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White Rabbit Standardization
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figs:
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documents/ISPCS2012-specialSession_submision/fig/Makefile
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documents/ISPCS2012-specialSession_submision/wrspec.tex
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......@@ -60,6 +60,7 @@
}
\newcommand{\eqdelay}[1]{{\text{delay}}_{#1}}
\newcommand{\eqasymm}{{\text{asymmetry}}}
%\renewcommand*{\refname}{\vspace*{-3em}}
\begin{document}
......@@ -84,12 +85,12 @@
\section {Title:} High accuracy extension/option/profile
\section {Author:} Maciej Lipi\'{n}ski
\section {Author:} Maciej Lipinski
\section {Affiliation:} European Organization for Nuclear Research (CERN)/Warsaw University of Technology (WUT)
\section {Date of submission:} 14 May 2012
\section {Clauses of IEEE 1588-2008 (V2) proposed for revision:}
\begin{itemize*}
\item Changes required in clauses: 7.6.2.5 and 14.1.1
\item Changes required in clauses: 7.6.2.5, 14.1.1, Annex F.4 and Annex J
\item Changes considered useful in clauses: 3.1, 5.3.3, 7.5.3, 9.3.1 and 9.5.10
\end{itemize*}
\section {Character of the proposed revision:}
......@@ -102,26 +103,28 @@ of accuracy (i.e. sub-nanosecond) beyond what is achievable by the current "stan
It has been shown (see \cite{WRinGS} and \cite{WRinISPCS2011}) that PTPv2 can be implemented such that
a sub-nanosecond accuracy and picoseconds jitter of synchronization can be achieved over a number of
boundary clocks and several kilometers of cables. Such implementation benefits from additional mechanisms
(i.e. Synchronous Ethernet \cite{SynchE}, phase detection \cite{icalepcs09}) incorporated into PTPv2 in a way that do not break interoperability
with "standard" implementations while improving greatly the performance. The mechanisms
used could be incorporated into the IEEE 1588 standard to indicate to the vendors the (optional) means to enhance
PTP's performance and to ensure interoperability of such high-accuracy implementations.
(i.e. Synchronous Ethernet \cite{SynchE}, phase detection \cite{icalepcs09}) incorporated into PTPv2 in
a way that does not break interoperability with "standard" implementations while improving greatly the performance.
The mechanisms used could be incorporated into the IEEE 1588 standard to indicate to the vendors the (optional) means to enhance
PTP's performance and to ensure interoperability of such high-accuracy implementations.
The presented solution (mainly in section~\ref{highAccuracy}) is based on \cite{WRPTP}, the author sees a potential for the solution's
further simplification/alignment with PTP in the process of standardization.
\section {Proposed revision}
%loads of text here
In this section four types of changes are proposed:
(1) addition/modification of a transport annex,
(2) addition of an optional "high accuracy" clause,
(3) addition of "Default High Accuracy" profile to Annex J, and
(1) addition/modification of the transport annex;
(2) addition of an optional "high accuracy" clause;
(3) addition of "Default High Accuracy" profile to Annex J and
(4) minor changes
to the existing clauses to accommodate (1)-(3).
\subsection{Syntonization capability of IEEE 802.3/Ethernet}
It is proposed to extend Annex F (it is also possible to add a new annex) such that physical syntonization
It is proposed to extend Annex F (it is also possible to add a new annex) such that the physical syntonization
of clocks is foreseen (i.e. by using Synchronous Ethernet). Proposed changes to Table F.2 and addition of
new Table F.3.
new Table F.3 are presented below.
\begin{table}[ht!]
\caption{Table F.2 -- Ethernet transportSpecific field}
\centering
......@@ -129,18 +132,21 @@ new Table F.3.
