awe chenkhov

Pengertian Frame Relay

2009-11-12T23:21:00.000-08:00

Pengertian

Frame Relay adalah protokol WAN yang beroperasi pada layer pertama dan kedua dari model OSI, dan dapat diimplementasikan pada beberapa jenis interface jaringan. Frame relay adalah teknologi komunikasi berkecepatan tinggi yang telah digunakan pada ribuan jaringan di seluruh dunia untuk menghubungkan LAN, SNA, Internet dan bahkan aplikasi suara/voice.

Frame relay adalah cara mengirimkan informasi melalui wide area network (WAN) yang membagi informasi menjadi frame atau paket. Masing-masing frame mempunyai alamat yang digunakan oleh jaringan untuk menentukan tujuan. Frame-frame akan melewati switch dalam jaringan frame relay dan dikirimkan melalui virtual circuit sampai tujuan.

Fitur Frame Relay

Beberapa fitur frame relay adalah sebagai berikut:

Kecepatan tinggi
Bandwidth Dinamik
Performansi yang baik/ Good Performance
Overhead yang rendah dan kehandalah tinggi (High Reliability)

Perangkat Frame Relay

Sebuah jaringan frame relay terdiri dari endpoint (PC, server, komputer host), perangkat akses frame relay (bridge, router, host, frame relay access device/FRAD) dan perangkat jaringan (packet switch, router, multiplexer T1/E1). Perangkat-perangkat tersebut dibagi menjadi dua kategori yang berbeda:

DTE: Data Terminating Equipment

DTE adalah node, biasanya milik end-user dan perangkat internetworking. Perangkat DTE ini mencakup endpoint dan perangkat akses pada jaringan Frame Relay. DTE yang memulai suatu pertukaran informasi.

DCE: Data Communication Equipment

DCE adalah perangkat internetworking pengontrol carrier. Perangkat-perangkat ini juga mencakup perangkat akses, teatpi terpusat di sekitar perangkat jaringan. DCE merespon pertukaran informasi yang dimulai oleh perangkat DTE.

Virtual Circuit (VC) Frame Relay

Pengantar Virtual Circuit (VC)

Suatu jaringan frame relay sering digambarkan sebagai awan frame relay (frame relay cloud), karena jaringan frame relay network bukan terdiri dari satu koneksi fisik antara endpoint dengan lainnya, melainkan jalur/path logika yang telah didefinisikan dalam jaringan. Jalur ini didasarkan pada konsep virtual circuit (VC). VC adalah dua-arah (two-way), jalur data yang didefinisikan secara software antara dua port yang membentuk saluran khusur (private line) untuk pertukaran informasi dalam jaringan.Terdapat dua tipe virtual circuit (VC):

Switched Virtual Circuit (SVC)
Permanent Virtual Circuit (PVC)

Switched Virtual Circuit (SVC)

Switched Virtual Circuits (SVC), adalah koneksi sementara yang digunakan ketika terjadi transfer data antar perangkat DTE melewati jaringan Frame Relay. Terdapat empat status pada sebuah SVC:

Empat status pada SVC :

Call setup
Data transfer
Idling
Call termination

Status SVC

Call Setup

Call Setup: Dalam status awal memulai komunikasi, virtual circuit (vc) antar dua perangkat DTE Frame Relay terbentuk.

Data Transfer

Data Transfer: Kemudian, data ditransfer antar perangkat DTE melalui virtual circuit (vc).

Idling

Idling: Pada kondisi idling, koneksi masih ada dan terbuka, tetapi transfer data telah berhenti.

Call Termination

Call Termination: Setelah koneksi idle untuk beberapa perioda waktu tertentu, koneksi antar dua DTE akan diputus.

Permanent Virtual Circuit (PVC)

PVC adalah jalur/path tetap, oleh karena itu tidak dibentuk berdasarkan permintaan atau berdasarkan call-by-call. Walaupun jalur aktual melalui jaringan berdasarkan variasi waktu ke waktu (TDM) tetapi circuit dari awal ke tujuan tidak akan berubah. PVC adalah koneksi permanen terus menerus seperti dedicated point-to-point circuit.

Perbandingan PVC vs SVC

PVC lebih populer karena menyediakan alternatif yang lebih murah dibandingkan leased line. Berbeda dengan SVC, PVC tidak pernah putus (disconnect), oleh karena itu, tidak pernah terdapat status call setup dan termination. Hanya terdapat 2 status :

Data transfer
Idling

Format Frame Frame Relay
Struktur Frame

Dalam sebuah frame Frame Relay, paket data user tidak berubah, Frame Relay menambahkan header dua-byte pada paket. Struktur frame adalah sebagai berikut:

Flags - menandakan awal dan akhir sebuah frame
Address - terdiri dari DCLI (data link connection identifier), Extended Address (EA), C/R, dan Congestion control information

DLCI Value - menunjukkan nilai dari â€œdata link connection identifier. Terdiri dari 10 bit pertama dari â€œAddress field/alamat.
Extended Address (EA) - menunjukkan panjang dari â€œAddress field, yang panjangnya 2 bytes.
C/R - Bit yang mengikuti byte DLCI dalam Address field. Bit C/R tidak didefinisikan saat ini.
Congestion Control - Tiga bit yang mengontrol mekanisme pemberitahuan antrian (congestion) Frame Relay.

Data - terdiri dari data ter-encapsulasi dari upper layer yang panjangnya bervariasi.
FCS - (Frame Check Sequence) terdiri dari informasi untuk meyakinkan keutuhan frame.

