802.3])
[IEEE802.3]).
4.2.4. 200GBASE-R and 400GBASE-R
The PCS layers of 200GBASE-R and 400GBASE-R (defined in Section 119
of [IEEE802.3]) are based on a 64B/66B code transcoded to a 256B/257B
code to reduce the overhead and make room for a mandatory FEC.
To gain access to the 64B/66B code stream, the PSN-bound NSP further
MUST perform:
* alignment lock and de-skew (Section 119.2.5.1 of [IEEE802.3]) [IEEE802.3]),
* PCS Lane lane reordering and de-interleaving (Section 119.2.5.2 of
[IEEE802.3])
[IEEE802.3]),
* FEC decoding (Section 119.2.5.3 of [IEEE802.3]) [IEEE802.3]),
* post-FEC interleaving (Section 119.2.5.4 of [IEEE802.3]) [IEEE802.3]),
* alignment-marker removal (Section 119.2.5.5 of [IEEE802.3]) [IEEE802.3]),
* descrambling (Section 119.2.5.6 of [IEEE802.3]) [IEEE802.3]), and
* reverse transcoding from 256B/257B to 64B/66B (Section 119.2.5.7
of [IEEE802.3]) [IEEE802.3]).
Further, the PSN-bound NSP MUST perform rate compensation and
scrambling (Section 49.2.6 of [IEEE802.3]) before the PSN-bound IWF
maps the same into the basic PLE payload.
Rate compensation is applied so that the rate of the 66B encoded bit bit-
stream carried by PLE is 528/544 times the nominal bitrate of the
200GBASE-R or 400GBASE-R at the PMA service interface. X number of
66-byte-long rate compensation blocks are inserted every X*20479
number of 66B client blocks. For 200GBASE-R, the value of X is 16;
for 400GBASE-R, the value of X is 32. Rate compensation blocks are
special 66B control characters of type 0x00 that can easily be
searched for by the CE-bound IWF in order to remove them.
The PSN-bound NSP function is also responsible for detecting
attachment circuit faults specific to 200GBASE-R and 400GBASE-R such
as LOS and loss of alignment.
The CE-bound NSP function MUST perform:
* PCS code sync (Section 49.2.13 of [IEEE802.3]) [IEEE802.3]),
* descrambling (Section 49.2.10 of [IEEE802.3]) [IEEE802.3]), and
* rate compensation block removal
in order to properly:
* transform invalid 66B code blocks into proper error control
characters /E/ (Section 119.2.3.9 of [IEEE802.3]) and
* insert Local Fault (LF) LF ordered sets (Section 81.3.4 of [IEEE802.3]) when the
CE-bound IWF is in PLOS state or when PLE packets are received
with the L bit set set.
| Note: Invalid 66B code blocks typically are a consequence of
| the CE-
bound CE-bound IWF inserting replacement data in case of lost PLE
| packets or the far-end PSN-bound NSP function not setting sync
| headers to 11 due to uncorrectable FEC errors.
When sending the bit stream bit-stream to the CE, the CE-bound NSP function MUST
also perform:
* transcoding from 64B/66B to 256B/257B (Section 119.2.4.2 of
[IEEE802.3])
[IEEE802.3]),
* scrambling (Section 119.2.4.3 of [IEEE802.3]) [IEEE802.3]),
* alignment-marker insertion (Section 119.2.4.4 of [IEEE802.3]) [IEEE802.3]),
* pre-FEC distribution (Section 119.2.4.5 of [IEEE802.3]) [IEEE802.3]),
* FEC encoding (Section 119.2.4.6 of [IEEE802.3]) [IEEE802.3]), and
* PCS Lane lane distribution (Section 119.2.4.8 of [IEEE802.3]) [IEEE802.3]).
4.2.5. Energy Efficient Ethernet (EEE)
Section 78 of [IEEE802.3] defines the optional Low Power Idle (LPI) LPI capability for
Ethernet. Two modes are defined:
* deep sleep
* fast wake
Deep sleep mode is not compatible with PLE due to the CE ceasing
transmission. Hence, there is no support for LPI for 10GBASE-R
services across PLE.
In fast wake mode, the CE transmits /LI/ control code blocks instead
of /I/ control code blocks and, therefore, PLE is agnostic to it.
For 25GBASE-R and higher services across PLE, LPI is supported as
only fast wake mode is applicable.
4.3. SONET/SDH Services
SONET/SDH services are special cases of the structured bit stream bit-stream
defined in Section 3.3.4 of [RFC3985].
SDH interfaces are defined in [G.707]; SONET interfaces are defined
in [GR253].
The PSN-bound NSP function does not modify the received data but is
responsible for detecting attachment circuit faults specific to
SONET/SDH such as LOS, LOF, and OOF.
Data received by the PSN-bound IWF is mapped into the basic PLE
payload without any awareness of SONET/SDH frames.
When the CE-bound IWF is in PLOS state or when PLE packets are
received with the L bit set, the CE-bound NSP function is responsible
for generating the:
* MS-AIS maintenance signal (defined in Section 6.2.4.1.1 of
[G.707]) for SDH services and
* AIS-L maintenance signal (defined in Section 6.2.1.2 of [GR253])
for SONET services
at client-frame boundaries.
4.4. Fibre Channel Services
Fibre Channel services are special cases of the structured bit stream bit-stream
defined in Section 3.3.4 of [RFC3985].
The T11 technical committee of INCITS has defined several layers for
Fibre Channel. PLE operates at the FC-1 layer that leverages
mechanisms defined by [IEEE802.3].
Over time, many different Fibre Channel interface types have been
specified with a varying set of characteristics such as optional
versus mandatory FEC and single-lane versus multi-lane transmission.
Speed negotiation is not supported by PLE.
All Fibre Channel services leverage the basic PLE payload, and
interface-specific mechanisms are confined to the respective service-
specific NSP functions.
4.4.1. 1GFC, 2GFC, 4GFC, and 8GFC
[FC-PI-2] specifies 1GFC and 2GFC. [FC-PI-5] and [FC-PI-5am1] define
4GFC and 8GFC.
The PSN-bound NSP function is responsible for detecting attachment
circuit faults specific to the Fibre Channel such as LOS and sync
loss.
The PSN-bound IWF maps the received 8B/10B code stream as is directly
into the basic PLE payload.
The CE-bound NSP function MUST perform transmission word sync in
order to properly:
* replace invalid transmission words with the special character
K30.7 and
* insert Not Operational (NOS) NOS ordered sets when the CE-bound IWF is in PLOS state or
when PLE packets are received with the L bit set set.
| Note: Invalid transmission words typically are a consequence of
| the CE-bound IWF inserting replacement data in case of lost PLE
| packets.