\textbf{Enumeration} & \textbf{Value}(hex) & \textbf{Specification} \\ \hline
DEFAULT & 0 & All PTP layer 2 Ethernet transmission not covered by another enumeration value. \\ \hline
ETHERNET\_AVB & 1 & This value is reserved for use in connection with the standard being developed by the IEEE 802.1 AVB Task Group as P802.1AS \\ \hline
ETHERNET\_SYNCE & 2-6 & Ethernet $+$ Syntonization, further specified in Table F.3 \\ \hline
ETHERNET\_SYNCE & 2-6 & Ethernet $+$ Synchronous Ethernet, further specified in Table~F.3 \\ \hline
Reserved & 6-F & Reserved for assignment in future version s of the standard \\ \hline
\end{tabular}
\label{tab:transportSpecific}
\end{table}
% \vspace*{-2em}
\begin{table}[ht!]
\caption{Table F.3 - Syntonization capable Ethernet transportSpecific values}
\centering
\begin{tabular}{| l | p{13cm} |} \hline
\textbf{Value}(hex) & \textbf{Specification} \\ \hline
2 or 3 & Syntonization distribution topology aligned with PTP topology (i.e SyncE without ESMC) \\ \hline
4 or 5 & Syntonization distribution topology independent from PTP topology (i.e. SyncE with ESMC) \\ \hline
2 or 3 & Syntonization distribution topology aligned with PTP topology
(i.e SyncE without using Ethernet Synchronization Messaging Channel (ESMC)) \\ \hline
4 or 5 & Syntonization distribution topology independent from PTP topology
(i.e. SyncE using Ethernet Synchronization Messaging Channel (ESMC)) \\ \hline
2 or 4 & Frequency loopback disabled \\ \hline
3 or 5 & Frequency loopback enabled \\ \hline
\end{tabular}
......@@ -153,38 +159,39 @@ shall, after proper phase alignment, encode such frequency into data stream and
\subsection{High Accuracy (optional) clause}
\label{highAccuracy}
It is proposed to add optional clause which could be implemented by devices for high accuracy synchronization.
The actions which are defined in this clause take place while a PTP link is being established -- in the
UNCALIBRATED state of BMC-selected slave port and in the MASTER state of BMC-selected master port.
This clause presents the following requirements to the hardware/implementation:
\begin{itemize*}
\item It shall feature constant rx/tx latencies during operation and inform higher layers
about these latencies (e.g. measure using calibration pattern).
about these latencies values (e.g. measure rx/tx latencies using calibration pattern).
\item It shall provide timestamps with a sufficient precision (i.e. using syntonization-capable Ethernet mapping,
transportSpecific=0x3, and phase detection techniques)
transportSpecific=0x3, and phase detection techniques), the fractional nanosecond part of a timestamps shall
be included in the correctionField as specified in PTPv2.
\item It shall be able to generate the calibration pattern on request
(RD+K28.7 code group, Appendix 36A.2 of \cite{IEEE802.3}).
\item It shall provide estimation of asymmetry using parameters provided by this clause
(e.g. using Link Delay Model, tx/rx latencies and relative delay coefficient as explained in \cite{WRPTP})
(RD+K28.7 code group, Appendix 36A.2 of IEEE802.3).
\item It shall provide estimation of the asymmetry using parameters provided by this clause
(e.g. using Link Delay Model, tx/rx latencies and relative delay coefficient as explained in \cite{WRPTP}).
\end{itemize*}
\subsubsection{Definition of Data Set Fields}
The implementation-specific data fields are defined to store clause specific data per-port:
(1) values of hardware characteristics (e.g.: rx/tx latencies);
(2) configuration parameters (e.g.: whether calibration patter is required, calibration period/pattern);
(3) current state of the Finite State Machine (section~\ref{fsm}).
The implementation-specific Data Set fields are defined to store (per-port) a clause specific data:
(1)~values of hardware characteristics (e.g.: rx/tx latencies);
(2)~configuration parameters (e.g.: whether calibration patter is required, calibration period/pattern);
(3)~current state of the Finite State Machine (section~\ref{fsm}).
The (re-)initialization methods and values are defined.
