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authorBjörn Gustavsson <[email protected]>2015-03-12 15:35:13 +0100
committerBjörn Gustavsson <[email protected]>2015-03-12 15:41:46 +0100
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Update OAM Principles
Language cleaned up by the technical writers xsipewe and tmanevik from Combitech. Proofreading and corrections by Björn Gustavsson.
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<rev>A</rev>
<file>oam_intro.xml</file>
</header>
- <p>The operation and maintenance support in OTP consists of a
- generic model for management subsystems in OTP, and some
- components to be used in these subsystems. This document
- describes the model.
- </p>
- <p>The main idea in the model is that it is management protocol
- independent. Thus, it is not tied to any specific management
- protocol. An API is defined which can be used to write
- adaptations for specific management protocols.
- </p>
- <p>Each OAM component in OTP is implemented as one sub application,
- which can be included in a management application for the system.
- Note that such a complete management application is not in the
- scope of this generic functionality. Examples illustrating how such an
- application can be built are included however.
- </p>
+ <marker id="oam principles"></marker>
+ <p>The Operation and Maintenance (OAM) support in OTP consists of a
+ generic model for management subsystems in OTP, and some components
+ to be used in these subsystems. This section describes the model.</p>
+
+ <p>The main idea in the model is that it is not tied to any specific
+ management protocol. An Application Programming Interface (API) is
+ defined, which can be used to write adaptations for specific
+ management protocols.</p>
+
+ <p>Each OAM component in OTP is implemented as one sub-application, which
+ can be included in a management application for the system. Notice that
+ such a complete management application is not in the scope of this
+ generic functionality. However, this section includes examples
+ illustrating how such an application can be built.</p>
<section>
<title>Terminology</title>
- <p>The protocol independent architectural model on the network
- level is the well-known <term id="Manager-Agent model"><termdef>Client-Server model for management operations</termdef></term>. This model is based on the client-server
- principle, where the manager (client) sends <term id="requests"><termdef>A request is sent from a manager to an agent when it accesses management information.</termdef></term>to the
- agent (server), the agent sends <term id="replies"><termdef>A reply is sent from the agent as a response to a request from a manager.</termdef></term>back to the manager. There are two main
- differences to the normal client-server model. First, there are
- usually a few managers that communicate with many agents; and
- second, the agent may spontaneously send <term id="notifications"><termdef>A notification is sent spontaneously from an agent to a manager, e.g. an alarm.</termdef></term>to the
- manager. The picture below illustrates the idea.</p>
+ <p>The protocol-independent architectural model on the network level
+ is the well-known client-server model for management operations. This
+ model is based on the client-server principle, where the manager
+ (client) sends a request from a manager to an agent (server) when it
+ accesses management information. The agent sends a reply back to the
+ manager. There are two main differences to the normal
+ client-server model:</p>
+ <list type="bulleted">
+ <item><p>Usually a few managers communicate with many agents.</p></item>
+ <item><p>The agent can spontaneously send a notification, for example,
+ an alarm, to the manager.</p></item>
+ </list>
+ <p>The following picture illustrates the idea:</p>
+
<image file="../oam/terminology.gif">
<icaption>Terminology</icaption>
</image>
- <p>The manager is often referred to as the <term id="NMS"></term>, to
- emphasize that it usually is realized as a program that presents
- data to an operator.
- </p>
- <p>The agent is an entity that executes within a <term id="NE"></term>.
- In OTP, the network element may be a distributed system, meaning
- that the distributed system is managed as one entity. Of
- course, the agent may be configured to be able to run on one of
- several nodes, making it a distributed OTP application.
- </p>
- <p>The management information is defined in an <term id="MIB"></term>.
- It is a formal definition of which information the agent makes
- available to the manager. The manager accesses the MIB through
- a management protocol, such as SNMP, CMIP, HTTP or CORBA. Each
- of these protocols have their own MIB definition language. In
- SNMP, it is a subset of ASN.1, in CMIP it is GDMO, in HTTP it is
- implicit, and using CORBA, it is IDL. Usually, the entities
- defined in the MIB are called <term id="MO"></term>, although these
- objects do not have to be objects in the OO way,for example, a simple
- scalar variable defined in an MIB is called a Managed Object.
- The Managed Objects are logical objects, not necessarily with a
- one-to-one mapping to the resources.
- </p>
+
+ <p>The manager is often referred to as the <em>Network Management
+ System (NMS)</em>, to emphasize that it usually is realized as a
+ program that presents data to an operator.</p>
+
+ <p>The agent is an entity that executes within a <em>Network
+ Element (NE)</em>. In OTP, the NE can be a distributed system,
+ meaning that the distributed system is managed as one entity.
