]> Verizon

steven.gringeri@verizon.com

Verizon

jeremy.whittaker@verizon.com

Deutsche Telekom

N.Leymann@telekom.de

Cisco Systems, Inc.

cschmutz@cisco.com

Ciena Corporation

cbrown@ciena.com

This document describes methods and requirements for implementing the encapsulation of high-speed bit-streams into virtual private wire services (VPWS) over packet switched networks (PSN) providing complete signal transport transparency.

Introduction and Motivation This document describes a method called Private Line Emulation (PLE) for encapsulating high-speed bit-streams as Virtual Private Wire Service (VPWS) over Packet Switched Networks (PSN). This emulation suits applications, where carrying Protocol Data Units (PDUs) as defined in or is not enough, physical layer signal transparency is required and data or framing structure interpretation of the PE would be counterproductive. One example of such case is two Ethernet connected Customer Edge (CE) devices and the need for Synchronous Ethernet operation between them without the intermediate Provider Edge (PE) devices interfering or addressing concerns about Ethernet control protocol transparency for PDU based carrier Ethernet services, beyond the behavior definitions of Metro Ethernet 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. Also, SONET/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 where demultiplexing and multiplexing is desired in order to operate per SONET Synchronous Payload Envelope (SPE) and Virtual Tributary (VT) or SDH Virtual Container (VC). Said in another way, PLE does provide an independent layer network underneath the SONET/SDH layer network, whereas CEP does operate at the same level and peer with the SONET/SDH layer network. The mechanisms described in this document follow principles similar to Structure-Agnostic Time Division Multiplexing (TDM) over Packet (SAToP) defined in . The applicability is expanded beyond the narrow set of PDH interfaces (T1, E1, T3 and E3) to allow the transport of signals from many different technologies such as Ethernet, Fibre Channel, SONET/SDH / and OTN 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.

Requirements Notation The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119.

Terminology and Reference Model

Terminology

• ACH - Associated Channel Header
• AIS - Alarm Indication Signal
• AIS-L - Line AIS
• AS - Autonomous System
• ASBR - Autonomous System Border Router
• MS-AIS - Multiplex Section AIS
• BITS - Building Integrated Timing Supply
• CBR - Constant Bit Rate
• CE - Customer Edge
• CEP - Circuit Emulation over Packet
• CSRC - Contributing SouRCe
• DEG - Degradation
• ES - Errored Second
• FEC - Forward Error Correction
• ICMP - Internet Control Message Protocol
• IEEE - Institute of Electrical and Electronics Engineers
• INCITS - InterNational Committee for Information Technology Standards
• IWF - InterWorking Function
• LDP - Label Distribution Protocol ,
• LF - Local Fault
• LOF - Loss Of Frame
• LOM - Loss Of Multiframe
• LOS - Loss Of Signal
• LPI - Low Power Idle
• LSP - Label Switched Path
• MEF - Metro Ethernet Forum
• MPLS - Multi Protocol Label Switching
• NOS - Not Operational
• NSP - Native Service Processor
• ODUk - Optical Data Unit k
• OTN - Optical Transport Network
• OTUk - Optical Transport Unit k
• PCS - Physical Coding Sublayer
• PDH - Plesiochronous Digital Hierarchy
• PDV - Packet Delay Variation
• PE - Provider Edge
• PLE - Private Line Emulation
• PLOS - Packet Loss Of Signal
• PLR - Packet Loss Ratio
• PMA - Physical Medium Attachment
• PMD - Physical Medium Dependent
• PSN - Packet Switched Network
• PTP - Precision Time Protocol
• PW - Pseudowire
• PWE3 - Pseudo Wire Emulation Edge-to-Edge
• P2P - Point-to-Point
• QOS - Quality Of Service
• RDI - Remote Defect Indication
• RSVP-TE - Resource Reservation Protocol Traffic Engineering
• RTCP - RTP Control Protocol
• RTP - Realtime Transport Protocol
• SAN - Storage Area Network
• SAToP - Structure-Agnostic Time Division Multiplexing (TDM) over Packet
• SD - Signal Degrade
• SES - Severely Errored Second
• SDH - Synchronous Digital Hierarchy
• SID - Segment Identifier
• SPE - Synchronous Payload Envelope
• SR - Segment Routing
• SRH - Segment Routing Header
• SR-TE - Segment Routing Traffic Engineering
• SRTP - Secure Realtime Transport Protocol
• SRv6 - Segment Routing over IPv6 Dataplane
• SSRC - Synchronization SouRCe
• SONET - Synchronous Optical Network
• TCP - Transmission Control Protocol
• TDM - Time Division Multiplexing
• TTS - Transmitter Training Signal
• UAS - Unavailable Second
• VPWS - Virtual Private Wire Service
• VC - Virtual Circuit
• VT - Virtual Tributary

The term Interworking Function (IWF) is used to describe the functional block that encapsulates bit streams into PLE packets and in the reverse direction decapsulates PLE packets and reconstructs bit streams.