[FC-PI-5am1] defines the use of scrambling for 8GFC; in this case,
the CE-bound NSP MUST also perform descrambling before replacing
invalid transmission words or inserting NOS ordered sets. Before
sending the bit stream bit-stream to the CE, the CE-bound NSP function MUST
scramble the 8B/10B code stream.
4.4.2. 16GFC
[FC-PI-5] and [FC-PI-5am1] specify 16GFC and define an optional FEC
layer.
If FEC is present, it must be indicated via transmitter training
signal (TTS) TTS when the attachment
circuit is brought up. Further, the PSN-bound NSP function MUST
terminate the FEC and the CE-bound NSP function must generate the
FEC.
The PSN-bound NSP function is responsible for detecting attachment
circuit faults specific to the Fibre Channel such as LOS and sync
loss.
The PSN-bound IWF maps the received scrambled 64B/66B code stream as
is into the basic PLE payload.
The CE-bound NSP function MUST perform:
* transmission word sync (Section 49.2.13 of [IEEE802.3]) and
* descrambling (Section 49.2.10 of [IEEE802.3])
in order to properly:
* replace invalid transmission words with the error transmission
word 1Eh and
* insert Not Operational (NOS) NOS ordered sets when the CE-bound IWF is in PLOS state or
when PLE packets are received with the L bit set set.
| Note: Invalid transmission words typically are a consequence of
| the CE-bound IWF inserting replacement data in case of lost PLE
| packets or the far-end PSN-bound NSP function not setting sync
| headers to 11 due to uncorrectable FEC errors.
Before sending the bit stream bit-stream to the CE, the CE-bound NSP function
MUST also scramble the 64B/66B code stream (Section 49.2.6 of
[IEEE802.3]).
4.4.3. 32GFC and 4-Lane 128GFC
[FC-PI-6] specifies 32GFC and [FC-PI-6P] specifies 4-lane 128GFC,
both with FEC layer and TTS support being mandatory.
To gain access to the 64B/66B code stream the PSN-bound NSP further
MUST perform:
* descrambling (Section of 49.2.10 of [IEEE802.3]) [IEEE802.3]),
* FEC decoding (Section 91.5.3.3 of [IEEE802.3]) [IEEE802.3]), and
* reverse transcoding from 256B/257B to 64B/66B (Section 119.2.5.7
of [IEEE802.3]) [IEEE802.3]).
Further, the PSN-bound NSP MUST perform scrambling (Section 49.2.6 of
[IEEE802.3]) before the PSN-bound IWF maps the same into the basic
PLE payload.
The PSN-bound NSP function is also responsible for detecting
attachment circuit faults specific to the Fibre Channel such as LOS
and sync loss.
The CE-bound NSP function MUST perform:
* transmission word sync (Section 119.2.6.3 of [IEEE802.3]) and
* descrambling (Section 49.2.10 of [IEEE802.3])
in order to properly:
* replace invalid transmission words with the error transmission
word 1Eh and
* insert Not Operational (NOS) NOS ordered sets when the CE-bound IWF is in PLOS state or
when PLE packets are received with the L bit set set.
| Note: Invalid transmission words typically are a consequence of
| the CE-bound IWF inserting replacement data in case of lost PLE
| packets or the far-end PSN-bound NSP function not setting sync
| headers to 11 due to uncorrectable FEC errors.
When sending the bit stream bit-stream to the CE, the CE-bound NSP function MUST
also perform:
* transcoding from 64B/66B to 256B/257B (Section 119.2.4.2 of
[IEEE802.3])
[IEEE802.3]),
* FEC encoding (Section 91.5.2.7 of [IEEE802.3]) [IEEE802.3]), and
* scrambling (Section 49.2.6 of [IEEE802.3]) [IEEE802.3]).
4.4.4. 64GFC
[FC-PI-7] specifies 64GFC with a mandatory FEC layer.
To gain access to the 64B/66B code stream, the PSN-bound NSP further
MUST perform:
* alignment lock (Section 134.5.4 of [IEEE802.3] modified to single
FEC lane operation) operation),
* FEC decoding (Section 134.5.3.3 of [IEEE802.3]) [IEEE802.3]),
* alignment-marker removal (Section 134.5.3.4 of [IEEE802.3]) [IEEE802.3]), and
* reverse transcoding from 256B/257B to 64B/66B (Section 91.5.3.5 of
[IEEE802.3])
[IEEE802.3]).
Further, the PSN-bound NSP MUST perform scrambling (Section 49.2.6 of
[IEEE802.3]) before the PSN-bound IWF maps the same into the basic
PLE payload.
The PSN-bound NSP function is also responsible for detecting
attachment circuit faults specific to the Fibre Channel such as LOS
and sync loss.
The CE-bound NSP function MUST perform:
* transmission word sync (Section 49.2.13 of [IEEE802.3]) and
* descrambling (Section 49.2.10 of [IEEE802.3])
in order to properly:
* replace invalid transmission words with the error transmission
word 1Eh and
* insert Not Operational (NOS) NOS ordered sets when the CE-bound IWF is in PLOS state or
when PLE packets are received with the L bit set set.
| Note: Invalid transmission words typically are a consequence of
| the CE-bound IWF inserting replacement data in case of lost PLE
| packets or the far-end PSN-bound NSP function not setting sync
| headers to 11 due to uncorrectable FEC errors.
When sending the bit stream bit-stream to the CE, the CE-bound NSP function MUST
also perform:
* transcoding from 64B/66B to 256B/257B (Section 91.5.2.5 of
[IEEE802.3])
[IEEE802.3]),
* alignment-marker insertion (Section 134.5.2.6 of [IEEE802.3]) [IEEE802.3]), and
* FEC encoding (Section 134.5.2.7 of [IEEE802.3]) [IEEE802.3]).
4.5. OTN Services
OTN services are special cases of the structured bit stream bit-stream defined
in Section 3.3.4 of [RFC3985].
OTN interfaces are defined in [G.709].
The PSN-bound NSP function MUST terminate the FEC and replace the
OTUk overhead in row 1, columns 8-14 with an all-zeros pattern; this
results in an extended ODUk frame as illustrated in Figure 3. The
frame alignment overhead (FA OH) in row 1, columns 1-7 is kept as it
is.
column #
1 7 8 14 15 3824
+--------+--------+------------------- .. --------------------+
1| FA OH | All-0s | |
+--------+--------+ |
r 2| | |
o | | |
w 3| ODUk overhead | |
# | | |
4| | |
+-----------------+------------------- .. --------------------+
Figure 3: Extended ODUk Frame
The PSN-bound NSP function is also responsible for detecting
attachment circuit faults specific to OTUk such as LOS, LOF, LOM, and
AIS.
