[system-administrators-guide] Add sec- to section IDs, s1 and s2 to sec

[stephenw]

commit d2aaa69d59d15bcc833f70e466cfcd4c7d50d2d2
Author: Stephen Wadeley <swadeley at redhat.com>
Date:   Wed Jul 30 23:40:13 2014 +0200

    Add sec- to section IDs, s1 and s2 to sec

 en-US/Configuring_PTP_Using_ptp4l.xml |   38 ++++++++++++++++----------------
 1 files changed, 19 insertions(+), 19 deletions(-)
---
diff --git a/en-US/Configuring_PTP_Using_ptp4l.xml b/en-US/Configuring_PTP_Using_ptp4l.xml
index c0ac008..7288ff7 100644
--- a/en-US/Configuring_PTP_Using_ptp4l.xml
+++ b/en-US/Configuring_PTP_Using_ptp4l.xml
@@ -5,7 +5,7 @@
 <chapter id="ch-Configuring_PTP_Using_ptp4l">
   <title>Configuring PTP Using ptp4l</title>
 
-  <section id="Introduction_to_PTP">
+  <section id="sec-Introduction_to_PTP">
     <title>Introduction to PTP</title>
     <para>
       The <firstterm>Precision Time Protocol</firstterm> (<acronym>PTP</acronym>) is a protocol used to synchronize clocks in a network. When used in conjunction with hardware support, <systemitem class="protocol">PTP</systemitem> is capable of sub-microsecond accuracy, which is far better than is normally obtainable with <systemitem class="protocol">NTP</systemitem>. <systemitem class="protocol">PTP</systemitem> support is divided between the kernel and user space. The kernel in <application>Fedora</application> includes support for <systemitem class="protocol">PTP</systemitem> clocks, which are provided by network drivers. The actual implementation of the protocol is known as <application>linuxptp</application>, a <systemitem class="protocol">PTPv2</systemitem> implementation according to the IEEE standard 1588 for Linux.
@@ -13,7 +13,7 @@
     <para>
       The <package>linuxptp</package> package includes the <application>ptp4l</application> and <application>phc2sys</application> programs for clock synchronization. The <application>ptp4l</application> program implements the <systemitem class="protocol">PTP</systemitem> boundary clock and ordinary clock. With hardware time stamping, it is used to synchronize the <systemitem class="protocol">PTP</systemitem> hardware clock to the master clock, and with software time stamping it synchronizes the system clock to the master clock. The <application>phc2sys</application> program is needed only with hardware time stamping, for synchronizing the system clock to the <systemitem class="protocol">PTP</systemitem> hardware clock on the <firstterm>network interface card</firstterm> (<acronym>NIC</acronym>).
     </para>
-    <section id="Understanding_PTP">
+    <section id="sec-Understanding_PTP">
       <title>Understanding PTP</title>
    <para>
      The clocks synchronized by <systemitem class="protocol">PTP</systemitem> are organized in a master-slave hierarchy. The slaves are synchronized to their masters which may be slaves to their own masters. The hierarchy is created and updated automatically by the <firstterm>best master clock</firstterm> (<acronym>BMC</acronym>) algorithm, which runs on every clock. When a clock has only one port, it can be <firstterm>master</firstterm> or <firstterm>slave</firstterm>, such a clock is called an <firstterm>ordinary clock</firstterm> (<acronym>OC</acronym>). A clock with multiple ports can be master on one port and slave on another, such a clock is called a <firstterm>boundary</firstterm> clock (<acronym>BC</acronym>). The top-level master is called the <firstterm>grandmaster clock</firstterm>, which can be synchronized by using a <firstterm>Global Positioning System</firstterm> (<acronym>GPS</acronym>) time source. By using a GPS-based time source, disparate networks can be 
 synchronized with a high-degree of accuracy.
@@ -32,7 +32,7 @@
       </mediaobject>
       </figure>
   </section>
-  <section id="s2-Advantages_of_PTP">
+  <section id="sec-Advantages_of_PTP">
     <title>Advantages of PTP</title>
   <para>
     One of the main advantages that <systemitem class="protocol">PTP</systemitem> has over the <firstterm>Network Time Protocol</firstterm> (<acronym>NTP</acronym>) is hardware support present in various <firstterm>network interface controllers</firstterm> (<acronym>NIC</acronym>) and network switches. This specialized hardware allows <systemitem class="protocol">PTP</systemitem> to account for delays in message transfer, and greatly improves the accuracy of time synchronization. While it is possible to use non-PTP enabled hardware components within the network, this will often cause an increase in jitter or introduce an asymmetry in the delay resulting in synchronization inaccuracies, which add up with multiple non-PTP aware components used in the communication path. To achieve the best possible accuracy, it is recommended that all networking components between <systemitem class="protocol">PTP</systemitem> clocks are <systemitem class="protocol">PTP</systemitem> hardware en
 abled. Time synchronization in larger networks where not all of the networking hardware supports <systemitem class="protocol">PTP</systemitem> might be better suited for <systemitem class="protocol">NTP</systemitem>.
@@ -45,13 +45,13 @@
 