Reference Models The reference model for PLE is illustrated in and is inline with the reference model defined in . PLE does rely on PWE3 pre-processing, in particular the concept of a Native Service Processing (NSP) function defined in .

PLE Reference Model | | | | |<-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 ]]>

PLE embraces the minimum intervention principle outlined in whereas 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), 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 are applicable and are shown in .

Relative Network Scenario Timing |.............................|--------->| | +-----+ |- - -|=================|- - -| ^ +-----+ ^ +-----+ +-----+ | | ^ C D ^ | A | | | +-----------+-----------+ E | +-+ |I| +-+ ]]>

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 does generate the attachment circuit clock J and the clock difference between G and D (locked to I) 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, but there are already several well established concepts for achieving frequency synchronization available. While using external timing inputs (aka BITS) or synchronous Ethernet as defined in the characteristics and limits defined in have to be considered. While relying on precision time protocol (PTP) as defined in , the network limits defined in have to be considered.

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 or structured bit streams, as defined in Section 3.3.3 and Section 3.3.4 of .

Generic PLE Service The generic PLE service is an example of the bit stream defined in . Under the assumption that the CE-bound IWF is not responsible for any service specific operation, a bit stream of any rate can be carried using the generic PLE payload. There is no NSP function present for this service.

Ethernet services Ethernet services are special cases of the structured bit stream defined in . IEEE has defined several layers for Ethernet in . Emulation is operating at the physical (PHY) layer, more precisely at the Physical Coding Sublayer (PCS). Over time many different Ethernet interface types have been specified in with a varying set of characteristics such as optional vs mandatory FEC and single-lane vs multi-lane transmission. Ethernet interface types with backplane physical media dependent (PMD) variants and ethernet interface types mandating 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.

1000BASE-X The PCS layer of 1000BASE-X defined in clause 36 of is based on 8B/10B code. The PSN-bound NSP function does not modify the received data and is transparent to auto-negotiation but is responsible to detect 1000BASE-X specific attachment circuit faults 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 being set, the CE-bound NSP function MAY disable its transmitter as no appropriate maintenance signal was defined for 1000BASE-X by IEEE.

10GBASE-R and 25GBASE-R The PCS layers of 10GBASE-R defined in clause 49 and 25GBASE-R defined in clause 107 of are based on a 64B/66B code. clauses 74 and 108 do 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 to detect 10GBASE-R and 25GBASE-R specific attachment circuit faults such as LOS and sync loss. The PSN-bound IWF is mapping the scrambled 64B/66B code stream into the basic PLE payload. The CE-bound NSP function MUST perform

• PCS code sync
• descrambling

in order to properly

• transform invalid 66B code blocks into proper error control characters /E/
• insert Local Fault (LF) ordered sets when the CE-bound IWF is in PLOS state or when PLE packets are received with the L-bit being set

Note: Invalid 66B code blocks typically are a consequence of the CE-bound IWF inserting replacement data in case of lost PLE packets, or if the far-end PSN-bound NSP function did set sync headers to 11 due to uncorrectable FEC errors. Before sending the bit stream to the CE, the CE-bound NSP function MUST also scramble the 64B/66B code stream.

40GBASE-R, 50GBASE-R and 100GBASE-R The PCS layers of 40GBASE-R and 100GBASE-R defined in clause 82 and of 50GBASE-R defined in clause 133 of are based on a 64B/66B code transmitted over multiple lanes. clauses 74 and 91 do 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
• PCS lane de-skew
• PCS lane reordering

The PSN-bound NSP function is also responsible to detect 40GBASE-R, 50GBASE-R and 100GBASE-R specific attachment circuit faults such as LOS and loss of alignment. The PSN-bound IWF is mapping the serialized, scrambled 64B/66B code stream including the alignment markers into the basic PLE payload. The CE-bound NSP function MUST perform

• PCS code sync
• alignment marker removal
• descrambling

in order to properly

• transform invalid 66B code blocks into proper error control characters /E/
• insert Local Fault (LF) ordered sets when the CE-bound IWF is in PLOS state or when PLE packets are received with the L-bit being set

Note: Invalid 66B code blocks typically are a consequence of the CE-bound IWF inserting replacement data in case of lost PLE packets, or if the far-end PSN-bound NSP function did set sync headers to 11 due to uncorrectable FEC errors. When sending the bit stream to the CE, the CE-bound NSP function MUST also perform

• scrambling of the 64B/66B code
• block distribution
• alignment marker insertion

200GBASE-R and 400GBASE-R The PCS layers of 200GBASE-R and 400GBASE-R defined in clause 119 of 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
• PCS Lane reordering and de-interleaving
• FEC decoding
• post-FEC interleaving
• alignment marker removal
• descrambling
• reverse transcoding from 256B/257B to 64B/66B