The PSN-bound IWF maps the extended ODUk frame into the byte-aligned
PLE payload.
The CE-bound NSP function will recover the ODUk by searching for the
frame alignment overhead in the extended ODUk received from the CE-
bound IWF and generating the FEC.
When the CE-bound IWF is in PLOS state or when PLE packets are
received with the L bit set, the CE-bound NSP function is responsible
for generating the ODUk-AIS maintenance signal defined in
Section 16.5.1 of [G.709] at client-frame boundaries.
5. PLE Encapsulation Layer
The basic packet format used by PLE is shown in Figure 4.
+-------------------------------+ -+
| PSN and VPWS Demux | \
| (MPLS/SRv6) | > PSN and VPWS
| | / Demux Headers
+-------------------------------+ -+
| PLE Control Word | \
+-------------------------------+ > PLE Header
| RTP Header | /
+-------------------------------+ --+
| Bit Stream Bit-Stream | \
| Payload | > Payload
| | /
+-------------------------------+ --+
Figure 4: PLE Encapsulation Layer
5.1. PSN and VPWS Demultiplexing Headers
This document does not suggest any specific technology be used for
implementing the VPWS demultiplexing and PSN layers.
The total size of a PLE packet for a specific PW MUST NOT exceed the
path MTU between the pair of PEs terminating this PW.
When an MPLS PSN layer is used, a VPWS label provides the
demultiplexing mechanism (as described in Section 5.4.2 of
[RFC3985]). The PSN tunnel can be a simple best-path Label Switched
Path (LSP) LSP established
using LDP (see [RFC5036]) or Segment Routing (SR) (see [RFC8402]); or
it can be a traffic-engineered LSP established using RSVP-TE (see
[RFC3209]) or SR policies (see [RFC9256]).
When an SRv6 PSN layer is used, an SRv6 service Segment Identifier
(SID) SID (as defined in
[RFC8402]) provides the demultiplexing mechanism and definitions of
Section 6 of [RFC9252] apply. Both SRv6 service SIDs with the full
IPv6 address format defined in [RFC8986] and compressed SIDs (C-SIDs)
with the format defined in [RFC9800] can be used.
5.1.1. New SRv6 Behaviors
Two new encapsulation behaviors, H.Encaps.L1 and H.Encaps.L1.Red, are
defined in this document. The behavior procedures are applicable to
both SIDs and C-SIDs.
The H.Encaps.L1 behavior encapsulates a frame received from an IWF in
an IPv6 packet with a segment routing header (SRH). The received
frame becomes the payload of the new IPv6 packet.
* The next header field of the SRH or the last extension header
present MUST be set to 147.
* The insertion of the SRH MAY be omitted per [RFC8986] when the
SRv6 policy only contains one segment and there is no need to use
any flag, tag, or TLV.
The H.Encaps.L1.Red behavior is an optimization of the H.Encaps.L1
behavior.
* H.Encaps.L1.Red reduces the length of the SRH by excluding the
first SID in the SRH. The first SID is only placed in the
destination
Destination Address field of the IPv6 address field. header.
* The insertion of the SRH MAY be omitted per [RFC8986] when the
SRv6 policy only contains one segment and there is no need to use
any flag, tag, or TLV.
Three new "Endpoint with decapsulation and bit-stream cross-connect"
behaviors called "End.DX1", "End.DX1 with NEXT-CSID", and "End.DX1
with REPLACE-CSID" are defined in this document. These new behaviors
are variants of End.DX2 defined in [RFC8986], and they all have the
following procedures in common:
The End.DX1 SID MUST be the last segment in an SR Policy, and it is
associated with a CE-bound IWF I. When N receives a packet destined
to S and S is a local End.DX1 SID, N does the following:
S01. When an SRH is processed {
S02. If (Segments Left != 0) {
S03. Send an ICMP Parameter Problem to the Source Address
with Code 0 (Erroneous header field encountered)
and Pointer set to the Segments Left field,
interrupt packet processing, and discard the packet.
S04. }
S05. Proceed to process the next header in the packet
S06. }
When processing the next (Upper-Layer) header of a packet matching a
FIB entry locally instantiated as an End.DX1 SID, N does the
following:
S01. If (Upper-Layer header type == 147 (bit-stream) ) {
S02. Remove the outer IPv6 header with all its extension headers
S03. Forward the remaining frame to the IWF I
S04. } Else {
S05. Process as per {{Section 4.1.1 of RFC 8986}}
S06. }
5.2. PLE Header
The PLE header MUST contain the PLE control word (4 bytes) and MUST
include a fixed-size RTP header [RFC3550]. The RTP header MUST
immediately follow the PLE control word.
5.2.1. PLE Control Word
The format of the PLE control word is in line with the guidance in
[RFC4385] and is shown in Figure 5.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0|L|R|RSV|FRG| LEN | Sequence number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: PLE Control Word
The bits 0..3 of the first nibble are set to 0 to differentiate a
control word or Associated Channel Header (ACH) ACH from an IP packet or Ethernet frame. The first
nibble MUST be set to 0000b to indicate that this header is a control
word as defined in Section 3 of [RFC4385].
The other fields in the control word are used as defined below:
L
L:
Set by the PE to indicate that data carried in the payload is
invalid due to an attachment circuit fault. The downstream PE
MUST send appropriate replacement data. The NSP MAY inject an
appropriate native specific fault propagation signal.
R
R:
Set by the downstream PE to indicate that the IWF experiences
packet loss from the PSN or a server layer backward fault
indication is present in the NSP. The R bit MUST be cleared by
the PE once the packet loss state or fault indication has cleared.
RSV
RSV:
These bits are reserved for future use. This field MUST be set to
zero by the sender and ignored by the receiver.
FRG
FRG:
These bits MUST be set to zero by the sender and ignored by the
receiver as PLE does not use payload fragmentation.
LEN
LEN:
In accordance with Section 3 of [RFC4385], the length field MUST
always be set to zero as there is no padding added to the PLE
packet. The preconfigured size of the PLE payload MUST be assumed
to be as described in Section 5.2; if the actual packet size is
inconsistent with this length, the packet MUST be considered
malformed. To detect malformed packets the default, preconfigured
or signaled payload size MUST be assumed.
