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From jpe...@apache.org
Subject [41/51] trafficserver git commit: Documentation reorganization
Date Tue, 03 Nov 2015 06:10:17 GMT
http://git-wip-us.apache.org/repos/asf/trafficserver/blob/ce162a6d/doc/admin-guide/files/records.config.en.rst
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+.. Licensed to the Apache Software Foundation (ASF) under one
+   or more contributor license agreements.  See the NOTICE file
+   distributed with this work for additional information
+   regarding copyright ownership.  The ASF licenses this file
+   to you under the Apache License, Version 2.0 (the
+   "License"); you may not use this file except in compliance
+   with the License.  You may obtain a copy of the License at
+
+      http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing,
+   software distributed under the License is distributed on an
+   "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+   KIND, either express or implied.  See the License for the
+   specific language governing permissions and limitations
+   under the License.
+
+==============
+records.config
+==============
+
+.. configfile:: records.config
+
+The :file:`records.config` file (by default, located in
+``/usr/local/etc/trafficserver/``) is a list of configurable variables used by
+the Traffic Server software. Many of the variables in the
+:file:`records.config` file are set automatically when you set configuration
+options in Traffic Line. After you modify the
+:file:`records.config` file,
+run the command :option:`traffic_ctl config reload` to apply the changes.
+When you apply changes to one node in a cluster, Traffic Server
+automatically applies the changes to all other nodes in the cluster.
+
+Format
+======
+
+Each variable has the following format::
+
+   SCOPE variable_name DATATYPE variable_value
+
+where
+
+``SCOPE`` is related to clustering and is either ``CONFIG`` (all members of
+the cluster) or ``LOCAL`` (only the local machine)
+
+``DATATYPE`` is one of ``INT`` (integer), ``STRING`` (string), ``FLOAT``
+(floating point).
+:
+A variable marked as ``Deprecated`` is still functional but should be avoided
+as it may be removed in a future release without warning.
+
+A variable marked as ``Reloadable`` can be updated via the command::
+
+   traffic_ctl config reload
+
+A variable marked as ``Overridable`` can be changed on a per-remap basis using plugins
+(like the :ref:`conf-remap-plugin`).
+
+``INT`` type configurations are expressed as any normal integer,
+e.g. *32768*. They can also be expressed using more human readable values
+using standard prefixes, e.g. *32K*. The following prefixes are supported
+for all ``INT`` type configurations
+
+   - ``K`` Kilobytes (1024 bytes)
+   - ``M`` Megabytes (1024^2 or 1,048,576 bytes)
+   - ``G`` Gigabytes (1024^3 or 1,073,741,824 bytes)
+   - ``T`` Terabytes (1024^4 or 1,099,511,627,776 bytes)
+
+.. note::
+
+    Traffic Server currently writes back configurations to disk periodically,
+    and when doing so, will not preserve the prefixes.
+
+Examples
+========
+
+In the following example, the variable `proxy.config.proxy_name`_ is
+a ``STRING`` datatype with the value ``my_server``. This means that the
+name of the Traffic Server proxy is ``my_server``. ::
+
+   CONFIG proxy.config.proxy_name STRING my_server
+
+If the server name should be ``that_server`` the line would be ::
+
+   CONFIG proxy.config.proxy_name STRING that_server
+
+In the following example, the variable ``proxy.config.arm.enabled`` is
+a yes/no flag. A value of ``0`` (zero) disables the option; a value of
+``1`` enables the option. ::
+
+   CONFIG proxy.config.arm.enabled INT 0
+
+In the following example, the variable sets the cluster startup timeout
+to 10 seconds. ::
+
+   CONFIG proxy.config.cluster.startup_timeout INT 10
+
+The last examples configures a 64GB RAM cache, using a human readable
+prefix. ::
+
+   CONFIG proxy.config.cache.ram_cache.size INT 64G
+
+Environment Overrides
+=====================
+
+Every :file:`records.config` configuration variable can be overridden
+by a corresponding environment variable. This can be useful in
+situations where you need a static :file:`records.config` but still
+want to tweak one or two settings. The override variable is formed
+by converting the :file:`records.config` variable name to upper
+case, and replacing any dot separators with an underscore.
+
+Overriding a variable from the environment is permanent and will
+not be affected by future configuration changes made in
+:file:`records.config` or applied with :program:`traffic_ctl`.
+
+For example, we could override the `proxy.config.product_company`_ variable
+like this::
+
+   $ PROXY_CONFIG_PRODUCT_COMPANY=example traffic_cop &
+   $ traffic_ctl config get proxy.config.product_company
+
+.. _configuration-variables:
+
+Configuration Variables
+=======================
+
+The following list describes the configuration variables available in
+the :file:`records.config` file.
+
+System Variables
+----------------
+
+.. ts:cv:: CONFIG proxy.config.product_company STRING Apache Software Foundation
+
+   The name of the organization developing Traffic Server.
+
+.. ts:cv:: CONFIG proxy.config.product_vendor STRING Apache
+
+   The name of the vendor providing Traffic Server.
+
+.. ts:cv:: CONFIG proxy.config.product_name STRING Traffic Server
+
+   The name of the product.
+
+.. ts:cv:: CONFIG proxy.config.proxy_name STRING build_machine
+   :reloadable:
+
+   The name of the Traffic Server node.
+
+.. ts:cv:: CONFIG proxy.config.bin_path STRING bin
+
+   The location of the Traffic Server ``bin`` directory.
+
+.. ts:cv:: CONFIG proxy.config.proxy_binary STRING traffic_server
+
+   The name of the executable that runs the :program:`traffic_server` process.
+
+.. ts:cv:: CONFIG proxy.config.proxy_binary_opts STRING -M
+
+   The command-line options for starting Traffic Server.
+
+.. ts:cv:: CONFIG proxy.config.manager_binary STRING traffic_manager
+
+   The name of the executable that runs the :program:`traffic_manager` process.
+
+.. ts:cv:: CONFIG proxy.config.env_prep STRING
+
+   The script executed before the :program:`traffic_manager` process spawns
+   the :program:`traffic_server` process.
+
+.. ts:cv:: CONFIG proxy.config.config_dir STRING etc/trafficserver
+
+   The directory that contains Traffic Server configuration files.
+   This is a read-only configuration option that contains the
+   ``SYSCONFDIR`` value specified at build time relative to the
+   installation prefix. The ``$TS_ROOT`` environment variable can
+   be used alter the installation prefix at run time.
+
+.. ts:cv:: CONFIG proxy.config.syslog_facility STRING LOG_DAEMON
+
+   The facility used to record system log files. Refer to :ref:`understanding-traffic-server-log-files`.
+
+.. ts:cv:: CONFIG proxy.config.cop.core_signal INT 0
+
+   The signal sent to :program:`traffic_cop`'s managed processes to stop them.
+
+A value of ``0`` means no signal will be sent.
+
+.. ts:cv:: CONFIG proxy.config.cop.linux_min_memfree_kb INT 0
+
+   The minimum amount of free memory space allowed before Traffic Server stops
+   the :program:`traffic_server` and :program:`traffic_manager` processes to
+   prevent the system from hanging.
+
+.. ts:cv:: CONFIG proxy.config.cop.linux_min_swapfree_kb INT 0
+
+   The minimum amount of free swap space allowed before Traffic Server stops
+   the :program:`traffic_server` and :program:`traffic_manager` processes to
+   prevent the system from hanging. This configuration variable applies if
+   swap is enabled in Linux 2.2 only.
+
+.. ts:cv:: CONFIG proxy.config.cop.init_sleep_time INT 0
+
+   The minimum amount of addtional duration allowed before Traffic Server detects
+   that the :program:`traffic_server` is not responsive and attempts a restart
+   during startup. This configuration variable allows Traffic Server a longer init
+   time to load potentially large configuration files such as remap config. Note that
+   this applies only during startup of Traffic Server and does not apply to the run
+   time heartbeat checking.
+
+.. ts:cv:: CONFIG proxy.config.output.logfile  STRING traffic.out
+
+   The name and location of the file that contains warnings, status messages, and error messages produced by the Traffic Server
+   processes. If no path is specified, then Traffic Server creates the file in its logging directory.
+
+.. ts:cv:: CONFIG proxy.config.output.logfile.rolling_enabled INT 0
+   :reloadable:
+
+   Specifies how the output log is rolled. You can specify the following values:
+
+   -  ``0`` = disables output log rolling
+   -  ``1`` = enables output log rolling at specific intervals (specified with the
+       :ts:cv:`proxy.config.output.logfile.rolling_interval_sec` variable). The "clock" starts ticking on Traffic Server boot
+   -  ``2`` = enables output log rolling when the output log reaches a specific size (specified with the :ts:cv:`proxy.config.output.logfile.rolling_size_mb` variable)
+
+.. ts:cv:: CONFIG proxy.config.output.logfile.rolling_interval_sec INT 3600
+   :reloadable:
+   :metric: seconds
+
+   Specifies how often the output log is rolled, in seconds. The timer starts on Traffic Server bootup.
+
+.. ts:cv:: CONFIG proxy.config.output.logfile.rolling_size_mb INT 100
+   :reloadable:
+   :metric: megabytes
+
+   Specifies at what size to roll the output log at.
+
+.. ts:cv:: CONFIG proxy.config.snapshot_dir STRING snapshots
+
+   The directory in which Traffic Server stores configuration
+   snapshots on the local system. Unless you specify an absolute
+   path, this directory is located in the Traffic Server ``SYSCONFDIR``
+   directory.
+
+.. ts:cv:: CONFIG proxy.config.exec_thread.autoconfig INT 1
+
+   When enabled (the default, ``1``), Traffic Server scales threads according to the available CPU cores. See the config option below.
+
+.. ts:cv:: CONFIG proxy.config.exec_thread.autoconfig.scale FLOAT 1.5
+
+   Factor by which Traffic Server scales the number of threads. The multiplier is usually the number of available CPU cores. By default
+   this is scaling factor is ``1.5``.
+
+.. ts:cv:: CONFIG proxy.config.exec_thread.limit INT 2
+
+   The number of threads Traffic Server will create if `proxy.config.exec_thread.autoconfig` is set to `0`, otherwise this option is ignored.
+
+.. ts:cv:: CONFIG proxy.config.accept_threads INT 1
+
+   The number of accept threads Traffic Server. If disabled (``0``), then accepts will be done in each of the worker threads.
+
+.. ts:cv:: CONFIG proxy.config.thread.default.stacksize  INT 1048576
+
+   The new default thread stack size, for all threads. The original default is set at 1 MB.
+
+.. ts:cv:: CONFIG proxy.config.exec_thread.affinity INT 1
+
+   Bind threads to specific processing units.
+
+===== ====================
+Value Effect
+===== ====================
+0     assign threads to machine
+1     assign threads to NUMA nodes [default]
+2     assign threads to sockets
+3     assign threads to cores
+4     assign threads to processing units
+===== ====================
+
+.. note::
+
+   This option only has an affect when Traffic Server has been compiled with ``--enable-hwloc``.