 <!-- Topics, Tasks -->
 
-<section id="Using_PTP">
+<section id="sec-Using_PTP">
   <title>Using PTP</title>
   <para>
     In order to use <systemitem class="protocol">PTP</systemitem>, the kernel network driver for the intended interface has to support either software or hardware time stamping capabilities.
   </para>
 
-  <section id="Checking_for_Driver_and_Hardware_Support">
+  <section id="sec-Checking_for_Driver_and_Hardware_Support">
     <title>Checking for Driver and Hardware Support</title>
   <para>
     In addition to hardware time stamping support being present in the driver, the NIC must also be capable of supporting this functionality in the physical hardware. The best way to verify the time stamping capabilities of a particular driver and NIC is to use the <application>ethtool</application> utility to query the interface as follows:
@@ -131,7 +131,7 @@ should include:
 </para>
 </section>
 
-<section id="Installing_PTP">
+<section id="sec-Installing_PTP">
   <title>Installing PTP</title>
   <para>
     The kernel in <application>Fedora</application> includes support for <systemitem class="protocol">PTP</systemitem>. User space support is provided by the tools in the <application>linuxptp</application> package. To install <application>linuxptp</application>, issue the following command as <systemitem class="username">root</systemitem>:
@@ -139,11 +139,11 @@ should include:
     This will install <application>ptp4l</application> and <application>phc2sys</application>.
   </para>
     <para>
-      Do not run more than one service to set the system clock's time at the same time. If you intend to serve <systemitem class="protocol">PTP</systemitem> time using <systemitem class="protocol">NTP</systemitem>, see <xref linkend="Serving_PTP_Time_with_NTP" />.
+      Do not run more than one service to set the system clock's time at the same time. If you intend to serve <systemitem class="protocol">PTP</systemitem> time using <systemitem class="protocol">NTP</systemitem>, see <xref linkend="sec-Serving_PTP_Time_with_NTP" />.
     </para>
 </section>
 
-<section id="Starting_ptp4l">
+<section id="sec-Starting_ptp4l">
   <title>Starting ptp4l</title>
   <para>
 The <application>ptp4l</application> program tries to use hardware time stamping by default. To use <application>ptp4l</application> with hardware time stamping capable drivers and NICs, you must provide the network interface to use with the <option>-i</option> option. Enter the following command as <systemitem class="username">root</systemitem>:
@@ -179,7 +179,7 @@ By default, messages are sent to <filename>/var/log/messages</filename>. However
     <screen>~]# <command>ptp4l -i <replaceable>em3</replaceable> -m -S</command></screen>
   </para>
 
-  <section id="Selecting_a_Delay_Mechanism">
+  <section id="sec-Selecting_a_Delay_Mechanism">
     <title>Selecting a Delay Measurement Mechanism</title>
     <para>
     There are two different delay measurement mechanisms and they can be selected by means of an option added to the <command>ptp4l</command> command as follows:
@@ -229,7 +229,7 @@ By default, messages are sent to <filename>/var/log/messages</filename>. However
   </section>
 </section>
 
-<section id="Specifying_a_Configuration_File">
+<section id="sec-Specifying_a_Configuration_File">
   <title>Specifying a Configuration File</title>
   <para>
     The command line options and other options, which cannot be set on the command line, can be set in an optional configuration file.
@@ -249,7 +249,7 @@ time_stamping         software
   </para>
 </section>
 
-<section id="Using_the_PTP_Management_Client">
+<section id="sec-Using_the_PTP_Management_Client">
   <title>Using the PTP Management Client</title>
   <para>
     The <systemitem class="protocol">PTP</systemitem> management client, <application>pmc</application>, can be used to obtain additional information from <application>ptp4l</application> as follows:
@@ -312,7 +312,7 @@ if <literal>gmPresent</literal> is true, the <systemitem class="protocol">PTP</s
 </para>
 </section>
 