Sequence number number:
The sequence number field is used to provide a common PW
sequencing function as well as detection of lost packets. It MUST
be generated in accordance with the rules defined in Section 5.1
of [RFC3550] and MUST be incremented with every PLE packet being
sent.
5.2.2. RTP Header
The RTP header MUST be included to explicitly convey timing
information.
The RTP header (as defined in [RFC3550]) is reused to align with
other bit-stream emulation pseudowires defined by [RFC4553],
[RFC5086], and [RFC4842] and to allow PLE implementations to reuse
preexisting work.
There is no intention to support full RTP topologies and protocol
mechanisms, such as header extensions, contributing source (CSRC)
list, padding, RTP Control Protocol (RTCP), RTCP, RTP header compression,
Secure Real-time Transport Protocol (SRTP), SRTP, etc., as these are
not applicable to PLE VPWS.
The format of the RTP header is as shown in Figure 6.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|V=2|P|X| CC |M| PT | Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Timestamp |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Synchronization Source (SSRC) Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6: RTP Header
V:
Version
The version field MUST be set to 2.
P:
Padding
The padding flag MUST be set to zero by the sender and ignored by
the receiver.
X:
Header extension
The X bit MUST be set to zero by sender and ignored by receiver.
CC:
CSRC count
The CC field MUST be set to zero by the sender and ignored by the
receiver.
M:
Marker
The M bit MUST be set to zero by the sender and ignored by the
receiver.
PT:
Payload type
A PT value MUST be allocated from the range of dynamic values
defined in Section 6 of [RFC3551] for each direction of the VPWS.
The same PT value MAY be reused for both for direction directions and
between different PLE VPWS. VPWSs.
The PT field MAY be used for detection of misconnections.
Sequence number number:
When using a 16-bit sequence number space, the sequence number in
the RTP header MUST be equal to the sequence number in the PLE
control word. When using a sequence number space of 32 bits, the
initial value of the RTP sequence number MUST be 0 and incremented
whenever the PLE control word sequence number cycles through from
0xFFFF to 0x0000.
Timestamp
Timestamp:
Timestamp values are used in accordance with the rules established
in [RFC3550]. For bit-streams up to 200 Gbps, the frequency of
the clock used for generating timestamps MUST be 125 MHz based on
a the common clock I. For bit-streams above 200 Gbps, the
frequency MUST be 250 MHz.
SSRC:
Synchronization source
The SSRC field MAY be used for detection of misconnections.
6. PLE Payload Layer
A bit-stream is mapped into a PLE packet with a fixed payload size,
which MUST be defined during VPWS setup, MUST be the same in both
directions of the VPWS, and MUST remain unchanged for the lifetime of
the VPWS.
All PLE implementations MUST be capable of supporting the default
payload size of 1024 bytes. The payload size SHOULD be configurable
to be able to address specific packetization delay and overhead
expectations. The smallest supported payload size is 64 bytes.
6.1. Basic Payload
The PLE payload is filled with incoming bits of the bit-stream
starting from the most significant to the least significant bit
without considering any structure of the bit-stream.
6.2. Byte-Aligned Payload
The PLE payload is filled in a byte-aligned manner, where the order
of the payload bytes corresponds to their order on the attachment
circuit. Consecutive bits coming from the attachment circuit fill
each payload byte starting from most significant bit to least
significant. The PLE payload size MUST be an integer number of
bytes.
7. PLE Operation
7.1. Common Considerations
A PLE VPWS can be established using manual configuration or
leveraging mechanisms of a signaling protocol.
Furthermore, emulation of bit-stream signals using PLE is only
possible when the two attachment circuits of the VPWS are of the same
service type (OC192, 10GBASE-R, ODU2, etc.) and are using the same
PLE payload type and payload size. This can be ensured via manual
configuration or via the mechanisms of a signaling protocol.
PLE-related control protocol extensions to LDP [RFC8077] or EVPN-VPWS
[RFC8214] are out of scope for this document.
Extensions for EVPN-VPWS are proposed in [EVPN-VPWS] and for LDP in
[LDP-PLE].
7.2. PLE IWF Operation
7.2.1. PSN-Bound Encapsulation Behavior
After the VPWS is set up, the PSN-bound IWF performs the following
steps:
* Packetize the data received from the CE into PLE payloads, all of
the same configured size size,
* Add PLE control word and RTP header with sequence numbers, flags,
and timestamps properly set set,
* Add the VPWS demultiplexer and PSN headers headers,
* Transmit the resulting packets over the PSN PSN,
* Set the L bit in the PLE control word whenever the attachment
circuit detects a fault fault, and
* Set the R bit in the PLE control word whenever the local CE-bound
IWF is in packet loss state state.
7.2.2. CE-Bound Decapsulation Behavior
The CE-bound IWF is responsible for removing the PSN and VPWS
demultiplexing headers, PLE control word, and RTP header from the
received packet stream and sending the bit-stream out via the local
attachment circuit.
A de-jitter buffer MUST be implemented where the PLE packets are
stored upon arrival. The size of this buffer SHOULD be locally
configurable to allow accommodation of specific PSN packet delay
variation (PDV) PDV expected.
The CE-bound IWF SHOULD use the sequence number in the control word
to detect lost and misordered packets. It MAY use the sequence
number in the RTP header for the same purpose. The CE-bound IWF MAY
support reordering of packets received out of order. If the CE-bound
IWF does not support reordering, it MUST drop the misordered packets.
The payload of a lost or dropped packet MUST be replaced with an
equivalent amount of replacement data. The contents of the
replacement data MAY be locally configurable. By default, all PLE
implementations MUST support generation of "0xAA" as replacement
data. The alternating sequence of 0s and 1s of the "0xAA" pattern
ensures clock synchronization is maintained and, for 64B/66B code-
based services, ensures no invalid sync headers are generated. While
sending out the replacement data, the IWF will apply a holdover
mechanism to maintain the clock.
Whenever the VPWS is not operationally up, the CE-bound NSP function
MUST inject the appropriate native specific downstream fault-indication
signal.
Whenever a VPWS comes up, the CE-bound IWF will enter the
intermediate state, will start receiving PLE packets, and will store
them in the jitter buffer. The CE-bound NSP function will continue
to inject the appropriate native specific downstream fault-indication signal
until a preconfigured number of payload s stored in the jitter
buffer.
After the preconfigured amount of payload is present in the jitter
buffer, the CE-bound IWF transitions to the normal operation state,
and the content of the jitter buffer is streamed out to the CE in
accordance with the required clock. In this state, the CE-bound IWF
MUST perform egress clock recovery.
