Transcript Presentation

8
Network Connectivity
Guide to Operating Systems
Second Edition
Chapter 8
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Objectives
After reading this chapter and completing the
exercises you will be able to:
• Explain basic networking theory, such as
network topologies, packaging data to
transport, and how devices connect to a
network
• Describe network transport and
communications protocols, and determine
which protocols are used in specific computer
operating systems
Chapter 8
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Objectives
After reading this chapter and completing the
exercises you will be able to:
• Explain how bridging and routing are used on
networks
• Explain LANs and WANs
• Describe how network and workstation
operating systems are used for remote
networking
Chapter 8
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Basic Networking
• A network is composed of communications
media such as communications cable, used to
link computers, printers, disk storage, CD-ROM
arrays, and network communications equipment
• The basic principle of networking is similar to
connecting telephones for communications
• The hardware components of a computer network
are computers, printers, communications cable,
and internetworking devices such as bridges,
switches, routers, and hubs
Chapter 8
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Telephone and
Computer Networks Compared
Chapter 8
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Basic Networking
• Computer networks also have software components
consisting of client and server network operating
systems
• Windows 95, Windows 98, Windows NT 4.0
Workstation, Windows 2000 Professional, and
Windows XP Professional are examples of client
operating systems
• A client operating system is one that enables a
workstation to run applications, process information
locally, and communicate with other computers and
devices over the network
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Basic Networking
• A workstation is a computer that has a CPU,
and can run applications locally, or obtain
applications and files from another computer
on the network
• Sometimes the term workstation is confused
with the term terminal
• The difference is that a terminal has no CPU or
local storage for running programs
independently
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Basic Networking
• A network operating system (NOS) is one that
enables the coordination of network activities
and the sharing of resources – network
communications, shared printing, shared
access to files, and shared access to software,
for example
• A server is a computer running a NOS, which
provides resources, such as shared files and
programs that are accessed by clients
Chapter 8
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Reasons for a Network
• Networks were invented for three interrelated
reasons: to share resources, save money, and
increase productivity
• Most important, networks allow organizations to save
money by sharing resources
• Windows NT Server 4.0, Windows 2000 Server, and
Windows .NET Server offer several ways to save
money and time by centralizing software and client
operating system installation through a server
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Sharing Resources in an Office
Chapter 8
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Reasons for a Network
• In Windows NT Server 4.0, the Network Client
Administrator enables you to install the MSDOS and Windows 95 operating systems on
any client connected to a network
• Windows 2000 Server and Windows .NET
Server use Remote Installation Services (RIS)
to install pre-configured client operating
systems, such as Windows 2000 Professional,
on a mass scale
Chapter 8
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Reasons for a Network
• Both Windows 2000 and Windows .NET Server
also enable you to either assign or publish
software applications through creating group
policies
• Assigning applications involves setting up an
Active Directory group policy so that a particular
version of software, such as Microsoft Word XP,
is automatically started through a desktop
shortcut or menu selection, or by clicking a file
type
Chapter 8
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Reasons for a Network
• Publishing an application means that the
Windows 2000 Professional or Windows XP
Professional client can open the Add/Remove
Programs (Add or Remove Programs in Windows
XP) icon in the Control Panel to install the preconfigured software from a central Windows 2000
or Windows .NET server
• Productivity is another reason for networks
• Electronic mail (e-mail) is another example of how
networking can increase productivity
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Reasons for a Network
• With e-mail, you can reach someone on the first
try
• You also can attach a file, such as a wordprocessing document or spreadsheet, so that the
recipient has it right away
• Electronic commerce is another network
application that increases productivity
• Another growing area for networks is electronic
conferencing
Chapter 8
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The Development of
Network Operating Systems
• Novell NetWare was one of the first network operating
systems, initially demonstrated in 1982 at the National
Computer Conference as a groundbreaking PC
networking system
• Windows 3.1, released in 1992, was one of the first
Windows-based operating systems with network
capabilities, enabling it to connect to NetWare,
Microsoft, and other networks
• Workgroups (pre-defined groups of member
computers) provide the ability to limit resource
sharing on the basis of group membership
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The Development of
Network Operating Systems
• Windows 95 represents yet another major step into
networking because it expands peer-to-peer
networking and has the ability to connect to more
kinds of networks
• Windows Me also comes with better networking
capabilities for home use
• Representing a different Windows operating system
track, Windows NT 3.1 was released just a little later
than Windows 3.1, but Windows NT 3.1 was intended
for industrial strength networking from the beginning
Chapter 8
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The Development of
Network Operating Systems
• The dawning of the millennium brought two new
