Utility Computing

While utility computing or utility can be called with more computers to the computing resource itself. As the calculation and storage, as metered services similar to traditional public utilities (such as electricity, water, natural gas, or telephone network). This system has the advantage of low or no initial cost to get the hardware, but the computing resources are basically rented. Customers with very large computations or a sudden peak in demand can also avoid the delays that will get results from the physical and assembling a large number of computers.
"Utility computing" usually imagine some form of virtualization so that the amount of storage or computing power available would be far greater than the single time-sharing computer. Some servers are used at the end of "return" to make this possible. Maybe this is a dedicated computer cluster specifically built for the purpose of being leased out, or even an under-utilized supercomputer. Techniques to run a single calculation on multiple computers is known as distributed computing.

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Green Computing

Green computing (computing or green IT green) is based computing refers to a sustainable environment. This is "the study and practice of designing, manufacturing, use, and dispose of computers, servers, and related subsystems, such as monitors, printers, storage devices, networking and communication-efficient and effective system with minimal or no impact on Green IT environment. also seeks to achieve economic viability and increase system performance and use, while abiding by the social responsibility and ethics. Thus, the scope of green IT environment, economics of energy efficiency, and total cost of ownership, which includes the cost of disposal and recycling. This is the study and practice of using computing resource sefficiently. With the increasing recognition that human-made emissions of greenhouse gases is a major factor of global warming, corporate, government, and society in general now have important new agenda: tackling environmental issues and adopt environmentally friendly practices. Greening of our IT products, applications, services, and practices are both an economic and environmental imperatives, as well as our social responsibility. Therefore, more and more IT vendors and users move towards green IT and thus help in building a green society and economy.
The goal of green computing is similar to green chemistry, reducing the use of hazardous materials, maximize energy efficiency during the product life, and promote recyclability or biodegradability of waste products and dead plants
Green computing researchers look at key issues and topics related to energy efficiency in computing and promoting computer technology and environmentally friendly energy systems, including efficient use of computers, design of algorithms and computer systems for environmentally friendly technologies, and other related topics

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PRONOUNS

Pronouns

Personal Pronouns

Personal pronouns represent specific people or things. We use them depending on:

• number: singular (eg: I) or plural (eg: we)
• person: 1st person (eg: I), 2nd person (eg: you) or 3rd person (eg: he)
• gender: male (eg: he), female (eg: she) or neuter (eg: it)
• case: subject (eg: we) or object (eg: us)

We use personal pronouns in place of the person or people that we are talking about. My name is Josef but when I am talking about myself I almost always use "I" or "me", not "Josef". When I am talking direct to you, I almost always use "you", not your name. When I am talking about another person, say John, I may start with "John" but then use "he" or "him". And so on.

Here are the personal pronouns, followed by some example sentences:

number	person	gender	personal pronouns
			subject	object
singular	1st	male/female	I	me
	2nd	male/female	you	you
	3rd	male	he	him
		female	she	her
		neuter	it	it
plural	1st	male/female	we	us
	2nd	male/female	you	you
	3rd	male/female/neuter	they	them

Examples (in each case, the first example shows a subject pronoun, the second an object pronoun):

• I like coffee.
• John helped me.
  
  
• Do you like coffee?
• John loves you.
  
  
• He runs fast.
• Did Ram beat him?
  
  
• She is clever.
• Does Mary know her?
  
  
• It doesn't work.
• Can the engineer repair it?
  
  
• We went home.
• Anthony drove us.
  
  
• Do you need a table for three?
• Did John and Mary beat you at doubles?
  
  
• They played doubles.
• John and Mary beat them.

When we are talking about a single thing, we almost always use it. However, there are a few exceptions. We may sometimes refer to an animal as he/him or she/her, especially if the animal is domesticated or a pet. Ships (and some other vessels or vehicles) as well as some countries are often treated as female and referred to as she/her. Here are some examples:

• This is our dog Rusty. He's an Alsation.
• The Titanic was a great ship but she sank on her first voyage.
• My first car was a Mini and I treated her like my wife.
• Thailand has now opened her border with Cambodia.

