computer science

Security service (telecommunication)

Security service (telecommunication) is a computer science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Security service (telecommunication) rather than just read about it. In short: Security service is a service, provided by a layer of communicating open systems, which ensures adequate security of the systems or of data transfers as defined by ITU-T X.800 Recommendation. X.800 and ISO 7498-2 (Information processing systems – Open systems interconnection – Basic Reference Model – Part 2: Security architecture) are technically aligned.

Key takeaways

Security service (telecommunication) belongs to computer science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Security service (telecommunication) to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Security service (telecommunication) from memory before moving on to harder problems.

Reference excerpt

Security service is a service, provided by a layer of communicating open systems, which ensures adequate security of the systems or of data transfers as defined by ITU-T X.800 Recommendation. X.800 and ISO 7498-2 (Information processing systems – Open systems interconnection – Basic Reference Model – Part 2: Security architecture) are technically aligned. This model is widely recognized

A more general definition is in CNSS Instruction No. 4009 dated 26 April 2010 by Committee on National Security Systems of United States of America:

A capability that supports one, or more, of the security requirements (Confidentiality, Integrity, Availability). Examples of security services are key management, access control, and authentication. Another authoritative definition is in W3C Web service Glossary adopted by NIST SP 800-95:

A processing or communication service that is provided by a system to give a specific kind of protection to resources, where said resources may reside with said system or reside with other systems, for example, an authentication service or a PKI-based document attribution and authentication service. A security service is a superset of AAA services. Security services typically implement portions of security policies and are implemented via security mechanisms.

Basic security terminology

Information security and Computer security are disciplines that are dealing with the requirements of Confidentiality, Integrity, Availability, the so-called CIA Triad, of information asset of an organization (company or agency) or the information managed by computers respectively. There are threats that can attack the resources (information or devices to manage it) exploiting one or more vulnerabilities. The resources can be protected by one or more countermeasures or security controls. So security services implement part of the countermeasures, trying to achieve the security requirements of an organization.

Basic OSI terminology

In order to let different devices (computers, routers, cellular phones) to communicate data in a standardized way, communication protocols had been defined. The ITU-T organization published a large set of protocols. The general architecture of these protocols is defined in recommendation X.200. The different means (air, cables) and ways (protocols and protocol stacks) to communicate are called a communication network. Security requirements are applicable to the information sent over the network. The discipline dealing with security over a network is called Network security. The X.800 Recommendation:

provides a general description of security services and related mechanisms, which may be provided by the Reference Model; and defines the positions within the Reference Model where the services and mechanisms may be provided. This Recommendation extends the field of application of Recommendation X.200, to cover secure communications between open systems. According to X.200 Recommendation, in the so-called OSI Reference model there are 7 layers, each one is generically called N layer. The N+1 entity ask for transmission services to the N entity. At each level two entities (N-entity) interact by means of the (N) protocol by transmitting Protocol Data Units (PDU). Service Data Unit (SDU) is a specific unit of data that has been passed down from an OSI layer, to a lower layer, and has not yet been encapsulated into a PDU, by the lower layer. It is a set of data that is sent by a user of the services of a given layer, and is transmitted semantically unchanged to a peer service user . The PDU at any given layer, layer 'n', is the SDU of the layer below, layer 'n-1'. In effect the SDU is the 'payload' of a given PDU. That is, the process of changing a SDU to a PDU, consists of an encapsulation process, performed by the lower layer. All the data contained in the SDU becomes encapsulated within the PDU. The layer n-1 adds headers or footers, or both, to the SDU, transforming it into a PDU of layer n-1. The added headers or footers are part of the process used to make it possible to get data from a source to a destination.

OSI security services description The following are considered to be the security services which can be provided optionally within the framework of the OSI Reference Model. The authentication services require authentication information comprising locally stored information and data that is transferred (credentials) to facilitate the authentication:

… excerpt ends here. Continue reading the full article.

Worked examples

Example 1 — a first encounter with Security service (telecommunication)

Start with the simplest possible case. Write down what Security service (telecommunication) claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Security service (telecommunication) before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Security service (telecommunication) ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Security service (telecommunication)

In research: Security service (telecommunication) appears in computer science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Security service (telecommunication) in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Security service (telecommunication) is common in secondary-school and first-year university syllabi. It links to neighbouring topics Computer network security, ISO standards, ITU-T X Series Recommendations, so understanding it makes those chapters shorter.
In everyday life: Look for Security service (telecommunication) outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Security service (telecommunication) in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Security service (telecommunication) means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Security service (telecommunication) out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Security service (telecommunication) in simple terms?

Why does Security service (telecommunication) matter?

Because it connects several computer science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Security service (telecommunication)?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Security service (telecommunication).