Week one - networks and Layered Communication Introduction to Networks Layered Communication OSI...

Week one - networks and Layered Communication• Introduction to Networks• Layered Communication• OSI Model• The Physical Layer• The Data Link Layer

Introduction to Networking (1)• Understand the concept of Networking

– Definition – What can be Networked – Reasons for Networking

• Understand the concept of an individual PC• Understand wide variety of computer types

– PC– MACINTOSH– Mainframe

Introduction to Networking (2) • Understand that what is important in

Networking is the Protocol used• Terminology used to describe Networks

– LANs– WANs– MANs

• Understand the difficulty of Networking a wide– variety of Networks– Hardware– Software

Networking

• Connecting of any collection of computers, printers, routers, switches, and other devices for the purpose of communication over some transmission medium.

Protocol

• Formal description of a set of rules and conventions that govern how devices on a network exchange information.

LAN, WAN and MAN (1)

• Local-area network [LAN]– High-speed, low-error data network covering

a relatively small geographic area. LANs connect workstations, peripherals, terminals, and other devices in a single building or other geographically limited area. LAN standards specify cabling and signaling at the physical and data link layers of the OSI model. Ethernet, FDDI, and Token Ring are widely used LAN technologies.

LAN, WAN and MAN (2)

• Wide Area Network [WAN]– Data communications network that

serves users across a broad geographic area and often uses transmission devices provided by common carriers. Frame Relay, SMDS, and X.25 are examples of WANs.

LAN, WAN and MAN (3)

• Metropolitan-area network (MAN)– Network that spans a

metropolitan area. Generally, a MAN spans a larger geographic area than aLAN, but a smaller geographic area than a WAN. Compare with LAN andWAN.

Hardware and Software

• hardware - A term used in computing to refer to physical parts or equipment.

• Software - A term used in computing to refer to programs or applications.

What is Networking?

• Networking is the interconnection of workstations, peripherals peripherals terminals and other devices. One of the most common types of networks is the Local Area Network or LAN.

• Peripherals– Device connected to a computer to

provide auxiliary functions such as printing, added disk space, scanning or CD-Rom

Why and how did networking start?• Applications written for business helped create

the PC industry. [Why]• Early computers were standalone devices.

[Why]• One early solution to these problems was the

creation of local area networks, or LANs. [When] – What was needed was a way to move

information efficiently and quickly from one business to another. The solutionwas the creation of metropolitan area networks, or MANs, and wide area networks, or WANs.

Why were networking standards needed?• Because many of the emerging network

technologies were built using different hardware and software implementations, one problem that soon surfaced was that many of the new network technologies were incompatible. Increasingly, it became difficult for networks using different specifications to communicate with each other.

OSI Model

• Understand concept of standards• Understand that OSI Model is model for• Know names of 7 layers of the OSI model• Understand what encapsulation is• Understand why it is desirable to network• Understand what data is data packet

Understand what a source is• Understand what a destination is

What model was developed to describe networking? • To address the problem, the International

Organization for Standardization (ISO) researched networks schemes like DECNET, SNA, and TCP/IP. As a result of this research, the ISO recognized there was a need to create a network model that would help vendors create networks that would work compatibly and interoperably with other networks. The OSI Reference Model, released in 1984, was the descriptive scheme they created. By creating the OSI model, the ISO was providing vendors with a set of standards .

What is the OSI Reference Model?• The OSI (Open System

Interconnection] reference model is not something tangible. Rather it is a conceptual framework specifying the network functions that occur at each layer. In simpler terms, a model is a way of picturing how information travels through networks.

What process does the OSI Reference Model describe? • Each of the seven problem areas is

solved by a layer of the model. The seven layers of the OSI reference model are: the physical layer, the data link layer, the network layer, the transport layer, the session layer, the presentation layer, and the application layer.

Why is Networking desirable? • By networking or connecting

computers, printers, routers, switches, and other devices so that they can communicate with each other, it is possible to share information, resources, or get to the Internet.

How does encapsulation allow computers to communicate data? • The information that is sent on a

network is referred to as data or data packets.

How does encapsulation allow computers to communicate data? • If one computer (host A) wants to send data to

another computer (host B), the data must first

be packaged in a process called encapsulation.

What is the first building block of the OSIReference Model?• In the OSI model, this foundation

is called the Physical layer.

The function of the physical layer• It is the transmission of data.

Typically such transmission is accomplished through the use of such things as wires, connectors, and voltages.

How is information stored in computers?• Information in computers is stored using the

binary number system, in which the only

possible symbols, or binary digits, 0 or 1.

What types of materials might one see in the Physical layer of the OSI model? • The materials used to connect

computers vary. They include twisted pair, coaxial, and fiber-optic cable.

What are some criteria for determining what type of media will be used?• The type of connecting material

used by a network will determine things such as how much data and how fast the data can travel across the network.

How do computers identify themselves? [Data link Layer]• Every computer has a unique way of

identifying itself. Every computer whether it is attached to a network or not has a physical address. No two physical addresses are ever alike. Referred to as the Media Access Control Address or MAC Address, the physical address is located on the Network Interface Card or NIC Card.

The Network card

Where is the NIC card on the OSI model?• It is located in that the data link

layer, layer 2, where the MAC address is located,