Pendeteksi Error pada Frame Relay

Frame Relay menerapkan pendeteksi error pada saluran transmisi, tetapi Frame Relay tidak memperbaiki error. Jika terdeteksi sebuah error, frame akan dibuang (discarded) dari saluran transmisi. Proses seperti ini disebut :

Cyclic redundancy check (CRC)

Cyclic redundancy check (CRC) adalah sebuah skema yang mendeteksi dan membuang data yang rusak (corrupted). Fungsi yang memperbaiki error (Error-correction) (seperti pengiriman kembali/retransmission data) diserahkan pada protokol layer yang lebih tinggi (higher-layer).

Implementasi Frame Relay

Frame Relay dapat digunakan untuk jaringan publik dan jaringan private perusahaan atau organisasi.

Jaringan Publik

Pada jaringan publik Frame Relay, Frame Relay switching equipment (DCE) berlokasi di kantor pusat (central) perusahaan penyedia jaringan telekomunikasi. Pelanggan hanya membayar biaya berdasarkan pemakain jaringan, dan tidak dibebani administrasi dan pemeliharan perangkat jaringan Frame Relay.

Jaringan Private

Pada jaringan private Frame Relay, administrasi dan pemeliharaan jaringan adalah tanggungjawab perusahaan (private company). Trafik Frame Relay diteruskan melalui interface Frame Relay pada jaringan data. Trafik Non-Frame Relay diteruskan ke jasa atau aplikasi yang sesuai (seperti private branch exchange [PBX] untuk jasa telepon atau untuk aplikasi video-teleconferencing).

Sumber : http://i-networking.net/archives/16

Contoh Surat Lamaran Kerja

2009-11-12T23:06:00.000-08:00

Jl. Raya bekasi 01
Bekasi
Bekasi Barat 17133

Phone : 021 - 88852859

August 17th, 2009

Attention To:
Mr. Joko
PT. Damai Indonesia
Jl. Sudirman
jakarta

Dear Mr. Joko,

I am a graduate student in Computer Science at Indonesia University, and I will be awarded an M.S. degree in July 2007. I am currently looking for a position related to Database/Graphics Package Design in the research and development department of a major company.

Before coming to Indonesia University, I designed, supervised, and completed a CAD system. The function covers vector, character and curve generation, windowing, shading, and transformations.

At Indonesia University, my research work involves Compilation of Relational Queries into Network DML. To enhance my background, I have taken some courses in computer graphics and database, and I have experience in and an understanding of the design of databases. With this b background, I certainly believe that I am competent to meet challenging tasks and can make a good contribution to your company.

Enclosed is my resume, which indicates in some detail my training and experience. I sincerely hope that my qualifications are of interest to you and that an interview might be arranged at your convenience.

Thank you for your consideration. I look forward to hearing from you soon.

Sincerely yours,

Lampard

Pronouns

2009-11-12T22:57:00.000-08:00

Definition
Generally (but not always) pronouns stand for (pro + noun) or refer to a noun, an individual or individuals or thing or things (the pronoun's antecedent) whose identity is made clear earlier in the text. For instance, we are bewildered by writers who claim something like

    * They say that eating beef is bad for you.

They is a pronoun referring to someone, but who are they? Cows? whom do they represent? Sloppy use of pronouns is unfair.
Not all pronouns will refer to an antecedent, however.

    * Everyone here earns over a thousand dollars a day.

The word "everyone" has no antecedent.
The problem of agreement between a pronoun and its antecedent and between a pronoun and its verb is treated in another section on Pronoun-Antecedent Consistency. The quizzes on pronoun usage are also listed at the end of that section.
This section will list and briefly describe the several kinds of pronouns.

PRONOUNS
KINDS OF PRONOUNS: Personal || Demonstrative || Indefinite || Relative ||
Reflexive || Intensive || Interrogative || Reciprocal
Personal Pronouns
Unlike English nouns, which usually do not change form except for the addition of an -s ending to create the plural or the apostrophe + s to create the possessive, personal pronouns (which stand for persons or things) change form according to their various uses within a sentence. Thus I is used as the subject of a sentence (I am happy.), me is used as an object in various ways (He hit me. He gave me a book. Do this for me.), and my is used as the possessive form (That's my car.) The same is true of the other personal pronouns: the singular you and he/she/it and the plural we, you, and they. These forms are called cases. An easily printable chart is available that shows the various Cases of the Personal Pronouns.

Personal pronouns can also be characterized or distinguished by person. First person refers to the speaker(s) or writer(s) ("I" for singular, "we" for plural). Second person refers to the person or people being spoken or written to ("you" for both singular and plural). Third personCases of the Personal Pronouns. As you will see there, each person can change form, reflecting its use within a sentence. Thus, "I" becomes "me" when used as an object ("She left me") and "my" when used in its possessive role (That's my car"); "they" becomes "them" in object form ("I like them") and "their" in possessive ("That's just their way"). refers to the person or people being spoken or written about ("he," "she," and "it" for singular, "they" for plural). The person of a pronoun is also demonstrated in the chart

When a personal pronoun is connected by a conjunction to another noun or pronoun, its case does not change. We would write "I am taking a course in Asian history"; if Talitha is also taking that course, we would write "Talitha and I are taking a course in Asian history." (Notice that Talitha gets listed before "I" does. This is one of the few ways in which English is a "polite" language.) The same is true when the object form is called for: "Professor Vendetti gave all her books to me"; if Talitha also received some books, we'd write "Professor Vendetti gave all her books to Talitha and me." For more on this, see cases of pronouns.

When a pronoun and a noun are combined (which will happen with the plural first- and second-person pronouns), choose the case of the pronoun that would be appropriate if the noun were not there.

    * We students are demanding that the administration give us two hours for lunch.
    * The administration has managed to put us students in a bad situation.

With the second person, we don't really have a problem because the subject form is the same as the object form, "you":

    * "You students are demanding too much."
    * "We expect you students to behave like adults."

Among the possessive pronoun forms, there is also what is called the nominative possessive: mine, yours, ours, theirs.