\subsubsection{Definition TLVs}
It is proposed to define TLVs recognized by newly defined tlvType HIGH\_ACCURACY\_OPTION
(extension to clause 14.1.1) of the format defined in Table~\ref{tab:TLVformat}. The TLV's type
is recognized by messageID as defined in Table~\ref{tab:MessageId}.These TLVs are used to
It is proposed to define TLVs recognized by tlvType HIGH\_ACCURACY\_OPTION
(extension to clause 14.1.1) of the format presented in Table~\ref{tab:TLVformat}. Different messages of such TLV type
are recognized by messageID as defined in Table~\ref{tab:MessageId}. These TLVs are used to
exchange clause-specific data and trigger transitions in the Finite State Machine (section~\ref{fsm}).
They are carried in Signaling Messages or as suffixed to Announce message (see Table~\ref{tab:MessageId}).
They are carried in Signaling Messages or suffixed to Announce message (see Table~\ref{tab:MessageId}).
\begin{table}[h!]
......@@ -204,7 +211,7 @@ They are carried in Signaling Messages or as suffixed to Announce message (see T
\end{tabular}
\label{tab:TLVformat}
\end{table}
\vspace*{-1em}
\begin{table}[tbp]
\caption{Message ID values/types}
\centering
......@@ -221,24 +228,26 @@ ANN\_SUFIX & 0x2000 & Announce \\ \hline
\label{tab:MessageId}
\end{table}
\newpage
\subsubsection{Finite State Machine}
\label{fsm}
The Finite State Machine (FSM) controls the process of establishing a high accuracy
link between a Master and a Slave implementing high accuracy option. It shall be non-preemptive with regards
The Finite State Machine (FSM) controls the process of establishing a high accuracy (HA)
link between two ports implementing high accuracy option. The FSM shall be non-preemptive with regards
to the execution of the PTP State Machine. It enables syntonization over the physical layer,
optional measurement of tx/rx latencies and exchange of their values across the link. The FSM shall be
executed in the PTP UNCALIBRATED state on the port which recommended (by BMC) state is SLAVE and in
the PTP MASTER state on the port which recommended state is MASTER. The FSM is depicted in
Figure~\ref{fig:wrFSM} and described in Table~\ref{tab:wrFSMdesc}.
executed in the PTP UNCALIBRATED state on the port which recommended (by BMC) state is SLAVE --
called Slave -- and in the PTP MASTER state on the port which recommended state is MASTER -- called
Master. The FSM is depicted in Figure~\ref{fig:wrFSM} and described in Table~\ref{tab:wrFSMdesc}.
The FSM shall be started when a port in non-Slave state is recommended to be Slave by the BMC and
appropriate conditions are fullfiled (e.g. both communicating ports implement the high accuracy option).
% \vspace*{-1.0em}
\begin{table}[hp!]
\caption{State definition}
\caption{State definitions}
\centering
\begin{tabular}{| c | p{12.2cm} |} \hline
\textbf{PTP portState} & \textbf{Description} \\
\textbf{Port State} & \textbf{Description} \\
%& \\
\hline
\small
......@@ -248,14 +257,14 @@ PRESENT & Slave-only state. Upon entering this state, the Slave send
message to the Master and waits for the $LOCK$ message.\\ \hline
M\_LOCK & Master-only state. Upon entering this state, the Master sends the $LOCK$
message. In this state, the Master waits for the Slave to finish
successfully the locking process (reception of the $LOCKED$ message). \\ \hline
successfully the frequency locking process (indicated by reception of the $LOCKED$ message). \\ \hline
S\_LOCK & Slave-only state. The Slave locks its clock signal to the frequency distributed
over the physical layer by the Master. \\ \hline
LOCKED & Slave-only state. Upon entering this state, the Slave sends the $LOCKED$ message
to inform that it is syntonized, and waits for the \textit{CALIBRATE} message.
\\ \hline
CALIBRATION & In this state, optional calibration of the port's reception and/or
transmission latencies can be performed.
CALIBRATION & In this state, optional calibration of the port's rx and/or
tx latencies can be performed.