+
+.. ts:cv:: CONFIG proxy.config.system.file_max_pct FLOAT 0.9
+
+   Set the maximum number of file handles for the traffic_server process as a percentage of the the fs.file-max proc value in Linux. The default is 90%.
+
+.. ts:cv:: CONFIG proxy.config.crash_log_helper STRING traffic_crashlog
+
+   This option directs :program:`traffic_server` to spawn a crash
+   log helper at startup. The value should be the path to an
+   executable program. If the path is not absolute, it is located
+   relative to configured ``bin`` directory.  Any user-provided
+   program specified here must behave in a fashion compatible with
+   :program:`traffic_crashlog`. Specifically, it must implement
+   the :option:`traffic_crashlog --wait` behavior.
+
+   This setting not reloadable because the helper must be spawned
+   before :program:`traffic_server` drops privilege. If this variable
+   is set to ``NULL``, no helper will be spawned.
+
+.. ts:cv:: CONFIG proxy.config.restart.active_client_threshold INT 0
+   :reloadable:
+
+  This setting specifies the number of active client connections
+  for use by :option:`traffic_ctl server restart --drain`.
+
+Network
+=======
+
+.. ts:cv:: CONFIG proxy.config.net.connections_throttle INT 30000
+
+   The total number of client and origin server connections that the server
+   can handle simultaneously. This is in fact the max number of file
+   descriptors that the :program:`traffic_server` process can have open at any
+   given time. Roughly 10% of these connections are reserved for origin server
+   connections, i.e. from the default, only ~9,000 client connections can be
+   handled. This should be tuned according to your memory size, and expected
+   work load.
+
+.. ts:cv:: CONFIG proxy.config.net.default_inactivity_timeout INT 86400
+   :reloadable:
+
+   The connection inactivity timeout (in seconds) to apply when
+   Traffic Server detects that no inactivity timeout has been applied
+   by the HTTP state machine. When this timeout is applied, the
+   `proxy.process.net.default_inactivity_timeout_applied` metric
+   is incremented.
+
+.. ts:cv:: CONFIG proxy.config.net.inactivity_check_frequency INT 1
+
+   How frequent (in seconds) to check for inactive connections. If you deal
+   with a lot of concurrent connections, increasing this setting can reduce
+   pressure on the system.
+
+.. ts:cv:: LOCAL proxy.local.incoming_ip_to_bind STRING 0.0.0.0 [::]
+
+   Controls the global default IP addresses to which to bind proxy server ports. The value is a space separated list of IP addresses, one per supported IP address family (currently IPv4 and IPv6).
+
+Unless explicitly specified in `proxy.config.http.server_ports`_ the server port will be bound to one of these addresses, selected by IP address family. The built in default is any address. This is used if no address for a family is specified. This setting is useful if most or all server ports should be bound to the same address.
+
+.. note::
+
+   This is ignored for inbound transparent server ports because they must be able to accept connections on arbitrary IP addresses.
+
+.. topic:: Example
+
+   Set the global default for IPv4 to ``192.168.101.18`` and leave the global default for IPv6 as any address.::
+
+      LOCAL proxy.local.incoming_ip_to_bind STRING 192.168.101.18
+
+.. topic:: Example
+
+   Set the global default for IPv4 to ``191.68.101.18`` and the global default for IPv6 to ``fc07:192:168:101::17``.::
+
+      LOCAL proxy.local.incoming_ip_to_bind STRING 192.168.101.18 [fc07:192:168:101::17]
+
+.. ts:cv:: LOCAL proxy.local.outgoing_ip_to_bind STRING 0.0.0.0 [::]
+
+   This controls the global default for the local IP address for outbound connections to origin servers. The value is a list of space separated IP addresses, one per supported IP address family (currently IPv4 and IPv6).
+
+   Unless explicitly specified in `proxy.config.http.server_ports`_ one of these addresses, selected by IP address family, will be used as the local address for outbound connections. This setting is useful if most or all of the server ports should use the same outbound IP addresses.
+
+.. note::
+
+   This is ignored for outbound transparent ports as the local outbound address will be the same as the client local address.
+
+.. topic:: Example
+
+   Set the default local outbound IP address for IPv4 connections to ``192.168.101.18``.::
+
+      LOCAL proxy.local.outgoing_ip_to_bind STRING 192.168.101.18
+
+.. topic:: Example
+
+   Set the default local outbound IP address to ``192.168.101.17`` for IPv4 and ``fc07:192:168:101::17`` for IPv6.::
+
+      LOCAL proxy.local.outgoing_ip_to_bind STRING 192.168.101.17 [fc07:192:168:101::17]
+
+.. ts:cv:: CONFIG proxy.config.net.event_period INT 10
+
+   How often, in milli-seconds, to schedule IO event processing. This is
+   unlikely to be necessary to tune, and we discourage setting it to a value
+   smaller than 10ms (on Linux).
+
+.. ts:cv:: CONFIG proxy.config.net.accept_period INT 10
+
+   How often, in milli-seconds, to schedule accept() processing. This is
+   unlikely to be necessary to tune, and we discourage setting it to a value
+   smaller than 10ms (on Linux).
+
+.. ts:cv:: CONFIG proxy.config.net.retry_delay INT 10
+   :reloadable:
+
+   How long to wait until we retry various events that would otherwise block
+   the network processing threads (e.g. locks). We discourage setting this to
+   a value smaller than 10ms (on Linux).
+
+.. ts:cv:: CONFIG proxy.config.net.throttle_delay INT 50
+   :reloadable:
+
+   When we trigger a throttling scenario, this how long our accept() are delayed.
+
+Cluster
+=======
+
+.. ts:cv:: LOCAL proxy.local.cluster.type INT 3
+
+   Sets the clustering mode:
+
+===== ====================
+Value Effect
+===== ====================
+1     full-clustering mode
+2     management-only mode
+3     no clustering
+===== ====================
+
+.. ts:cv:: CONFIG proxy.config.cluster.ethernet_interface INT eth0
+
+The network interface to be used for cluster communication. This has to be
+identical on all members of a clsuter. ToDo: Is that reasonable ?? Should
+this be local"
+
+.. ts:cv:: CONFIG proxy.config.cluster.rsport INT 8088
+
+   The reliable service port. The reliable service port is used to send configuration information between the nodes in a cluster. All nodes
+   in a cluster must use the same reliable service port.
+
+.. ts:cv:: CONFIG proxy.config.cluster.threads INT 1
+
+   The number of threads for cluster communication. On heavy cluster, the number should be adjusted. It is recommend that take the thread
+   CPU usage as a reference when adjusting.
+
+.. ts:cv:: CONFIG proxy.config.clustger.ethernet_interface STRING
+
+   Set the interface to use for cluster communications.
+
+.. ts:cv:: CONFIG proxy.config.http.cache.cluster_cache_local INT 0
+   :overridable:
+
+   This turns on the local caching of objects in cluster mode. The point of
+   this is to allow for popular or **hot** content to be cached on all nodes
+   in a cluster. Be aware that the primary way to configure this behavior is
+   via the :file:`cache.config` configuration file using
+   ``action=cluster-cache-local`` directives.
+
+   This particular :file:`records.config` configuration can be controlled per
+   transaction or per remap rule. As such, it augments the
+   :file:`cache.config` directives, since you can turn on the local caching
+   feature without complex regular expression matching.
+
+   This implies that turning this on in your global :file:`records.config` is
+   almost never what you want; instead, you want to use this either via
+   e.g. ``conf_remap.so`` overrides for a certain remap rule, or through a
+   custom plugin using the appropriate APIs.
+
+Local Manager
+=============
+
+.. ts:cv:: CONFIG proxy.config.lm.sem_id INT 11452
+
+   The semaphore ID for the local manager.
+
+.. ts:cv:: CONFIG proxy.config.admin.synthetic_port INT 8083
+
+   The synthetic healthcheck port.
+
+.. ts:cv:: CONFIG proxy.config.admin.number_config_bak INT 3
+
+   The maximum number of copies of rolled configuration files to keep.
+
+.. ts:cv:: CONFIG proxy.config.admin.user_id STRING nobody
+
+   Option used to specify who to run the :program:`traffic_server` process as; also used to specify ownership of config and log files.
+
+The nonprivileged user account designated to Traffic Server.
+
+As of version 2.1.1 if the user_id is prefixed with pound character (#) the remaining of the string is considered to be
+a `numeric user identifier <http://en.wikipedia.org/wiki/User_identifier>`_. If the value is set to ``#-1`` Traffic
+Server will not change the user during startup.
+
+Setting ``user_id`` to ``root`` or ``#0`` is now forbidden to
+increase security. Trying to do so, will cause the
+:program:`traffic_server` fatal failure. However there are two ways to
+bypass that restriction
+
+* Specify ``-DBIG_SECURITY_HOLE`` in ``CXXFLAGS`` during compilation.
+* Set the ``user_id=#-1`` and start trafficserver as root.
+
+.. ts:cv:: CONFIG proxy.config.admin.api.restricted INT 0
+
+This setting specifies whether the management API should be restricted
+to root processes. If this is set to ``0``, then on platforms that
+support passing process credentials, non-root processes will be
+allowed to make read-only management API calls. Any management API
+calls that modify server state (eg. setting a configuration variable)
+will still be restricted to root processes.
+
+This setting is not reloadable, since it is must be applied when
+program:`traffic_manager` initializes.
+
+Process Manager
+===============
+
+.. ts:cv:: CONFIG proxy.config.process_manager.mgmt_port  INT 8084
+
+   The port used for internal communication between the :program:`traffic_manager` and :program:`traffic_server` processes.
+
+Alarm Configuration
+===================
+
+.. ts:cv:: CONFIG proxy.config.alarm_email STRING
+   :reloadable:
+
+   The address to which the alarm script should send email.
+
+.. ts:cv:: CONFIG proxy.config.alarm.bin STRING example_alarm_bin.sh
+   :reloadable:
+
+   Name of the script file that can execute certain actions when
+   an alarm is signaled. The script is invoked with up to 4 arguments:
+
+       - the alarm message
+       - the value of :ts:cv:`proxy.config.product_name`
+       - the value of :ts:cv:`proxy.config.admin.user_id`
+       - the value of :ts:cv:`proxy.config.alarm_email`
+
+.. ts:cv:: CONFIG proxy.config.alarm.abs_path STRING NULL
+   :reloadable:
+
+   The absolute path to the directory containing the alarm script.
+   If this is not set, the script will be located relative to
+   :ts:cv:`proxy.config.bin_path`.
+
+.. ts:cv:: CONFIG proxy.config.alarm.script_runtime INT 5
+   :reloadable:
+
+   The number of seconds that Traffic Server allows the alarm script
+   to run before aborting it.
+
+HTTP Engine
+===========
+
+.. ts:cv:: CONFIG proxy.config.http.server_ports STRING 8080
+
+   Ports used for proxying HTTP traffic.