    * Look at those cars. Theirs is really ugly; ours is beautiful.
    * This new car is mine.
    * Mine is newer than yours.

Demonstrative Pronouns
The family of demonstratives (this/that/these/those/such) can behave either as pronouns or as determiners.
As pronouns, they identify or point to nouns.

    * That is incredible! (referring to something you just saw)
    * I will never forget this. (referring to a recent experience)
    * Such is my belief. (referring to an explanation just made)

As determiners, the demonstratives adjectivally modify a noun that follows. A sense of relative distance (in time and space) can be conveyed through the choice of these pronouns/determiners:

    * These [pancakes sitting here now on my plate] are delicious.
    * Those [pancakes that I had yesterday morning] were even better.
    * This [book in my hand] is well written;
    * that [book that I'm pointing to, over there, on the table] is trash.

A sense of emotional distance or even disdain can be conveyed with the demonstrative pronouns:

    * You're going to wear these?
    * This is the best you can do?

Pronouns used in this way would receive special stress in a spoken sentence.
When used as subjects, the demonstratives, in either singular or plural form, can be used to refer to objects as well as persons.

    * This is my father.
    * That is my book.

In other roles, however, the reference of demonstratives is non-personal. In other words, when referring to students, say, we could write "Those were loitering near the entrance during the fire drill" (as long as it is perfectly clear in context what "those" refers to). But we would not write "The principal suspended those for two days"; instead, we would have to use "those" as a determiner and write "The principal suspended those students for two days."

Relative Pronouns
The relative pronouns (who/whoever/which/that) relate groups of words to nouns or other pronouns (The student who studies hardest usually does the best.). The word who connects or relates the subject, student, to the verb within the dependent clause (studies). Choosing correctly between which and that and between who and whom leads to what are probably the most Frequently Asked Questions about English grammar. For help with which/that, refer to the Notorious Confusables article on those words (including the hyperlink to Michael Quinion's article on this usage and the links to relevant quizzes). Generally, we use "which" to introduce clauses that are parenthetical in nature (i.e., that can be removed from the sentence without changing the essential meaning of the sentence). For that reason, a "which clause" is often set off with a comma or a pair of commas. "That clauses," on the other hand, are usually deemed indispensable for the meaning of a sentence and are not set off with commas. The pronoun which refers to things; who (and its forms) refers to people; thatwho/whom refer to the section on Consistency. We also recommend that you take the quizzes on the use of who and whom at the end of that section. usually refers to things, but it can also refer to people in a general kind of way. For help with

The expanded form of the relative pronouns — whoever, whomever, whatever — are known as indefinite relative pronouns. A couple of sample sentences should suffice to demonstrate why they are called "indefinite":

    * The coach will select whomever he pleases.
    * He seemed to say whatever came to mind.
    * Whoever crosses this line first will win the race.

What is often an indefinite relative pronoun:

    * She will tell you what you need to know.

Indefinite Pronouns
The indefinite pronouns (everybody/anybody/somebody/all/each/every/some/none/one) do not substitute for specific nouns but function themselves as nouns (Everyone is wondering if any is left.)
One of the chief difficulties we have with the indefinite pronouns lies in the fact that "everybody" feels as though it refers to more than one person, but it takes a singular verb. (Everybody is accounted for.) If you think of this word as meaning "every single body," the confusion usually disappears. The indefinite pronoun none can be either singular or plural, depending on its context. None is nearly always plural (meaning "not any") except when something else in the sentence makes us regard it as a singular (meaning "not one"), as in "None of the food is fresh." Some can be singular or plural depending on whether it refers to something countable or noncountable. Refer to the section on Pronoun Consistency for help on determining the number of the indefinite pronouns (and the number [singular/plural] of the verbs that accompany them). There is a separate section on the uses of the pronoun one.
There are other indefinite pronouns, words that double as Determiners:

    enough, few, fewer, less, little, many, much, several, more, most, all, both, every, each, any, either, neither, none, some

    * Few will be chosen; fewer will finish.
    * Little is expected.

See the section on Pronoun Consistency for help in determining the number (singular/plural) characteristics of these pronouns.

Intensive Pronouns
The intensive pronouns (such as myself, yourself, herself, ourselves, themselves) consist of a personal pronoun plus self or selves and emphasize a noun. (I myself don't know the answer.) It is possible (but rather unusual) for an intensive pronoun to precede the noun it refers to. (Myself, I don't believe a word he says.)

Reflexive Pronouns
The reflexive pronouns (which have the same forms as the intensive pronouns) indicate that the sentence subject also receives the action of the verb. (Students who cheat on this quiz are only hurting themselves. You paid yourself a million dollars? She encouraged herself to do well.) What this means is that whenever there is a reflexive pronoun in a sentence there must be a person to whom that pronoun can "reflect." In other words, the sentence "Please hand that book to myself" would be incorrect because there is no "I" in that sentence for the "myself" to reflect to (and we would use "me" instead of "myself"). A sentence such as "I gave that book to myself for Christmas" might be silly, but it would be correct.
Be alert to a tendency to use reflexive pronoun forms (ending in -self) where they are neither appropriate nor necessary. The inappropriate reflexive form has a wonderful name: the untriggered reflexive. "Myself" tends to sound weightier, more formal, than little ol' me or I, so it has a way of sneaking into sentences where it doesn't belong.

    * Bob and myself I are responsible for this decision.
    * These decisions will be made by myself me.
    * If you have any questions, please contact myself me or Bob Jones.

When pronouns are combined, the reflexive will take either the first person

    * Juanita, Carlos, and I have deceived ourselves into believing in my uncle.

or, when there is no first person, the second person:

    * You and Carlos have deceived yourselves.