Considerations for choosing the preconfigured amount of payload
required to be present for transitioning into the normal state:
* Typically set to 50% of the de-jitter buffer size to equally allow
compensating for increasing and decreasing delay
* A compromise between the maximum amount of tolerable PDV and delay
introduced to the emulated service
The recovered clock MUST comply with the jitter and wander
requirements applicable to the type of attachment circuit, specified
in:
* [G.825], [G.783], and [G.823] for SDH
* [GR253] and [GR499] for SONET
* [G.8261] for synchronous Ethernet
* [G.8251] for OTN
Whenever the L bit is set in the PLE control word of a received PLE
packet, the CE-bound NSP function SHOULD inject the appropriate
native
specific downstream fault-indication signal instead of streaming out
the payload.
If the CE-bound IWF detects loss of consecutive packets for a
preconfigured amount of time (default is 1 millisecond), it enters
packet loss (PLOS)
PLOS state and a corresponding defect is declared.
If the CE-bound IWF detects a packet loss ratio (PLR) PLR above a configurable signal-degrade (SD) SD threshold
for a configurable amount of consecutive 1-second intervals, it
enters the degradation (DEG) DEG state and a corresponding defect is declared. The SD-PLR SD-
PLR threshold can be defined as a percentage with the default being
15% or absolute packet count for finer granularity for higher rate
interfaces. Possible values for consecutive intervals are 2..10 with
the default 7.
While the PLOS defect is declared, the CE-bound NSP function MUST
inject the appropriate native specific downstream fault-indication signal.
If the emulated service does not have an appropriate maintenance
signal defined, the CE-bound NSP function MAY disable its transmitter
instead. Also, the PSN-bound IWF SHOULD set the R bit in the PLE
control word of every packet transmitted.
The CE-bound IWF changes from the PLOS to normal state after the
preconfigured amount of payload has been received similar to the
transition from intermediate to normal state.
Whenever the R bit is set in the PLE control word of a received PLE
packet, the PLE performance monitoring statistics SHOULD get updated.
7.3. PLE Performance Monitoring
Attachment circuit performance monitoring SHOULD be provided by the
NSP. The performance monitors are service specific, documented in
related specifications, and beyond the scope of this document.
The PLE IWF SHOULD provide functions to monitor the network
performance to be inline with expectations of transport network
operators.
The near-end performance monitors defined for PLE are as follows:
* ES-PLE : PLE Errored Seconds
* SES-PLE : PLE Severely Errored Seconds
* UAS-PLE : PLE Unavailable Seconds
Each second with at least one packet lost or a PLOS/DEG PLOS or DEG defect
SHALL be counted as an ES-PLE. Each second with a PLR greater than
15% or a PLOS/DEG PLOS or DEG defect SHALL be counted as an SES-PLE.
UAS-PLE SHALL be counted after a configurable number of consecutive
SES-PLEs have been observed, and no longer counted after a
configurable number of consecutive seconds without an SES-PLE have
been observed. The default value for each is 10 seconds.
Once unavailability is detected, ES ES-PLE and SES SES-PLE counts SHALL be
inhibited up to the point where the unavailability was started. Once
unavailability is removed, ES ES-PLE and SES SES-PLE that occurred along the
clearing period SHALL be added to the ES ES-PLE and SES SES-PLE counts.
A PLE far-end performance monitor provides insight into the CE-bound
IWF at the far end of the PSN. The statistics are based on the PLE-
RDI indication carried in the PLE control word via the R bit.
The PLE VPWS performance monitors are derived from the definitions in
accordance with [G.826].
Performance monitoring data MUST be provided by the management
interface and SHOULD be provided by a YANG data model. The YANG data
model specification is out of scope for this document.
7.4. PLE Fault Management
Attachment circuit faults applicable to PLE are detected by the NSP,
are service specific, and are documented in Section 4.
The two PLE faults, PLOS and DEG, are detected by the IWF.
Faults MUST be timestamped as they are declared and cleared; fault-
related information MUST be provided by the management interface and
SHOULD be provided by a YANG data model. The YANG data model
specification is out of scope for this document.
8. QoS and Congestion Control
The PSN carrying PLE VPWS may be subject to congestion. Congestion
considerations for PWs are described in Section 6.5 of [RFC3985].
PLE VPWS represent inelastic constant bit-rate (CBR) CBR flows that cannot respond to
congestion in a TCP-friendly manner (as described in [RFC2914]) and
are sensitive to jitter, packet loss, and packets received out of
order.
The PSN providing connectivity between PE devices of a PLE VPWS has
to ensure low jitter and low loss. The exact mechanisms used are
beyond the scope of this document and may evolve over time. Possible
options, but not exhaustively, are as follows follows:
* a Diffserv-enabled [RFC2475] PSN with a per-domain behavior (see
[RFC3086]) supporting Expedited Forwarding (see [RFC3246]),
* traffic-engineered paths through the PSN with bandwidth
reservation and admission control applied, or
* capacity over-provisioning.
9. Security Considerations
As PLE is leveraging VPWS as transport mechanism, the security
considerations described in [RFC3985] are applicable.
PLE does not enhance or detract from the security performance of the
underlying PSN. It relies upon the PSN mechanisms for encryption,
integrity, and authentication whenever required.
The PSN (MPLS or SRv6) is assumed to be trusted and secure.
Attackers who manage to send spoofed packets into the PSN could
easily disrupt the PLE service. This MUST be prevented by following
best practices for the isolation of the PSN. These protections are
described in Section 3.4 of [RFC4381], Section 4.2 of [RFC5920],
Section 8 of [RFC8402], and Section 9.3 of [RFC9252].
PLE PWs share susceptibility to a number of pseudowire-layer attacks
and will use whatever mechanisms for confidentiality, integrity, and
authentication that are developed for general PWs. These methods are
beyond the scope of this document.
Random initialization of sequence numbers, in both the control word
and the RTP header, makes known-plaintext attacks more difficult.
Misconnection detection using the SSRC and/or PT field of the RTP
header can increase the resilience to misconfiguration and some types
of denial-of-service (DoS) attacks. Randomly chosen expected values
decrease the chance of a spoofing attack being successful.
A data plane attack may force PLE packets to be dropped, reordered,
or delayed beyond the limit of the CE-bound IWF's dejitter buffer
leading to either degradation or service disruption. Considerations
outlined in [RFC9055] are a good reference.