+ Of course, the agent can be configured to be able to run on one
+ of several nodes, making it a distributed OTP application.</p>
+
+ <p>The management information is defined in a <em>Management
+ Information Base (MIB)</em>. It is a formal definition of which
+ information the agent makes available to the manager. The
+ manager accesses the MIB through a management protocol, such
+ as SNMP, CMIP, HTTP, or CORBA. Each protocol has its own MIB
+ definition language. In SNMP, it is a subset of ASN.1, in CMIP
+ it is GDMO, in HTTP it is implicit, and using CORBA, it is IDL.</p>
+
+ <p>Usually, the entities defined in the MIB are
+ called <em>Managed Objects (MOs)</em>, although they do not
+ have to be objects in the object-oriented way. For example,
+ a simple scalar variable defined in a MIB is called an MO. The
+ MOs are logical objects, not necessarily with a one-to-one
+ mapping to the resources.</p>
</section>
<section>
<title>Model</title>
- <p>In this section, the generic protocol independent model for use
- within an OTP based network element is presented. This model is
- used by all operation and maintenance components, and may be
- used by the applications. The advantage of the model is that it
- clearly separates the resources from the management protocol.
- The resources do not need to be aware of which management
- protocol is used to manage the system. This makes it possible
- to manage the same resources with different protocols.
- </p>
- <p>The different entities involved in this model are the <term id="agent"></term>which terminates the management protocol, and the
- <term id="resources"></term>which is to be managed, i.e. the actual
- application entities. The resources should in general have no
- knowledge of the management protocol used, and the agent should
- have no knowledge of the managed resources. This implies that
- some sort of translation mechanism must be used, to translate
- the management operations to operations on the resources. This
- translation mechanism is usually called
- <em>instrumentation</em>, and the function that implements it is
- called <term id="instrumentation function"></term>. The
- instrumentation functions are written for each combination of
- management protocol and resource to be managed. For example, if
- an application is to be managed by SNMP and HTTP, two sets of
- instrumentation functions are defined; one that maps SNMP
- requests to the resources, and one that e.g. generates an HTML
- page for some resources.
- </p>
- <p>When a manager makes a request to the agent, we have the
- following picture:</p>
+ <p>This section presents the generic protocol-independent model
+ for use within an OTP-based NE. This model is used by
+ all OAM components and can be used by the applications. The
+ advantage of the model is that it clearly separates the
+ resources from the management protocol. The resources do not
+ need to be aware of which management protocol is used to manage
+ the system. The same resources can therefore be managed with
+ different protocols.</p>
+
+ <p>The entities involved in this model are the agent, which
+ terminates the management protocol, and the resources, which
+ is to be managed, that is, the actual application entities.
+ The resources should in general have no knowledge of the
+ management protocol used, and the agent should have no
+ knowledge of the managed resources. This implies that a
+ translation mechanism is needed, to translate the management
+ operations to operations on the resources. This translation
+ mechanism is usually called <em>instrumentation</em> and the
+ function that implements it is called <em>instrumentation
+ function</em>. The instrumentation functions are written for
+ each combination of management protocol and resource to be
+ managed. For example, if an application is to be managed by
+ SNMP and HTTP, two sets of instrumentation functions are
+ defined; one that maps SNMP requests to the resources, and
+ one that, for example, generates an HTML page for some
+ resources.</p>
+
+ <p>When a manager makes a request to the agent, the following
+ illustrates the situation:</p>
+
<image file="../oam/snmp_model_1.gif">
- <icaption>Request to an agent by a manager</icaption>
+ <icaption>Request to An Agent by a Manager</icaption>
</image>
- <p>Note that the mapping between instrumentation function and
- resource is not necessarily 1-1. It is also possible to write
- one instrumentation function for each resource, and use that
- function from different protocols.
- </p>
- <p>The agent receives a request and maps this request to calls to
- one or several instrumentation functions. The instrumentation
- functions perform operations on the resources to implement the
- semantics associated with the managed object.
- </p>
- <p>For example, a system that is managed with SNMP and HTTP may be
- structured in the following way:</p>
+
+ <p>The mapping between an instrumentation function and a
+ resource is not necessarily 1-1. It is also possible to write
+ one instrumentation function for each resource, and use that
+ function from different protocols.</p>
+
+ <p>The agent receives a request and maps it to calls to one or
+ more instrumentation functions. These functions perform
+ operations on the resources to implement the semantics
+ associated with the MO.</p>
+
+ <p>For example, a system that is managed with SNMP and HTTP
+ can be structured as follows:</p>
+
<image file="../oam/snmp_model_2.gif">
- <icaption>Structure of a system managed with SNMP and HTTP</icaption>
+ <icaption>Structure of a System Managed with SNMP and HTTP</icaption>
</image>
- <p>The resources may send notifications to the manager as well.