The indefinite pronoun (see above) one has its own reflexive form ("One must have faith in oneself."), but the other indefinite pronouns use either himself or themselves as reflexives. (There is an entire page on the pronoun one.) It is probably better to pluralize and avoid the clumsy himself or herself construction.

    * No one here can blame himself or herself.
    * The people here cannot blame themselves.

Interrogative Pronouns
The interrogative pronouns (who/which/what) introduce questions. (What is that? Who will help me? Which do you prefer?) Which is generally used with more specific reference than what. If we're taking a quiz and I ask "Which questions give you the most trouble?", I am referring to specific questions on that quiz. If I ask "What questions give you most trouble"? I could be asking what kind of questions on that quiz (or what kind of question, generically, in general) gives you trouble. The interrogative pronouns also act as Determiners: It doesn't matter which beer you buy. He doesn't know whose car he hit. In this determiner role, they are sometimes called interrogative adjectives.

Like the relative pronouns, the interrogative pronouns introduce noun clauses, and like the relative pronouns, the interrogative pronouns play a subject role in the clauses they introduce:

    * We know who is guilty of this crime.
    * I already told the detective what I know about it.

Reciprocal Pronouns
The reciprocal pronouns are each other and one another. They are convenient forms for combining ideas. If Bob gave Alicia a book for Christmas and Alicia gave Bob a book for Christmas, we can say that they gave each other books (or that they gave books to each other).

    * My mother and I give each other a hard time.

If more than two people are involved (let's say a whole book club), we would say that they gave one another books. This rule (if it is one) should be applied circumspectly. It's quite possible for the exchange of books within this book club, for example, to be between individuals, making "each other" just as appropriate as "one another."
Reciprocal pronouns can also take possessive forms:

    * They borrowed each other's ideas.
    * The scientists in this lab often use one another's equipment.

Two authorities used for this section on pronouns are: The Little, Brown Handbook by H. Ramsay Fowler and Jane E. Aaron, & Kay Limburg. 6th ed. HarperCollins: New York. 1995. By permission of Addison-Wesley Educational Publishers Inc. and A University Grammar of English by Randolph Quirk and Sidney Greenbaum. Longman Group: Essex, England. 1993. Used with permission.

Sumber : http://grammar.ccc.commnet.edu

Simple Present and Present Progressive

2009-11-12T20:39:00.000-08:00

Simple Present

FORM

[VERB] + s/es in third person

Examples:

You speak English.
Do you speak English?
You do not speak English.

Complete List of Simple Present Forms

USE 1 Repeated Actions

Use the Simple Present to express the idea that an action is repeated or usual. The action can be a habit, a hobby, a daily event, a scheduled event or something that often happens. It can also be something a person often forgets or usually does not do.

Examples:

I play tennis.
She does not play tennis.
Does he play tennis?
The train leaves every morning at 8 AM.
The train does not leave at 9 AM.
When does the train usually leave?
She always forgets her purse.
He never forgets his wallet.
Every twelve months, the Earth circles the Sun.
Does the Sun circle the Earth?

USE 2 Facts or Generalizations

The Simple Present can also indicate the speaker believes that a fact was true before, is true now, and will be true in the future. It is not important if the speaker is correct about the fact. It is also used to make generalizations about people or things.

Examples:

Cats like milk.
Birds do not like milk.
Do pigs like milk?
California is in America.
California is not in the United Kingdom.
Windows are made of glass.
Windows are not made of wood.
New York is a small city. It is not important that this fact is untrue.

USE 3 Scheduled Events in the Near Future

Speakers occasionally use Simple Present to talk about scheduled events in the near future. This is most commonly done when talking about public transportation, but it can be used with other scheduled events as well.

Examples:

The train leaves tonight at 6 PM.
The bus does not arrive at 11 AM, it arrives at 11 PM.
When do we board the plane?
The party starts at 8 o'clock.
When does class begin tomorrow?

USE 4 Now (Non-Continuous Verbs)

Speakers sometimes use the Simple Present to express the idea that an action is happening or is not happening now. This can only be done with Non-Continuous Verbs and certain Mixed Verbs.

Examples:

I am here now.
She is not here now.
He needs help right now.
He does not need help now.
He has his passport in his hand.
Do you have your passport with you?

ADVERB PLACEMENT

The examples below show the placement for grammar adverbs such as: always, only, never, ever, still, just, etc.

Examples:

You only speak English.
Do you only speak English?

ACTIVE / PASSIVE

Examples:

Once a week, Tom cleans the car. Active
Once a week, the car is cleaned by Tom. Passive

Present Continuous

FORM

[am/is/are + present participle]

Examples:

You are watching TV.
Are you watching TV?
You are not watching TV.

Complete List of Present Continuous Forms

USE 1 Now

Use the Present Continuous with Normal Verbs to express the idea that something is happening now, at this very moment. It can also be used to show that something is not happening now.

Examples:

You are learning English now.
You are not swimming now.
Are you sleeping?
I am sitting.
I am not standing.
Is he sitting or standing?
They are reading their books.
They are not watching television.
What are you doing?
Why aren't you doing your homework?

USE 2 Longer Actions in Progress Now

In English, "now" can mean: this second, today, this month, this year, this century, and so on. Sometimes, we use the Present Continuous to say that we are in the process of doing a longer action which is in progress; however, we might not be doing it at this exact second.

Examples: (All of these sentences can be said while eating dinner in a restaurant.)

I am studying to become a doctor.
I am not studying to become a dentist.
I am reading the book Tom Sawyer.
I am not reading any books right now.
Are you working on any special projects at work?
Aren't you teaching at the university now?

USE 3 Near Future

Sometimes, speakers use the Present Continuous to indicate that something will or will not happen in the near future.

Examples:

I am meeting some friends after work.
I am not going to the party tonight.
Is he visiting his parents next weekend?
Isn't he coming with us tonight?