names for Windows NT: Windows 2000 Server and
Windows 2000 Professional (Workstation)
• Windows 2000 has evolved into two products,
Windows XP and Windows .NET Server, both
containing the core elements of the Windows 2000
kernel
• Both Windows 2000 and Windows XP have built-in
options to configure home and small office networks,
such as sharing a one modem-based Internet
connection between multiple computers connected
through a small network
Chapter 8
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The Development of
Network Operating Systems
• Besides the NetWare and Windows-based
operating systems, there are several others
designed for networking:
– UNIX
– Banyan Vines
– Pathworks
– LAN Manager
• All three are server operating systems that may
be in use on networks, and that run on small to
mid-sized computers
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The Basics of Network Topologies
• A topology is the design of the network, as if you
were looking at it from above in a helicopter, or
following the path information takes when it goes
from one computer to another
• A network that uses a bus topology is designed
like a climbing rope with knots tied along the way
for a foothold
• There is a beginning and end to the rope, and
junctures along the way for your feet
Chapter 8
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Bus Topology
Chapter 8
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The Basics of Network Topologies
• A ring topology is one in which the data-carrying
signal goes from station to station around the ring,
until it reaches the target destination
• There is no beginning or end point, so there are no
terminators (see Figure 8-4)
• The star topology is one in which there is a hub in the
middle, with cable segments coming out of the hub in
all directions, as shown in Figure 8-5
• The hub sends the signal onto each segment, which
has a computer at the end
Chapter 8
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Ring Topology
Chapter 8
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Star Topology
Chapter 8
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The Basics of Network Topologies
• Some hubs, called passive hubs, just pass the signal
onto a segment without modifying the signal in any
way
• The disadvantage in using a passive hub is that the
signal grows weaker each time it goes through the
hub to the next segment
• Networks that use active hubs support more
computers because the signal is amplified to its
original strength each time it goes through the hub
Chapter 8
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The Basics of Network Topologies
• Switched networks use switches in place of
hubs
• The switch learns what devices are located on
each of the segments attached to it, and only
transmits the information on the segment
where the destination device resides
• Traffic is not transmitted on all segments at
once, as happens on hubs
Chapter 8
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Packets, Frames, and Cells
• Each computer or network device translates data
into individual units, and then places the units
onto the network cable
• Each data unit is called a packet or frame
• These terms are sometimes used
interchangeably, but they are not the same
• Both consist of data and transmission control
information contained in a header that is
appended to the front of the data
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Packets, Frames, and Cells
• The difference is that a packet contains routing
information that can be read by specialized devices that
are able to forward packets to specific networks
• The actual data is placed after the header information,
and followed by a footer or trailer that enables detection
of a transmission error
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Packets, Frames, and Cells
• Older networks transmit at speeds of 4 Mbps
(megabits per second), 10 Mbps, and 16 Mbps
• Newer networks transmit at 100 Mbps to 10
Gbps and faster, or consist of segments that
transmit at 10 Mbps, 100 Mbps, 1 Gbps, or 10
Gbps
• Network backbones, which are segments that
join main networks, typically run at 100 Mbps or
higher
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Packets, Frames, and Cells
• A cell is a data unit designed for high-speed
communications; it has a control header and
a fixed-length payload
• The payload is that portion of a frame, packet,
or cell that contains the actual data, which
might be a portion of an e-mail message or
word-processing file
Chapter 8
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Packets, Frames, and Cells
•
One element of the cell header is path information that enables the
cell to take the route through the network that is most appropriate
to the type of data carried within the cell
Chapter 8
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Packets, Frames, and Cells
• A protocol is a set of formatting guidelines for
network communications, like a language, so that the
information sent by one computer can be accurately
decoded by another
• Protocols also coordinate network communications
so that data is transported in an orderly fashion,
preventing chaos when two or more computers want
to transmit at the same time
• A network may use several different protocols,
depending on the NOS and the types of devices that
are connected
Chapter 8
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Connecting to a Network
• Computers and internetworking devices connect to a
network through a network interface card (NIC)
• A NIC is usually a card that goes into a computer’s
expansion slot, or that is built into a network device
or a computer
• Each NIC has a unique hexadecimal address, called a
device or physical address, which identifies it to the
network
• It is also called the Media Access Control (MAC)
address
Chapter 8
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Devices on a Network
With Unique Physical Addresses
Chapter 8
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Connecting to a Network
• Some NICs also transform data into radio frequency
communications, called packet radio, for wireless
networks
• The software logic consists of one or more programs
called firmware because it resides in a programmable
chip on the card
• Communication between the operating system and its
NIC, like communication between the operating
system and carious input, output, and storage
