Lecture 4: Fundamental Concepts of Computer Networks PDF

Fundamental concepts of computer networks. Lecture 4 CSC 329 Chapter 1 Fundamental concepts of computer networks. 1.1  1-3 THE...

Fundamental concepts of computer networks. Lecture 4 CSC 329 Chapter 1 Fundamental concepts of computer networks. 1.1  1-3 THE INTERNET The Internet has changed many aspects of our daily lives. It has affected the way we do business as well as the way we spend our leisure time. The Internet is a communication system that has brought a wealth of information to our fingertips and organized it for our use. Topics discussed in this section: A Brief History → ARPANET 1967 ACM 1969 UCLA, UCSB, SRI, UoU 1972 TCP The Internet Today (ISPs) CSC 329 Chapter 1 Fundamental concepts of computer networks. 1.2  Hierarchical organization of the Internet CSC 329 Chapter 1 Fundamental concepts of computer networks. 1.3  1-4 PROTOCOLS AND STANDARDS protocols and standards. Protocol is synonymous with rule. protocol is an established set of rules that determine how data is transmitted between different devices in the same network. Essentially, it allows connected devices to communicate with each other, regardless of any differences in their internal processes, structure or design Standards are agreed-upon rules. Standard is a document that's been developed to provide technical requirements, specifications, and guidelines that must be employed consistently to ensure devices, equipment, and software which govern networking are fit for their intended purpose CSC 329 Chapter 1 Fundamental concepts of computer networks. 1.4  Key Elements of a Protocol Syntax Data formats Signal levels Semantics Control information Error handling Timing Speed transmission Sequencing CSC 329 Chapter 1 Fundamental concepts of computer networks.  PROTOCOLS AND STANDARDS Protocols Syntax → format of the data Semantics → meaning of each section Timing → when data should be sent and how fast. Standards De facto → by fact (not approved as a standard) De jure → by Law (approved) CSC 329 Chapter 1 Fundamental concepts of computer networks. 1.6  PROTOCOLS AND STANDARDS Standards Organizations International Organization for Standardization (ISO) International Telecommunication Union - Telecommunication Standards (ITU-T) American National Standards Institute (ANSI) Institute of Electrical and Electronics Engineers (IEEE) Electronic Industries Association (EIA) CSC 329 Chapter 1 Fundamental concepts of computer networks. 1.7  Tasks involved in sending a letter Topics discussed in this section: Sender, Receiver, and Carrier Hierarchy (services) CSC 329 Chapter 1 Fundamental concepts of computer networks. 1.8  1-5.1 THE OSI MODEL Established in 1947, the International Standards Organization (ISO) is a multinational body dedicated to worldwide agreement on international standards. An ISO is the Open Systems Interconnection (OSI) model is the standard that covers all aspects of network communications from ISO. It was first introduced in the late 1970s. CSC 329 Chapter 1 Fundamental concepts of computer networks. 1.9  ISO is the organization. OSI is the model. Topics discussed in this section: Layered Architecture Peer-to-Peer Processes Encapsulation CSC 329 Chapter 1 Fundamental concepts of computer networks. 1.10  Layered Architecture Layers Seven layers of the OSI model Layer 7. Application Layer 6. Presentation Layer 5. Session Receiver Layer 4. Transport Sender Layer 3. Network Layer 2. Data Link Layer 1. Physical CSC 329 Chapter 1 Fundamental concepts of computer networks. 1.11  Figure 2.4 the OSI model CSC 329 Chapter 1 Fundamental concepts of computer networks. 2.12  Layered Architecture A layered model Each layer performs a subset of the required communication functions Each layer relies on the next lower layer to perform more primitive functions Each layer provides services to the next higher layer Changes in one layer should not require changes in other layers The processes on each machine at a given layer are called peer-to-peer process CSC 329 Chapter 1 Fundamental concepts of computer networks. 