+
+This is a list, separated by space or comma, of :index:`port descriptors`. Each descriptor is a sequence of keywords and values separated by colons. Not all keywords have values, those that do are specifically noted. Keywords with values can have an optional '=' character separating the keyword and value. The case of keywords is ignored. The order of keywords is irrelevant but unspecified results may occur if incompatible options are used (noted below). Options without values are idempotent. Options with values use the last (right most) value specified, except for ``ip-out`` as detailed later.
+
+Quick reference chart.
+
+=========== =============== ========================================
+Name        Note            Definition
+=========== =============== ========================================
+*number*    **Required**    The local port.
+blind                       Blind (``CONNECT``) port.
+compress    **N/I**         Compressed. Not implemented.
+ipv4        **Default**     Bind to IPv4 address family.
+ipv6                        Bind to IPv6 address family.
+ip-in       **Value**       Local inbound IP address.
+ip-out      **Value**       Local outbound IP address.
+ip-resolve  **Value**       IP address resolution style.
+proto       **Value**       List of supported session protocols.
+ssl                         SSL terminated.
+tr-full                     Fully transparent (inbound and outbound)
+tr-in                       Inbound transparent.
+tr-out                      Outbound transparent.
+tr-pass                     Pass through enabled.
+=========== =============== ========================================
+
+*number*
+   Local IP port to bind. This is the port to which ATS clients will connect.
+
+blind
+   Accept only the ``CONNECT`` method on this port.
+
+   Not compatible with: ``tr-in``, ``ssl``.
+
+compress
+   Compress the connection. Retained only by inertia, should be considered "not implemented".
+
+ipv4
+   Use IPv4. This is the default and is included primarily for completeness. This forced if the ``ip-in`` option is used with an IPv4 address.
+
+ipv6
+   Use IPv6. This is forced if the ``ip-in`` option is used with an IPv6 address.
+
+ssl
+   Require SSL termination for inbound connections. SSL :ref:`must be configured <admin-ssl-termination>` for this option to provide a functional server port.
+
+   Not compatible with: ``blind``.
+
+proto
+   Specify the :ref:`session level protocols <session-protocol>` supported. These should be
+   separated by semi-colons. For TLS proxy ports the default value is
+   all available protocols. For non-TLS proxy ports the default is HTTP
+   only. SPDY can be enabled on non-TLS proxy ports but that must be done explicitly.
+
+tr-full
+   Fully transparent. This is a convenience option and is identical to specifying both ``tr-in`` and ``tr-out``.
+
+   Not compatible with: Any option not compatible with ``tr-in`` or ``tr-out``.
+
+tr-in
+   Inbound transparent. The proxy port will accept connections to any IP address on the port. To have IPv6 inbound transparent you must use this and the ``ipv6`` option. This overrides :ts:cv:`proxy.local.incoming_ip_to_bind` for this port.
+
+   Not compatible with: ``ip-in``, ``blind``
+
+tr-out
+   Outbound transparent. If ATS connects to an origin server for a transaction on this port, it will use the client's address as its local address. This overrides :ts:cv:`proxy.local.outgoing_ip_to_bind` for this port.
+
+   Not compatible with: ``ip-out``, ``ip-resolve``
+
+tr-pass
+   Transparent pass through. This option is useful only for inbound transparent proxy ports. If the parsing of the expected HTTP header fails, then the transaction is switched to a blind tunnel instead of generating an error response to the client. It effectively enables :ts:cv:`proxy.config.http.use_client_target_addr` for the transaction as there is no other place to obtain the origin server address.
+
+ip-in
+   Set the local IP address for the port. This is the address to which clients will connect. This forces the IP address family for the port. The ``ipv4`` or ``ipv6`` can be used but it is optional and is an error for it to disagree with the IP address family of this value. An IPv6 address **must** be enclosed in square brackets. If this option is omitted :ts:cv:`proxy.local.incoming_ip_to_bind` is used.
+
+   Not compatible with: ``tr-in``.
+
+ip-out
+   Set the local IP address for outbound connections. This is the address used by ATS locally when it connects to an origin server for transactions on this port. If this is omitted :ts:cv:`proxy.local.outgoing_ip_to_bind` is used.
+
+   This option can used multiple times, once for each IP address family. The address used is selected by the IP address family of the origin server address.
+
+   Not compatible with: ``tr-out``.
+
+ip-resolve
+   Set the :ts:cv:`host resolution style <proxy.config.hostdb.ip_resolve>` for transactions on this proxy port.
+
+   Not compatible with: ``tr-out`` - this option requires a value of ``client;none`` which is forced and should not be explicitly specified.
+
+.. topic:: Example
+
+   Listen on port 80 on any address for IPv4 and IPv6.::
+
+      80 80:ipv6
+
+.. topic:: Example
+
+   Listen transparently on any IPv4 address on port 8080, and
+   transparently on port 8080 on local address ``fc01:10:10:1::1``
+   (which implies ``ipv6``).::
+
+      IPv4:tr-FULL:8080 TR-full:IP-in=[fc02:10:10:1::1]:8080
+
+.. topic:: Example
+
+   Listen on port 8080 for IPv6, fully transparent. Set up an SSL port on 443. These ports will use the IP address from :ts:cv:`proxy.local.incoming_ip_to_bind`.  Listen on IP address ``192.168.17.1``, port 80, IPv4, and connect to origin servers using the local address ``10.10.10.1`` for IPv4 and ``fc01:10:10:1::1`` for IPv6.::
+
+      8080:ipv6:tr-full 443:ssl ip-in=192.168.17.1:80:ip-out=[fc01:10:10:1::1]:ip-out=10.10.10.1
+
+.. topic:: Example
+
+   Listen on port 9090 for TSL enabled SPDY or HTTP connections, accept no other session protocols.::
+
+      9090:proto=spdy;http:ssl
+
+.. ts:cv:: CONFIG proxy.config.http.connect_ports STRING 443 563
+
+   The range of origin server ports that can be used for tunneling via ``CONNECT``.
+
+Traffic Server allows tunnels only to the specified ports.
+Supports both wildcards ('\*') and ranges ("0-1023").
+
+.. note::
+
+   These are the ports on the *origin server*, not Traffic Server :ts:cv:`proxy ports <proxy.config.http.server_ports>`.
+
+.. ts:cv:: CONFIG proxy.config.http.insert_request_via_str INT 1
+   :reloadable:
+   :overridable:
+
+   Set how the ``Via`` field is handled on a request to the origin server.
+
+===== ============================================
+Value Effect
+===== ============================================
+0     Do not modify / set this via header
+1     Update the via, with normal verbosity
+2     Update the via, with higher verbosity
+3     Update the via, with highest verbosity
+===== ============================================
+
+.. note::
+
+   The ``Via`` header string can be decoded with the `Via Decoder Ring <http://trafficserver.apache.org/tools/via>`_.
+
+.. ts:cv:: CONFIG proxy.config.http.insert_response_via_str INT 0
+   :reloadable:
+   :overridable:
+
+   Set how the ``Via`` field is handled on the response to the client.
+
+===== ============================================
+Value Effect
+===== ============================================
+0     Do not modify / set this via header
+1     Update the via, with normal verbosity
+2     Update the via, with higher verbosity
+3     Update the via, with highest verbosity
+===== ============================================
+
+.. note::
+
+   The ``Via`` header string can be decoded with the `Via Decoder Ring <http://trafficserver.apache.org/tools/via>`_.
+
+.. ts:cv:: CONFIG proxy.config.http.send_100_continue_response INT 0
+   :reloadable:
+
+   You can specify one of the following:
+
+   -  ``0`` ATS buffer the request until the post body has been recieved and then send the request to origin.
+   -  ``1`` immediately return a 100 Continue from ATS without waiting for the post body
+
+.. ts:cv:: CONFIG proxy.config.http.response_server_enabled INT 1
+   :reloadable:
+   :overridable:
+
+   You can specify one of the following:
+
+   -  ``0`` no Server: header is added to the response.
+   -  ``1`` the Server: header is added (see string below).
+   -  ``2`` the Server: header is added only if the response from origin does not have one already.
+
+.. ts:cv:: CONFIG proxy.config.http.insert_age_in_response INT 1
+   :reloadable:
+   :overridable:
+
+   This option specifies whether Traffic Server should insert an ``Age`` header in the response. The Age field value is the cache's
+   estimate of the amount of time since the response was generated or revalidated by the origin server.
+
+   -  ``0`` no ``Age`` header is added
+   -  ``1`` the ``Age`` header is added
+
+.. ts:cv:: CONFIG proxy.config.http.response_server_str STRING ATS/
+   :reloadable:
+   :overridable:
+
+   The Server: string that ATS will insert in a response header (if requested, see above). Note that the current version number is
+   always appended to this string.
+
+.. ts:cv:: CONFIG proxy.config.http.enable_url_expandomatic INT 0
+   :reloadable:
+
+   Enables (``1``) or disables (``0``) ``.com`` domain expansion. This configures the Traffic Server to resolve unqualified hostnames by
+   prepending with ``www.`` and appending with ``.com`` before redirecting to the expanded address. For example: if a client makes
+   a request to ``host``, then Traffic Server redirects the request to ``www.host.com``.
+
+.. ts:cv:: CONFIG proxy.config.http.chunking_enabled INT 1
+   :reloadable:
+   :overridable:
+
+   Specifies whether Traffic Sever can generate a chunked response:
+
+   -  ``0`` Never
+   -  ``1`` Always
+   -  ``2`` Generate a chunked response if the server has returned HTTP/1.1 before
+   -  ``3`` = Generate a chunked response if the client request is HTTP/1.1 and the origin server has returned HTTP/1.1 before
+
+   .. note::
+
+       If HTTP/1.1 is used, then Traffic Server can use
+       keep-alive connections with pipelining to origin servers. If
+       HTTP/0.9 is used, then Traffic Server does not use ``keep-alive``
+       connections to origin servers. If HTTP/1.0 is used, then Traffic
+       Server can use ``keep-alive`` connections without pipelining to
+       origin servers.
+
+.. ts:cv:: CONFIG proxy.config.http.send_http11_requests INT 1
+   :reloadable:
+   :overridable:
+
+   Specifies when and how Traffic Sever uses HTTP/1.1 to communicate with the origin server
+
+   -  ``0`` Never
+   -  ``1`` Always
+   -  ``2`` If the server has returned HTTP/1.1 before
+   -  ``3`` If the client request is HTTP/1.1 and the server has returned HTTP/1.1 before
+
+   .. note::
+
+       If :ts:cv:`proxy.config.http.use_client_target_addr` is set to 1, options 2 and 3 cause the proxy to use
+       the client HTTP version for upstream requests.
+
+.. ts:cv:: CONFIG proxy.config.http.auth_server_session_private INT 1
+
+   If enabled (``1``) anytime a request contains a (``Authorization``), (``Proxy-Authorization``)
+   or (``Www-Authenticate``) header the connection will be closed and not reused. This marks
+   the connection as private. When disabled (``0``) the connection will be available for reuse.
