Exercises

1. Translate the text.

2. Scan the table and discuss it with your group mates

OSI Model
	Data unit	Layer	Function
Host layers	Data	7. Application	Network process to application
		6. Presentation	Data representation, encryption and decryption, convert machine dependent data to machine independent data
		5. Session	Interhost communication, managing sessions between applications
	Segments	4. Transport	Reliable delivery of packets between points on a network.
Media layers	Packet /Datagram	3. Network	Addressing, routing and (not necessarily reliable) delivery of datagrams between points on a network.
	Bit/Frame	2. Data link	A reliable direct point-to-point data connection.
	Bit	1. Physical	A (not necessarily reliable) direct point-to-point data connection.

3). Connect each layer with its name, then translate it into English.

сеансовий рівень Layer 1

прикладний рівень Layer 2

фізичний рівень Layer 3

транспортний рівень Layer 4

канальний рівень Layer 5

рівень представлення Layer 6

мережевий рівень Layer 7

4). Fill the gaps.

1.______controls the dialogues (connections) between computers. 2.______provides a reliable link between two directly connected nodes. 3.______may define the protocol for flow control. 4.______interacts with software applications that implement a communicating component. 5.______provides the functional and procedural means of transferring variable length data sequences from one node to another connected to the same network. 6.______provides the acknowledgement of the successful data transmission and sends the next data if no errors occurred. 7.______ transforms data into the form that the application accepts.

5). Retell the text.

Lesson 10

Communications protocols

1. Read words with their translations.

communications protocol - Комунікаційний протокол

protocol stack - набір протоколів

leverage [li:v(ə)ridʒ] - використовувати

Ethernet - ([ˈiːθərˌnɛt]

Internet Protocol Suite [swiːt] - стек протоколів IP

diverse set - різноманітний набір

inherently [in'hi(ə)rəntli] – по-суті

traverse  [trə'vɜːs] - прослідковувати

Synchronous optical networking - мережа синхронно-оптичного зв’язку

Plesiochronous Digital Hierarchy - Плезіохронна Цифрова Ієрархія

Asynchronous [eɪ'sɪŋkrənəs] Transfer Mode - Асинхронний Режим Передачі

high-throughput ['θru:put] - висока пропускна спроможність

low-latency ['leit(ə)nsi] - низька затримка

connection-oriented - орієнтований на з'єднання

2. Read the text

 A communications protocol is a system of digital rules for data exchange within or between computers. In a protocol stack, each protocol leverages the services of the protocol below it. An important example of a protocol stack is HTTP running over TCP over  IP over IEEE 802. 11. (TCP and IP are members of the Internet Protocol Suite. IEEE 802.11 is a member of the Ethernet protocol suite.) Communication protocols have various characteristics. They may be connection-oriented or connectionless, they may use circuit mode or packet switching, and they may use hierarchical addressing or flat addressing.

There are many communication protocols, a few of which are described below.

Ethernet

Ethernet is a family of protocols used in LANs, described by a set of standards together called IEEE 802 published by the Institute of Electrical and Electronics Engineers. It has a flat addressing scheme. It operates mostly at levels 1 and 2 of the OSI model. For home users today, the most well-known member of this protocol family is IEEE 802.11, otherwise known as Wireless LAN (WLAN). The complete IEEE 802 protocol suite provides a diverse set of networking capabilities.

Internet Protocol Suite

The Internet Protocol Suite, also called TCP/IP, is the foundation of all modern internetworking. It offers connection-less as well as connection-oriented services over an inherently unreliable network traversed by datagram transmission at the Internet protocol (IP) level. At its core, the protocol suite defines the addressing, identification, and routing specifications for Internet Protocol Version 4 (IPv4) and for IPv6, the next generation of the protocol with a much enlarged addressing capability.

SONET/SDH

Synchronous optical networking (SONET) and Synchronous Digital Hierarchy (SDH) are standardized multiplexing protocols that transfer multiple digital bit streams over optical fiber using lasers. At low transmission rates data can also be transferred via an electrical interface. The method was developed to replace the Plesiochronous Digital Hierarchy (PDH) system for transporting large amounts of telephone calls and data traffic over the same fiber without synchronization problems. 

Both SDH and SONET are widely used today: SONET in the United States and Canada, and SDH in the rest of the world. Although the SONET standards were developed before SDH, it is considered a variation of SDH because of SDH's greater worldwide market penetration.

Asynchronous Transfer Mode

Asynchronous Transfer Mode (ATM) is a switching technique for telecommunication networks. It uses asynchronous time-division multiplexing and encodes data into small, fixed-sized cells. This differs from other protocols such as the Internet Protocol Suite or Ethernet that use variable sized packets or frames. ATM has similarity with both circuit and packet switched networking. This makes it a good choice for a network that must handle both traditional high-throughput data traffic, and real-time, low-latency content such as voice and video. ATM uses a connection-oriented model in which a virtual circuit must be established between two endpoints before the actual data exchange begins.