For a single person, sometimes we don't know whether to use he or she. There are several solutions to this:

• If a teacher needs help, he or she should see the principal.
• If a teacher needs help, he should see the principal.
• If a teacher needs help, they should see the principal.

We often use it to introduce a remark:

• It is nice to have a holiday sometimes.
• It is important to dress well.
• It's difficult to find a job.
• Is it normal to see them together?
• It didn't take long to walk here.

We also often use it to talk about the weather, temperature, time and distance:

• It's raining.
• It will probably be hot tomorrow.
• Is it nine o'clock yet?
• It's 50 kilometres from here to Cambridge.

Demonstrative Pronouns

A demonstrative pronoun represents a thing or things:

• near in distance or time (this, these)
• far in distance or time (that, those)

	near	far
singular	this	that
plural	these	those

Here are some examples with demonstrative pronouns, followed by an illustration:

• This tastes good.
• Have you seen this?
• These are bad times.
• Do you like these?
  
  
• That is beautiful.
• Look at that!
• Those were the days!
• Can you see those?
  
  
• This is heavier than that.
• These are bigger than those.

Possessive Pronouns

We use possessive pronouns to refer to a specific person/people or thing/things (the "antecedent") belonging to a person/people (and sometimes belonging to an animal/animals or thing/things).

We use possessive pronouns depending on:

• number: singular (eg: mine) or plural (eg: ours)
• person: 1st person (eg: mine), 2nd person (eg: yours) or 3rd person (eg: his)
• gender: male (his), female (hers)

Below are the possessive pronouns, followed by some example sentences. Notice that each possessive pronoun can:

• be subject or object
• refer to a singular or plural antecedent

number	person	gender (of "owner")	possessive pronouns
singular	1st	male/female	mine
	2nd	male/female	yours
	3rd	male	his
		female	hers
plural	1st	male/female	ours
	2nd	male/female	yours
	3rd	male/female/neuter	theirs

• Look at these pictures. Mine is the big one. (subject = My picture)
• I like your flowers. Do you like mine? (object = my flowers)
  
  
• I looked everywhere for your key. I found John's key but I couldn't find yours. (object = your key)
• My flowers are dying. Yours are lovely. (subject = Your flowers)
  
  
• All the essays were good but his was the best. (subject = his essay)
• John found his passport but Mary couldn't find hers. (object = her passport)
• John found his clothes but Mary couldn't find hers. (object = her clothes)
  
  
• Here is your car. Ours is over there, where we left it. (subject = Our car)
• Your photos are good. Ours are terrible. (subject = Our photos)
  
  
• Each couple's books are colour-coded. Yours are red. (subject = Your books)
• I don't like this family's garden but I like yours. (subject = your garden)
  
  
• These aren't John and Mary's children. Theirs have black hair. (subject = Their children)
• John and Mary don't like your car. Do you like theirs? (object = their car)

Interrogative Pronouns

We use interrogative pronouns to ask questions. The interrogative pronoun represents the thing that we don't know (what we are asking the question about).

There are four main interrogative pronouns: who, whom, what, which

Notice that the possessive pronoun whose can also be an interrogative pronoun (an interrogative possessive pronoun).

	subject	object
person	who	whom
thing	what
person/thing	which
person	whose		(possessive)

Look at these example questions. In the sample answers, the noun phrase that the interrogative pronoun represents is shown in bold.

question	answer
Who told you?	John told me.	subject
Whom did you tell?	I told Mary.	object
What's happened?	An accident's happened.	subject
What do you want?	I want coffee.	object
Which came first?	The Porsche 911 came first.	subject
Which will the doctor see first?	The doctor will see the patient in blue first.	object
There's one car missing. Whose hasn't arrived?	John's (car) hasn't arrived.	subject
We've found everyone's keys. Whose did you find?	I found John's (keys).	object

Note that we sometimes use the suffix "-ever" to make compounds from some of these pronouns (mainly whoever, whatever, whichever). When we add "-ever", we use it for emphasis, often to show confusion or surprise. Look at these examples:

• Whoever would want to do such a nasty thing?
• Whatever did he say to make her cry like that?
• They're all fantastic! Whichever will you choose?