Further the PSN-bound NSP MUST perform rate compensation and scrambling before the PSN-bound IWF is mapping the same into the basic PLE payload. Rate compensation is applied so that the rate of the 66B encoded 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 and 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 to detect 200GBASE-R and 400GBASE-R specific attachment circuit faults such as LOS and loss of alignment. The CE-bound NSP function MUST perform

• PCS code sync
• descrambling
• rate compensation block removal

in order to properly

• transform invalid 66B code blocks into proper error control characters /E/
• insert Local Fault (LF) ordered sets when the CE-bound IWF is in PLOS state or when PLE packets are received with the L-bit being set

Note: Invalid 66B code blocks typically are a consequence of the CE-bound IWF inserting replacement data in case of lost PLE packets, or if the far-end PSN-bound NSP function did set sync headers to 11 due to uncorrectable FEC errors. When sending the bit stream to the CE, the CE-bound NSP function MUST also perform

• transcoding from 64B/66B to 256B/257B
• scrambling
• alignment marker insertion
• pre-FEC distribution
• FEC encoding
• PCS Lane distribution

Energy Efficient Ethernet (EEE) Section 78 of does define the optional Low Power Idle (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. When 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.

SONET/SDH Services SONET/SDH services are special cases of the structured bit stream defined in . SDH interfaces are defined in and SONET interfaces are defined in . The PSN-bound NSP function does not modify the received data but is responsible to detect SONET/SDH interface specific attachment circuit faults 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 being set, the CE-bound NSP function is responsible for generating the

• MS-AIS maintenance signal defined in clause 6.2.4.1.1 of for SDH services
• AIS-L maintenance signal defined in clause 6.2.1.2 of for SONET services

at client frame boundaries.

Fibre Channel Services Fibre Channel services are special cases of the structured bit stream defined in . The T11 technical committee of INCITS has defined several layers for Fibre Channel. Emulation is operating at the FC-1 layer. Over time many different Fibre Channel interface types have been specified with a varying set of characteristics such as optional vs mandatory FEC and single-lane vs multi-lane transmission. Speed negotiation is out of scope for this document. All Fibre Channel services are leveraging the basic PLE payload and interface specific mechanisms are confined to the respective service specific NSP functions.

1GFC, 2GFC, 4GFC and 8GFC specifies 1GFC and 2GFC. and do define 4GFC and 8GFC. The PSN-bound NSP function is responsible to detect Fibre Channel specific attachment circuit faults such as LOS and sync loss. The PSN-bound IWF is mapping 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
• insert Not Operational (NOS) ordered sets when the CE-bound IWF is in PLOS state or when PLE packets are received with the L-bit being set

Note: Invalid transmission words typically are a consequence of the CE-bound IWF inserting replacement data in case of lost PLE packets. does define 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. And before sending the bit stream to the, the CE-bound NSP function MUST scramble the 8B/10B code stream.

16GFC and 32GFC and specify 16GFC and define a optional FEC layer. specifies 32GFC with the FEC layer and transmitter training signal (TTS) support being mandatory. If FEC is present it must be indicated via TTS during attachment circuit bring 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 to detect Fibre Channel specific attachment circuit faults such as LOS and sync loss. The PSN-bound IWF is mapping the received 64B/66B code stream as is into the basic PLE payload. The CE-bound NSP function MUST perform

• transmission word sync
• descrambling

in order to properly

• replace invalid transmission words with the error transmission word 1Eh
• insert Not Operational (NOS) ordered sets when the CE-bound IWF is in PLOS state or when PLE packets are received with the L-bit being set

Note: Invalid transmission words typically are a consequence of the CE-bound IWF inserting replacement data in case of lost PLE packets, or if the far-end PSN-bound NSP function did set sync headers to 11 due to uncorrectable FEC errors. Before sending the bit stream to the CE, the CE-bound NSP function MUST also scramble the 64B/66B code stream.

64GFC and 4-lane 128GFC specifies 64GFC and specifies 4-lane 128GFC. Both specify a mandatory FEC layer. The PSN-bound NSP function MUST terminate the FEC and the CE-bound NSP function must generate the FEC. To gain access to the 64B/66B code stream the PSN-bound NSP further MUST perform

• alignment lock and de-skew
• Lane reordering and de-interleaving
• FEC decoding
• post-FEC interleaving
• alignment marker removal
• descrambling
• reverse transcoding from 256B/257B to 64B/66B

Further the PSN-bound NSP MUST perform scrambling before the PSN-bound IWF is mapping the same into the basic PLE payload. Note : The use of rate compensation is for further study and out of scope for this document. The PSN-bound NSP function is also responsible to detect Fibre Channel specific attachment circuit faults such as LOS and sync loss. The CE-bound NSP function MUST perform

• transmission word sync
• descrambling

in order to properly

• replace invalid transmission words with the error transmission word 1Eh
• insert Not Operational (NOS) ordered sets when the CE-bound IWF is in PLOS state or when PLE packets are received with the L-bit being set