+
+.. ts:cv:: CONFIG proxy.config.http.server_session_sharing.match STRING both
+
+   Enable and set the ability to re-use server connections across client connections. The valid values are
+
+   none
+      Do not match, do not re-use server sessions.
+
+   ip
+      Re-use server sessions, check only that the IP address and port of the origin server matches.
+
+   host
+      Re-use server sessions, check only that the fully qualified domain name matches.
+
+   both
+      Re-use server sessions, but only if the IP address and fully qualified domain name match.
+
+   It is strongly recommended to use either *none* or *both* for this value unless you have a specific need to use *ip*
+   or *host*. The most common reason is virtual hosts that share an IP address in which case performance can be enhanced
+   if those sessions can be re-used. However, not all web servers support requests for different virtual hosts on the
+   same connection so use with caution.
+
+   .. note: Server sessions to different ports never match even if the FQDN and IP address match.
+
+.. ts:cv:: CONFIG proxy.config.http.server_session_sharing.pool STRING thread
+
+   Control the scope of server session re-use if it is enabled by :ts:cv:`proxy.config.http.server_session_sharing.match`. The valid values are
+
+   global
+      Re-use sessions from a global pool of all server sessions.
+
+   thread
+      Re-use sessions from a per-thread pool.
+
+.. ts:cv:: CONFIG proxy.config.http.attach_server_session_to_client INT 0
+
+   Control the re-use of an server session by a user agent (client) session.
+
+   If a user agent performs more than one HTTP transaction on its connection to Traffic Server a server session must be
+   obtained for the second (and subsequent) transaction as for the first. This settings affects how that server session
+   is selected.
+
+   If this setting is ``0`` then after the first transaction the server session for that transaction is released to the
+   server pool (if any). When a server session is needed for subsequent transactions one is selected from the server
+   pool or created if there is no suitable server session in the pool.
+
+   If this setting is not ``0`` then the current server session for the user agent session is "sticky". It will be
+   preferred to any other server session (either from the pool or newly created). The server session will be detached
+   from the user agent session only if it cannot be used for the transaction. This is determined by the
+   :ts:cv:`proxy.config.http.server_session_sharing.match` value. If the server session matches the next transaction
+   according to this setting then it will be used, otherwise it will be released to the pool and a different session
+   selected or created.
+
+.. ts:cv:: CONFIG proxy.config.http.record_heartbeat INT 0
+   :reloadable:
+
+   Enables (``1``) or disables (``0``) :program:`traffic_cop` heartbeat logging.
+
+.. ts:cv:: CONFIG proxy.config.http.use_client_target_addr  INT 0
+
+   For fully transparent ports use the same origin server address as the client.
+
+This option causes Traffic Server to avoid where possible doing DNS
+lookups in forward transparent proxy mode. The option is only
+effective if the following three conditions are true -
+
+*  Traffic Server is in forward proxy mode.
+*  The proxy port is inbound transparent.
+*  The target URL has not been modified by either remapping or a plugin.
+
+If any of these conditions are not true, then normal DNS processing
+is done for the connection.
+
+There are three valid values.
+*  0 - Disables the feature.
+*  1 - Enables the feature with address verification.  The Proxy does the
+regular DNS processing.  If the client-specified origin address is not in the
+set of addresses found by the Proxy, the request continues to the client
+specified address, but the result is not cached.
+*  2 - Enables the feature with no address verification.  No DNS processing
+is performed.  The result is cached (if allowed otherwise).  This option is
+vulnerable to cache poisoning if an incorrect Host header is specified, so
+this option should be used with extreme caution.  See bug TS-2954 for
+details.
+
+If all of these conditions are met, then the origin server IP
+address is retrieved from the original client connection, rather
+than through HostDB or DNS lookup. In effect, client DNS resolution
+is used instead of Traffic Server DNS.
+
+This can be used to be a little more efficient (looking up the
+target once by the client rather than by both the client and Traffic
+Server) but the primary use is when client DNS resolution can differ
+from that of Traffic Server. Two known uses cases are:
+
+#. Embedded IP addresses in a protocol with DNS load sharing. In
+   this case, even though Traffic Server and the client both make
+   the same request to the same DNS resolver chain, they may get
+   different origin server addresses. If the address is embedded in
+   the protocol then the overall exchange will fail. One current
+   example is Microsoft Windows update, which presumably embeds the
+   address as a security measure.
+
+#. The client has access to local DNS zone information which is not
+   available to Traffic Server. There are corporate nets with local
+   DNS information for internal servers which, by design, is not
+   propagated outside the core corporate network. Depending a
+   network topology it can be the case that Traffic Server can
+   access the servers by IP address but cannot resolve such
+   addresses by name. In such as case the client supplied target
+   address must be used.
+
+This solution must be considered interim. In the longer term, it
+should be possible to arrange for much finer grained control of DNS
+lookup so that wildcard domain can be set to use Traffic Server or
+client resolution. In both known use cases, marking specific domains
+as client determined (rather than a single global switch) would
+suffice. It is possible to do this crudely with this flag by
+enabling it and then use identity URL mappings to re-disable it for
+specific domains.
+
+.. ts:cv:: CONFIG proxy.config.http.keep_alive_enabled_in  INT 1
+   :overridable:
+
+   Enables (``1``) or disables (``0``) incoming keep-alive connections.
+
+.. ts:cv:: CONFIG proxy.config.http.keep_alive_enabled_out  INT 1
+   :overridable:
+
+   Enables (``1``) or disables (``0``) outgoing keep-alive connections.
+
+  .. note::
+        Enabling keep-alive does not automatically enable purging of keep-alive
+        requests when nearing the connection limit, that is controlled by
+        :ts:cv:`proxy.config.http.server_max_connections`.
+
+.. ts:cv:: CONFIG proxy.config.http.keep_alive_post_out  INT 1
+   :overridable:
+
+   Controls wether new POST requests re-use keep-alive sessions (``1``) or
+   create new connections per request (``0``).
+
+.. ts:cv:: CONFIG proxy.config.http.disallow_post_100_continue INT 0
+
+   Allows you to return a 405 Method Not Supported with Posts also
+   containing an Expect: 100-continue.
+
+   When a Post w/ Expect: 100-continue is blocked the stat
+   proxy.process.http.disallowed_post_100_continue will be incremented.
+
+Parent Proxy Configuration
+==========================
+
+.. ts:cv:: CONFIG proxy.config.http.parent_proxy_routing_enable INT 0
+   :reloadable:
+
+   Enables (``1``) or disables (``0``) the parent caching option. Refer to :ref:`admin-hierarchical-caching`.
+
+.. ts:cv:: CONFIG proxy.config.http.parent_proxy.retry_time INT 300
+   :reloadable:
+
+   The amount of time allowed between connection retries to a parent cache that is unavailable.
+
+.. ts:cv:: CONFIG proxy.config.http.parent_proxy.fail_threshold INT 10
+   :reloadable:
+
+   The number of times the connection to the parent cache can fail before Traffic Server considers the parent unavailable.
+
+.. ts:cv:: CONFIG proxy.config.http.parent_proxy.total_connect_attempts INT 4
+   :reloadable:
+
+   The total number of connection attempts allowed to a parent cache before Traffic Server bypasses the parent or fails the request
+   (depending on the ``go_direct`` option in the :file:`parent.config` file).
+
+.. ts:cv:: CONFIG proxy.config.http.parent_proxy.per_parent_connect_attempts INT 2
+   :reloadable:
+
+   The total number of connection attempts allowed per parent, if multiple parents are used.
+
+.. ts:cv:: CONFIG proxy.config.http.parent_proxy.connect_attempts_timeout INT 30
+   :reloadable:
+
+   The timeout value (in seconds) for parent cache connection attempts.
+
+.. ts:cv:: CONFIG proxy.config.http.forward.proxy_auth_to_parent INT 0
+   :reloadable:
+   :overridable:
+
+   Configures Traffic Server to send proxy authentication headers on to the parent cache.
+
+.. ts:cv:: CONFIG proxy.config.http.no_dns_just_forward_to_parent INT 0
+   :reloadable:
+
+   Don't try to resolve DNS, forward all DNS requests to the parent. This is off (``0``) by default.
+
+HTTP Connection Timeouts
+========================
+
+.. ts:cv:: CONFIG proxy.config.http.keep_alive_no_activity_timeout_in INT 115
+   :reloadable:
+   :overridable:
+
+   Specifies how long Traffic Server keeps connections to clients open for a
+   subsequent request after a transaction ends. A value of ``0`` will disable
+   the no activity timeout.
+
+.. ts:cv:: CONFIG proxy.config.http.keep_alive_no_activity_timeout_out INT 120
+   :reloadable:
+   :overridable:
+
+   Specifies how long Traffic Server keeps connections to origin servers open
+   for a subsequent transfer of data after a transaction ends. A value of
+   ``0`` will disable the no activity timeout.
+
+.. ts:cv:: CONFIG proxy.config.http.transaction_no_activity_timeout_in INT 30
+   :reloadable:
+   :overridable:
+
+   Specifies how long Traffic Server keeps connections to clients open if a transaction stalls.
+
+.. ts:cv:: CONFIG proxy.config.http.transaction_no_activity_timeout_out INT 30
+   :reloadable:
+   :overridable:
+
+   Specifies how long Traffic Server keeps connections to origin servers open if the transaction stalls.
+
+.. ts:cv:: CONFIG proxy.config.http.transaction_active_timeout_in INT 900
+   :reloadable:
+
+   The maximum amount of time Traffic Server can remain connected to a client. If the transfer to the client is not complete before this
+   timeout expires, then Traffic Server closes the connection.
+
+The value of ``0`` specifies that there is no timeout.
+
+.. ts:cv:: CONFIG proxy.config.http.transaction_active_timeout_out INT 0
+   :reloadable:
+   :overridable:
+
+   The maximum amount of time Traffic Server waits for fulfillment of a connection request to an origin server. If Traffic Server does not
+   complete the transfer to the origin server before this timeout expires, then Traffic Server terminates the connection request.
+
+The default value of ``0`` specifies that there is no timeout.
+
+.. ts:cv:: CONFIG proxy.config.http.accept_no_activity_timeout INT 120
+   :reloadable:
+
+   The timeout interval in seconds before Traffic Server closes a connection that has no activity.
+
+.. ts:cv:: CONFIG proxy.config.http.background_fill_active_timeout INT 0
+   :reloadable:
+   :overridable:
+
+   Specifies how long Traffic Server continues a background fill before giving up and dropping the origin server connection.
+
+.. ts:cv:: CONFIG proxy.config.http.background_fill_completed_threshold FLOAT 0.0
+   :reloadable:
+   :overridable:
+
+   The proportion of total document size already transferred when a client aborts at which the proxy continues fetching the document
+   from the origin server to get it into the cache (a **background fill**).
+
+HTTP Redirection
+================
+
+.. ts:cv:: CONFIG proxy.config.http.redirection_enabled INT 0
+
+   This setting indicates whether Trafficserver does a redirect follow location on receiving a 3XX Redirect response from the Origin
+   server. The redirection attempt is transparent to the client and the client is served the final response from the redirected-to
+   location.