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THE ARTICLES

The articels

The three articles — a, an, the — are a kind of adjective. The is called the definite article because it usually precedes a specific or previously mentioned noun; a and an are called indefinite articles because they are used to refer to something in a less specific manner (an unspecified count noun). These words are also listed among the noun markers or determiners because they are almost invariably followed by a noun (or something else acting as a noun).


The is used with specific nouns. The is required when the noun it refers to represents something that is one of a kind:

The moon circles the earth.

The is required when the noun it refers to represents something in the abstract:

The United States has encouraged the use of the private automobile as opposed to the use of public transit.

The is required when the noun it refers to represents something named earlier in the text. (See below..)

If you would like help with the distinction between count and non-count nouns, please refer to Count and Non-Count Nouns.
We use a before singular count-nouns that begin with consonants (a cow, a barn, a sheep); we use an before singular count-nouns that begin with vowels or vowel-like sounds (an apple, an urban blight, an open door). Words that begin with an h sound often require an a (as in a horse, a history book, a hotel), but if an h-word begins with an actual vowel sound, use an an (as in an hour, an honor). We would say a useful device and a union matter because the u of those words actually sounds like yoo (as opposed, say, to the u of an ugly incident). The same is true of a European and a Euro (because of that consonantal "Yoo" sound). We would say a once-in-a-lifetime experience or a one-time hero because the words once and one begin with a w sound (as if they were spelled wuntz and won).

Merriam-Webster's Dictionary says that we can use an before an h- word that begins with an unstressed syllable. Thus, we might say an hisTORical moment, but we would say a HIStory book. Many writers would call that an affectation and prefer that we say a historical, but apparently, this choice is a matter of personal taste.

For help on using articles with abbreviations and acronyms (a or an FBI agent?), see the section on Abbreviations.

First and subsequent reference: When we first refer to something in written text, we often use an indefinite article to modify it.

A newspaper has an obligation to seek out and tell the truth.

In a subsequent reference to this newspaper, however, we will use the definite article:

There are situations, however, when the newspaper must determine whether the public's safety is jeopardized by knowing the truth.

Another example:
"I'd like a glass of orange juice, please," John said.
"I put the glass of juice on the counter already," Sheila replied.

Exception:
When a modifier appears between the article and the noun, the subsequent article will continue to be indefinite:
"I'd like a big glass of orange juice, please," John said.
"I put a big glass of juice on the counter already," Sheila replied.

Generic reference: We can refer to something in a generic way by cautionusing any of the three articles. We can do the same thing by omitting the article altogether.

* A beagle makes a great hunting dog and family companion.
* An airedale is sometimes a rather skittish animal.
* The golden retriever is a marvelous pet for children.
* Irish setters are not the highly intelligent animals they used to be.

The difference between the generic indefinite pronoun and the normal indefinite pronoun is that the latter refers to any of that class ("I want to buy a beagle, and any old beagle will do.") whereas the former (see beagle sentence) refers to all members of that class.

Proper nouns: We use the definite article with certain kinds of proper nouns:

* Geographical places: the Sound, the Sea of Japan, the Mississippi, the West, the Smokies, the Sahara (but often not when the main part of the proper noun seems to be modified by an earlier attributive noun or adjective: We went swimming at the Ocean Park)
* Pluralized names (geographic, family, teams): the Netherlands, the Bahamas, the Hamptons, the Johnsons, the New England Patriots
* Public institutions/facilities/groups: the Wadsworth Atheneum, the Sheraton, the House, the Presbyterian Church
* Newspapers: the Hartford Courant, the Times
* Nouns followed by a prepositional phrase beginning with "of": the leader of the gang, the president of our club

Abstract nouns: Abstract nouns—the names of things that are not tangible—are sometimes used with articles, sometimes not:

* The storm upset my peace of mind. He was missing just one thing: peace of mind.
* Injustice was widespread within the judicial system itself. He implored the judge to correct the injustice.
* Her body was racked with grief. It was a grief he had never felt before.