Note: Invalid transmission words typically are a consequence of the CE-bound IWF inserting replacement data in case of lost PLE packets, or if the far-end PSN-bound NSP function did set sync headers to 11 due to uncorrectable FEC errors. When sending the bit stream to the CE, the CE-bound NSP function MUST also perform

• transcoding from 64B/66B to 256B/257B
• scrambling
• alignment marker insertion
• pre-FEC distribution
• FEC encoding
• Lane distribution

OTN Services OTN services are special cases of the structured bit stream defined in . OTN interfaces are defined in . The PSN-bound NSP function MUST terminate the FEC and replace the OTUk overhead in row 1 columns 8-14 with all-0s fixed stuff which results in a extended ODUk frame as illustrated in . The frame alignment overhead (FA OH) in row 1 columns 1-7 is kept as it is.

Extended ODUk Frame

The PSN-bound NSP function is also responsible to detect OTUk specific attachment circuit faults such as LOS, LOF, LOM and AIS. The PSN-bound IWF is mapping 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 generates the FEC. When the CE-bound IWF is in PLOS state or when PLE packets are received with the L-bit being set, the CE-bound NSP function is responsible for generating the ODUk-AIS maintenance signal defined in clause 16.5.1 of at client frame boundaries.

PLE Encapsulation Layer The basic packet format used by PLE is shown in the .

PLE Encapsulation Layer PSN and VPWS | | / Demux Headers +-------------------------------+ -+ | PLE Control Word | \ +-------------------------------+ > PLE Header | RTP Header | / +-------------------------------+ --+ | Bit Stream | \ | Payload | > Payload | | / +-------------------------------+ --+ ]]>

PSN and VPWS Demultiplexing Headers This document does not imply any specific technology to 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 a MPLS PSN layer is used, a VPWS label provides the demultiplexing mechanism as described in . The PSN tunnel can be a simple best path Label Switched Path (LSP) established using LDP or Segment Routing or a traffic engineered LSP established using RSVP-TE or SR-TE . When a SRv6 PSN layer is used, a SRv6 service segment identifier (SID) as defined in does provide the demultiplexing mechanism and definitions of do apply. Both SRv6 service SIDs with the full IPv6 address format defined in and compressed SIDs (C-SIDs) with format defined in can be used. 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 a IPv6 packet with an segment routing header (SRH). The received frame becomes the payload of the new IPv6 packet.

• The next header field of the SRH or last extension header present MUST be set to TBA1.
• The push of the SRH MAY be omitted 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 of the pushed IPv6 header. The first SID is only placed in the destination address field of the pushed IPv6 header.
• The push of the SRH MAY be omitted 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 and 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: 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:

PLE Header The PLE header MUST contain the PLE control word (4 bytes) and MUST include a fixed size RTP header . The RTP header MUST immediately follow the PLE control word.

PLE Control Word The format of the PLE control word is in line with the guidance in and is shown in .

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) 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 . The other fields in the control word are used as defined below:

• 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 fault propagation signal.

• 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

• These bits are reserved for future use. This field MUST be set to zero by the sender and ignored by the receiver.

• FRG

• These bits MUST be set to zero by the sender and ignored by the receiver as PLE does not use payload fragmentation.

• LEN

• In accordance to the length field MUST always be set to zero as there is no padding added to the PLE packet. To detect malformed packets the default, preconfigured or signaled payload size MUST be assumed.

• Sequence 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 and MUST be incremented with every PLE packet being sent.

RTP Header The RTP header MUST be included and is used for explicit transfer of timing information. The RTP header is purely a formal reuse and RTP mechanisms, such as header extensions, contributing source (CSRC) list, padding, RTP Control Protocol (RTCP), RTP header compression, Secure Realtime Transport Protocol (SRTP), etc., are not applicable to PLE VPWS. The format of the RTP header is as shown in .

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 for each direction of the VPWS. The same PT value MAY be reused both for direction and between different PLE VPWS.

• Sequence 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 bit, 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 values are used in accordance with the rules established in . 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.

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.

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.

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.

PLE Operation

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 or EVPN-VPWS are out of scope for this document. Extensions for EVPN-VPWS are proposed in and for LDP in .