+
+.. ts:cv:: CONFIG proxy.config.http.number_of_redirections INT 1
+
+   This setting determines the maximum number of times Trafficserver does a redirect follow location on receiving a 3XX Redirect response
+   for a given client request.
+
+.. ts:cv:: CONFIG proxy.config.http.redirect_host_no_port INT 1
+
+   This setting enables Trafficserver to not include the port in the Host header in the redirect follow request for default/standard ports
+   (e.g. 80 for HTTP and 443 for HTTPS). Note that the port is still included in the Host header if it's non-default.
+
+Origin Server Connect Attempts
+==============================
+
+.. ts:cv:: CONFIG proxy.config.http.connect_attempts_max_retries INT 3
+   :reloadable:
+   :overridable:
+
+   The maximum number of connection retries Traffic Server can make when the origin server is not responding.
+   Each retry attempt lasts for `proxy.config.http.connect_attempts_timeout`_ seconds.  Once the maximum number of retries is
+   reached, the origin is marked dead.  After this, the setting  `proxy.config.http.connect_attempts_max_retries_dead_server`_
+   is used to limit the number of retry attempts to the known dead origin.
+
+.. ts:cv:: CONFIG proxy.config.http.connect_attempts_max_retries_dead_server INT 1
+   :reloadable:
+   :overridable:
+
+   Maximum number of connection retries Traffic Server can make while an origin is marked dead.  Typically this value is smaller than
+   `proxy.config.http.connect_attempts_max_retries`_ so an error is returned to the client faster and also to reduce the load on the dead origin.
+   The timeout interval `proxy.config.http.connect_attempts_timeout`_ in seconds is used with this setting.
+
+.. ts:cv:: CONFIG proxy.config.http.server_max_connections INT 0
+   :reloadable:
+
+   Limits the number of socket connections across all origin servers to the value specified. To disable, set to zero (``0``).
+
+   .. note::
+        This value is used in determining when and if to prune active origin sessions. Without this value set connections
+        to origins can consume all the way up to ts:cv:`proxy.config.net.connections_throttle` connections, which in turn can
+        starve incoming requests from available connections.
+
+.. ts:cv:: CONFIG proxy.config.http.origin_max_connections INT 0
+   :reloadable:
+   :overridable:
+
+   Limits the number of socket connections per origin server to the value specified. To enable, set to one (``1``).
+
+.. ts:cv:: CONFIG proxy.config.http.origin_min_keep_alive_connections INT 0
+   :reloadable:
+
+   As connection to an origin server are opened, keep at least 'n' number of connections open to that origin, even if
+   the connection isn't used for a long time period. Useful when the origin supports keep-alive, removing the time
+   needed to set up a new connection from
+   the next request at the expense of added (inactive) connections. To enable, set to one (``1``).
+
+.. ts:cv:: CONFIG proxy.config.http.connect_attempts_rr_retries INT 3
+   :reloadable:
+   :overridable:
+
+   The maximum number of failed connection attempts allowed before a round-robin entry is marked as 'down' if a server
+   has round-robin DNS entries.
+
+.. ts:cv:: CONFIG proxy.config.http.connect_attempts_timeout INT 30
+   :reloadable:
+   :overridable:
+
+   The timeout value (in seconds) for **time to first byte** for an origin server connection.
+
+.. ts:cv:: CONFIG proxy.config.http.post_connect_attempts_timeout INT 1800
+   :reloadable:
+   :overridable:
+
+   The timeout value (in seconds) for an origin server connection when the client request is a ``POST`` or ``PUT``
+   request.
+
+.. ts:cv:: CONFIG proxy.config.http.down_server.cache_time INT 60
+   :reloadable:
+   :overridable:
+
+   Specifies how long (in seconds) Traffic Server remembers that an origin server was unreachable.
+
+.. ts:cv:: CONFIG proxy.config.http.down_server.abort_threshold INT 10
+   :reloadable:
+   :overridable:
+
+   The number of seconds before Traffic Server marks an origin server as unavailable after a client abandons a request
+   because the origin server was too slow in sending the response header.
+
+.. ts:cv:: CONFIG proxy.config.http.uncacheable_requests_bypass_parent INT 1
+
+   When enabled (1), Traffic Server bypasses the parent proxy for a request that is not cacheable.
+
+Congestion Control
+==================
+
+.. ts:cv:: CONFIG proxy.config.http.congestion_control.enabled INT 0
+
+   Enables (``1``) or disables (``0``) the Congestion Control option, which configures Traffic Server to stop forwarding
+   HTTP requests to origin servers when they become congested. Traffic Server sends the client a message to retry the
+   congested origin server later. Refer to :ref:`using-congestion-control`.
+
+.. ts:cv:: CONFIG proxy.config.http.flow_control.enabled INT 0
+   :overridable:
+
+   Transaction buffering / flow control is enabled if this is set to a non-zero value. Otherwise no flow control is done.
+
+.. ts:cv:: CONFIG proxy.config.http.flow_control.high_water INT 0
+   :metric: bytes
+   :overridable:
+
+   The high water mark for transaction buffer control. External source I/O is halted when the total buffer space in use
+   by the transaction exceeds this value.
+
+.. ts:cv:: CONFIG proxy.config.http.flow_control.low_water INT 0
+   :metric: bytes
+   :overridable:
+
+   The low water mark for transaction buffer control. External source I/O is resumed when the total buffer space in use
+   by the transaction is no more than this value.
+
+.. ts:cv:: CONFIG proxy.config.http.websocket.max_number_of_connections INT -1
+   :reloadable:
+
+   When enabled >= (``0``), Traffic Server will enforce a maximum number of simultaneous websocket connections.
+
+Negative Response Caching
+=========================
+
+.. ts:cv:: CONFIG proxy.config.http.negative_caching_enabled INT 0
+   :reloadable:
+   :overridable:
+
+   When enabled (``1``), Traffic Server caches negative responses (such as ``404 Not Found``) when a requested page does
+   not exist. The next time a client requests the same page, Traffic Server serves the negative response directly from
+   cache. When disabled (``0``) Traffic Server will only cache the response if the response has ``Cache-Control`` headers.
+
+   .. note::
+
+      The following negative responses are cached by Traffic Server:::
+
+         204  No Content
+         305  Use Proxy
+         400  Bad Request
+         403  Forbidden
+         404  Not Found
+         405  Method Not Allowed
+         500  Internal Server Error
+         501  Not Implemented
+         502  Bad Gateway
+         503  Service Unavailable
+         504  Gateway Timeout
+
+   The cache lifetime for objects cached from this setting is controlled via
+   :ts:cv:`proxy.config.http.negative_caching_lifetime`.
+
+.. ts:cv:: CONFIG proxy.config.http.negative_caching_lifetime INT 1800
+   :overridable:
+
+   How long (in seconds) Traffic Server keeps the negative responses  valid in cache. This value only affects negative
+   responses that do NOT have explicit ``Expires:`` or ``Cache-Control:`` lifetimes set by the server.
+
+Proxy User Variables
+====================
+
+.. ts:cv:: CONFIG proxy.config.http.anonymize_remove_from INT 0
+   :reloadable:
+   :overridable:
+
+   When enabled (``1``), Traffic Server removes the ``From`` header to protect the privacy of your users.
+
+.. ts:cv:: CONFIG proxy.config.http.anonymize_remove_referer INT 0
+   :reloadable:
+
+   When enabled (``1``), Traffic Server removes the ``Referrer`` header to protect the privacy of your site and users.
+
+.. ts:cv:: CONFIG proxy.config.http.anonymize_remove_user_agent INT 0
+   :reloadable:
+   :overridable:
+
+   When enabled (``1``), Traffic Server removes the ``User-agent`` header to protect the privacy of your site and users.
+
+.. ts:cv:: CONFIG proxy.config.http.anonymize_remove_cookie INT 0
+   :reloadable:
+   :overridable:
+
+   When enabled (``1``), Traffic Server removes the ``Cookie`` header to protect the privacy of your site and users.
+
+.. ts:cv:: CONFIG proxy.config.http.anonymize_remove_client_ip INT 0
+   :reloadable:
+   :overridable:
+
+   When enabled (``1``), Traffic Server removes ``Client-IP`` headers for more privacy.
+
+.. ts:cv:: CONFIG proxy.config.http.anonymize_insert_client_ip INT 1
+   :reloadable:
+   :overridable:
+
+   When enabled (``1``), Traffic Server inserts ``Client-IP`` headers to retain the client IP address.
+
+.. ts:cv:: CONFIG proxy.config.http.anonymize_other_header_list STRING NULL
+   :reloadable:
+
+   Comma separated list of headers Traffic Server should remove from outgoing requests.
+
+.. ts:cv:: CONFIG proxy.config.http.insert_squid_x_forwarded_for INT 1
+   :reloadable:
+   :overridable:
+
+   When enabled (``1``), Traffic Server adds the client IP address to the ``X-Forwarded-For`` header.
+
+.. ts:cv:: CONFIG proxy.config.http.normalize_ae_gzip INT 1
+   :reloadable:
+   :overridable:
+
+   Enable (``1``) to normalize all ``Accept-Encoding:`` headers to one of the following:
+
+   -  ``Accept-Encoding: gzip`` (if the header has ``gzip`` or ``x-gzip`` with any ``q``) **OR**
+   -  *blank* (for any header that does not include ``gzip``)
+
+   This is useful for minimizing cached alternates of documents (e.g. ``gzip, deflate`` vs. ``deflate, gzip``). Enabling this option is
+   recommended if your origin servers use no encodings other than ``gzip``.
+
+Security
+========
+
+.. ts:cv:: CONFIG proxy.config.http.push_method_enabled INT 0
+   :reloadable:
+
+   Enables (``1``) or disables (``0``) the HTTP ``PUSH`` option, which allows you to deliver content directly to the cache without a user
+   request.
+
+   .. important::
+
+       If you enable this option, then you must also specify
+       a filtering rule in the ip_allow.config file to allow only certain
+       machines to push content into the cache.
+
+.. ts:cv:: CONFIG proxy.config.http.max_post_size INT 0
+   :reloadable:
+
+   This feature is disabled by default with a value of (``0``), any positive
+   value will limit the size of post bodies. If a request is received with a
+   post body larger than this limit the response will be terminated with
+   413 - Request Entity Too Large and logged accordingly.
+
+Cache Control
+=============
+
+.. ts:cv:: CONFIG proxy.config.cache.enable_read_while_writer INT 1
+   :reloadable:
+
+   Specifies when to enable the ability to read a cached object while another
+   connection is completing the write to cache for that same object. The goal
+   here is to avoid multiple origin connections for the same cacheable object
+   upon a cache miss. The possible values of this config are:
+
+   -  ``0`` = never read while writing
+   -  ``1`` = always read while writing
+   -  ``2`` = always read while writing, but allow non-cached Range requests through to the origin
+
+   The ``2`` option is useful to avoid delaying requests which can not easily
+   be satisfied by the partially written response.