Zero articles: Several kinds of nouns never use articles. We do not use articles with the names of languages ("He was learning Chinese." [But when the word Chinese refers to the people, the definite article might come into play: "The Chinese are hoping to get the next Olympics."]), the names of sports ("She plays badminton and basketball."), and academic subjects ("She's taking economics and math. Her major is Religious Studies.")

When they are generic, non-count nouns and sometimes plural count-nouns are used without articles. "We like wine with our dinner. We adore Baroque music. We use roses for many purposes." But if an "of phrase" comes after the noun, we use an article: "We adore the music of the Baroque." Also, when a generic noun is used without an article and then referred to in a subsequent reference, it will have become specific and will require a definite article: "The Data Center installed computers in the Learning Center this summer. The computers, unfortunately, don't work."

Common count nouns are used without articles in certain special situations:
idiomatic expressions
using be and go We'll go by train. (as opposed to "We'll take the train.)
He must be in school.
with seasons In spring, we like to clean the house.
with institutions He's in church/college/jail/class.
with meals Breakfast was delicious.
He's preparing dinner by himself.
with diseases He's dying of pneumonia.
Appendicitis nearly killed him.
She has cancer
(You will sometimes hear "the measles," "the mumps," but these, too, can go without articles.)
with time of day We traveled mostly by night.
We'll be there around midnight.

Principles of Choosing an Article

Choosing articles and determiners: Briefly defined, a determiner is a noun-marker: when you see one, you know that what follows is a noun or noun phrase. There is a list of such words in the table below. When you place your mouse-cursor over a word or pair of related words (such as either/neither), you will see in the right-hand frame an image describing the kinds of words that word can modify.

Zero article (see table below) means either that no article would be appropriate with that kind of noun or that that kind of noun can be used (in that context) without an article.


If you would like to see these images listed on one page, click HERE.

Notice that there is a difference between a "stressed" some or any and an "unstressed" some or any. Consider the words in ALL CAPS as shouted words and you will hear the difference between these two:

* That is SOME car you've got there!
* I don't want to hear ANY excuse!

As opposed to. . .

* We have some cars left in the lot.
* Isn't there any furniture in the living room?

In terms of the words they usually modify, the unstressed some and any do not modify singular count nouns.

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MULTIPLEXING

FDM yaitu pemakaian secara bersama kabel yang mempunyai bandwidth yang tinggi terhadap beberapa frekuensi (setiap channel akan menggunakan frekuensi yang berbeda). Contoh metoda multiplexer ini dapat dilihat pada kabel coaxial TV, dimana beberapa channel TV terdapat beberapa chanel, dan kita hanya perlu tunner (pengatur channel) untuk gelombang yang dikehendaki. Pada teknik FDM, tidak perlu ada MODEM karena multiplexer juga bertindak sebagai modem (membuat permodulatan terhadap data digital). Kelemahan Modem disatukan dengan multiplexer adalah sulitnya meng-upgrade ke komponen yang lebih maju dan mempunyai kecepatan yang lebih tinggi (seperti teknik permodulatan modem yang begitu cepat meningkat). Kelemahannya adalah jika ada channel (terminal) yang tidak menghantar data, frekuensi yang dikhususkan untuk membawa data pada channel tersebut tidak tergunakan dan ini merugikandan juga harganya agak mahal dari segi pemakaian (terutama dibandingkan dengan TDM) kerana setiap channel harus disediakan frekuensinya. Kelemahan lain adalah kerana bandwidth jalur atau media yang dipakai bersama-sama tidak dapat digunakan sepenuhnya, kerana sebagian dari frekuensi terpaksa digunakan untuk memisahkan antara frekuensi channelchannel yang ada. Frekuensi pemisah ini dipanggil guardband
Prinsip dari FDM adalah pembagian bandwidth saluran transmisi atas sejumlah kanal (dengan lebar pita frekuensi yang sama atau berbeda) dimana masing-masing kanal dialokasikan ke pasangan entitas yang berkomunikasi. Contoh aplikasi FDM ini yang polpuler pada saat ini adalah Jaringan Komunikasi Seluler, seperti GSM ( Global System Mobile) yang dapat menjangkau jarak 100 m s/d 35 km. Tingkatan generasi GSM adalah sbb:
•First-generation: Analog cellular systems (450-900 MHz)
– Frequency shift keying for signaling
– FDMA for spectrum sharing
– NMT (Europe), AMPS (US)
•Second-generation: Digital cellular systems (900, 1800 MHz)
– TDMA/CDMA for spectrum sharing
– Circuit switching
– GSM (Europe), IS-136 (US), PDC (Japan)
•2.5G: Packet switching extensions
– Digital: GSM to GPRS
– Analog: AMPS to CDPD
•3G:
– High speed, data and Internet services
– IMT-2000