PLE IWF Operation

PSN-bound Encapsulation Behavior After the VPWS is set up, the PSN-bound IWF does perform the following steps:

• Packetize the data received from the CE is into a fixed size PLE payloads
• Add PLE control word and RTP header with sequence numbers, flags and timestamps properly set
• Add the VPWS demultiplexer and PSN headers
• Transmit the resulting packets over the PSN
• Set L bit in the PLE control word whenever attachment circuit detects a fault
• Set R bit in the PLE control word whenever the local CE-bound IWF is in packet loss state

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 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 purposes. The CE-bound IWF MAY support re-ordering of packets received out of order. If the CE-bound IWF does not support re-ordering it MUST drop the misordered packets. The payload of a lost or dropped packet MUST be replaced with 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 does ensure clock synchronization is maintained and for 64B/66B code based services 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 downstream fault indication signal. Whenever a VPWS comes up, the CE-bound IWF enters 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 downstream fault indication signal until a pre-configured number of payload s stored in the jitter buffer. After the pre-configured 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. The recovered clock MUST comply with the jitter and wander requirements applicable to the type of attachment circuit, specified in:

• and for SDH
• for SONET
• for synchronous Ethernet
• 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 downstream fault indication signal instead of streaming out the payload. If the CE-bound IWF detects loss of consecutive packets for a pre-configured amount of time (default is 1 millisecond), it enters packet loss (PLOS) state and a corresponding defect is declared. If the CE-bound IWF detects a packet loss ratio (PLR) above a configurable signal-degrade (SD) threshold for a configurable amount of consecutive 1-second intervals, it enters the degradation (DEG) state and a corresponding defect is declared. The SD-PLR threshold can be defined as 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 SHOULD inject the appropriate native downstream fault indication signal. Also the PSN-bound IWF SHOULD set the R bit in the PLE control word of every packet transmitted. The CE-bound IWF does change from the PLOS to normal state after the pre-configured amount of payload has been received similarly 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.

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 defect SHALL be counted as ES-PLE. Each second with a PLR greater than 15% or a PLOS/DEG defect SHALL be counted as SES-PLE. UAS-PLE SHALL be counted after a configurable number of consecutive SES-PLE have been observed, and no longer counted after a configurable number of consecutive seconds without SES-PLE have been observed. Default value for each is 10 seconds. Once unavailability is detected, ES and SES counts SHALL be inhibited up to the point where the unavailability was started. Once unavailability is removed, ES and SES that occurred along the clearing period SHALL be added to the ES and SES counts. A PLE far-end performance monitor is providing 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 Performance monitoring data MUST be provided by the management interface and SHOULD be provided by a YANG model. The YANG model specification is out of scope for this document.

PLE Fault Management Attachment circuit faults applicable to PLE are detected by the NSP, are service specific and are documented in relevant section of . The two PLE faults, PLOS and DEG are detected by the IWF. Faults MUST be time stamped as they are declared and cleared and fault related information MUST be provided by the management interface and SHOULD be provided by a YANG model. The YANG model specification is out of scope for this document.

QoS and Congestion Control The PSN carrying PLE VPWS may be subject to congestion. Congestion considerations for PWs are described in . PLE VPWS represent inelastic constant bit-rate (CBR) flows that cannot respond to congestion in a TCP-friendly manner as described in 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 a Diffserv-enabled PSN with a per domain behavior supporting Expedited Forwarding . Traffic-engineered paths through the PSN with bandwidth reservation and admission control applied. Or capacity over-provisioning.

Security Considerations As PLE is leveraging VPWS as transport mechanism, the security considerations described 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 is assumed to be trusted and secure. Considerations about the MPLS core network outlined in are applicable. For MPLS based PSNs, one of the requirements for protecting the data plane is that the MPLS packets be accepted only from valid interfaces. For a PE, valid interfaces comprise links from other routers in the PE's own AS. For an ASBR, valid interfaces comprise links from other routers in the ASBR's own AS, and links from other ASBRs in ASes that have instances of a given PLE PWs. It is especially important in the case of multi-AS PLE PWs that one accepts PLE packets only from valid interfaces. When a Segment Routing (SR) based PSN is used (MPLS or SRv6) the considerations in and are applicable. 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 of the RTP header can increase the resilience to misconfiguration and some types of denial-of-service (DoS) attacks. A randomly chosen expected SSRC value does decrease the chance of a spoofing attack being successful. Control plane mechanisms for signaling the expected SSRC value are described in and . A data plane attack may force PLE packets to be dropped, re-ordered or delayed beyond the limit of the CE-bound IWF's dejitter buffer leading to either degradation or service disruption. Considerations outlined in are a good reference. Clock synchronization leveraging PTP is sensitive to Packet Delay Variation (PDV) and vulnerable to various threads and attack vectors. Considerations outlined in should be taken into account.

IANA Considerations

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 a emulated bit-stream. IANA is requested to assign the following from the "Assigned Internet Protocol Numbers" registry (see https://www.iana.org/assignments/protocol-numbers/).

Decimal	Keyword	Protocol	IPv6 Extension Header	Reference
TBA1	BIT-EMU	Bit-stream Emulation	Y	this document

SRv6 Endpoint Behaviors This document introduces three new SRv6 Endpoint behaviors. IANA is requested to assign identifier values in the "SRv6 Endpoint Behaviors" sub-registry under "Segment Routing Parameters" registry.

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

Acknowledgements The authors would like to thank all reviewers, contributors and the working group for reviewing this document and providing useful comments and suggestions.