Clock synchronization leveraging PTP is sensitive to Packet Delay
Variation (PDV) PDV and
vulnerable to various threads threats and attack vectors. Considerations
outlined in [RFC7384] should be taken into account.
10. IANA Considerations
10.1. Bit-Stream Next Header Type
This document introduces a new value to be used in the next header
field of an IPv6 header or any extension header indicating that the
payload is an emulated bit-stream. IANA has assigned the following
from the "Assigned Internet Protocol Numbers" registry [IANA-Proto].
+=========+=========+============+================+===========+
| Decimal | Keyword | Protocol | IPv6 Extension | Reference |
| | | | Header | |
+=========+=========+============+================+===========+
| 147 | BIT-EMU | Bit-stream | Y | This |
| | | Emulation | | document |
+---------+---------+------------+----------------+-----------+
Table 1
10.2. SRv6 Endpoint Behaviors
This document introduces three new SRv6 Endpoint behaviors. IANA has
assigned identifier values in the "SRv6 Endpoint Behaviors" registry
under the "Segment Routing" registry group [IANA-SRv6-End].
+=======+========+===========================+===============+
| Value | Hex | Endpoint Behavior | Reference |
+=======+========+===========================+===============+
| 158 | 0x009E | End.DX1 | This document |
+-------+--------+---------------------------+---------------+
| 159 | 0x009F | End.DX1 with NEXT-CSID | This document |
+-------+--------+---------------------------+---------------+
| 160 | 0x00A0 | End.DX1 with REPLACE-CSID | This document |
+-------+--------+---------------------------+---------------+
Table 2
11. References
11.1. Normative References
[G.707] ITU-T, "Network node interface for the synchronous digital
hierarchy (SDH)", ITU-T Recommendation G.707, January
2007, <https://www.itu.int/rec/T-REC-G.707>.
[G.709] ITU-T, "Interfaces for the optical transport network",
ITU-T Recommendation G.709, June 2020,
<https://www.itu.int/rec/T-REC-G.709>.
[G.783] ITU-T, "Characteristics of synchronous digital hierarchy
(SDH) equipment functional blocks", ITU-T
Recommendation G.783, March 2006,
<https://www.itu.int/rec/T-REC-G.783>.
[G.823] ITU-T, "The control of jitter and wander within digital
networks which are based on the 2048 kbit/s hierarchy",
ITU-T Recommendation G.823, March 2000,
<https://www.itu.int/rec/T-REC-G.823>.
[G.824] ITU-T, "The control of jitter and wander within digital
networks which are based on the 1544 kbits hierarchy",
ITU-T Recommendation G.824, March 2000,
<https://www.itu.int/rec/T-REC-G.824>.
[G.825] ITU-T, "The control of jitter and wander within digital
networks which are based on the synchronous digital
hierarchy (SDH)", ITU-T Recommendation G.825, March 2000,
<https://www.itu.int/rec/T-REC-G.825>.
[G.8251] ITU-T, "The control of jitter and wander within the
optical transport network (OTN)", ITU-T
Recommendation G.8251, November 2022,
<https://www.itu.int/rec/T-REC-G.8251>.
[G.8261] ITU-T, "Timing and synchronization aspects in packet
networks", ITU-T Recommendation G.8261, August 2019,
<https://www.itu.int/rec/T-REC-G.8261>.
[G.8261.1] ITU-T, "Packet delay variation network limits applicable
to packet-based methods (Frequency synchronization)",
ITU-T Recommendation G.8261.1, February 2012,
<https://www.itu.int/rec/T-REC-G.8261.1>.
[G.8262] ITU-T, "Timing characteristics of synchronous equipment
clocks", ITU-T Recommendation G.8262, October 2024,
<https://www.itu.int/rec/T-REC-G.8262>.
[G.8265.1] ITU-T, "Precision time protocol telecom profile for
frequency synchronization", ITU-T Recommendation G.8265.1,
November 2022, <https://www.itu.int/rec/T-REC-G.8265.1>.
[GR253] Telcordia, "Synchronous Optical Network (SONET) Transport
Systems: Common Generic Criteria", GR-253, October 2009,
<https://telecom-info.njdepot.ericsson.net/site-cgi/ido/
docs.cgi?ID=2111701336SEARCH&DOCUMENT=GR-253>.
[GR499] Telcordia, "Transport Systems Generic Requirements (TSGR)
- Common Requirements", GR-499, November 2009,
<https://telecom-info.njdepot.ericsson.net/site-cgi/ido/
docs.cgi?ID=2111701336SEARCH&DOCUMENT=GR-499>.
[IANA-Proto]
IANA, "Assigned Internet Protocol Numbers",
<https://www.iana.org/assignments/protocol-numbers>.
[IANA-SRv6-End]
IANA, "SRv6 Endpoint Behaviors",
<https://www.iana.org/assignments/segment-routing>.
[IEEE802.3]
IEEE, "IEEE Standard for Ethernet", IEEE Std 802.3-2022,
DOI 10.1109/IEEESTD.2022.9844436, July 2022,
<https://ieeexplore.ieee.org/document/9844436>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V.
Jacobson, "RTP: A Transport Protocol for Real-Time
Applications", STD 64, RFC 3550, DOI 10.17487/RFC3550,
July 2003, <https://www.rfc-editor.org/info/rfc3550>.
[RFC3551] Schulzrinne, H. and S. Casner, "RTP Profile for Audio and
Video Conferences with Minimal Control", STD 65, RFC 3551,
DOI 10.17487/RFC3551, July 2003,
<https://www.rfc-editor.org/info/rfc3551>.
[RFC3985] Bryant, S., Ed. and P. Pate, Ed., "Pseudo Wire Emulation
Edge-to-Edge (PWE3) Architecture", RFC 3985,
DOI 10.17487/RFC3985, March 2005,
<https://www.rfc-editor.org/info/rfc3985>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
Decraene, B., Litkowski, S., and R. Shakir, "Segment
Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
July 2018, <https://www.rfc-editor.org/info/rfc8402>.
[RFC8986] Filsfils, C., Ed., Camarillo, P., Ed., Leddy, J., Voyer,
D., Matsushima, S., and Z. Li, "Segment Routing over IPv6
(SRv6) Network Programming", RFC 8986,
DOI 10.17487/RFC8986, February 2021,
<https://www.rfc-editor.org/info/rfc8986>.
[RFC9252] Dawra, G., Ed., Talaulikar, K., Ed., Raszuk, R., Decraene,
B., Zhuang, S., and J. Rabadan, "BGP Overlay Services
Based on Segment Routing over IPv6 (SRv6)", RFC 9252,
DOI 10.17487/RFC9252, July 2022,
<https://www.rfc-editor.org/info/rfc9252>.
