Home > Articles > Information Technology

  • Print
  • + Share This
This chapter is from the book

1.2 Policy-Based Self-Configuration

One of the most time-consuming operations in the management of any system is the initial configuration of a new installation, or the reconfiguration that needs to be performed when new requirements are received. The basic approach in self-configuration is to offer a simplified set of abstractions that the administrator needs to manipulate, while the detailed configuration of a myriad of parameters in the system are hidden to a large extent. Although there are several instances in which policy-based self-configuration mechanisms can be used, we will use the example of a hosting service provider for illustration purposes.

For the sake of simplicity of illustration, let us assume that all the customers of this service provider run their Web sites only within the premises of the service provider, and each Web site is supported by one or more instances of a Web server such as Apache or IIS. The service provider has a pool of stand-by servers that can be deployed for any customers after a proper installation of applications. Some of the customers whose Web sites draw heavy traffic may need multiple servers at the site with a load-balancer in front of them, whereas customers whose sites are not as popular may be sharing a single server with other customers. The service provider can set up a hosting Web site with a set of routers, virtual LAN switches, load-balancers, and server blades that can enable this service. All of these devices make up the target system of the policies. Because most hosting service providers will have system administrators who can write scripts to automate common processes, we further assume that they will have developed a series of scripts so that they can automatically allocate a server from a shared pool to a specific customer, and conversely return a server back to the pool once the busy period is over or the contract with a corresponding customer expires. A similar script can be developed for automating the addition or removal of a new virtual server for smaller customers. A more detailed discussion about how such a system can be developed can be found in [APPL].

When a new customer is added or an existing customer removed, the configuration of the site needs to be changed according to the change in the set of customers being supported. If there are mechanisms available for servers to be assigned in an automated manner to different customers from a shared pool, then the number of servers or processors assigned to a specific customer may change depending on the intensity of traffic to that site. Sometimes the hosting site may want to enforce limits on how much bandwidth a customer’s site can use in a month, and may want to reconfigure the site to restrict the throughput available to a hosted site if the traffic to that site exceeds predetermined thresholds. Let us assume that the service provider characterizes its customers into two groups: large and small. It may instantiate policies for self-configuration of its site, which may look like the following:

If a large customer has 75% or more utilization of all its servers, and
has less than its maximum allowed number of servers, then allocate an
additional server from the free pool to it.

If a large customer has 30% utilization or less on all its servers, and
has more than its minimum allowed number of servers, then remove a
server from it to the free pool.

If a small customer has reached 125% of the monthly bandwidth allowed
to its site, then disallow further access to the site for the rest of
the month.

If the addition of a new small customer causes the number of small
customers at a server to exceed a threshold, allocate a new server from
the free pool and migrate half of the existing small customers to that
new server.

In the preceding example, we can identify several attributes: utilization rate, number of servers, numbers of free servers, monthly bandwidth, and so on. Each of the policies provides a constraint on the new configuration of the system. The behavior of the system (allocation of servers between customers and the free pool) is constrained to conform to the guidelines set earlier. The guidelines may change based on the experience of the service provider—instead of using server utilization, it may opt to use the bandwidth consumed as a trigger for reallocation of servers, or it may use a combination of both. Also it may choose to not block small customers that exceed their throughput limits, opting instead to charge them an additional amount of money. Looking back at the discussion of policy types, we can recognize all of these policies as instances of action policies.

These sets of policies allow the administrator to manage the customers using attributes (utilization, number of servers, bandwidth rate, and so on) that are decoupled from the details of actual server configuration (their IP addresses, commands to control bandwidth, their operating system version, and so forth). Thus, the goal is to allow administrators to view system management in terms of the abstracted attributes that lets them specify what needs to be done, leaving the details of how it can be done to the underlying mechanisms that support a policy-based management system. Policies do not describe the mechanisms for the reallocation of the servers, the migration of customers to the new server, or disabling access to any site. However, assuming that appropriate scripts to do these tasks exist, the ability to specify the policies and invoke the right scripts for the required actions would enable the system to self-configure itself in accordance with the wishes of the service provider.

Building a policy enabled management system for this scenario would involve three steps:

  1. Determining a way to specify the policies.
  2. Enabling support within the system to interpret and enforce the policies.
  3. Invoking a mechanism to distribute policies from the entity specifying them to the entities interpreting and enforcing them.

To specify policies, a language that can capture the semantics of policies needs to be selected and a tool to specify the policies needs to be developed. Later we will discuss that having an information model is also an important aspect of the specification process in addition to selecting a policy language. The system management software that allocates and reallocates servers needs to understand policies specified in this language so that it can enforce the policies by transferring the servers under various operation conditions. Finally, it is important that the policy specification from a system administrator is distributed to a system that can enforce the policies. In this particular case, if there is only one instance of the system management software, the third problem of distribution is trivial because there is no need for synchronizing among multiple copies of the policy.

  • + Share This
  • 🔖 Save To Your Account

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.

Overview


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information


To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

Newsletters

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information


Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.

Security


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

Children


This site is not directed to children under the age of 13.

Marketing


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information


If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

Choice/Opt-out


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information


Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents


California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure


Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

Links


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact


Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice


We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020