References Normative References This document describes a profile called "RTP/AVP" for the use of the real-time transport protocol (RTP), version 2, and the associated control protocol, RTCP, within audio and video multiparticipant conferences with minimal control. It provides interpretations of generic fields within the RTP specification suitable for audio and video conferences. In particular, this document defines a set of default mappings from payload type numbers to encodings. This document also describes how audio and video data may be carried within RTP. It defines a set of standard encodings and their names when used within RTP. The descriptions provide pointers to reference implementations and the detailed standards. This document is meant as an aid for implementors of audio, video and other real-time multimedia applications. This memorandum obsoletes RFC 1890. It is mostly backwards-compatible except for functions removed because two interoperable implementations were not found. The additions to RFC 1890 codify existing practice in the use of payload formats under this profile and include new payload formats defined since RFC 1890 was published. [STANDARDS-TRACK] The Segment Routing over IPv6 (SRv6) Network Programming framework enables a network operator or an application to specify a packet processing program by encoding a sequence of instructions in the IPv6 packet header. Each instruction is implemented on one or several nodes in the network and identified by an SRv6 Segment Identifier in the packet. This document defines the SRv6 Network Programming concept and specifies the base set of SRv6 behaviors that enables the creation of interoperable overlays with underlay optimization. This document defines procedures and messages for SRv6-based BGP services, including Layer 3 Virtual Private Network (L3VPN), Ethernet VPN (EVPN), and Internet services. It builds on "BGP/MPLS IP Virtual Private Networks (VPNs)" (RFC 4364) and "BGP MPLS-Based Ethernet VPN" (RFC 7432). Segment Routing (SR) leverages the source routing paradigm. A node steers a packet through an ordered list of instructions, called "segments". A segment can represent any instruction, topological or service based. A segment can have a semantic local to an SR node or global within an SR domain. SR provides a mechanism that allows a flow to be restricted to a specific topological path, while maintaining per-flow state only at the ingress node(s) to the SR domain. SR can be directly applied to the MPLS architecture with no change to the forwarding plane. A segment is encoded as an MPLS label. An ordered list of segments is encoded as a stack of labels. The segment to process is on the top of the stack. Upon completion of a segment, the related label is popped from the stack. SR can be applied to the IPv6 architecture, with a new type of routing header. A segment is encoded as an IPv6 address. An ordered list of segments is encoded as an ordered list of IPv6 addresses in the routing header. The active segment is indicated by the Destination Address (DA) of the packet. The next active segment is indicated by a pointer in the new routing header. China Mobile Cisco Systems, Inc. Huawei Technologies Orange Cisco Systems, Inc. Segment Routing over IPv6 (SRv6) is the instantiation of Segment Routing (SR) on the IPv6 dataplane. This document specifies new flavors for the SRv6 endpoint behaviors defined in RFC 8986, which enable the compression of an SRv6 SID list. Such compression significantly reduces the size of the SRv6 encapsulation needed to steer packets over long segment lists. Informative References This document describes an architecture for Pseudo Wire Emulation Edge-to-Edge (PWE3). It discusses the emulation of services such as Frame Relay, ATM, Ethernet, TDM, and SONET/SDH over packet switched networks (PSNs) using IP or MPLS. It presents the architectural framework for pseudo wires (PWs), defines terminology, and specifies the various protocol elements and their functions. This memo provides information for the Internet community. This document defines the specific requirements for edge-to-edge emulation of circuits carrying Time Division Multiplexed (TDM) digital signals of the Plesiochronous Digital Hierarchy as well as the Synchronous Optical NETwork/Synchronous Digital Hierarchy over packet-switched networks. It is aligned to the common architecture for Pseudo Wire Emulation Edge-to-Edge (PWE3). It makes references to the generic requirements for PWE3 where applicable and complements them by defining requirements originating from specifics of TDM circuits. This memo provides information for the Internet community. This document describes the preferred design of a Pseudowire Emulation Edge-to-Edge (PWE3) Control Word to be used over an MPLS packet switched network, and the Pseudowire Associated Channel Header. The design of these fields is chosen so that an MPLS Label Switching Router performing MPLS payload inspection will not confuse a PWE3 payload with an IP payload. [STANDARDS-TRACK] This memorandum describes RTP, the real-time transport protocol. RTP provides end-to-end network transport functions suitable for applications transmitting real-time data, such as audio, video or simulation data, over multicast or unicast network services. RTP does not address resource reservation and does not guarantee quality-of- service for real-time services. The data transport is augmented by a control protocol (RTCP) to allow monitoring of the data delivery in a manner scalable to large multicast networks, and to provide minimal control and identification functionality. RTP and RTCP are designed to be independent of the underlying transport and network layers. The protocol supports the use of RTP-level translators and mixers. Most of the text in this memorandum is