+
+   Several other configuration values need to be set for this to be
+   usable. See :ref:`admin-configuration-reducing-origin-requests`.
+
+.. ts:cv:: CONFIG proxy.config.cache.read_while_writer.max_retries INT 10
+   :reloadable:
+
+   Specifies how many retries trafficserver attempts to trigger read_while_writer on failing
+   to obtain the write VC mutex or until the first fragment is downloaded for the
+   object being downloaded. The retry duration is specified using the setting
+   :ts:cv:`proxy.config.cache.read_while_writer_retry.delay`
+
+.. ts:cv:: CONFIG proxy.config.cache.read_while_writer_retry.delay INT 50
+   :reloadable:
+
+   Specifies the delay in msec, trafficserver waits to reattempt read_while_writer
+   on failing to obtain the write VC mutex or until the first fragment is downloaded
+   for the object being downloaded. Note that trafficserver implements a progressive
+   delay in reattempting, by doubling the configured duration from the third reattempt
+   onwards.
+
+.. ts:cv:: CONFIG proxy.config.cache.force_sector_size INT 0
+   :reloadable:
+
+   Forces the use of a specific hardware sector size, e.g. 4096, for all disks.
+
+   SSDs and "advanced format” drives claim a sector size of 512; however, it is safe to force a higher
+   size than the hardware supports natively as we count atomicity in 512 byte increments.
+
+   4096-sized drives formatted for Windows will have partitions aligned on 63 512-byte sector boundaries,
+   so they will be unaligned. There are workarounds, but you need to do some research on your particular
+   drive. Some drives have a one-time option to switch the partition boundary, while others might require
+   reformatting or repartitioning.
+
+   To be safe in Linux, you could just use the entire drive: ``/dev/sdb`` instead of ``/dev/sdb1`` and
+   Traffic Server will do the right thing. Misaligned partitions on Linux are auto-detected.
+
+   For example: If ``/sys/block/sda/sda1/alignment_offset`` is non-zero, ATS will offset reads/writes to
+   that disk by that alignment. If Linux knows about any existing partition misalignments, ATS will compensate.
+
+   Partitions formatted to support hardware sector size of more than 512 (e.g. 4096) will result in all
+   objects stored in the cache to be integral multiples of 4096 bytes, which will result in some waste for
+   small files.
+
+.. ts:cv:: CONFIG proxy.config.http.cache.http INT 1
+   :reloadable:
+   :overridable:
+
+   Enables (``1``) or disables (``0``) caching of HTTP requests.
+
+.. ts:cv:: CONFIG proxy.config.http.cache.generation INT -1
+   :reloadable:
+   :overridable:
+
+   If set to a value other than ``-1``, the value if this configuration
+   option is combined with the cache key at cache lookup time.
+   Changing this value has the effect of an instantaneous, zero-cost
+   cache purge since it will cause all subsequent cache keys to
+   change. Since this is an overrideable configuration, it can be
+   used to purge the entire cache, or just a specific :file:`remap.config`
+   rule.
+
+.. ts:cv:: CONFIG proxy.config.http.cache.allow_empty_doc INT 1
+   :reloadable:
+   :deprecated:
+
+   Enables (``1``) or disables (``0``) caching objects that have an empty
+   response body. This is particularly useful for caching 301 or 302 responses
+   with a ``Location`` header but no document body. This only works if the
+   origin response also has a ``Content-Length`` header.
+
+.. ts:cv:: CONFIG proxy.config.http.cache.ignore_client_no_cache INT 1
+   :reloadable:
+   :overridable:
+
+   When enabled (``1``), Traffic Server ignores client requests to bypass the cache.
+
+.. ts:cv:: CONFIG proxy.config.http.cache.ims_on_client_no_cache INT 1
+   :reloadable:
+   :overridable:
+
+   When enabled (``1``), Traffic Server issues a conditional request to the origin server if an incoming request has a ``No-Cache`` header.
+
+.. ts:cv:: CONFIG proxy.config.http.cache.ignore_server_no_cache INT 0
+   :reloadable:
+   :overridable:
+
+   When enabled (``1``), Traffic Server ignores origin server requests to bypass the cache.
+
+.. ts:cv:: CONFIG proxy.config.http.cache.cache_responses_to_cookies INT 1
+   :reloadable:
+   :overridable:
+
+   Specifies how cookies are cached:
+
+   -  ``0`` = do not cache any responses to cookies
+   -  ``1`` = cache for any content-type
+   -  ``2`` = cache only for image types
+   -  ``3`` = cache for all but text content-types
+
+.. ts:cv:: CONFIG proxy.config.http.cache.ignore_authentication INT 0
+   :overridable:
+
+   When enabled (``1``), Traffic Server ignores ``WWW-Authentication`` headers in responses ``WWW-Authentication`` headers are removed and
+   not cached.
+
+.. ts:cv:: CONFIG proxy.config.http.cache.cache_urls_that_look_dynamic INT 1
+   :reloadable:
+   :overridable:
+
+   Enables (``1``) or disables (``0``) caching of URLs that look dynamic, i.e.: URLs that end in ``.asp`` or contain a question
+   mark (``?``), a semicolon (``;``), or ``cgi``. For a full list, please refer to
+   `HttpTransact::url_looks_dynamic </link/to/doxygen>`_
+
+.. ts:cv:: CONFIG proxy.config.http.cache.enable_default_vary_headers INT 0
+   :reloadable:
+
+   Enables (``1``) or disables (``0``) caching of alternate versions of HTTP objects that do not contain the ``Vary`` header.
+
+.. ts:cv:: CONFIG proxy.config.http.cache.when_to_revalidate INT 0
+   :reloadable:
+   :overridable:
+
+   Specifies when to revalidate content:
+
+   -  ``0`` = use cache directives or heuristic (the default value)
+   -  ``1`` = stale if heuristic
+   -  ``2`` = always stale (always revalidate)
+   -  ``3`` = never stale
+   -  ``4`` = use cache directives or heuristic (0) unless the request
+       has an ``If-Modified-Since`` header
+
+   If the request contains the ``If-Modified-Since`` header, then
+   Traffic Server always revalidates the cached content and uses the
+   client's ``If-Modified-Since`` header for the proxy request.
+
+.. ts:cv:: CONFIG proxy.config.http.cache.required_headers INT 2
+   :reloadable:
+   :overridable:
+
+   The type of headers required in a request for the request to be cacheable.
+
+   -  ``0`` = no headers required to make document cacheable
+   -  ``1`` = either the ``Last-Modified`` header, or an explicit lifetime header, ``Expires`` or ``Cache-Control: max-age``, is required
+   -  ``2`` = explicit lifetime is required, ``Expires`` or ``Cache-Control: max-age``
+
+.. ts:cv:: CONFIG proxy.config.http.cache.max_stale_age INT 604800
+   :reloadable:
+   :overridable:
+
+   The maximum age allowed for a stale response before it cannot be cached.
+
+.. ts:cv:: CONFIG proxy.config.http.cache.range.lookup INT 1
+   :overridable:
+
+   When enabled (``1``), Traffic Server looks up range requests in the cache.
+
+.. ts:cv:: CONFIG proxy.config.http.cache.range.write INT 0
+   :overridable:
+
+   When enabled (``1``), Traffic Server will attempt to write (lock) the URL
+   to cache. This is rarely useful (at the moment), since it'll only be able
+   to write to cache if the origin has ignored the ``Range:`` header. For a use
+   case where you know the origin will respond with a full (``200``) response,
+   you can turn this on to allow it to be cached.
+
+.. ts:cv:: CONFIG proxy.config.http.cache.ignore_accept_mismatch INT 2
+   :reloadable:
+
+   When enabled with a value of ``1``, Traffic Server serves documents from cache with a
+   ``Content-Type:`` header even if it does not match the ``Accept:`` header of the
+   request. If set to ``2`` (default), this logic only happens in the absence of a
+   ``Vary`` header in the cached response (which is the recommended and safe use).
+
+   .. note::
+      This option should only be enabled with ``1`` if you're having
+      problems with caching *and* you origin server doesn't set the ``Vary``
+      header. Alternatively, if the origin is incorrectly setting
+      ``Vary: Accept`` or doesn't respond with ``406 (Not Acceptable)``,
+      you can also enable this configuration with a ``1``.
+
+.. ts:cv:: CONFIG proxy.config.http.cache.ignore_accept_language_mismatch INT 2
+   :reloadable:
+
+   When enabled with a value of ``1``, Traffic Server serves documents from cache with a
+   ``Content-Language:`` header even if it does not match the ``Accept-Language:``
+   header of the request. If set to ``2`` (default), this logic only happens in the absence of a
+   ``Vary`` header in the cached response (which is the recommended and safe use).
+
+   .. note::
+
+      This option should only be enabled with ``1`` if you're having
+      problems with caching *and* you origin server doesn't set the ``Vary``
+      header. Alternatively, if the origin is incorrectly setting
+      ``Vary: Accept-Language`` or doesn't respond with ``406 (Not Acceptable)``,
+      you can also enable this configuration with a ``1``.
+
+.. ts:cv:: CONFIG proxy.config.http.cache.ignore_accept_encoding_mismatch INT 2
+   :reloadable:
+
+   When enabled with a value of ``1``, Traffic Server serves documents from cache with a
+   ``Content-Encoding:`` header even if it does not match the ``Accept-Encoding:``
+   header of the request. If set to ``2`` (default), this logic only happens in the absence of a
+   ``Vary`` header in the cached response (which is the recommended and safe use).
+
+   .. note::
+
+      This option should only be enabled with ``1`` if you're having
+      problems with caching *and* you origin server doesn't set the ``Vary``
+      header. Alternatively, if the origin is incorrectly setting
+      ``Vary: Accept-Encoding`` or doesn't respond with ``406 (Not Acceptable)``
+      you can also enable this configuration with a ``1``.
+
+.. ts:cv:: CONFIG proxy.config.http.cache.ignore_accept_charset_mismatch INT 2
+   :reloadable:
+
+   When enabled with a value of ``1``, Traffic Server serves documents from cache with a
+   ``Content-Type:`` header even if it does not match the ``Accept-Charset:`` header
+   of the request. If set to ``2`` (default), this logic only happens in the absence of a
+   ``Vary`` header in the cached response (which is the recommended and safe use).
+
+   .. note::
+
+      This option should only be enabled with ``1`` if you're having
+      problems with caching *and* you origin server doesn't set the ``Vary``
+      header. Alternatively, if the origin is incorrectly setting
+      ``Vary: Accept-Charset`` or doesn't respond with ``406 (Not Acceptable)``,
+      you can also enable this configuration with a ``1``.
+
+.. ts:cv:: CONFIG proxy.config.http.cache.ignore_client_cc_max_age INT 1
+   :reloadable:
+   :overridable:
+
+   When enabled (``1``), Traffic Server ignores any ``Cache-Control:
+   max-age`` headers from the client. This technically violates the HTTP RFC,
+   but avoids a problem where a client can forcefully invalidate a cached object.