-<section id="Synchronizing_the_Clocks">
+<section id="sec-Synchronizing_the_Clocks">
   <title>Synchronizing the Clocks</title>
   <para>
     The <application>phc2sys</application> program is used to synchronize the system clock to the <systemitem class="protocol">PTP</systemitem> hardware clock (<acronym>PHC</acronym>) on the NIC. To start <application>phc2sys</application>, where <replaceable>em3</replaceable> is the interface with the <systemitem class="protocol">PTP</systemitem> hardware clock, enter the following command as <systemitem class="username">root</systemitem>:
@@ -335,7 +335,7 @@ When running as a service, options are specified in the <filename>/etc/sysconfig
   </para>
 </section>
 
-<section id="Verifying_Time_Synchronization">
+<section id="sec-Verifying_Time_Synchronization">
   <title>Verifying Time Synchronization</title>
   <para>
     When <systemitem class="protocol">PTP</systemitem> time synchronization is working properly, new messages with offsets and frequency adjustments will be printed periodically to the <application>ptp4l</application> and <application>phc2sys</application> (if hardware time stamping is used) outputs. These values will eventually converge after a short period of time. These messages can be seen in <filename>/var/log/messages</filename> file. An example of the output follows:
@@ -426,7 +426,7 @@ phc2sys[1060.984]: rms  266 max  675 freq -36759 ± 234 delay  2753 ±  17
   </para>
 </section>
 
-<section id="Serving_PTP_Time_with_NTP">
+<section id="sec-Serving_PTP_Time_with_NTP">
   <title>Serving PTP Time with NTP</title>
   <para>
     The <systemitem class="daemon">ntpd</systemitem> daemon can be configured to distribute the time from the system clock synchronized by <application>ptp4l</application> or <application>phc2sys</application> by using the LOCAL reference clock driver. To prevent <systemitem class="daemon">ntpd</systemitem> from adjusting the system clock, the <filename>ntp.conf</filename> file must not specify any <systemitem class="protocol">NTP</systemitem> servers. The following is a minimal example of <filename>ntp.conf</filename>:
@@ -442,7 +442,7 @@ fudge    127.127.1.0 stratum 0</screen>
   </note>
 </section>
 
-<section id="Serving_NTP_Time_with_PTP">
+<section id="sec-Serving_NTP_Time_with_PTP">
   <title>Serving NTP Time with PTP</title>
   <para>
     <systemitem class="protocol">NTP</systemitem> to <systemitem class="protocol">PTP</systemitem> synchronization in the opposite direction is also possible. When <systemitem class="daemon">ntpd</systemitem> is used to synchronize the system clock, <application>ptp4l</application> can be configured with the <option>priority1</option> option (or other clock options included in the best master clock algorithm) to be the grandmaster clock and distribute the time from the system clock via <systemitem class="protocol">PTP</systemitem>:
@@ -462,7 +462,7 @@ With hardware time stamping, <application>phc2sys</application> needs to be used
   </para>
 </section>
 
-<section id="Improving_Accuracy">
+<section id="sec-Improving_Accuracy">
   <title>Improving Accuracy</title>
   <para>
     Test results indicate that disabling the tickless kernel capability can significantly improve the stability of the system clock, and thus improve the <systemitem class="protocol">PTP</systemitem> synchronization accuracy (at the cost of increased power consumption). The kernel tickless mode can be disabled by adding <option>nohz=off</option> to the kernel boot option parameters.
@@ -471,12 +471,12 @@ With hardware time stamping, <application>phc2sys</application> needs to be used
 
 <!-- Topics, Resources -->
 
-  <section id="s1-PTP_additional_resources">
+  <section id="sec-PTP_additional_resources">
 <title>Additional Resources</title>
     <para>
       The following sources of information provide additional resources regarding <systemitem class="protocol">PTP</systemitem> and the <application>ptp4l</application> tools.
     </para>
-<section id="s2-PTP-docs-inst">
+<section id="sec-PTP-docs-inst">
   <title>Installed Documentation</title>
       <itemizedlist>
     <listitem>
@@ -498,7 +498,7 @@ With hardware time stamping, <application>phc2sys</application> needs to be used
   </itemizedlist>
 </section>
 
-<section id="s2-PTP_useful-websites">
+<section id="sec-PTP_useful-websites">
   <title>Useful Websites</title>
   <para>
   <variablelist>