devices, is controlled by driver software written by the
manufacturer of the device
Chapter 8
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Networking Protocols
• Protocols are used for many types of network
communications, including the following:
– Coordinating transport of packets and frames among network
devices
– Encapsulating data and communication control information
– Providing communications to accomplish a specific function,
such as enabling the destination computer to tell the source
computer to slow its transmission speed because it is too fast
for the destination computer
– Enabling communications over a long-distance network, such
as the Internet
– Enabling remote users to dial into networks
Chapter 8
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Transport Protocols
• The commonly used transport protocols are Ethernet
and token ring
• Ethernet is in more installations than token ring
because there are more network equipment options
for it, and because modern Ethernet network designs
are most easily expanded for high-speed networking
• Token ring, an IBM-proprietary protocol, is used
because it is reliable, and network problems were
initially easier to troubleshoot on token ring networks
than on early Ethernet networks
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Ethernet
• In Ethernet communications, only one station on the
network should transmit at a given moment
• If two or more stations transmit at the same time,
frames collide
• The transmission control method used by Ethernet is
called Carrier Sense Multiple Access with Collision
Detection (CSMA/CD)
• In CSMA/CD, the NICs of computers and devices
check the network communications cable for a carrier
signal that contains an encoded frame
Chapter 8
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Ethernet
• If the device’s NIC detects a carrier signal, and if the NIC
decodes its own device address within the frame, it
forwards that packet to its firmware for further decoding
• If the frame does not contain its device address, then the
NIC does not process the signal any further
• There are two mainstream varieties of Ethernet protocol
communications: the IEEE 802.3 standard and Ethernet II
• Both are nearly identical, but Ethernet II uses a slightly
different frame format for modern network
communications
Chapter 8
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Ethernet
•
In IEEE 802.3 and in Ethernet II, frames contain a
header that has control information, along with
source and destination addressing
• The data portion of both frame types contains 576 to
12,208 bytes
• Also, both frame formats contain a frame change
sequence field as a trailer, which is used to alert the
receiving station when a transmission error occurs,
by showing that some portion of the received frame
contents is not the same as when the frame was sent
Chapter 8
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Ethernet
• Networks that use Ethernet are designed in a bus
topology, or a star topology, in which the
internetworking devices simulate a logical bus
• Ethernet hybrid star-bus networks are very
common in modern network design because they
are easier to troubleshoot and expand for highspeed networking than simple bus networks
• Fast Ethernet is becoming commonplace, and
most NICs are currently designed to handle either
10 or 100 Mbps communications
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Ethernet
• All versions of Ethernet are compatible with
popular network operating systems such as:
– UNIX
– NetWare
– Windows NT, 2000, XP, and .NET Server
– Windows 3.x
– Windows 95/98/Me
– Mac OS
– Banyan Vines
– Pathworks
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Token Ring
• In most versions of token ring, only one
network station transmits at a time
• The sequence of frame and packet
transmissions is controlled by the use of a
specialized frame, called a token
• A token without data is transmitted around the
network until it is captured by a station that
wants to transmit
Chapter 8
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Station with the Token in Token Ring
Chapter 8
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Token Ring
• Token ring is compatible with the same mainstream
network operating systems that are used in Ethernet,
including:
– UNIX
– NetWare
– Windows NT, 2000, XP, and .NET Server
– Windows 3.x
– Windows 95/98/Me
– Mac OS
– Banyan Vines
– Pathworks
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Implementing a Transport
Protocol in an Operating System
• A transport protocol is interfaced with an
operating system through three elements: a
network driver specification built into the
operating system, a NIC, and a NIC driver
• Network operating systems are built to offer
special elements, that programmers call
“hooks,” in the operating system kernel
(program code), which enable the operating
system to interface with a network
Chapter 8
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Implementing a Transport
Protocol in an Operating System
• Microsoft designed the Network Device
Interface Specification (NDIS) and Windowsbased NDIS drivers for this purpose
• When you set up an operating system to work
on an Ethernet or token ring network, the first
step is to purchase an Ethernet or token ring
NIC for the computer running the operating
system
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Implementing a Transport
Protocol in an Operating System
• The NIC cable interface must also match the
type of cable used on the network
• After the NIC setup is complete, and the
computer is connected to the network, the
operating system, NIC, and driver handle the
work of converting data created at the
computer to an Ethernet or token ring format
for transport over the network
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Communications Protocols
• The development of communications protocols
(the protocols that carry data between two
communicating stations, and are encapsulated
in Ethernet or token ring transport protocols)
has been interrelated to the network operating
systems in which they are used
• The Internet Packet Exchange (IPX) protocol
was developed to enable a NetWare file server
to communicate with its client workstations
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Communications Protocols
• Also, in 1982, researchers implemented and
