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White Rabbit Standardization
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c02b1562
Commit
c02b1562
authored
Apr 12, 2015
by
Maciej Lipinski
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[ISPCS-HA] removing text that will surely not be needed
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L1SynOp.tex
documents/ISPCS2015-HA/L1SynOp.tex
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documents/ISPCS2015-HA/L1SynOp.tex
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c02b1562
...
...
@@ -30,7 +30,7 @@
% \date{\today}
\maketitle
\color
{
gray
}
\begin{abstract}
The High Accuracy (HA) sub-committee (SC) is a part of the P1588 Working Group (WG). It works
...
...
@@ -154,7 +154,7 @@ In Figure~\ref{fig:refModel}, the transmission circuit (Tx) of \textit{Node A} i
of
\textit
{
Node B
}
, and vice versa. Consequently, thanks to the clock and data recovery (CDR) circuit in
each receiver, the frequency of the
\textit
{
L1 Tx clock signal
}
in
\textit
{
Node A
}
is equal to the frequency of the
\textit
{
L1 Rx clock signal
}
in
\textit
{
Node B
}
(
$
clk
_{
L
1
\_
Tx
\_
A
}$
and
$
clk
_{
L
1
\_
Rx
\_
B
}$
respectively), and vice versa.
\color
{
black
}
and
$
clk
_{
L
1
\_
Rx
\_
B
}$
respectively), and vice versa.
The phase offset between the rising edge of the
\textit
{
PTP clock signal
}
and the transmission
\textit
{
L1 Tx clock signal
}
, captured with respect to the
\textit
{
PTP clock signal
}
, is
marked as
$
x
_{
Tx
\_
A
}$
and
$
x
_{
Tx
\_
B
}$
for
\textit
{
Node A
}
and
\textit
{
Node B
}
respectively.
...
...
@@ -172,7 +172,7 @@ is marked as $x_{Rx\_A}$ and $x_{Rx\_B}$ for \textit{Node A} and \textit{Node B}
The fine part of the round-trip can be calculated when the values of all the phase offsets,
i.e.
$
x
_{
Tx
\_
A
}$
,
$
x
_{
Tx
\_
B
}$
,
$
x
_{
Rx
\_
A
}$
, and
$
x
_{
Rx
\_
B
}$
, are known for the appropriate
instances (i.e the transmission and reception time of the relevant event messages).
\color
{
gray
}
instances (i.e the transmission and reception time of the relevant event messages).
Therefore, both nodes participating in the link must "know" their phase offsets.
The PTP Slave must be informed about the phase offsets of the PTP Master.
...
...
@@ -215,7 +215,7 @@ As an example, the \textit{reference model} is applied to White Rabbit:
\end{itemize}
\color
{
black
}
\section
{
High Accuracy in multi-domain PTP networks
}
\label
{
HAinMultiDomain
}
...
...
@@ -252,7 +252,6 @@ The SyncE spanning tree in the network is irrelevant as long as the
information required to recreate the
\textit
{
PTP clock signal
}
is distributed from the
PTP master to the PTP slave.
\\
\color
{
gray
}
\section
{
(Non-) Congruency between L1 syntonization and PTP synchronization
}
...
...
@@ -461,7 +460,6 @@ embeds its phase offsets into timestamps by correcting their values.
\textit
{
L1 clock signal
}
used for transmitting data and the
\textit
{
PTP clock signal
}
in the domain in which the PTP messages are exchanged.
These parameters can enable an optional multi-domain syntonization.
\\
\textbf
{
Parameters Flag
}
informs that the
\textit
{
Parameters
}
are provided by the
sending
\textit
{
L1SynOp port
}
.
...
...
@@ -475,7 +473,6 @@ details in the following section. %To be investigated.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\color
{
black
}
\subsection
{
Parameters
}
\label
{
parameters
}
...
...
@@ -556,76 +553,8 @@ These arguments are presented below and need to be evaluated:
\end{figure}
\subsection
{
Frequency Class
}
\label
{
FrequencyClass
}
\textit
{
Frequency Class
}
is a numerical representation of the syntonization characteristics
of the
\textit
{
L1 clock signal
}
provided by an
\textit
{
L1SynOp node
}
; the
lower the value, the "better" the characteristics.
It is not based on a real-time measurement but rather a set of requirements that are fulfilled
by the equipment. The requirements shall rather concern noise transfer/generation than
holdover/stability (to be discussed). For example, if an ITU-T SyncE is used by the
\textit
{
L1SynOp node
}
for the L1 syntonization, the
\textit
{
Frequency Class
}
represents the
characteristics specified by the appropriate ITU-T Recommendation.