[RFC9800] Cheng, W., Ed., Filsfils, C., Li, Z., Decraene, B., and F.
Clad, Ed., "Compressed SRv6 Segment List Encoding (CSID)",
RFC 9800, DOI 10.17487/RFC9800, June 2025,
<https://www.rfc-editor.org/info/rfc9800>.
11.2. Informative References
[ATIS-0900105.09.2013]
ATIS, "Synchronous Optical Network (SONET) - Network
Element Timing and Synchronization", ATIS-
0900105.09.2013(S2023), 2023,
<https://webstore.ansi.org/standards/atis/
atis0900105092013s2023>.
[EVPN-VPWS]
Gringeri, S., Whittaker, J., Schmutzer, C., Ed.,
Vasudevan, B., and P. Brissette, "Ethernet VPN Signalling
Extensions for Bit-stream VPWS", Work in Progress,
Internet-Draft, draft-schmutzer-bess-bitstream-vpws-
signalling-02, 18 October 2024,
<https://datatracker.ietf.org/doc/html/draft-schmutzer-
bess-bitstream-vpws-signalling-02>.
[FC-PI-2] INCITS, "Information Technology - Fibre Channel Physical
Interfaces - 2 (FC-PI-2)", INCITS 404-2006 (S2016), 2016,
<https://webstore.ansi.org/standards/incits/
incits4042006s2016>.
[FC-PI-5] INCITS, "Information Technology - Fibre Channel - Physical
Interface-5 (FC-PI-5)", INCITS 479-2011, 2011, 479-2011 (S2021), 2021,
<https://webstore.ansi.org/standards/incits/
incits4792011>.
incits4792011s2021>.
[FC-PI-5am1]
INCITS, "Information Technology - Fibre Channel - Physical
Interface - 5/Amendment 1 (FC-PI-5/AM1)",
INCITS 479-2011/AM1-2016, 2016, 479-2011/AM1-2016 (R2021), 2021,
<https://webstore.ansi.org/standards/incits/
incits4792011am12016>.
incits4792011am2016r2021>.
[FC-PI-6] INCITS, "Information Technology - Fibre Channel - Physical
Interface - 6 (FC-PI-6)", INCITS 512-2015, 2015, 512-2015 (R2020), 2020,
<https://webstore.ansi.org/standards/incits/
incits5122015>.
incits5122015r2020>.
[FC-PI-6P] INCITS, "Information Technology - Fibre Channel - Physical
Interface - 6P (FC-PI-6P)", INCITS 533-2016, 2016, 533-2016 (R2021), 2021,
<https://webstore.ansi.org/standards/incits/
incits5332016>.
incits5332016r2021>.
[FC-PI-7] ISO/IEC, "Information technology – Fibre channel - Part
147: Physical interfaces - 7 (FC-PI-7)", ISO/
IEC 14165-147:2021, 2021,
<https://www.iso.org/standard/80933.html>.
[G.826] ITU-T, "End-to-end error performance parameters and
objectives for international, constant bit-rate digital
paths and connections", ITU-T Recommendation G.826,
December 2002, <https://www.itu.int/rec/T-REC-G.826>.
[LDP-PLE] Schmutzer, C., Ed., "LDP Extensions to Support Private
Line Emulation (PLE)", Work in Progress, Internet-Draft,
draft-schmutzer-pals-ple-signaling-02, 20 October 2024,
<https://datatracker.ietf.org/doc/html/draft-schmutzer-
pals-ple-signaling-02>.
[RFC2475] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z.,
and W. Weiss, "An Architecture for Differentiated
Services", RFC 2475, DOI 10.17487/RFC2475, December 1998,
<https://www.rfc-editor.org/info/rfc2475>.
[RFC2914] Floyd, S., "Congestion Control Principles", BCP 41,
RFC 2914, DOI 10.17487/RFC2914, September 2000,
<https://www.rfc-editor.org/info/rfc2914>.
[RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
Label Switching Architecture", RFC 3031,
DOI 10.17487/RFC3031, January 2001,
<https://www.rfc-editor.org/info/rfc3031>.
[RFC3086] Nichols, K. and B. Carpenter, "Definition of
Differentiated Services Per Domain Behaviors and Rules for
their Specification", RFC 3086, DOI 10.17487/RFC3086,
April 2001, <https://www.rfc-editor.org/info/rfc3086>.
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001,
<https://www.rfc-editor.org/info/rfc3209>.
[RFC3246] Davie, B., Charny, A., Bennet, J.C.R., Benson, K., Le
Boudec, J.Y., Courtney, W., Davari, S., Firoiu, V., and D.
Stiliadis, "An Expedited Forwarding PHB (Per-Hop
Behavior)", RFC 3246, DOI 10.17487/RFC3246, March 2002,
<https://www.rfc-editor.org/info/rfc3246>.
[RFC3711] Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K.
Norrman, "The Secure Real-time Transport Protocol (SRTP)",
RFC 3711, DOI 10.17487/RFC3711, March 2004,
<https://www.rfc-editor.org/info/rfc3711>.
[RFC4197] Riegel, M., Ed., "Requirements for Edge-to-Edge Emulation
of Time Division Multiplexed (TDM) Circuits over Packet
Switching Networks", RFC 4197, DOI 10.17487/RFC4197,
October 2005, <https://www.rfc-editor.org/info/rfc4197>.
[RFC4381] Behringer, M., "Analysis of the Security of BGP/MPLS IP
Virtual Private Networks (VPNs)", RFC 4381,
DOI 10.17487/RFC4381, February 2006,
<https://www.rfc-editor.org/info/rfc4381>.
[RFC4385] Bryant, S., Swallow, G., Martini, L., and D. McPherson,
"Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for
Use over an MPLS PSN", RFC 4385, DOI 10.17487/RFC4385,
February 2006, <https://www.rfc-editor.org/info/rfc4385>.
[RFC4443] Conta, A., Deering, S., and M. Gupta, Ed., "Internet
Control Message Protocol (ICMPv6) for the Internet
Protocol Version 6 (IPv6) Specification", STD 89,
RFC 4443, DOI 10.17487/RFC4443, March 2006,
<https://www.rfc-editor.org/info/rfc4443>.
[RFC4448] Martini, L., Ed., Rosen, E., El-Aawar, N., and G. Heron,
"Encapsulation Methods for Transport of Ethernet over MPLS
Networks", RFC 4448, DOI 10.17487/RFC4448, April 2006,
<https://www.rfc-editor.org/info/rfc4448>.