1.13  PEER – TO – PEER PROCESS Communication must move downward through the layers on the sending device, over the communication channel, and upward to the receiving device Each layer in the sending device adds its own information to the message it receives from the layer just above it and passes the whole package to the layer just below it At the receiving device, the message is unwrapped layer by layer, with each process receiving and removing the data meant for it CSC 329 Chapter 1 Fundamental concepts of computer networks. 1.14  PEER – TO – PEER PROCESS The passing of the data and network information down through the layers of the sending device and backup through the layers of the receiving device is made possible by interface between each pair of adjacent layers Interface defines what information and services a layer must provide for the layer above it. CSC 329 Chapter 1 Fundamental concepts of computer networks. 1.15  The interaction between layers in the OSI model CSC 329 Chapter 1 Fundamental concepts of computer networks. 1.16  An exchange using the OSI model CSC 329 Chapter 1 Fundamental concepts of computer networks. 1.17  LAYERS IN THE OSI MODEL Topics discussed in this section: 1. Physical Layer 2. Data Link Layer 3. Network Layer 4. Transport Layer 5. Session Layer 6. Presentation Layer 7. Application Layer CSC 329 Chapter 1 Fundamental concepts of computer networks. 1.18  Physical Layer The physical layer is responsible for movements of individual bits from one hop (node) to the next. Function Physical characteristics of interfaces and media Representation of bits Data rate Synchronization of bits Line configuration (point-to-point or multipoint) Physical topology (mesh, star, ring or bus) Transmission mode ( simplex, half-duplex or duplex) CSC 329 Chapter 1 Fundamental concepts of computer networks. 1.19  Physical layer CSC 329 Chapter 1 Fundamental concepts of computer networks. 1.20  Data Link Layer The data link layer is responsible for moving frames from one hop (node) to the next. Function Framing Physical addressing Flow control Error control Access control CSC 329 Chapter 1 Fundamental concepts of computer networks. 1.21  A frame is a digital data transmission unit in computer networking and telecommunication. In packet-switched systems, a frame is a simple container for a single network packet. In other telecommunications systems, a frame is a repeating structure supporting time-division multiplexing CSC 329 2.22 Chapter 1 Fundamental concepts of computer networks.  ADDRESSING Four levels of addresses are used in an internet employing the TCP/IP protocols: physical, logical, port, and specific. Topics discussed in this section: Physical Addresses Logical Addresses Port Addresses Specific Addresses CSC 329 Chapter 1 Fundamental concepts of computer networks. 2.23  Figure 2.17 Addresses in TCP/IP CSC 329 Chapter 1 Fundamental concepts of computer networks. 2.24  Error control Error control in data link layer is the process of detecting and correcting data frames that have been corrupted or lost during transmission. In case of lost or corrupted frames, the receiver does not receive the correct data-frame and sender is ignorant about the loss. Error control in data link layer of detecting or identifying and re-transmitting data frames that might be lost or corrupted during transmission . CSC 329 Chapter 1 Fundamental concepts of computer networks. 25  Flow control & Access control Flow control is the process of managing the rate of data transmission between two nodes to prevent a fast sender from overwhelming a slow receiver. Access control is a fundamental component of data security that dictates who's allowed to access and use company information and resources. Through authentication and authorization, access control policies make sure users are who they say they are and that they have appropriate access to company data CSC 329 Chapter 1 Fundamental concepts of computer networks. 26  Data link layer CSC 329 Chapter 1 Fundamental concepts of computer networks. 1.27  Hop-to-hop delivery CSC 329 Chapter 1 Fundamental concepts of computer networks. 1.28  Example 1 In following Figure a node with physical address 10 sends a frame to a node with physical address 87. The two nodes are connected by a link. At the data link level this frame contains physical addresses in the header. These are the only addresses needed. The rest of the header contains other information needed at this level. The trailer usually contains extra bits needed for error detection CSC 329 Chapter 1 Fundamental concepts of computer networks. 1.29