Table~
\ref
{
tab:freqClass
}
defines
\textit
{
Frequency Classes
}
. The
\textit
{
Ideal
}
class
represents a clock signal characteristics that are impossible to provide, thus the value
should never be used and new frequency classes should be added in the reserved spaces
(values greater than 0x0000). The
\textit
{
No L1
}
class represents a node with a free-running
oscillator. In between
\textit
{
Ideal
}
and
\textit
{
No L1
}
, different
\textit
{
L1 clock signal
}
characteristics are mapped into
\textit
{
Frequency Class
}
values.
\begin{table}
[!t]
\centering
\begin{tabular}
{
| c | c | c |
}
\hline
\textbf
{
Value
}
&
\textbf
{
Name
}
&
\textbf
{
Specification
}
\\
\hline
0x0000
&
Ideal
&
\\
\hline
\textcolor
{
gray
}{
Reserved
}&
&
\\
\hline
0x0010
&
WR
&
IEEE1588-201x Appendix
\\
\hline
\textcolor
{
gray
}{
Reserved
}&
&
\\
\hline
0x0100--0x0200
&
SyncE
&
ITU-T Recommendations
\\
\hline
\textcolor
{
gray
}{
Reserved
}&
&
\\
\hline
0xF000
&
PTP
&
No specification
\\
\hline
\textcolor
{
gray
}{
Reserved
}&
&
\\
\hline
0xFFFF
&
No L1
&
\\
\hline
\end{tabular}
\caption
{
Frequency Classes -- initial proposal, to be finished.
}
\label
{
tab:freqClass
}
\end{table}
The
\textit
{
L1SynOp
}
specifies the rules for exchanging
\textit
{
Frequency Class
}
in the
\textit
{
L1InfoTLV
}
but leaves to the profile the specification of how the information
is used and propagated by the
\textit
{
L1SynOp nodes
}
. Two ideas of how the
\textit
{
Frequency Class
}
could be used by a profile are presented below:
\subsubsection
{
Worst class in the path
}
The
\textit
{
L1InfoTLV
}
carries the value of the "worst"
\textit
{
Frequency Class
}
node in the
path from the source of frequency. An
\textit
{
L1SynOp node
}
knows the value of its
\textit
{
Frequency Class
}
, the node sends this value if it is "worse" than the
value received from the direction of the frequency source. Otherwise, it forwards the
value of the
\textit
{
Frequency Class
}
received. This enables, for example, to ensure that an
\textit
{
L1SynOp node
}
with the White Rabbit
\textit
{
Frequency Class
}
is connected with the
frequency source through a path consisting only of
\textit
{
L1SynOp nodes
}
of the same
\textit
{
Frequency Class
}
. Connecting an
\textit
{
L1SynOp node
}
of a "worse" class to an
\textit
{
L1SynOp node
}
of a "better" class can be allowed, but not the other way around.
\subsubsection
{
Path trail
}
The
\textit
{
L1InfoTLV
}
carries a dynamic list of 2-tuples which trails the path from the frequency
source. Each 2-tuple contains two values:
\textit
{
Frequency Class
}
, and
\textit
{
Counter
}
of the
\textit
{
L1SynOp nodes
}
of that
\textit
{
Frequency Class
}
in the path from the source
of frequency.
An
\textit
{
L1SynOp node
}
is required to update the
\textit
{
Frequency Class
}
list by either (1)
incrementing the counter in an existing 2-tuple, or (2) adding a new tuple with its
\textit
{
Frequency Class
}
.
A profile that uses
\textit
{
L1SynOp
}
defines how the information is used. For example, a WR
Profile would not use the path that contains non-WR nodes. A different profile could define
an algorithm that uses the
\textit
{
Frequency Class
}
list to compare different paths; then, the
result of the comparison could be used to construct syntonization and/or synchronization
spanning tree.
\color
{
gray
}
\subsection
{
Media independent interface
}
\label
{
mediaIndependentIF
}
...
...
@@ -670,79 +599,7 @@ by PTP on ports in the Passive state.
The mutual exchange of information on the "passive link" enables to verify the link and
the applicability of the
\textit
{
reference model
}
; the L1SynOp information can be kept up to date.
\section
{
A White Rabbit profile using L1SynOp
}
\begin{figure}
[!t]
\centering
\includegraphics
[width=0.35\textwidth]
{
figs/MessageExchangeWR.eps
}
\caption
{
Exchange of L1InfoTLVs in a White Rabbit profile using L1SynOp.
}
\label
{
fig:HAexchange
}
\end{figure}
The White Rabbit HA profile that uses L1SynOp can be defined as follows (see Figure~
\ref
{
fig:HAexchange
}
):
\begin{itemize}
\item
IEEE 802.3/Ethernet Mapping.