+
+.. ts:cv:: CONFIG proxy.config.cache.max_doc_size INT 0
+
+   Specifies the maximum object size that will be cached. ``0`` is unlimited.
+
+.. ts:cv:: CONFIG proxy.config.cache.permit.pinning INT 0
+   :reloadable:
+
+   When enabled (``1``), Traffic Server will keep certain HTTP objects in the cache for a certain time as specified in cache.config.
+
+.. ts:cv:: CONFIG proxy.config.cache.hit_evacuate_percent INT 0
+
+   The size of the region (as a percentage of the total content storage in a :term:`cache stripe`) in front of the
+   :term:`write cursor` that constitutes a recent access hit for evacutating the accessed object.
+
+   When an object is accessed it can be marked for evacuation, that is to be copied over the write cursor and
+   thereby preserved from being overwritten. This is done if it is no more than a specific number of bytes in front of
+   the write cursor. The number of bytes is a percentage of the total number of bytes of content storage in the cache
+   stripe where the object is stored and that percentage is set by this variable.
+
+   By default, the feature is off (set to 0).
+
+.. ts:cv:: CONFIG proxy.config.cache.hit_evacuate_size_limit INT 0
+   :metric: bytes
+
+   Limit the size of objects that are hit evacuated.
+
+   Objects larger than the limit are not hit evacuated. A value of 0 disables the limit.
+
+.. ts:cv:: CONFIG proxy.config.cache.limits.http.max_alts INT 5
+
+   The maximum number of alternates that are allowed for any given URL.
+   Disable by setting to 0.
+
+.. ts:cv:: CONFIG proxy.config.cache.target_fragment_size INT 1048576
+
+   Sets the target size of a contiguous fragment of a file in the disk cache.
+   When setting this, consider that larger numbers could waste memory on slow
+   connections, but smaller numbers could increase (waste) seeks.
+
+RAM Cache
+=========
+
+.. ts:cv:: CONFIG proxy.config.cache.ram_cache.size INT -1
+
+   By default the RAM cache size is automatically determined, based on
+   disk cache size; approximately 10 MB of RAM cache per GB of disk cache.
+   Alternatively, it can be set to a fixed value such as
+   **20GB** (21474836480)
+
+.. ts:cv:: CONFIG proxy.config.cache.ram_cache_cutoff INT 4194304
+
+   Objects greater than this size will not be kept in the RAM cache.
+   This should be set high enough to keep objects accessed frequently
+   in memory in order to improve performance.
+   **4MB** (4194304)
+
+.. ts:cv:: CONFIG proxy.config.cache.ram_cache.algorithm INT 0
+
+   Two distinct RAM caches are supported, the default (0) being the **CLFUS**
+   (*Clocked Least Frequently Used by Size*). As an alternative, a simpler
+   **LRU** (*Least Recently Used*) cache is also available, by changing this
+   configuration to 1.
+
+.. ts:cv:: CONFIG proxy.config.cache.ram_cache.use_seen_filter INT 0
+
+   Enabling this option will filter inserts into the RAM cache to ensure that
+   they have been seen at least once.  For the **LRU**, this provides scan
+   resistance. Note that **CLFUS** already requires that a document have history
+   before it is inserted, so for **CLFUS**, setting this option means that a
+   document must be seen three times before it is added to the RAM cache.
+
+.. ts:cv:: CONFIG proxy.config.cache.ram_cache.compress INT 0
+
+   The **CLFUS** RAM cache also supports an optional in-memory compression.
+   This is not to be confused with ``Content-Encoding: gzip`` compression.
+   The RAM cache compression is intended to try to save space in the RAM,
+   and is not visible to the User-Agent (client).
+
+   Possible values are:
+
+   - ``0`` = no compression
+   - ``1`` = fastlz (extremely fast, relatively low compression)
+   - ``2`` = libz (moderate speed, reasonable compression)
+   - ``3`` = liblzma (very slow, high compression)
+
+   .. note::
+
+      Compression runs on task threads.  To use more cores for RAM cache compression, increase :ts:cv:`proxy.config.task_threads`.
+
+Heuristic Expiration
+====================
+
+.. ts:cv:: CONFIG proxy.config.http.cache.heuristic_min_lifetime INT 3600
+   :reloadable:
+   :overridable:
+
+   The minimum amount of time an HTTP object without an expiration date can remain fresh in the cache before is
+   considered to be stale.
+
+.. ts:cv:: CONFIG proxy.config.http.cache.heuristic_max_lifetime INT 86400
+   :reloadable:
+   :overridable:
+
+   The maximum amount of time an HTTP object without an expiration date can remain fresh in the cache before is
+   considered to be stale.
+
+.. ts:cv:: CONFIG proxy.config.http.cache.heuristic_lm_factor FLOAT 0.10
+   :reloadable:
+   :overridable:
+
+   The aging factor for freshness computations. Traffic Server stores an object for this percentage of the time that
+   elapsed since it last changed.
+
+.. ts:cv:: CONFIG proxy.config.http.cache.fuzz.time INT 240
+   :reloadable:
+   :overridable:
+
+   How often Traffic Server checks for an early refresh, during the period before the document stale time. The interval
+   specified must be in seconds. See :ref:`fuzzy-revalidation`
+
+.. ts:cv:: CONFIG proxy.config.http.cache.fuzz.probability FLOAT 0.005
+   :reloadable:
+   :overridable:
+
+   The probability that a refresh is made on a document during the specified fuzz time.
+
+.. ts:cv:: CONFIG proxy.config.http.cache.fuzz.min_time INT 0
+   :reloadable:
+   :overridable:
+
+   Handles requests with a TTL less than fuzz.time – it allows for different times to evaluate the probability of revalidation for small TTLs and big TTLs. Objects with small TTLs will start "rolling the revalidation dice" near the fuzz.min_time, while objects with large TTLs would start at fuzz.time. A logarithmic like function between determines the revalidation evaluation start time (which will be between fuzz.min_time and fuzz.time). As the object gets closer to expiring, the window start becomes more likely. By default this setting is not enabled, but should be enabled anytime you have objects with small TTLs. The default value is ``0``.
+
+Dynamic Content & Content Negotiation
+=====================================
+
+.. ts:cv:: CONFIG proxy.config.http.cache.vary_default_text STRING NULL
+   :reloadable:
+
+   The header on which Traffic Server varies for text documents.
+
+For example: if you specify ``User-agent``, then Traffic Server caches
+all the different user-agent versions of documents it encounters.
+
+.. ts:cv:: CONFIG proxy.config.http.cache.vary_default_images STRING NULL
+   :reloadable:
+
+   The header on which Traffic Server varies for images.
+
+.. ts:cv:: CONFIG proxy.config.http.cache.vary_default_other STRING NULL
+   :reloadable:
+
+   The header on which Traffic Server varies for anything other than text and images.
+
+.. ts:cv:: CONFIG proxy.config.http.cache.open_read_retry_time INT 10
+   :reloadable:
+
+    The number of milliseconds a cacheable request will wait before requesting the object from cache if an equivalent request is in flight.
+
+.. ts:cv:: CONFIG proxy.config.http.cache.max_open_read_retries INT -1
+   :reloadable:
+
+    The number of times to attempt fetching an object from cache if there was an equivalent request in flight.
+
+.. ts:cv:: CONFIG proxy.config.http.cache.max_open_write_retries INT 1
+   :reloadable:
+
+    The number of times to attempt a cache open write upon failure to get a write lock.
+
+.. ts:cv:: CONFIG proxy.config.http.cache.open_write_fail_action INT 0
+   :reloadable:
+
+    This setting indicates the action taken on failing to obtain the cache open write lock on either a cache miss or a cache
+    hit stale. This typically happens when there is more than one request to the same cache object simultaneously. During such
+    a scenario, all but one (which goes to the origin) request is served either a stale copy or an error depending on this
+    setting.
+
+   -  ``0`` = default, disable cache and goto origin server
+   -  ``1`` = return a 502 error on a cache miss
+   -  ``2`` = serve stale if object's age is under :ts:cv:`proxy.config.http.cache.max_stale_age`, else, goto origin server
+   -  ``3`` = return a 502 error on a cache miss or serve stale on a cache revalidate
+              if object's age is under :ts:cv:`proxy.config.http.cache.max_stale_age`, else, goto origin server
+   -  ``4`` = return a 502 error on either a cache miss or on a revalidate
+
+Customizable User Response Pages
+================================
+
+.. ts:cv:: CONFIG proxy.config.body_factory.enable_customizations INT 1
+
+   Specifies whether customizable response pages are language specific
+   or not:
+
+   -  ``1`` = enable customizable user response pages in the default directory only
+   -  ``2`` = enable language-targeted user response pages
+   -  ``3`` = enable host-targeted user response pages
+
+.. ts:cv:: CONFIG proxy.config.body_factory.enable_logging INT 0
+
+   Enables (``1``) or disables (``0``) logging for customizable response pages. When enabled, Traffic Server records a message in
+   the error log each time a customized response page is used or modified.
+
+.. ts:cv:: CONFIG proxy.config.body_factory.template_sets_dir STRING etc/trafficserver/body_factory
+
+   The customizable response page default directory. If this is a
+   relative path, Traffic Server resolves it relative to the
+   ``PREFIX`` directory.
+
+.. ts:cv:: CONFIG proxy.config.body_factory.template_base STRING ""
+    :reloadable:
+    :overridable:
+
+    A prefix for the file name to use to find an error template file. If set (not the empty string)
+    this value and an underscore are predended to the file name to find in the template sets
+    directory. See :ref:`body-factory`.
+
+.. ts:cv:: CONFIG proxy.config.body_factory.response_suppression_mode INT 0
+
+   Specifies when Traffic Server suppresses generated response pages:
+
+   -  ``0`` = never suppress generated response pages
+   -  ``1`` = always suppress generated response pages
+   -  ``2`` = suppress response pages only for intercepted traffic
+
+.. ts:cv:: CONFIG proxy.config.http_ui_enabled INT 0
+
+   Specifies which http UI endpoints to allow within :file:`remap.config`:
+
+   -  ``0`` = disable all http UI endpoints
+   -  ``1`` = enable only cache endpoints
+   -  ``2`` = enable only stats endpoints
+   -  ``3`` = enable all http UI endpoints
+
+   To enable any enpoint there needs to be an entry in :file:`remap.config` which
+   specifically enables it. Such a line would look like: ::
+
+        map / http://{stat}
+
+   The following are the cache endpoints:
+
+   - ``cache`` = UI to interact with the cache
+
+   The following are the stats endpoints:
+
+   - ``cache-internal`` = statistics about cache evacuation and volumes
+   - ``hostdb`` = lookups against the hostdb
+   - ``http`` = HTTPSM details, this endpoint is also gated by `proxy.config.http.enable_http_info`
+   - ``net`` = lookup and listing of open connections
+   - ``stat`` = list of all records.config options and metrics
+   - ``test`` = test callback page
+
+.. ts:cv:: CONFIG proxy.config.http.enable_http_info INT 0
+
+   Enables (``1``) or disables (``0``) access to an endpoint within `proxy.config.http_ui_enabled`
+   which shows details about inflight transactions (HttpSM).
