11 CHAPTER ONE Introducing Networks. Objectives Identify and describe the functions of each of the...
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Transcript of 11 CHAPTER ONE Introducing Networks. Objectives Identify and describe the functions of each of the...
11 11
CHAPTERONE
Introducing Networks
Objectives
Identify and describe the functions of each of the seven layers of the OSI reference modelIdentify the reasons why the networking industry uses a layered modelDefine and explain the conversion steps of data encapsulationDefine and describe the function of a MAC addressDescribe connection-oriented network service and connectionless network service, and identify the key differences between them
Introduction to Networking
Network Term that describes the connection of
two or more computers by some type of medium, including: Wire cable Fiber-optic cable Infrared Radio equipment
Origin of Networking
Difficult to place actual origin as many devices have been networked throughout historyToday, networks include a wide variety of computers and peripheral componentsSystems that are part of a network do not have to be identical
Why Do We Use Networks?
ConveniencePeople expect interoperability from electronic devicesComputer networks allow for the transfer of files, data, and even shared applications without copying anything to floppy disk
Connection Media
Media Cable, glass, or telephone lines that host
the signal from one computer to another on the network
Electromagnetic interference (EMI) Electric noise that disrupts signals on
cables
Wireless Communications that are not conducted
over physical wires or cables
Client/Server Networks
Networks that have computers that are servers and computers that act as clients to those serversYou may see a variety of servers on a network: Print server File server Database server Remote access server (RAS) Web server
Peer-to-Peer
When every computer on a network acts as both a client and a server, the network is a peer-to-peer networkIn a peer-to-peer network, all computers can share resources with other computersPeer-to-peer networks are also known as “workgroups”
LAN, WAN, MAN, SAN
A local area network (LAN) is a group of computers and other devices typically connected by a cableA wide area network (WAN) is a network that spans two or more geographically diverse locationsA metropolitan area network (MAN) is an intermediate specification that defines networks confined to a fairly restricted geographic areaA storage area network (SAN) is a subsystem of networked storage devices physically separated from servers
Network Operating System
Network operating system (NOS) Allows communication over a network
End system The location and/or set of controls
that the user can manipulate to interact with a computer or a network
NIC, Networking Hardware, and Networking Software
Network interface card (NIC) Hardware device that transmits and
receives electronic signals on a network
Networking hardware is a generic term that describes all the physical components of a networkNetworking software is a generic term that describes the software programs used to run a network
Understanding the OSI Model
International Organization for Standardization (ISO) Multi-industry association that attempts to
standardize and define items that increase communication and compatibility in many different countries
Open Systems Interconnection (OSI) Seven layer reference model created by the
ISO Defines and separates networking hardware
and software into distinct layers and functions
Reasons for Layering
Simplifies the network modelEnables programmers to specialize in a particular level or layer of the networking modelProvides design modularityEncourages interoperabilityAllows for standardized interfaces to be produced by networking vendors
Seven Layers of the OSI Model
Physical layerData Link layerNetwork layerTransport layerSessions layerPresentation layerApplication layer
Reasons for Layering
As a group, these layers form the OSI protocol stack
Figure 1-1:OSI Reference Model
Peer OSI Communication
The seven layers of the OSI reference model communicate with each other via peer communication
Figure 1-2:Peer communication
Layer Functions:Physical (Layer 1)
Layer 1 in the OSI modelHas the following responsibilities: Definition of the physical
characteristics of the network hardware
Representation of binary digits as voltages (encoding)
Transmission of signals on the wire
Layer Functions:Physical (Layer 1)
Figure 1-3:568B twisted pair wiring scheme
Layer Functions:Physical (Layer 1)
Connectors, cables, and devices like repeaters and hubs can be associated with the physical layerWhen choosing cable, consider the following: Expense Physical location Distance Security requirements Transmission speed required
Layer Functions:Data Link (Layer 2)
Has several responsibilities: NIC software functions, including
identification of source and destination nodes via physical addresses
Definition of how data is packaged for transport as frames
Error detection Flow control of information sent across
the link
Layer Functions:Data Link (Layer 2)
Data Link layer has two sublayers that further articulate its function: Logical Link Control (LLC) layer Media Access Control (MAC) layer
The Institute of Electrical and Electronics Engineers (IEEE) created these sublayers to identify and isolate the separate responsibilities required at this level of the protocol stack
Layer Functions:Data Link (Layer 2)
Figure 1-4:Data Link layer subdivision
Layer Functions:Data Link (Layer 2)
MAC layer defines the media access method and provides a unique identifier for the network cardThe unique identifier is a 48-bit address represented as 12-digit hexadecimal number given to each network card during productionEvery network interface card must have a unique physical address (also called the MAC address)
Layer Functions:Data Link (Layer 2)
Figure 1-5:MAC address
Layer Functions:Data Link (Layer 2)
Ethernet A standard networking architecture that
defines the physical layout, lengths, and types of media that can be used
Carrier Sense Multiple Access with Collision Detection (CSMA/CD) Network access method used by
Ethernet networks
Layer Functions:Network (Layer 3)
Has the following function: Error handling Software addressing for data packets Best path selection
The Network layer contains the logical address for the computer
Layer Functions:Transport (Layer 4)
Provides point-to-point data transportationResponsibilities include: End-to-end error-free transmission and
delivery Data segmentation into maximum
transmission unit (MTU) size Messaging service for the Session layer
Layer Functions:Transport (Layer 4)
Protocols that reside at the Transport layer can be: Connection-oriented Connectionless
A packet sent by a connectionless protocol is also called a datagram
Layer Functions:Session (Layer 5)
Enables two applications on the network to have an ongoing conversation or dialogExamples of Session layer protocols include: SQL RPC X-Windows
Layer Functions:Session (Layer 5)
Provides the following services: Control for data exchange Data synchronization definition Failure recovery Communication setup and teardown
Layer Functions:Presentation (Layer 6)
Prepares the data from Application layer for transmission over the networkComponents include extensions and coding schemes such as: BMP WAV EBCDIC ASCII
Layer Functions:Presentation (Layer 6)
Has these responsibilities: Data translation Data formatting Data syntax restructuring Data encryption Data compression
Layer Functions:Application (Layer 7)
Has the following responsibilities: Initiating the request for network
service Providing services to applications
Data Encapsulation
Data is sent from one computer to another in a data packetThe packet contains data from the sending application and additional information added by the protocol stackPrior to transmission across the network, the data is organized into a data frame at layer 2
Data Encapsulation
Protocol data unit (PDU) Information added to a data packet by
the layers of the protocol stack
Encapsulation Process that occurs during
transmission through the protocol stack in which data from the higher layers is wrapped in a protocol header and/or trailer
Data Encapsulation
Figure 1-6: Encapsulation
Data Encapsulation
Table 1-1:Five steps of data encapsulation
Chapter Summary
Two or more computers connected by media form a networkThe ISO developed the OSI model in the mid-1980s to standardize networking models Data transmission can be connection-oriented or connectionless
Chapter Summary
The OSI model has seven layers: Physical layer Data Link layer Network layer Transport layer Session layer Presentation layer Application layer
Chapter Summary
When the network user sends data to the network, it goes through a five-step data encapsulation processThis process takes place as the data packet travels down the OSI stack