Upon entering this state, the Port sends a \textit{CALIBRATE} message to
the other Port -- in the message the characteristics of calibration pattern
are sent. If calibration is not needed, the next state is entered, otherwise an
......@@ -264,13 +273,12 @@ CALIBRATION & In this state, optional calibration of the port's reception a
CALIBRATED & Upon entering this state, the WR Port sends a \text{CALIBRATED} message with the
values of its rx/tx latencies. \\ \hline
RESP\_CALIB\_REQ & The Port's action in this state depends on the content of CALIBRATION message.
If required, the pattern shall be enabled. The pattern shall be
disabled on exiting the state (after the timeout specified in the
\textit{CALIBRATED} message). On reception of the \textit{CALIBRATED} message,
the next state is entered.\\ \hline
If required, the calibration pattern shall be enabled (sent). The pattern shall be
disabled on exiting the state (after the timeout or reception of the
\textit{CALIBRATED} message).\\ \hline
HA\_LINK\_ON & Upon entering this state, the Master sends the HIGH\_ACCURACY\_LINK\_ON message.
In this state, the values of clause-defined Data Set fields (i.e. \textit{modeOn}
and \textit{parentModeOn}) are set to TRUE and the \textit{IDLE} state is entered unconditionally.
In this state, the values of the clause-defined Data Set fields are set.
The \textit{IDLE} state is entered unconditionally.
The execution of the FSM is considered to be completed successfully. \\ \hline
\end{tabular}
\label{tab:wrFSMdesc}
......@@ -280,54 +288,54 @@ HA\_LINK\_ON & Upon entering this state, the Master sends the HIGH\_ACCUR
\begin{figure}[ht!]
\centering
% \vspace{-1.3cm}
\includegraphics[width=1.00\textwidth]{fig/wrFSM.ps}
\includegraphics[width=.70\textwidth]{fig/wrFSM.eps}
\caption{Finite State Machine}
\label{fig:wrFSM}
\end{figure}
\newpage
\subsubsection{Event definition}
Implementation of two events defined in PTPv2 as "implementation-specific" are defined in the clause.
Implementation of two PTP State Machine transition events described as \textit{implementation-specific} is defined in this clause.
The \textbf{SYNCHRONIZATION\_FAULT} shall occur when syntonization break is detected by hardware
(link disconnected) or high accuracy mode is exited out of other reason (e.g. management). It shall result in
clearing the record of foreign masters. The \textbf{MASTER\_CLOCK\_SELECTED} shall occur on successful
clearing the record of foreign masters. The \textbf{MASTER\_CLOCK\_SELECTED} shall occur on the successful
completion of the FSM execution on the port selected by BMC as Slave and
being in PTP\_UNCALIBRATED state. Consequently, the PTP\_SLAVE state shall be entered.
\subsection{High Accuracy Default Profile}
It is proposed that the profile uses request-response mechanism and defines default mapping using Annex F
with transportSpecific flag set to ETHERNET\_SYNCE (i.e. SyncE without ECMS and frequency loopback).
However, using transportSpecific flag set to DEFAULT (ETHERNET) is allowed if the link partner is not
SyncE-capable. This is to enable backward-compatibility. This might be realized by defining
two PTP ports per single physical port (one defining High Accuracy profile, second by defining
Default Request-response mechanism), as suggested in Clause 7.5.1.
The delay request-response mechanism shall be the only path delay measurement mechanism for this profile.
It shall define default mapping using Annex F (networkProtocol=0003)
with transportSpecific flag set to 3 (i.e. SyncE without ECMS and with frequency loopback enabled).
However, using transportSpecific flag set to 0 (DEFAULT) is allowed if the link partner is not
SyncE-capable. Such situation shall be detected and handled properly by a port implementing this profile to ensure
backward-compatibility and interoperability. \\
By default, the "High Accuracy" option shall be active. If a link-partner uses mapping defined in Annex F
with DEFAULT transport Specific field, the "High Accuracy" option shall be disabled.
The delay request-response mechanism shall be the only path delay measurement mechanism.