- Examples of notifications are events and alarms. There is a
- need for the resource to generate protocol independent
- notifications. The following picture illustrates how this is
- achieved:</p>
+
+ <p>The resources can send notifications to the manager as well.
+ Examples of notifications are events and alarms. The resource
+ needs to generate protocol-independent notifications.
+ The following picture illustrates how this is achieved:</p>
+
<image file="../oam/snmp_model_3.gif">
- <icaption>Notification handling</icaption>
+ <icaption>Notification Handling</icaption>
</image>
- <p>The main idea is that the resource sends the notfications as
- Erlang terms to a dedicated <c>gen_event</c> process. Into this
- process, handlers for the different management protocols are
- installed. When an event is received by this process, it is
- forwarded to each installed handler. The handlers are
- responsible for translating the event into a notification to be
- sent over the management protocol. For example, a handler for
- SNMP would translate each event into an SNMP trap.
- </p>
+
+ <p>The main idea is that the resource sends the notifications as
+ Erlang terms to a dedicated <c>gen_event</c> process. Into this
+ process, handlers for the different management protocols are
+ installed. When an event is received by this process, it is
+ forwarded to each installed handler. The handlers are
+ responsible for translating the event into a notification to be
+ sent over the management protocol. For example, a handler for
+ SNMP translates each event into an SNMP trap.</p>
</section>
<section>
- <title>SNMP based OAM</title>
- <p>For all OAM components, SNMP adaptations are provided. Other
- adaptations may be defined in the future.
- </p>
+ <title>SNMP-Based OAM</title>
+ <p>For all OAM components, SNMP adaptations are provided. Other
+ adaptations might be defined in the future.</p>
+
<p>The OAM components, and some other OTP applications, define
- SNMP MIBs. All these MIBs are written in SNMPv2 SMI syntax, as
- defined in RFC1902. For convenience we also deliver the SNMPv1
- SMI equivalent. All MIBs are designed to be v1/v2 compatible,
- i.e. the v2 MIBs do not use any construct not available in v1.
- </p>
+ SNMP MIBs. These MIBs are written in SNMPv2 SMI syntax, as
+ defined in RFC 1902. For convenience we also deliver the SNMPv1
+ SMI equivalent. All MIBs are designed to be v1/v2 compatible,
+ that is, the v2 MIBs do not use any construct not available in
+ v1.</p>
<section>
- <title>MIB structure</title>
- <p>The top-level OTP MIB is called <c>OTP-REG</c>, and it is
- included in the <c>sasl</c> application. All other OTP mibs
- import some objects from this MIB.
- </p>
- <p>Each MIB is contained in one application. The MIB text files
- are stored under <c><![CDATA[mibs/<MIB>.mib]]></c> in the application
- directory. The generated <c>.hrl</c> files with constant
- declarations are stored under <c><![CDATA[include/<MIB>.hrl]]></c>, and
- the compiled MIBs are stored under
- <c><![CDATA[priv/mibs/<MIB>.bin]]></c>. For example, the <c>OTP-MIB</c>
- is included in the <c>sasl</c> application:
- </p>
+ <title>MIB Structure</title>
+ <p>The top-level OTP MIB is called <c>OTP-REG</c> and it is
+ included in the <c>sasl</c> application. All other OTP MIBs
+ import some objects from this MIB.</p>
+
+ <p>Each MIB is contained in one application. The MIB text
+ files are stored under <c><![CDATA[mibs/<MIB>.mib]]></c> in
+ the application directory. The generated <c>.hrl</c> files
+ with constant declarations are stored under
+ <c><![CDATA[include/<MIB>.hrl]]></c>, and the compiled MIBs
+ are stored under <c><![CDATA[priv/mibs/<MIB>.bin]]></c>.
+ For example, the <c>OTP-MIB</c> is included in the
+ <c>sasl</c> application:</p>
+
<code type="none">
sasl-1.3/mibs/OTP-MIB.mib
- include/OTP-MIB.hrl
- priv/mibs/OTP-MIB.bin</code>
- <p>An application that needs to IMPORT this mib into another
- MIB, should use the <c>il</c> option to the snmp mib compiler:
- </p>
+include/OTP-MIB.hrl
+priv/mibs/OTP-MIB.bin</code>
+
+ <p>An application that needs to import this MIB into another
+ MIB is to use the <c>il</c> option to the SNMP MIB compiler:</p>
+
<code type="none">
snmp:c("MY-MIB", [{il, ["sasl/priv/mibs"]}]).</code>
+
<p>If the application needs to include the generated
- <c>.hrl</c> file, it should use the <c>-include_lib</c>
- directive to the Erlang compiler.
- </p>
+ <c>.hrl</c> file, it is to use the <c>-include_lib</c>
+ directive to the Erlang compiler:</p>
+
<code type="none">
-module(my_mib).