USE 4 Repetition and Irritation with "Always"

The Present Continuous with words such as "always" or "constantly" expresses the idea that something irritating or shocking often happens. Notice that the meaning is like Simple Present, but with negative emotion. Remember to put the words "always" or "constantly" between "be" and "verb+ing."

Examples:

She is always coming to class late.
He is constantly talking. I wish he would shut up.
I don't like them because they are always complaining.

Sumber : http://www.englishpage.com

Articles and Determiners

2009-11-12T20:25:00.000-08:00

Articles and Determiners

Part 1

English sometimes uses "articles" - the (the definite article) and a/an (the indefinite articles) - before nouns. Many languages (Asian and Eastern European, for example) do not use equivalent words, thus causing many problems for learners of English. If you use articles incorrectly, or don't use them at all, your tutors will probably understand your writing, but many will find the misuse extremely irritating, which in some cases could affect your mark. It is important, therefore, that you make an effort to use articles correctly.

The biggest problem is probably when students don't write an article when they need to. Here's a simplified guide which should cover most of these cases.

Step 1

First, it is important that you recognise the difference between countable and uncountable nouns.

A countable noun is one which can be made plural, almost always by the addition of '-s' or '-es'. For example,

table - tables ; report - reports ; match - matches

An uncountable noun cannot be made plural. For example:

traffic; pollution; information

Some nouns can be countable or uncountable. For example, glass is uncountable when it refers to the material (this glass is extremely fragile) or countable when referring to wine glasses, for instance.

If you're not sure, check in a good dictionary.

Step 2

Remember this golden rule:

If the noun is COUNTABLE and SINGULAR it must almost always be preceded by an article (or some other 'determiner', such as this, his etc).

If you apply this rule while you are writing or proofreading your work, you should make far fewer mistakes. Remember that the noun may be preceded by an adjective or may be a 'compound noun' made up of two or more words.

Look at this sentence:

UK mobile phone market has been flourishing since the 1990s.

The first noun, here the subject of the sentence, is UK mobile phone market. Is it countable? Yes, you can say markets. Is it singular here? Yes again, so there must be an article or determiner:

The UK mobile phone market has been flourishing since the 1990s.

If you're not sure when to use the and when to use a/an, go to Step 3.

Step 3

The is the definite article, which means that it is used when the writer expects that the reader knows which particular thing or person the writer is referring to.

A is the indefinite article and is used when things or people are referred to which are not already known to the reader.

Compare:

Birmingham has a large fish market. (The first time the market has been mentioned, so 'a')
The market is closed on Mondays. (We now know which market, so 'the')

Also note:

Some and any are often used as the plural of a/an.

An is used before words which begin with a vowel sound, not simply a vowel. (eg, an hour, an SSDD office, an MA; but, a university).

Part 2

Unfortunately, it's not quite as simple as the above. Here is some further guidance.

If you speak a Western European language, then article usage is probably very similar in English. You might find the following rules useful, however:

1 When we are talking about things or people in general, the is not normally used if the noun is plural or uncountable.

For example:

People are strange. (NOT the people)
Traffic is a problem in most countries. (NOT the traffic)

If you want to refer to particular traffic, however, you would then use the article:

The traffic was terrible this morning.

2 We use a/an when we are classifying people or objects into groups or types, a good example being jobs:

My father's an architect.
I use my computer as a fax machine.

3 Some nouns are uncountable in English - and therefore cannot be used with a/an - but may be countable in other languages. For example:

advice, information, weather, progress, knowledge, equipment, news, research, work

You cannot say: Let me give you an advice (better: some advice)

1 THE

As you have seen, the is used when the reader (or listener) already knows, or can guess, what the writer (or speaker) is talking about. Compare:

I saw a really good film at the weekend (the listener doesn't know yet what film)
The film was set in Elizabethan times. (now the listener does know which film).

Similarly, the is used if we're talking about something unique, if there's only one of them, either in the world as a whole, or in our environment:

The Earth revolves around the sun.
The centre of Birmingham was closed due to a bomb scare.

The is almost always used with superlatives, and with words such as first, last and only:

That was the most expensive wine I've ever drunk.
Thatcher is the only woman Prime Minister this country has ever had.

The is not used with possessives:

The results of our experiments were very encouraging. (NOT ~~the our~~)

With a few exceptions, the is not used with proper names:

Could I speak to Vicky? (NOT the Vicky)
Society is changing rapidly in parts of China. (NOT the China)

2 A/AN

A/an are usually used with singular, countable nouns. The word one is not interchangeable: we usually use one when there is some connection with number, i.e. one, not two, three or four.

We carried out a survey amongst Birmingham City University students. (NOT one survey, unless you did several)

You cannot use a/an with an adjective alone.

You can't say Do you like my watch? ~~It's an expensive~~.
You say It's expensive or It's an expensive one.

Remember that the use of an depends on pronunciation, not spelling. So:

An SOS message was received by the coastguards.
It's an honour to represent my country.
Birmingham City University is a university situated on several sites.

Sometimes countable nouns are considered to be uncountable and used without an article. This happens quite often with places/institutions, for example: school, university, church, prison, hospital

I went to school in Birmingham
She's in hospital having a minor operation on her leg.
He was sent to prison for 10 years.

Note that in these examples I went to school as a pupil; She's in hospital as a patient; he went to prison as a prisoner. If you use similar expressions with an article, then the meaning changes; instead, you are in the place as a visitor, or you work there:

We're going to the school to see my daughter's teacher.
I went to the hospital to visit my uncle.

Other phrases which do not use an article include:
on foot, by car/bus/train etc,
to/in/from town, to/at/from home
by day, at night

Do not use an article when you are referring to tables, figures, pages, appendices, chapters or sections in your written work.
Table 3 shows the percentage of ...
As can be seen in Fig.8, ...
The results of the survey can be found in Appendix 1.