Tujuan Muliplexing
- meningkatkan effisiensi penggunaan bandwidth / kapasitas saluran transmisi dengan cara berbagi akses bersama.

Jenis Teknik Multiplexing
Teknik Multiplexing yang umum digunakan adalah :
a. Time Division Multiplexing (TDM) : - Synchronous TDM
- Asynchronous TDM
b. Frequency Division Multiplexing (FDM)
c. Code Division Multiplexing (CDM)
d. Wavelength Division Multiplexing (WDM)
e. Optical code Division Multiplexing (ODM)

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Protocol x.25

Protocol x.25 adalah Standar internasional untuk akses jaringan dengan penyakelaran paket (packet switching) yang pertama muncul adalah X.25, yang direkomendasikan oleh CCITT (sekarang ITU-T) pada tahun 1976. Frame Relay yang muncul setelah X.25 ternyata jauh lebih efektif daripada X.25, karena X.25 kerjanya menjadi lambat karena adanya koreksi dan deteksi kesalahan. Frame Relay memiliki sedikit perbedaan, ia mendefinisikan secara berulang header-nya pada bagian awal dari frame seperti terlihat pada Gambar 1d, sehingga dihasilkan header frame normal 2-byte. Header Frame Relay dapat juga diperluas menjadi 3-byte atau 4-byte untuk menambah ruang alamat total yang disediakan. Dalam gambar-gambar yang mengilustrasikan jaringan-jaringan Frame Relay, piranti-piranti pengguna ditunjukkan sebagai pengarah-pengarah LAN, karena hal tersebut merupakan aplikasi Frame Relay yang berlaku secara umum. Tentu saja mereka dapat juga merupakan jembatan-jembatan LAN, Host atau front-end processor atau piranti lainnya dengan sebuah antarmuka Frame Relay.
Header Frame Relay terdiri dari deretan angka sepuluh bit, DLCI (Data Link Connection Identifier) merupakan nomor rangkaian virtual Frame Relay yang berkaitan dengan arah tujuan frame tersebut. Dalam hal hubungan antar kerja LAN-WAN, DLCI ini akan menunjukkan port-port yang merupakan LAN pada sisi tujuan yang akan dicapai.

Device pada X.25 ini terbagi menjadi tiga kategori:

* Data Terminal Equipment (DTE),
* Data Circuit-terminating Equipment (DCE) serta
* Packet Switching Exchange (PSE).
* Device yang digolongkan DTE adalah end-system seperti terminal, PC, host jaringan (user device).
* Sedang device DCE adalah device komunikasi seperti modem dan switch. Device inilah yang menyediakan interface bagi komunikasi antara DTE dan PSE. Adapun PSE ialah switch yang yang menyusun sebagian besar carrier network. Hubungan antar ketiga kategori ini diilustrasikan pada gambar dibawah ini.

Protokol Pada X.25

* Penggunaan protokol pada model standar X.25 ini meliputi tiga layer terbawah dari model referensi OSI. Terdapat tiga protokol yang biasa digunakan pada implementasi X.25 yaitu:
* Packet-Layer Protocol (PLP),
* Link Access Procedure, Balanced (LAPB)
* Serta beberapa standar elektronik dari interface layer fisik seperti EIA/TIA-232, EIA/TIA-449, EIA-530, dan G.703.
* Gambar di bawah ini mengilustrasikan protokol-protokol X.25 ini pada model OSI.

ebelum dua titik saling berkomunikasi dengan menggunakan protokol X.25 maka kedua titik ini harus terlehih dahulu membangun hubungan. Terdapat dua jenis mode dalam X.25 untuk membangun hubungan yaitu:

· SVC (Switched Virtual Channel), Dalam mode ini node yang berinisiatif untuk membangun koneksi harus mengirimkan sinyal call request ke node tujuan. Bila diterima maka node tujuan akan mengirimkan sinyal call accepted dan sebaliknya bila ditolak maka node tujuan akan mengirimkan sinyal call rejected. Analogi dari mode koneksi ini adalah komunikasi melalui telepon, bila seseorang ingin menghubungi orang lain maka orang tersebut terlebih dahulu harus men-dial nomor tertentu. Diterima tidaknya panggilan ini tergantung dari titik tujuan. Virtual channel yang digunakan dalam mode SVC adalah per call basis.

· PVC (Permanent Virtual Channel), Dalam mode ini virtual channel yang digunakan bersifat dedicated dan tidak perlu adanya ritual call setup. Analogi dari mode ini ini adalah saluran leased line dimana secara end-t-end hubungan fisik dan logik sudah terbentuk.

Kelebihan:

· Protokol X.25 memiliki kecepatan yang lebih tinggi dibanding RS-232 (64 kbps dibanding 9600 bps).

· Protokol X.25 memiliki kemampuan untuk menyediakan logical channel per aplikasi.

· Pendudukan logical channel dapat dilakukan secara permanen dengan mode PVC (Permanent Virtual Channel) maupun temporary dengan mode SVC (Switched Virtual Channel) disesuaikan dengan kebutuhan.

· Data transfer pada X.25 bersifat reliable, data dijamin bahwa urutan penerimaan akan sama dengan waktu data dikirimkan.

· Protokol X.25 memiliki kemampuan error detection dan error correction.

Kekurangan:

· Tidak semua sentral memiliki antarmuka X.25. Sehingga diperlukan pengadaan modul X.25 dengan syarat bahwa sentral sudah support X.25.

· Untuk pengembangan aplikasi berbasis protokol X.25 membutuhkan biaya yang relatif lebih besar dibanding dengan RS-232 terutama untuk pembelian card adapter X.25.

· Untuk komunikasi data antara sentral dengan perangkat OMT beberapa sentral diidentifikasi menggunakan protokol proprietary vendor tertentu yang berjalan di atas protokol X.25.

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Frame Relay

Frame relay merupakan protocol WAN yang mempunyai performance tinggi yang bisa memberikan koneksi jaringan WAN sampai 2,048 Mbps (dan bahkan bisa lebih tinggi) ke berbagai belahan dunia. Frame relay menggunakan circuit virtual untuk koneksi site-2 dan memberikan lebar pipa bandwidth berskala yang bisa dijamin (dengan menggunakan apa yang disebut sebagai CIR- committed information rate). Frame relay begitu popular karena penawaran bandwidth yan berskala melalui jalur digital. Dengan menggunakan konfigurasi standard frame relay akan merupakan cara yang sederhana untuk meminimalkan masalah jaringan-2 frame relay.

Frame relay didesign untuk transmisi digital melalui medium yang sudah handal, yang pada umumnya adalah fiber optic, bandingkan dengan jaringan yang menggunakan X.25 yang pada awalnya didesign untuk jaringan transmisi analog melalui medium yang dianggap tidak handal seperti standard line telpon.

Standarisasi Frame Relay
Proposal awal mengenai teknologi Frame Relay sudah diajukan ke CCITT semenjak tahun 1984, namun perkembangannya saat itu tidak signifikan karena kurangnya interoperasi dan standarisasi dalam teknologi ini. Perkembangan teknologi ini dimulai di saat Cisco, Digital Equipment Corporation (DEC), Northern Telecom, dan StrataCom membentuk suatu konsorsium yang berusaha mengembangkan frame relay. Selain membahas dasar-dasar protokol Frame Relay dari CCITT, konsorsium ini juga mengembangkan kemampuan protokol ini untuk berinteroperasi pada jaringan yang lebih rumit. Kemampuan ini di kemudian hari disebut Local Management Interface (LMI).