+
+DNS
+===
+
+.. ts:cv:: CONFIG proxy.config.dns.search_default_domains INT 0
+   :Reloadable:
+
+   - ``0`` = disables local domain expansion
+   - ``1`` = enable local domain expansion
+   - ``2`` = enable local domain expansion, but restrain splitting local domain name
+
+Traffic Server can attempt to resolve unqualified hostnames by
+expanding to the local domain. For example if a client makes a
+request to an unqualified host (``host_x``) and the Traffic Server
+local domain is ``y.com`` , then Traffic Server will expand the
+hostname to ``host_x.y.com``.
+
+.. ts:cv:: CONFIG proxy.config.dns.splitDNS.enabled INT 0
+   :reloadable:
+
+   Enables (``1``) or disables (``0``) DNS server selection. When enabled, Traffic Server refers to the :file:`splitdns.config` file for
+   the selection specification. Refer to :ref:`Configuring DNS Server Selection <admin-split-dns>`.
+
+.. ts:cv:: CONFIG proxy.config.dns.url_expansions STRING NULL
+
+   Specifies a list of hostname extensions that are automatically added to the hostname after a failed lookup. For example: if you want
+   Traffic Server to add the hostname extension .org, then specify ``org`` as the value for this variable (Traffic Server automatically
+   adds the dot (.)).
+
+.. note::
+
+   If the variable :ts:cv:`proxy.config.http.enable_url_expandomatic` is set to ``1`` (the default value), then you do not have to
+   add ``www.`` and ``.com`` to this list because Traffic Server automatically tries www. and .com after trying the values
+   you've specified.
+
+.. ts:cv:: CONFIG proxy.config.dns.resolv_conf STRING /etc/resolv.conf
+
+   Allows to specify which ``resolv.conf`` file to use for finding resolvers. While the format of this file must be the same as the
+   standard ``resolv.conf`` file, this option allows an administrator to manage the set of resolvers in an external configuration file,
+   without affecting how the rest of the operating system uses DNS.
+
+.. ts:cv:: CONFIG proxy.config.dns.round_robin_nameservers INT 1
+   :reloadable:
+
+   Enables (``1``) or disables (``0``) DNS server round-robin.
+
+.. ts:cv:: CONFIG proxy.config.dns.nameservers STRING NULL
+   :reloadable:
+
+   The DNS servers.
+
+.. ts:cv:: CONFIG proxy.config.srv_enabled INT 0
+   :reloadable:
+
+   Indicates whether to use SRV records for orgin server lookup.
+
+.. ts:cv:: CONFIG proxy.config.dns.dedicated_thread INT 0
+
+   Create and dedicate a thread entirely for DNS processing. This is probably
+   most useful on system which do a significant number of DNS lookups,
+   typically forward proxies. But even on other systems, it can avoid some
+   contention on the first worker thread (which otherwise takes on the burden of
+   all DNS lookups).
+
+.. ts:cv:: CONFIG proxy.config.dns.validate_query_name INT 0
+
+   When enabled (1) provides additional resilience against DNS forgery (for instance
+   in DNS Injection attacks), particularly in forward or transparent proxies, but
+   requires that the resolver populates the queries section of the response properly.
+
+HostDB
+======
+
+.. ts:cv:: CONFIG proxy.config.hostdb.lookup_timeout INT 30
+   :metric: seconds
+   :reloadable:
+
+   Time to wait for a DNS response in seconds.
+
+.. ts:cv:: CONFIG proxy.config.hostdb.serve_stale_for INT
+   :metric: seconds
+   :reloadable:
+
+   The number of seconds for which to use a stale NS record while initiating a
+   background fetch for the new data.
+
+   If not set then stale records are not served.
+
+.. ts:cv:: CONFIG proxy.config.hostdb.storage_size INT 33554432
+   :metric: bytes
+
+   The amount of space (in bytes) used to store ``hostdb``.
+   The value of this variable must be increased if you increase the size of the
+   `proxy.config.hostdb.size`_ variable.
+
+.. ts:cv:: CONFIG proxy.config.hostdb.size INT 120000
+
+   The maximum number of entries that can be stored in the database.
+
+.. note::
+
+   For values above ``200000``, you must increase :ts:cv:`proxy.config.hostdb.storage_size` by at least 44 bytes per entry.
+
+.. ts:cv:: CONFIG proxy.config.hostdb.ttl_mode INT 0
+   :reloadable:
+
+   A host entry will eventually time out and be discarded. This variable controls how that time is calculated. A DNS
+   request will return a TTL value and an internal value can be set with :ts:cv:`proxy.config.hostdb.timeout`. This
+   variable determines which value will be used.
+
+   =====    ===
+   Value    TTL
+   =====    ===
+   0        The TTL from the DNS response.
+   1        The internal timeout value.
+   2        The smaller of the DNS and internal TTL values. The internal timeout value becomes a maximum TTL.
+   3        The larger of the DNS and internal TTL values. The internal timeout value become a minimum TTL.
+   =====    ===
+
+.. ts:cv:: CONFIG proxy.config.hostdb.timeout INT 1440
+   :metric: minutes
+   :reloadable:
+
+   Internal time to live value for host DB entries, **in minutes**.
+
+   See :ts:cv:`proxy.config.hostdb.ttl_mode` for when this value is used.
+
+.. ts:cv:: CONFIG proxy.config.hostdb.strict_round_robin INT 0
+   :reloadable:
+
+   Set host resolution to use strict round robin.
+
+When this and :ts:cv:`proxy.config.hostdb.timed_round_robin` are both disabled (set to ``0``), Traffic Server always
+uses the same origin server for the same client, for as long as the origin server is available. Otherwise if this is
+set then IP address is rotated on every request. This setting takes precedence over
+:ts:cv:`proxy.config.hostdb.timed_round_robin`.
+
+.. ts:cv:: CONFIG proxy.config.hostdb.timed_round_robin INT 0
+   :reloadable:
+
+   Set host resolution to use timed round robin.
+
+When this and :ts:cv:`proxy.config.hostdb.strict_round_robin` are both disabled (set to ``0``), Traffic Server always
+uses the same origin server for the same client, for as long as the origin server is available. Otherwise if this is
+set to :arg:`N` the IP address is rotated if more than :arg:`N` seconds have past since the first time the
+current address was used.
+
+.. ts:cv:: CONFIG proxy.config.hostdb.host_file.path STRING NULL
+
+   Set the file path for an external host file.
+
+If this is set (non-empty) then the file is presumed to be a hosts file in the standard `host file format <http://tools.ietf.org/html/rfc1123#page-13>`_. It is read and the entries there added to the HostDB. The file is periodically checked for a more recent modification date in which case it is reloaded. The interval is set by the value :ts:cv:`proxy.config.hostdb.host_file.interval`.
+
+While not technically reloadable, the value is read every time the file is to be checked so that if changed the new
+value will be used on the next check and the file will be treated as modified.
+
+.. ts:cv:: CONFIG proxy.config.hostdb.host_file.interval INT 86400
+   :metric: seconds
+   :reloadable:
+
+   Set the file changed check timer for :ts:cv:`proxy.config.hostdb.host_file.path`.
+
+The file is checked every this many seconds to see if it has changed. If so the HostDB is updated with the new values in the file.
+
+.. ts:cv:: CONFIG proxy.config.hostdb.ip_resolve STRING NULL
+
+   Set the host resolution style.
+
+This is an ordered list of keywords separated by semicolons that specify how a host name is to be resolved to an IP address. The keywords are case
+insensitive.
+
+=======  =======
+Keyword  Meaning
+=======  =======
+ipv4     Resolve to an IPv4 address.
+ipv6     Resolve to an IPv6 address.
+client   Resolve to the same family as the client IP address.
+none     Stop resolving.
+=======  =======
+
+The order of the keywords is critical. When a host name needs to be resolved it is resolved in same order as the
+keywords. If a resolution fails, the next option in the list is tried. The keyword ``none`` means to give up resolution
+entirely. The keyword list has a maximum length of three keywords, more are never needed. By default there is an
+implicit ``ipv4;ipv6`` attached to the end of the string unless the keyword ``none`` appears.
+
+.. topic:: Example
+
+   Use the incoming client family, then try IPv4 and IPv6. ::
+
+      client;ipv4;ipv6
+
+   Because of the implicit resolution this can also be expressed as just ::
+
+      client
+
+.. topic:: Example
+
+   Resolve only to IPv4. ::
+
+      ipv4;none
+
+.. topic:: Example
+
+   Resolve only to the same family as the client (do not permit cross family transactions). ::
+
+      client;none
+
+This value is a global default that can be overridden by :ts:cv:`proxy.config.http.server_ports`.
+
+.. note::
+
+   This style is used as a convenience for the administrator. During a resolution the *resolution order* will be
+   one family, then possibly the other. This is determined by changing ``client`` to ``ipv4`` or ``ipv6`` based on the
+   client IP address and then removing duplicates.
+
+.. important::
+
+   This option has no effect on outbound transparent connections The local IP address used in the connection to the
+   origin server is determined by the client, which forces the IP address family of the address used for the origin
+   server. In effect, outbound transparent connections always use a resolution style of "``client``".
+
+Logging Configuration
+=====================
+
+.. ts:cv:: CONFIG proxy.config.log.logging_enabled INT 3
+   :reloadable:
+
+   Enables and disables event logging:
+
+   -  ``0`` = logging disabled
+   -  ``1`` = log errors only
+   -  ``2`` = log transactions only
+   -  ``3`` = full logging (errors + transactions)
+
+   Refer to :ref:`working-with-log-files`.
+
+.. ts:cv:: CONFIG proxy.config.log.max_secs_per_buffer INT 5
+   :reloadable:
+
+   The maximum amount of time before data in the buffer is flushed to disk.
+
+.. ts:cv:: CONFIG proxy.config.log.max_space_mb_for_logs INT 25000
+   :metric: megabytes
+   :reloadable:
+
+   The amount of space allocated to the logging directory (in MB).
+
+.. note::
+
+   All files in the logging directory contribute to the space used, even if they are not log files. In collation client
+   mode, if there is no local disk logging, or :ts:cv:`proxy.config.log.max_space_mb_for_orphan_logs` is set to a higher
+   value than :ts:cv:`proxy.config.log.max_space_mb_for_logs`, TS will take
+   :ts:cv:`proxy.config.log.max_space_mb_for_orphan_logs` for maximum allowed log space.
+
+.. ts:cv:: CONFIG proxy.config.log.max_space_mb_for_orphan_logs INT 25
+   :metric: megabytes
+   :reloadable:
+
+   The amount of space allocated to the logging directory (in MB) if this node is acting as a collation

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