identical to RFC 1889 which it obsoletes. There are no changes in the packet formats on the wire, only changes to the rules and algorithms governing how the protocol is used. The biggest change is an enhancement to the scalable timer algorithm for calculating when to send RTCP packets in order to minimize transmission in excess of the intended rate when many participants join a session simultaneously. [STANDARDS-TRACK] INCITS INCITS INCITS INCITS INCITS INCITS International Telecommunication Union (ITU) International Telecommunication Union (ITU) International Telecommunication Union (ITU) International Telecommunication Union (ITU) International Telecommunication Union (ITU) International Telecommunication Union (ITU) International Telecommunication Union (ITU) International Telecommunication Union (ITU) International Telecommunication Union (ITU) International Telecommunication Union (ITU) Telcordia IEEE This document describes methods for transporting the Protocol Data Units (PDUs) of layer 2 protocols such as Frame Relay, Asynchronous Transfer Mode (ATM) Adaption Layer 5 (AAL5), and Ethernet, and for providing a Synchronized Optical Network (SONET) circuit emulation service across an MPLS network. This document describes the so-called "draft-martini" protocol, which has since been superseded by the Pseudowire Emulation Edge to Edge Working Group specifications described in RFC 4447 and related documents. This memo defines a Historic Document for the Internet community. An Ethernet pseudowire (PW) is used to carry Ethernet/802.3 Protocol Data Units (PDUs) over an MPLS network. This enables service providers to offer "emulated" Ethernet services over existing MPLS networks. This document specifies the encapsulation of Ethernet/802.3 PDUs within a pseudowire. It also specifies the procedures for using a PW to provide a "point-to-point Ethernet" service. [STANDARDS-TRACK] This document provides encapsulation formats and semantics for emulating Synchronous Optical Network/Synchronous Digital Hierarchy (SONET/SDH) circuits and services over MPLS. [STANDARDS-TRACK] This document describes a pseudowire encapsulation for Time Division Multiplexing (TDM) bit-streams (T1, E1, T3, E3) that disregards any structure that may be imposed on these streams, in particular the structure imposed by the standard TDM framing. [STANDARDS-TRACK] The MPLS Generic Associated Channel (G-ACh) provides an auxiliary logical data channel associated with a Label Switched Path (LSP), a pseudowire, or a section (link) over which a variety of protocols may flow. These protocols are commonly used to provide Operations, Administration, and Maintenance (OAM) mechanisms associated with the primary data channel. This document specifies simple procedures by which an endpoint of an LSP, pseudowire, or section may inform the other endpoints of its capabilities and configuration parameters, or other application-specific information. This information may then be used by the receiver to validate or adjust its local configuration, and by the network operator for diagnostic purposes. The architecture for Multiprotocol Label Switching (MPLS) is described in RFC 3031. A fundamental concept in MPLS is that two Label Switching Routers (LSRs) must agree on the meaning of the labels used to forward traffic between and through them. This common understanding is achieved by using a set of procedures, called a label distribution protocol, by which one LSR informs another of label bindings it has made. This document defines a set of such procedures called LDP (for Label Distribution Protocol) by which LSRs distribute labels to support MPLS forwarding along normally routed paths. [STANDARDS-TRACK] Layer 2 services (such as Frame Relay, Asynchronous Transfer Mode, and Ethernet) can be emulated over an MPLS backbone by encapsulating the Layer 2 Protocol Data Units (PDUs) and then transmitting them over pseudowires (PWs). It is also possible to use pseudowires to provide low-rate Time-Division Multiplexed and Synchronous Optical NETworking circuit emulation over an MPLS-enabled network. This document specifies a protocol for establishing and maintaining the pseudowires, using extensions to the Label Distribution Protocol (LDP). Procedures for encapsulating Layer 2 PDUs are specified in other documents. This document is a rewrite of RFC 4447 for publication as an Internet Standard. This document specifies the architecture for Multiprotocol Label Switching (MPLS). [STANDARDS-TRACK] This document describes extensions to Resource Reservation Protocol - Traffic Engineering (RSVP-TE) for the set up of Traffic Engineered (TE) point-to-multipoint (P2MP) Label Switched Paths (LSPs) in Multi- Protocol Label Switching (MPLS) and Generalized MPLS (GMPLS) networks. The solution relies on RSVP-TE without requiring a multicast routing protocol in the Service Provider core. Protocol elements and procedures for this solution are described. There can be various applications for P2MP TE LSPs such as IP multicast. Specification of how such applications will use a P2MP TE LSP is outside the scope of this document. [STANDARDS-TRACK] Segment Routing (SR) allows a node to steer a packet flow along any path. Intermediate per-path states are eliminated thanks to source routing. SR Policy is an ordered list of segments (i.e., instructions) that represent a source-routed policy. Packet flows are steered into an SR Policy on a node where it is instantiated called a headend node. The packets steered into an SR Policy carry an ordered list of segments associated with that SR Policy. This document updates RFC 8402 as it details the concepts of SR Policy and steering into an SR Policy. This document describes the Secure Real-time Transport Protocol (SRTP), a profile of the Real-time Transport Protocol (RTP), which can provide