Do not use an article with a noun after an '-s' posssessive.
The Constitution used in America = America's constitution (NOT the America's constitution)

Articles are not used with days and months, unless you are talking about a particular day or month. So:
The agreement was signed in November.
The examination will take place on Thursday.
Courses start on Monday. The Monday I intended to start, however, was a public holiday.

Note the following when talking about television, radio, cinema and the theatre.
Do not use an article with television when you are referring to the medium.
Television has become a very powerful way of influencing people.
The President made his statement on television.

Do use an article, however, if you are referring to a television set:
We have a vase of flowers on the television.
Articles are usually used with radio, cinema and theatre, although we do also say Radio is becoming less important as a medium.

The is not used with titles which include the name of the person:
The professor introduced himself to the audience.
Professor Philpot will be retiring at the end of the year.
Queen Elizabeth has says she will never abdicate.

We usually uses possessives rather than the when we talk about parts of the body:
He hit his head getting into the car.
They all crossed their fingers before starting.

Sumber : http://www.englishpage.com

TDM, FDM, CDM

2009-11-11T00:36:00.000-08:00

MULTIPLEXING

Pembagian suatu saluran komunikasi untuk dipakai secara bersama diistilahkan
sebagai multiplexing
Keuntungannya :

* Komputer host hanya butuh satu port I/O untuk banyak terminal
* Hanya satu line transmisi yang dibutuhkan

Tiga teknik multiplexing

· Frequency-Division Multiplexing (FDM), paling umum dipakai untuk radio
atau TV

· Time-Division Multiplexing (TDM) atau synchronous TDM, dipakai untuk
multiplexing digital voice dan banyak digunakan untuk menggabungkan
aliran suara digital dan aliran data
· Peningkatan efisiensi Synchronous TDM dengan variasi sebagai berikut :
· Statistical TDM atau
· Asynchronous TDM atau

· Intelligent TDM

Bertujuan memperbaiki efisiensi synchronous TDM dengan cara menambahkan
rangkaian yang lebih kompleks di sisi multiplexer

Frequency Division Multiplexing

Tiap sinyal dimodulasikan ke dalam frekuensi carrier yang berbeda dan
frekuensi carrier tersebut terpisah dimana bandwidth dari sinyal-sinyal tersebut
tidak overlap

Ø FDM dimungkinkan jika bandwidth media transmisi jauh lebih besar daripada
required BW sinyal yang akan dikirim. Contoh: sistem siaran televisi, CATV,
AMPS analog
Ø Pada gambar di atas , ada 6 sumber sinyal input mux, kemudian masing-masing
dimodulasi menjadi frekuensi berbeda (f1, …, f6)

Ø Untuk menghindari interferensi, antar kanal dipisahkan oleh guard band (menjadi
bagian dari spektrum yang tak terpakai)

Ø Sejumlah sinyal analog atau digital [mi(t); i=1,…n] dimultiplex pada media transmisi
yang sama.

Ø Masalah yang harus diatasi sistem FDM: crosstalk dan derau intermodulasi.

Synchronous Time-Division Multiplexing

Ø Time division multiplexing dimungkinkan apabila data rate yang dapat dicapai
oleh media transmisi lebih besar daripada data rate sinyal digital yang akan dikirim.
Ø Pada gambar berikut, sejumlah sinyal digital [mi(t); i=1,…n] dimultiplex pada
media transmisi yang sama. Data yang datang dari tiap sumber mula-mula dimasukkan
ke buffer.
Ø Buffer di-scan secara sekuensial untuk membentuk sinyal digital gabungan mc(t).
Operasi scan harus berlangsung cukup cepat agar tiap buffer dapat berada dalam
keadaan kosong sebelum data berikutnya masuk.
Ø Jadi, besarnya laju data mc(t) harus lebih dari atau sama dengan penjumlahan
laju data masing-masing sumber (mi(t)). Sinyal digital mc(t) dapat dikirim langsung,
atau dilewatkan melalui modem untuk membentuk sinyal analog.

Dalam hal ini dipakai 2 teknik interlaving :

Ø Character-interlaving :

1. Dipakai dengan sumber asynchronous.

2. Tiap time slot mengandung 1 karakter dari data.

Ø Bit-interlaving :

1. Dipakai dengan sumber synchronous dan boleh juga dengan sumber
asynchronous.

2. Tiap time slot mengandung hanya 1 bit.

Synchronous TDM :

Ø Disebut synchronous karena time slot-time slot-nya di alokasikan ke sumber-sumber
dan tertentu dimana time slot untuk tiap sumber ditransmisi. Biar bagaimanapun
sumber mempunyai data untuk dikirim.

Ø Dapat mengendalikan sumber-sumber dengan kecepatan yang berbeda-beda.

Statistical Time-Division Multiplexing

Ø Statistical TDM yang dikenal juga sebagai Asynchronous TDM dan
Intelligent TDM, sebagai alternative synchronous TDM.