\item
Medium-dependent mechanism used: WR-SyncE
\\
(
\textit
{
FrequencyClass
}
= WR).
\item
Configuration:
\\
\textit
{
Congruent
}
=
\textit
{
True
}
;
\\
\textit
{
Coupled
}
=
\textit
{
True
}
;
\\
\textit
{
Parameters Flag
}
= False.
\item
Timestamps are corrected with the phase offset values:
\\
\textit
{
Timestamps corrected
}
=
\textit
{
True
}
.
\item
Announce-L1InfoTLV exchange rules:
\begin{itemize}
\item
PTP Master state: it is suffixed to the PTP Announce Message
\item
PTP Uncalibrated state: it is sent in Signaling Messages at
small intervals.
\end{itemize}
\item
Response-L1InfoTLV is sent in Signaling Messages addressed to 01-80-C2-00-00-0E
\item
L1SynOp is considered active on a link if the conditions below are fulfilled:
\begin{itemize}
\item
The profile-specific configuration agrees on both
\textit
{
L1SynOp ports
}
,
\item
The
\textit
{
FrequencyClass
}
indicates that the path from the PRTC is exclusively WR,
\item
The
\textit
{
L1 configuration
}
agrees on both
\textit
{
L1SynOp ports
}
,
\item
Before a timeout expires, the
\textit
{
L1SynOp port
}
in the PTP Uncalibrated state:
\\
(1) confirms that the
\textit
{
Link-verified flag
}
of both nodes is
\textit
{
True
}
;
\\
(2) confirms that the
\textit
{
L1 state
}
of the PTP Master is L1-master;
\\
(3) requests to
\textit
{
become L1-Slave
}
and confirms that its
\textit
{
L1 state
}
is L1-Slave;
\\
(4) confirms that the
\textit
{
Phase offsets known flag
}
s of both ports are
\textit
{
True
}
;
\item
As soon as all the above steps and conditions are fulfilled, the port exits the PTP Uncalibrated
state and activates the mechanisms to account for the fine part of the round-trip.
Otherwise, if the timeout expires, the port exits the PTP Uncalibrated
state but does not activate the mechanisms.
\end{itemize}
If the conditions above are not fulfilled, PTP synchronization is performed without activating L1SynOp-related mechanisms.
\end{itemize}
\section
{
A Telecom profile to use L1SynOp
}
A Telecom PTP
\textit
{
time and phase profile
}
that uses L1SynOp can be defined as follows:
\begin{itemize}
\item
IEEE 802.3/Ethernet Mapping.
\item
Medium-dependent mechanism: ITU-T-SyncE
\\
(
\textit
{
FrequencyClass
}
= SyncE).
\item
Configuration:
\\
\textit
{
Congruent
}
= False;
\\
\textit
{
Coupled
}
= False;
\\
\textit
{
Parameters Flag
}
=
\textit
{
True
}
.
\item
Timestamps are corrected with the phase offset values:
\\
\textit
{
Timestamps corrected
}
=
\textit
{
True
}
.
\item
Announce-L1InfoTLV is suffixed to the PTP Announce Message.
\item
Response-L1InfoTLV is sent in Signaling Messages addressed to 01-80-C2-00-00-0E.
\item
L1SynOp is considered active on a link if the conditions below are fulfilled:
\begin{itemize}
\item
The profile-specific configuration agrees on both
\textit
{
L1SynOp ports
}
,
\item
The
\textit
{
FrequencyClass
}
indicates the path from the PRTC is not worse than SyncE,
\item
The
\textit
{
L1 configuration
}
agrees on both
\textit
{
L1SynOp ports
}
,
\item
The
\textit
{
Link-verified flag
}
of both nodes is
\textit
{
True
}
.
\end{itemize}
If the conditions above are not fulfilled, PTP synchronization is performed without
activating L1SynOp-related mechanisms. If they are fulfilled, L1SynOp is activated
immediately.
\end{itemize}
\color
{
black
}
\section
{
Potential applications of the information exchanged in the L1SynOp TLV
}
This section explains different functionalities provided by
\textit
{
L1SynOp
}
to
...
...
@@ -891,7 +748,7 @@ Section~\ref{HAinMultiDomain}.
The value of phase measurement carried as one of the parameters can be used
to correct received timestamps (interpolated correction), if the value is not embedded at the
timestamping node, as described in Section~
\ref
{
MediaFlexibility
}
.
\color
{
gray
}
\bibliographystyle
{
IEEEtran
}
\bibliography
{
IEEEabrv,./L1SynOp
}
...
...
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