Format Frame Relay
Format Frame Relay terdiri atas bagian-bagian sebagai berikut:
Flags
Membatasi awal dan akhir suatu frame. Nilai field ini selalu sama dan dinyatakan dengan bilangan hexadesimal 7E atau 0111 1110 dalam format biner. Untuk mematikan bilangan tersebut tidak muncul pada bagian frame lainnya, digunakan prosedur Bit-stuffing dan Bit-destuffing.

Address
Terdiri dari beberapa informasi:
1. Data Link Connection Identifier (DLCI), terdiri dari 10 bita, bagian pokok dari header Frame Relay dan merepresentasikan koneksi virtual antara DTE dan Switch Frame Relay. Tiap koneksi virtual memiliki 1 DLCI yang unik.
2. Extended Address (EA), menambah kemungkinan pengalamatan transmisi data dengan menambahkan 1 bit untuk pengalamatan
3. C/R, menentukan apakah frame ini termasuk dalam kategori Perintah (Command) atau Tanggapan (Response)
4. FECN (Forward Explicit Congestion Notification), indikasi jumlah frame yang dibuang karena terjadinya kongesti di jaringan tujuan
5. BECN (Backward Explicit Congestion Notification), indikasi jumlah frame yang mengarah ke switch FR tersebut tetapi dibuang karena terjadinya kongesti di jaringan asal
6. Discard Eligibility, menandai frame yang dapat dibuang jika terjadi kongesti di jaringan

Data
Terdiri dari data pada layer di atasnya yang dienkapsulasi. Tiap frame yang panjangnya bervariasi ini dapat mencapai hingga 4096 oktet.

Frame Check Sequence
Bertujuan untuk memastikan integritas data yang ditransmisikan. nilai ini dihitung perangkat sumber dan diverifikasi oleh penerima.

Sirkuit Virtual
Frame pada Frame Relay dikirimkan ke tujuannya dengan menggunakan sirkit virtual (jalur logikal dalam jaringan). Sirkit Virtual ini bisa berupa Sirkit Virtual Permanen (Permanent Virtual Circuit / PVC), atau Sirkit Virtual Switch (Switched Virtual Circuit / SVC).

Berikut ini adalah fitur utama dari frame relay:

* Frame relay memberikan deteksi error tapi tidak memberikan recovery error.
* Frame relay memberikan transfer data sampai 1.54Mbs
* Frame relay mempunyai ukuran paket yang bervariable (disebut frame)
* Frame relay bisa dipakai sebagai koneksi backbone kepada jaringan LAN
* Frame relay bisa dimplementasikan melalui berbagai macam koneksi sambungan (56K, T1, T3)
* Frame relay beroperasi pada layer physical dan layer Data link pada model OSI

2. KEUNTUNGAN FRAME RELAY
Frame Relay menawarkan alternatif bagi teknologi Sirkuit Sewa lain seperti jaringan X.25 dan sirkuit Sewa biasa. Kunci positif teknologi ini adalah:[3]
•Sirkuit Virtual hanya menggunakan lebar pita saat ada data yang lewat di dalamnya, banyak sirkuit virtual dapat dibangun secara bersamaan dalam satu jaringan transmisi.
•Kehandalan saluran komunikasi dan peningkatan kemampuan penanganan error pada perangkat-perangkat telekomunikasi memungkinkan protokol Frame Relay untuk mengacuhkan Frame yang bermasalah (mengandung error) sehingga mengurangi data yang sebelumnya diperlukan untuk memproses penanganan error.

Frame relay addressing
Frame relay menggunakan Data-link Connection Identifier (DLCI) untuk setiap circuit virtual
1. Range DLCI ada antara 16 dan 1007
2. DLCI mewakili koneksi antara dua piranti frame relay
3. Penyedia layanan frame relay memerikan DLCI saat vitual circuit di setup
4. Setiap DLCI adalah unik pada jaringan local akan tetapi tidak pada jaringan WAN secara keseluruhan.

Local Management Interface (LMI)
LMI merupakan satu set ekstensi management protocol yang mengautomasikan banyak tugas-2 management frame relay. LMI bertanggungjawab untuk memanage koneksi dan melaporkan status koneksi.

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