Ø Pada synchronous TDM, banyak kasus time slot kosong (tidak berisi data).
Statistical TDM memanfaatkan fakta bahwa tidak semua terminal mengirim
data setiap saat, sehingga data rate pada saluran output lebih kecil dari
penjumlahan data rate semua terminal.
Ø Ada n saluran input, tetapi hanya k time slot yang tersedia pada sebuah frame
TDM. Di mana k <>
Ø Di sisi pengirim, fungsi multiplexer adalah scanning buffer, mengumpulkan
data sampai frame penuh, kemudian mengirimkan frame tersebut.
Ø Konsekuensi: tambahan overhead, karena diperlukan field address dan
length. Informasi address dibutuhkan untuk memastikan bahwa data diantarkan
kepada penerima yang tepat.
Ø Pada gambar berikut, ada 4 sumber data yang transmit pada waktu t0, t1, t2, t3.
Multiplexer statistik tidak mengirimkan slot kosong jika terdapat data dari user lain

Sumber : http://brahm.staff.gunadarma.ac.id/Downloads/files/8932/MULTIPLEXING.doc

KEAMANAN SYSTEM dan JARINGAN KOMPUTER

2009-10-28T18:38:00.000-07:00

KEAMANAN SYSTEM dan JARINGAN KOMPUTER
Perkembangan teknologi informasi, Internet seringkali disebut sebagai dunia tanpa batas. Beragam informasi bisa didapat di internet tak hanya memberikan kontribusi positif bagi kehidupan tetapi juga memberikan ancaman lebih menakutkan dari dunia maya atau Sekalipun sesuatu berasal dari sumber yang terpercaya dan aman untuk dijalankan. Maka ntuk itu, komputer membutuhkan suatu benteng yang mampu melindungi komputer dari ancaman berbahaya di internet. Keamanan komputer maupun jaringan komputer, terutama yang terhubung ke internetharus direncanakan dan dikoordinasikan dengan baik agar dapat melindungi sumber daya yang ada agar dapat mengoptimalisasikan keamanan system pada jaringan sehingga dapat mengurangi ancaman yang terdapat di dalam dunia internet dan kita menjadi merasa lebih nyaman menjelajahi dunia internet

Klafisifikasi Keamanan Sistem Informasi menurut David Icove ada 4 macam yaitu:

1. Fisik ( Physycal Security)
2. Manusia ( Personal Security)
3. Data, media dan teknik komunikasi
4. Kebijakan dan prosedur

Berdasarkan Elemen System Terdapat 3 bagian Keamanan

1. Network security
difokuskan pada saluran (media) pembawa informasi atau jalur yang dilalui.

2. Application security
difokuskan pada aplikasinya sistem tersebut, termasuk database dan servicesnya.

3. Computer security
difokuskan pada keamanan dari komputer pengguna (end system) yang digunakan untuk mengakses aplikasi,termasuk operating system (OS)

Prinsip security menurut Jay Ramachandran

 Authentication
 Authorization atau Access Control
 Privacy / confidentiality
 Integrity
 Availability
 Non-repudiation
 Auditing

Authentication

➔ Menyatakan bahwa data atau informasi yang digunakan atau diberikan oleh pengguna
adalah asli milik orang tersebut, begitu juga dengan server dan sistem informasi yang
diakses.
➔ Serangan pada jaringan berupa DNS Corruption atau DNS Poison, terminal palsu
(spooffing), situs aspal dan palsu, user dan password palsu.
➔ Countermeasure : Digital Signature misalnya teknologi SSL/TLS untuk web dan mail
server

Authorization atau Access Control

➔ Pengaturan siapa dapat melakukan apa, atau dari mana menuju kemana. Dapat
menggunakan mekanisme user/password atau mekanisme lainnya.
➔ Ada pembagian kelas atau tingkatan.
➔ Implementasi : pada “ACL” antar jaringan, pada “ACL” proxy server (mis. Pembatasan
bandwidth/delaypools).

Privacy/confidentiality

➔ Keamanan terhadap data data pribadi, messages/pesan-pesan atau informasi
lainnya yang sensitif.
➔ Serangan pada jaringan berupa aktifitas sniffing (menyadap) dan adanya keylogger.
Umumnya terjadi karena kebijakan/policy yang kurang jelas.
➔ Coutermeasure : gunakan teknologi enkripsi/kriptografi.

Integrity

➔ Bahwa informasi atau pesan dipastikan tidak dirubah atau berubah.
➔ Serangan pada jaringan dapat berupa aktifitas spoofing, mail modification, Trojan
horse, MITM Attack.
➔ Countermeasure : dengan teknologi digita signature dan Kriptografi spt PGP, 802.1x,
WEP, WPA

Availability

➔ Keamanan atas ketersediaan layanan informasi.
➔ Serangan pada jaringan: DoS (denial of services) baik disadari/sengaja maupun tidak.
Aktifitas malware, worm, virus dan bomb mail sering memacetkan jaringan.
➔ Countermeasure : Firewall dan router filtering, backup dan redundancy, IDS dan IPS

Non-repudiation

➔ Menjaga agar jika sudah melakukan transaksi atau aktifitas online, maka tidak dapat di
sangkal.
➔ Umumnya digunakan untuk aktifitas e-commerce. Misalnya email yang digunakan untuk
Bertransaksi menggunakan digital signature.
➔ Pada jaringan dapat menggunakan digital signature, sertifikat dan kriptografi.
➔ Contoh kasus, smtp.ugm.ac.id ?? Setiap pengguna di jaringan lokal UGM dapat
Menggunakannya tanpa adanya authentikasi.

Auditing

➔ Adanya berkas semacam rekaman komunikasi data yang terjadi pada jaringan
untuk keperluan audit seperti mengidentifikasi serangan serangan pada
jaringan atau server.
➔ Implementasi : pada firewall (IDS/IPS) atau router menggunakan system logging
(syslog)

Refferensi : Network Security Josua M.Sinambela
Jay Ramachandran pada bukunya “Designing Security Architecture Solutions