[RFC4553] Vainshtein, A., Ed. and YJ. Stein, Ed., "Structure-
Agnostic Time Division Multiplexing (TDM) over Packet
(SAToP)", RFC 4553, DOI 10.17487/RFC4553, June 2006,
<https://www.rfc-editor.org/info/rfc4553>.
[RFC4664] Andersson, L., Ed. and E. Rosen, Ed., "Framework for Layer
2 Virtual Private Networks (L2VPNs)", RFC 4664,
DOI 10.17487/RFC4664, September 2006,
<https://www.rfc-editor.org/info/rfc4664>.
[RFC4842] Malis, A., Pate, P., Cohen, R., Ed., and D. Zelig,
"Synchronous Optical Network/Synchronous Digital Hierarchy
(SONET/SDH) Circuit Emulation over Packet (CEP)",
RFC 4842, DOI 10.17487/RFC4842, April 2007,
<https://www.rfc-editor.org/info/rfc4842>.
[RFC4875] Aggarwal, R., Ed., Papadimitriou, D., Ed., and S.
Yasukawa, Ed., "Extensions to Resource Reservation
Protocol - Traffic Engineering (RSVP-TE) for Point-to-
Multipoint TE Label Switched Paths (LSPs)", RFC 4875,
DOI 10.17487/RFC4875, May 2007,
<https://www.rfc-editor.org/info/rfc4875>.
[RFC4906] Martini, L., Ed., Rosen, E., Ed., and N. El-Aawar, Ed.,
"Transport of Layer 2 Frames Over MPLS", RFC 4906,
DOI 10.17487/RFC4906, June 2007,
<https://www.rfc-editor.org/info/rfc4906>.
[RFC5036] Andersson, L., Ed., Minei, I., Ed., and B. Thomas, Ed.,
"LDP Specification", RFC 5036, DOI 10.17487/RFC5036,
October 2007, <https://www.rfc-editor.org/info/rfc5036>.
[RFC5086] Vainshtein, A., Ed., Sasson, I., Metz, E., Frost, T., and
P. Pate, "Structure-Aware Time Division Multiplexed (TDM)
Circuit Emulation Service over Packet Switched Network
(CESoPSN)", RFC 5086, DOI 10.17487/RFC5086, December 2007,
<https://www.rfc-editor.org/info/rfc5086>.
[RFC5920] Fang, L., Ed., "Security Framework for MPLS and GMPLS
Networks", RFC 5920, DOI 10.17487/RFC5920, July 2010,
<https://www.rfc-editor.org/info/rfc5920>.
[RFC7212] Frost, D., Bryant, S., and M. Bocci, "MPLS Generic
Associated Channel (G-ACh) Advertisement Protocol",
RFC 7212, DOI 10.17487/RFC7212, June 2014,
<https://www.rfc-editor.org/info/rfc7212>.
[RFC7384] Mizrahi, T., "Security Requirements of Time Protocols in
Packet Switched Networks", RFC 7384, DOI 10.17487/RFC7384,
October 2014, <https://www.rfc-editor.org/info/rfc7384>.
[RFC8077] Martini, L., Ed. and G. Heron, Ed., "Pseudowire Setup and
Maintenance Using the Label Distribution Protocol (LDP)",
STD 84, RFC 8077, DOI 10.17487/RFC8077, February 2017,
<https://www.rfc-editor.org/info/rfc8077>.
[RFC8214] Boutros, S., Sajassi, A., Salam, S., Drake, J., and J.
Rabadan, "Virtual Private Wire Service Support in Ethernet
VPN", RFC 8214, DOI 10.17487/RFC8214, August 2017,
<https://www.rfc-editor.org/info/rfc8214>.
[RFC8754] Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J.,
Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header
(SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020,
<https://www.rfc-editor.org/info/rfc8754>.
[RFC9055] Grossman, E., Ed., Mizrahi, T., and A. Hacker,
"Deterministic Networking (DetNet) Security
Considerations", RFC 9055, DOI 10.17487/RFC9055, June
2021, <https://www.rfc-editor.org/info/rfc9055>.
[RFC9256] Filsfils, C., Talaulikar, K., Ed., Voyer, D., Bogdanov,
A., and P. Mattes, "Segment Routing Policy Architecture",
RFC 9256, DOI 10.17487/RFC9256, July 2022,
<https://www.rfc-editor.org/info/rfc9256>.
[RFC9293] Eddy, W., Ed., "Transmission Control Protocol (TCP)",
STD 7, RFC 9293, DOI 10.17487/RFC9293, August 2022,
<https://www.rfc-editor.org/info/rfc9293>.
[T11] INCITS, "T11 - Fibre Channel",
<https://www.incits.org/committees/t11>.
Acknowledgements
The authors would like to thank Alexander Vainshtein, Yaakov Stein,
Erik van Veelen, Faisal Dada, Giles Heron, Luca Della Chiesa, and
Ashwin Gumaste for their early contributions, review, comments, and
suggestions.
Special thank you to:
* Carlos Pignataro and Nagendra Kumar Nainar for giving the authors
new-to-the-IETF guidance on how to get started
* Stewart Bryant for being our shepherd
* Tal Mizahi, Joel Halpern, Christian Huitema, Tony Li, and Tommy
Pauly for their reviews and suggestions during Last Call
* Andrew Malis and Gunter van de Velde for their guidance through
the process
Contributors
Andreas Burk
1&1 Versatel
Email: andreas.burk@magenta.de
Faisal Dada
AMD
Email: faisal.dada@amd.com
Gerald Smallegange
Ciena Corporation
Email: gsmalleg@ciena.com
Erik van Veelen
Aimvalley
Email: erik.vanveelen@aimvalley.com
Luca Della Chiesa
Cisco Systems, Inc.
Email: ldellach@cisco.com
Nagendra Kumar Nainar
Cisco Systems, Inc.
Email: naikumar@cisco.com
Carlos Pignataro
Blue Fern Consulting
Email: Carlos@Bluefern.consulting
Authors' Addresses
Steven Gringeri
Verizon
Email: steven.gringeri@verizon.com
Jeremy Whittaker
Verizon
Email: jeremy.whittaker@verizon.com
Nicolai Leymann
Deutsche Telekom
Email: N.Leymann@telekom.de
Christian Schmutzer (editor)
Cisco Systems, Inc.
Email: cschmutz@cisco.com
Chris Brown
Ciena Corporation
Email: cbrown@ciena.com