\subsection{Changes to clauses of PTPv2}
\subsubsection{Required changes}
\vspace{1em}
\begin{table}[ph!]
\begin{tabular}{ l l}
\begin{tabular}{ l p{12.5cm}}
\multicolumn{2}{l}{\textbf{Required changes:}} \\
Clause 7.6.2.5: & Table 6 -- add accuracies greater then 25ns \\
Clause 14.1.1: & Table 34 -- add HIGH\_ACCURACY\_OPTION tlvType \\
\end{tabular}
\end{table}
\subsubsection{Possibly helpful changes}
\begin{table}[ph!]
\begin{tabular}{ l p{12.2cm}}
\multicolumn{2}{l}{ \textbf{Possibly helpful changes:}} \\
Clause 3.1: & Add time definition (time = time of day and/or frequency) \\
Clause 5.3.3: & Add picoseconds to Timestamp structure \\
Clause 5.3.3: & Add picoseconds to the Timestamp structure \\
Clause 7.5.3: & Add High Accuracy FSM as an example in the NOTE \\
% Clause 8.2.5.1 & Add portMode field to portDS (Master-only/Slave-only/Master-and-Slave \\
% Clause 9.3.2 & Modify default BMC in such way that port with portMode=Slave-only will not enter Slave
% state and the functioning of Boundary Clock (other ports) is not broken. Similarly
% with Master-only \\
Clause 9.3.1: & Add profile-specific decision code to enable e.g. choice of
secondarySlave \\
Clause 9.5.10: & Waver the necessity of sending Follow\_Up message prior to transmission
Clause 9.5.10: & Waive the requirement of sending Follow\_Up message prior to the transmission
of a subsequent Sync Message -- this is to enable resending Sync Messages
when detecting that Sync Message was sent on clock-adjustment and the timestamp
is faulty. \\
......@@ -343,60 +351,46 @@ Additionally, using SyncE with PTP is considered by Telecom profile, therefore a
transport annex can be useful for telecommunication applications.
\section {Backward compatibility to IEEE-1588:} Complete backward compatibility.
\section {Backward compatibility to IEEE-1588:} A: Complete backward compatibility, i.e. V2 and the
revised version interoperate although V2 devices do not receive benefits of revision.
\newpage
\begin{thebibliography}{9}
\footnotesize
\bibitem{WRinGS}
M. Lipi\'{n}ski, T. W\l{}ostowski, J. Serrano, P. Alvarez and P. Moreira
\emph{Performance results of the first White Rabbit installation for CNGS time transfer}.
ISPCS2012 Proccedings,
2012 \\
\vspace*{-2em}
\bibitem{WRinISPCS2011}
M. Lipi\'{n}ski, T. W\l{}ostowski, J. Serrano, P. Alvarez
\emph{White Rabbit: a PTP Application for Robust Sub-nanosecond Synchronization}.
ISPCS2011 Proccedings,
2011 \\
\vspace*{-2em}
\bibitem{SynchE}
ITU-T G.8262/Y.1362
\emph{Timing characteristics of a synchronous
Ethernet equipment slave clock}.
TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU,
07/2010.
\bibitem{tomekMSC}
Tomasz W\l{}ostowski
\emph{Precise time and frequency transfer in a White Rabbit network}.
Warsaw University of Technology,
05/2011.
07/2010.\\
\vspace*{-2em}
\bibitem{icalepcs09}
J. Serrano, P. Alvarez, M. Cattin, E. G. Cota, J. H. Lewis, P. Moreira, T. W\l{}ostowski
and others,
\emph{The White Rabbit Project}.
ICALEPCS TUC004,
2009.\\
\bibitem{IEEE802.3}
IEEE Std 802.3-2008
\emph{IEEE Standard for Information technology -- Telecommunications and information exchange
between systems -- Local and Metropolitan area networks -- Specific requirements}.
IEEE Computer Society, New York,
2008.
\vspace*{-2em}
\bibitem{WRPTP} %done x
Emilio G. Cota, Maciej Lipinski, Tomasz Wostowski, Erik van der Bij, Javier
Serrano
\emph{White Rabbit Specification: Draft for Comments}.
CERN, Geneva
07/2011.
\vspace*{-2em}
\end{thebibliography}
......
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