File Name: data communication feroz and behrouz .zip
After completing this tutorial, you will find yourself at a moderate level of expertise in knowing Data Communication and Computer Networks Page 3 1. The message is the information data to be communicated. Popular forms of information include text, numbers, pictures, audio, and video.
Course Teacher: Md. Reference Book. Data and Computer Communications by William Stallings 2.
Course Teacher: Md. Reference Book. Data and Computer Communications by William Stallings 2. Data Communications and Networking by Behrouz A.
Two computers are said to be interconnected if they are able to exchange information. A system with one control unit and many slaves is not a network. Single communication channel that Many connections between is shared by all the machines on individual pairs of machines the network. An address field within the packet Routing algorithms play an specifies for whom it is intended.
Each bus has a head-end, a device that initiates transmission activity. Traffic that is destined for a computer to the right of the sender uses the upper bus, traffics to the left uses the lower one. Host end system. Subnet communication subnet. WANs typically have irregular topologies. Internet Collection of interconnected networks. Circuit Switching Dedicated communications path established for the duration of the conversation E.
The purpose of each layer is to offer certain services to the higher layers. Layer n on one-machine carries on a conversation with layer n on another machine. Protocol: is an agreement between the communicating parties on how communication is to proceed. Peers communicate using the protocol. In reality, no data directly transferred from layer n on one machine to layer n on another machine. Protocol Hierarchies Cont. Each layer passes data and control information to the layer immediately below it.
The design of layers helps in: Minimizing the amount of information that must be passed between layers Make it simpler to reduce the implementation of one layer with a completely different one Protocol stack: A list of protocol used by a certain system, one protocol per layer. Data transfer. Simplex communication. Half-duplex communication. Full-duplex communication. Number and priorities of the logical connection channels.
Many networks provide at least two logical channels per connection, one for normal data and one for urgent data. Error control. Error detecting code. Error correcting code. Design Issues Cont. How to receive data in order sequence no. How to keep a fast sender from swamping a slow receiver with data flow control. Routing: multiple paths between source and destination. Software [example: process. Layer n called service provider. Each SAP has an address that uniquely identifies it.
Interfaces and Services Cont. IDU: interface data unit. ICI: interface control info. SDU: service data unit. In order to transfer the SDU, the layer n entity may have to fragment it into several pieces, each of which is given a header and send to as a separate PDU protocol data unit such as a packet. Use the Connection Release the connection Acts like a tube: receive data by the Messages could be received in same order was sent different order than it was sent with.
Used to implement communication in the client-server model. Primitive tells the service to Perform some action OR Report an action by a peer entity. Example: Connection oriented service with 8 service primitives. Example Cont. Service Could be. Relationship of Services to Protocols Service: is a set of primitives operations that a layer provides to the layer above it. A set of rules governing the format and meaning of the frames, packets, or messages that are exchanged by the peer entities within a layer.
Entities use protocols in order to implement their service definitions. Entities are free to change their protocols, provided they do not change the service visible to their users.
Used by the global internet. No official model but a working one. Application layer. Host to host or transport layer. Internet layer. Network access layer. Physical layer. Physical Layer Physical interface between data transmission device e.
Computer and transmission medium or network Characteristics of transmission medium Signal levels Data rates Etc. Application Layer Support for user applications e. Reference model: deals with connecting open systems that are; Open for communication with other systems. Principles A layer should be created where a different level of abstraction is needed. Each layer should perform a well-defined function.
The function of each layer should be chosen with an eye toward defining internationally standardized protocols. The layer boundaries should be chosen to minimize the information flow across the interfaces. The number of layers should be large enough that distinct functions need not be thrown together on the same layer out of necessity.
How many volts for 1 or 0. How many microseconds a bit lasts. Mechanics, electrical and procedural interfaces. Data link Layer Break the input data up into data frames. Process the acknowledgement frames sent back by the receiver. Insert the frame delimiter. Solve the problems caused by damaged, lost and duplicate frames. Flow control. Full duplex transmission piggybacking Medium access sub layer deals with how to control access to the shared channel in broadcast networks.
Network Layer Routing packets from source to destination. Routes can be static or dynamic Bottleneck, congestion Connect heterogeneous networks different addressing method, larger packet service. In broadcast networks, routing problem is simple, so the network layer is thin. Transport layer determines what type of service to provide the session layer with and ultimately, the users of the entire network The transport layer is a true end-to-end layer, from source to destination Multiple connections will be entering and leaving each host.
Only the side holding the token may perform the critical operation. Synchronization: insert a checkpoint. Example: sending file for 20 hours. After a crash the portion after the checkpoint will be resend again. Presentation Layer Concerned with the syntax and semantics of the information transmitted. A typical example of a presentation service is encoding data in a standard agreed upon way.
Application Layer The application layer contains a variety of protocols that are commonly needed. Example: incompatible terminal type. One way to solve this problem is to define an abstract network virtual terminal that editor can be written to deal with. Other application is file transfer ftp. Client-server model. Network layer runs IPX internet packet exchange.
IPX uses 10 byte address IP uses 4 bytes flat addressing. Transport protocol. Example Of Networks Cont. About once a minute, each server broadcasts a packet giving its address and telling what services it offers.
An Introduction to Computer Networksis a free and open general-purpose computer-networking textbook, complete with diagrams and exercises. No headers. Download CN notes pdf unit — 1. These devices can be computers, printers, scanners, Fax machines etc. Data communications and networking Behrouz A. In this masterpiece, Andrew Tanenbaum explains how computer networks work from the inside out. From the Preface: Peter Lars Dordal wrote: This book is meant as a serious and more-or-less thorough text for an introductory college or graduate course in computer networks, carefully researched, with consistent notation and style, and complete with diagrams and exercises.
Information Technology and theory Aksoy Cengage Learnings. It is a relational database management system from Microsoft that combines. Like relational databases MS access also stores all the data in tabular form. One can also modify the contents of the stored table. Tables enable the users to sort and update data Users can also filter the data. STEP 1 click on Microsoft office button and then click on new option.
Эй! - услышал он за спиной сердитый женский голос и чуть не подпрыгнул от неожиданности. - Я… я… прошу прощения, - заикаясь, сказал Беккер и застегнул молнию на брюках. Повернувшись, он увидел вошедшую в туалет девушку. Молоденькая, изысканной внешности, ну прямо сошла со страниц журнала Севентин. Довольно консервативные брюки в клетку, белая блузка без рукавов. В руке красная туристская сумка фирмы Л.
Это очень важная часть! - заявил лейтенант. - Это не ребро или палец, как в церквях Галиции.
- Она через силу улыбнулась. - Остальное будет зависеть от. Сьюзан знала, что остальное - это штурмовая группа АНБ, которая, перерезав электрические провода, ворвется в дом с автоматами, заряженными резиновыми пулями.
Подождите, мистер. Ну что еще? - застонал. - Хочет предъявить мне обвинение во вторжении в личную жизнь.
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