-
-include_lib("sasl/include/OTP-MIB.hrl").</code>
- <p>The following MIBs are defined in the OTP system:
- </p>
- <taglist>
- <tag>OTP-REG (sasl)</tag>
- <item>
- <p>This MIB contains the top-level OTP registration
- objects, used by all other MIBs.
- </p>
- </item>
- <tag>OTP-TC (sasl)</tag>
- <item>
- <p>This MIB contains the general Textual Conventions,
- which can be used by any other MIB.
- </p>
- </item>
- <tag>OTP-MIB (sasl)</tag>
- <item>
- <p>This MIB contains objects for instrumentation of the
- Erlang nodes, the Erlang machines and the applications in
- the system.
- </p>
- </item>
- <tag>OTP-OS-MON-MIB (os_mon)</tag>
- <item>
- <p>This MIB contains objects for instrumentation of disk,
- memory and cpu usage of the nodes in the system.
- </p>
- </item>
- <tag>OTP-SNMPEA-MIB (snmp)</tag>
- <item>
- <p>This MIB contains objects for instrumentation and
- control of the extensible snmp agent itself. Note that
- the agent also implements the standard SNMPv2-MIB (or v1
- part of MIB-II, if SNMPv1 is used).
- </p>
- </item>
- <tag>OTP-EVA-MIB (eva)</tag>
- <item>
- <p>This MIB contains objects for instrumentation and
- control of the events and alarms in the system.
- </p>
- </item>
- <tag>OTP-LOG-MIB (eva)</tag>
- <item>
- <p>This MIB contains objects for instrumentation and
- control of the logs and FTP transfer of logs.
- </p>
- </item>
- <tag>OTP-EVA-LOG-MIB (eva)</tag>
- <item>
- <p>This MIB contains objects for instrumentation and
- control of the events and alarm logs in the system.
- </p>
- </item>
- <tag>OTP-SNMPEA-LOG-MIB (eva)</tag>
- <item>
- <p>This MIB contains objects for instrumentation and
- control of the snmp audit trail log in the system.
- </p>
- </item>
- </taglist>
+
+ <p>The following MIBs are defined in the OTP system:</p>
+ <list type="bulleted">
+ <item><p><c>OTP-REG)</c> (in <c>sasl</c>) contains the top-level
+ OTP registration objects, used by all other MIBs.</p></item>
+ <item><p><c>OTP-TC</c> (in <c>sasl</c>) contains the general
+ Textual Conventions, which can be used by any other MIB.</p></item>
+ <item><p><c>OTP-MIB</c> (in <c>sasl</c>) contains objects for
+ instrumentation of the Erlang nodes, the Erlang machines,
+ and the applications in the system.</p></item>
+ <item><p><c>OTP-OS-MON-MIB</c> (in <c>oc_mon</c>) contains
+ objects for instrumentation of disk, memory, and CPU use
+ of the nodes in the system.</p></item>
+ <item><p><c>OTP-SNMPEA-MIB</c> (in <c>snmp</c>)
+ contains objects for instrumentation and control of the extensible
+ SNMP agent itself. The agent also implements the standard SNMPv2-MIB
+ (or v1 part of MIB-II, if SNMPv1 is used).</p></item>
+ <item><p><c>OTP-EVA-MIB</c> (in <c>eva</c>) contains objects
+ for instrumentation and control of the events and alarms in
+ the system.</p></item>
+ <item><p><c>OTP-LOG-MIB</c> (in <c>eva</c>) contains objects
+ for instrumentation and control of the logs and FTP transfer of
+ logs.</p></item>
+ <item><p><c>OTP-EVA-LOG-MIB</c> (in <c>eva</c>) contains objects
+ for instrumentation and control of the events and alarm logs
+ in the system.</p></item>
+ <item><p><c>OTP-SNMPEA-LOG-MIB</c> (in <c>eva</c>) contains
+ objects for instrumentation and control of the SNMP audit
+ trail log in the system.</p></item>
+ </list>
+
<p>The different applications use different strategies for
- loading the MIBs into the agent. Some MIB implementations are
- code-only, while others need a server. One way, used by the
- code-only mib implementations, is for the user to call a
- function such as <c>otp_mib:init(Agent)</c> to load the MIB,
- and <c>otp_mib:stop(Agent)</c> to unload the MIB. See the
- application manual page for each application for a description
- of how to load each MIB.
- </p>
+ loading the MIBs into the agent. Some MIB implementations are
+ code-only, while others need a server. One way, used by the
+ code-only MIB implementations, is for the user to call a
+ function such as <c>otp_mib:init(Agent)</c> to load the MIB,
+ and <c>otp_mib:stop(Agent)</c> to unload the MIB. See the
+ manual page for each application for a description of how
+ to load each MIB.</p>
</section>
</section>
</chapter>