Menyatukan Kemampuan Audio-Video Definisi Tinggi

2009-10-14T00:04:00.001-07:00

Teknologi Informasi
Menyatukan Kemampuan Audio-Video Definisi Tinggi
Berbagai kemajuan di bidang teknologi komunikasi informasi memang mampu memberikan kesan impresif, serta tidak lagi terpaku pada bidang-bidang tertentu saja. Kemajuan tersebut juga mampu memperluas spektrum kehadirannya di berbagai bidang untuk menjadikannya lebih mudah digunakan, lebih luas penggunaannya, dan menyenangkan siapa saja.
Kemajuan yang paling menonjol dalam perkembangan teknologi komunikasi informasi dan akan memasuki era penting kehidupan kita sehari-hari adalah di bidang multimedia dengan upaya untuk mengonvergensi audio dan video menjadi sebuah kesatuan yang tidak terpisahkan.
Kehadiran teknologi definisi tinggi untuk menampilkan tayangan televisi yang lebih tajam dan lebih realistis dalam persaingan HD-DVD maupun Bluray ikut memacu konvergensi yang sekejap saja meluas ke mana-mana. Tercapainya skala ekonomi menyebabkan televisi definisi tinggi menjadi lebih realistis untuk dimiliki siapa saja.
Bersamaan dengan itu, perkembangan teknologi komunikasi informasi di sisi audio pun sangat pesat untuk menghasilkan sistem tata suara yang ingin memanjakan telinga siapa saja yang mendengarnya, baik untuk keperluan gegap gempitanya adegan seru di layar lebar maupun mendengarkan irama musik menghadirkan bunyi berbagai instrumen dalam sebuah lagu.
Berbagai teknologi diciptakan untuk menghadirkan kualitas tayangan film menjadi lebih realistis seperti menonton di layar bioskop. Upaya memisahkan suara berbagai instrumen pun dikembangkan dengan membuat berbagai komponen cip yang mampu menghadirkan nuansa orkestra di ruang kehidupan kita.

Tanpa kabel
Kemajuan konvergensi audio-video dalam keseluruhan perkembangan teknologi ini diterjemahkan oleh Koninklijke Philips Electronics NV menjadi perangkat yang disebut HTS8100 Ambisound SoundBar DVD, sebuah perangkat bioskop rumah yang dirancang secara elegan dan futuristik. Perangkat yang memenangi penghargaan 2007 CES Innovations Award ini merupakan sistem bioskop rumah yang terbaru di pasaran sekarang ini.
Dewasa ini, banyak orang mulai menyadari bahwa untuk menjadikan ruang tamu sebagai sebuah bioskop, diperlukan banyak sekali kabel yang melintang ke mana-mana, mengganggu keseluruhan tata letak ruang. Kabel memang menjadi sebuah persoalan dalam sistem audio-video di era digitalisasi sekarang ini.
Philips HTS8100 berusaha menjadi sebuah solusi lengkap menggabungkan kemampuan definisi tinggi tayangan video, dan sekaligus sistem tata suara yang dirancang untuk memiliki kemampuan yang setara dengan sistem yang menggunakan banyak kabel. Hasilnya adalah sebuah sistem suara multi-channel surround yang lengkap, cocok dan serasi untuk berbagai ruang keperluan di rumah maupun di kantor.
Setelah sukses memperkenalkan teknologi Ambilight yang mengatur keluarnya cahaya dari layar televisi LCD untuk menyesuaikan kondisi pencahayaan ruangan, Philips yang menjadi pemain penting dalam industri konsumen elektronik memperkenalkan teknologi Ambisound pada perangkat HTS8100.
Teknologi Ambisound sebenarnya merupakan gabungan dari lima jenis amplifier yang setara dengan kanal sistem audio 5.1 high-end untuk menghasilkan kualitas suara surround di dalam ruangan. Teknologi ini mengandalkan teknik audio canggih yang membantu menciptakan apa yang disebut sebagai "sweet spot" secara lebih luas.
Secara ringkas, yang dimaksud adalah posisi duduk pada saat mendengarkan di mana presentasi suara panggung (soundstage) bisa didengar secara baik. Biasanya, posisi ini terletak di tengah dalam jarak yang seimbang dengan pengeras suara. Kemampuan Ambisound HTS8100 ini menjadikan perangkat ini ideal untuk menonton bioskop rumah tanpa harus memiliki pengeras suara dalam jumlah yang banyak.
Teknologi Faroudja
Dilengkapi dengan three-band sound equalizer dan subwoofer, HTS8100 menghasilkan kinerja nada rendah yang dalam melalui teknologi DoubleBASS sehingga perpindahan antarsuara yang dihasilkan pun berlangsung mulus. Dalam percobaan menggunakan koneksi high definifition multimedia interface (HDMI), kualitas tayangan DVD dalam format 1080p menjadi menyenangkan untuk dijadikan perangkat menonton bioskop di rumah.
Dilengkapi dengan penggunaan teknologi pemrosesan video directional correlation de-interlace (DCDi) buatan Faroudja, keseluruhan pengalaman menonton di era digital menjadi lebih menyenangkan setara dengan menonton di bioskop dalam skala yang sesuai dengan ruangan di rumah kita.
Harus diakui bahwa HTS8100 buatan Philips ini mampu menggabungkan beberapa ragam teknologi audio-video secara impresif dalam sistem home theatre yang akan terus mengonsumsi kebutuhan hiburan digital kita. Di sisi lain, kualitas audio yang dihasilkan memang akan dianggap tidak memadai bagi mereka yang memiliki telinga peka dan terbiasa dengan perangkat audiophile. Ketika dihubungkan dengan sistem audio digital Sonos, terasa soundstaging yang diinginkan tidak mencapai kepuasan yang diharapkan.
Namun, sebagai kesatuan perangkat multimedia dengan kemampuan playback format kompresi MP3, WMA, Audio CD, CD-R/RW, serta USB Flash Drive, HTS8100 memberikan kesan yang berbeda. Digitalisasi yang diterjemahkan Philips dalam perangkat HTS8100 tidak hanya mampu menghadirkan sistem audio-video yang ringkas dengan kemampuan tata suara surround, tetapi juga tampil beda dan berkelas.