confidentiality, message authentication, and replay protection to the RTP traffic and to the control traffic for RTP, the Real-time Transport Control Protocol (RTCP). [STANDARDS-TRACK] This document specifies the Transmission Control Protocol (TCP). TCP is an important transport-layer protocol in the Internet protocol stack, and it has continuously evolved over decades of use and growth of the Internet. Over this time, a number of changes have been made to TCP as it was specified in RFC 793, though these have only been documented in a piecemeal fashion. This document collects and brings those changes together with the protocol specification from RFC 793. This document obsoletes RFC 793, as well as RFCs 879, 2873, 6093, 6429, 6528, and 6691 that updated parts of RFC 793. It updates RFCs 1011 and 1122, and it should be considered as a replacement for the portions of those documents dealing with TCP requirements. It also updates RFC 5961 by adding a small clarification in reset handling while in the SYN-RECEIVED state. The TCP header control bits from RFC 793 have also been updated based on RFC 3168. This document describes the use of RSVP (Resource Reservation Protocol), including all the necessary extensions, to establish label-switched paths (LSPs) in MPLS (Multi-Protocol Label Switching). Since the flow along an LSP is completely identified by the label applied at the ingress node of the path, these paths may be treated as tunnels. A key application of LSP tunnels is traffic engineering with MPLS as specified in RFC 2702. [STANDARDS-TRACK] This document describes how Ethernet VPN (EVPN) can be used to support the Virtual Private Wire Service (VPWS) in MPLS/IP networks. EVPN accomplishes the following for VPWS: provides Single-Active as well as All-Active multihoming with flow-based load-balancing, eliminates the need for Pseudowire (PW) signaling, and provides fast protection convergence upon node or link failure. Verizon Verizon Cisco Systems, Inc. Cisco Systems, Inc. Cisco Systems, Inc. This document specifies the mechanisms to allow for dynamic signalling of Virtual Private Wire Services (VPWS) carrying bit- stream signals over Packet Switched Networks (PSN). Cisco Systems, Inc. This document defines extension to the Pseudowire Emulation Edge-to- Edge (PWE3) control protocol [RFC4447] required for the setup of Private Line Emulation (PLE) pseudowires in MPLS networks. The goal of this document is to explain the need for congestion control in the Internet, and to discuss what constitutes correct congestion control. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements. This document defines an architecture for implementing scalable service differentiation in the Internet. This memo provides information for the Internet community. This document defines and discusses Per-Domain Behaviors in detail and lays out the format and required content for contributions to the Diffserv WG on PDBs and the procedure that will be applied for individual PDB specifications to advance as WG products. This format is specified to expedite working group review of PDB submissions. This memo provides information for the Internet community. This document defines a PHB (per-hop behavior) called Expedited Forwarding (EF). The PHB is a basic building block in the Differentiated Services architecture. EF is intended to provide a building block for low delay, low jitter and low loss services by ensuring that the EF aggregate is served at a certain configured rate. This document obsoletes RFC 2598. [STANDARDS-TRACK] This document analyses the security of the BGP/MPLS IP virtual private network (VPN) architecture that is described in RFC 4364, for the benefit of service providers and VPN users. The analysis shows that BGP/MPLS IP VPN networks can be as secure as traditional layer-2 VPN services using Asynchronous Transfer Mode (ATM) or Frame Relay. This memo provides information for the Internet community. A DetNet (deterministic network) provides specific performance guarantees to its data flows, such as extremely low data loss rates and bounded latency (including bounded latency variation, i.e., "jitter"). As a result, securing a DetNet requires that in addition to the best practice security measures taken for any mission-critical network, additional security measures may be needed to secure the intended operation of these novel service properties. This document addresses DetNet-specific security considerations from the perspectives of both the DetNet system-level designer and component designer. System considerations include a taxonomy of relevant threats and attacks, and associations of threats versus use cases and service properties. Component-level considerations include ingress filtering and packet arrival-time violation detection. This document also addresses security considerations specific to the IP and MPLS data plane technologies, thereby complementing the Security Considerations sections of those documents. As time and frequency distribution protocols are becoming increasingly common and widely deployed, concern about their exposure to various security threats is increasing. This document defines a set of security requirements for time protocols, focusing on the Precision Time Protocol (PTP) and the Network Time Protocol (NTP). This document also discusses the security impacts of time protocol practices, the performance implications of external security practices on time protocols, and the dependencies between other security services and time synchronization.

Contributors 1&1 Versatel

andreas.burk@magenta.de

AMD

faisal.dada@amd.com

Ciena Corporation

gsmalleg@ciena.com

Aimvalley

erik.vanveelen@aimvalley.com

Cisco Systems, Inc.

ldellach@cisco.com

Cisco Systems, Inc.

naikumar@cisco.com

North Carolina State University

cmpignat@ncsu.edu