combined two protocols for use on the
Advanced Research Projects Agency network,
ARPANET, which was the long-distance
network that set the foundation for the Internet
• The ARPANET protocols now used worldwide
over the Internet are Transmission Control
Protocol (TCP) and Internet Protocol (IP)
Chapter 8
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IPX
• IPX is a protocol developed by Novell and modeled
after the Xerox Network System (XNS) protocol
• IPX encapsulates data and transports it within a host
transport protocol format—Ethernet or token ring
• When there is a need for more reliable data transport,
such as for data from a database, an application
running via NetWare can use Sequence Packet
Exchange (SPX), a protocol that provides connectionoriented communications
Chapter 8
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IPX
• IPX relies upon SPX at the transport layer to
provide reliable, error-free communication
• IPX works with other specialized service and
NetWare protocols as follows:
– Link Support Layer (LSL)
– NetWare Core Protocol (NCP)
– NetWare Link Services Protocol (NLSP)
– Routing Information Protocol (RIP)
– Service Advertising Protocol (SAP)
Chapter 8
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NetBEUI
• NetBEUI (NetBIOS Extended User Interface)
was introduced in the early nineties as the main
protocol for LAN Manager, a network server
operating system developed by Microsoft and
IBM, and the forerunner of Windows NT Server
• NetBEUI was developed from the Network
Basic Input/Output System (NetBIOS), which is
a technique used to interface software with
network services
Chapter 8
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NetBEUI
• NetBIOS should not be confused with a protocol
• It acts as a software interface only, providing a
way for an application to export data to a network
service, such as linking data in a word-processed
document to a network mail service that attaches
the document to an e-mail
• NetBEUI is designed for networks consisting of
fewer than 200 stations, and is well suited for
Microsoft networks
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NetBEUI
• It is particularly compatible with applications
that use NetBIOS and computers that run
Microsoft operating systems, such as
Windows NT, 3.x, 95, 98, and Me
• Another advantage of NetBEUI is that later
versions of this protocol can handle nearly
limitless communication sessions
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NetBEUI
• An important limitation of NetBEUI is that it is not
designed to carry routing information, which
means that it is not a good choice for medium
and large networks
• Other advantages of NetBEUI are:
– Low use of memory resources
– Quick transport of information on small networks
– Strong error detection and recovery
– Relatively easy configuration in the host operating
system
Chapter 8
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NetBEUI Flooding All
Networks with a Large Network Setup
Chapter 8
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TCP/IP
• TCP/IP is one of the oldest protocols, initially
developed for long-distance networking on
ARPANET, and now used on most networks
• One of the strongest influences on TCP/IP use
has been the growth of the Internet
• UNIX has always used TCP/IP as its main network
communications protocol
• TCP was developed for extremely reliable pointto-point communications between computers on
the same network
Chapter 8
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TCP/IP
• TCP/IP is also compatible with the following
operating systems:
– Windows 3.1 and 3.11
– Windows 95/98/Me
– Windows NT 3.0, 3.5, 3.51, and 4.0
– Windows 2000/XP/.NET Server
– Mac OS
– Banyan Vines
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TCP/IP
• Some of the communication functions
performed by TCP are:
– Establishes the communication session between
two computers
– Ensures that data transmissions are accurate
– Encapsulates, transmits, and receives the payload
data
– Closes the communication session between two
computers
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TCP/IP
• The IP portion of TCP/IP is used to make sure that a
frame or packet reaches the intended destination
• IP performs the following complementary functions
with TCP:
– Handles packet addressing
– Handles packet routing
– Fragments packets, as needed, for transport across
different types of networks
– Provides simple packet error detection in conjunction with
the more thorough error detection provided by TCP
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TCP/IP
• IP addressing uses the dotted decimal notation
that consists of four 8-bit binary numbers
(octets) separated by periods
• There are five IP address classes, Class A
through Class E, each used with a different
type of network
• The address classes reflect the size of the
network, and whether the packet is unicast or
multicast
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TCP/IP
• In the unicast method of transmission, one copy
of each packet is sent to each target destination
• In the multicast method, the recipients are placed
in a group, such as a group of all eight
workstations since they are on the same network
• Classes A through C are intended as unicast
addressing methods, but each class represents a
different network size
• Class A is used for the largest networks
composed of up to 16,777,216 nodes
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TCP/IP
• Class A networks are identified by a value
between 1 and 126 in the first position of the
dotted decimal address
• The network ID is the first eight bits, and the host
ID is the last 24 bits
• Class B is a unicast addressing format for
medium-sized networks composed of up to
65,536 nodes, and it is identified by the first octet
of bits ranging from decimal 128 to 191
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TCP/IP
• The first two octets are the network ID, and the
last two are the host ID
• Class C addresses are used for unicast network
communications on small networks of 256 nodes
or less
• The first octet translates to a decimal value in the
range of 192 to 223, and the network ID is
contained in the first 24 bits, while the host ID is
contained in the last eight bits
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TCP/IP
• Class D addresses do not reflect the network size, only
that the communication is a multicast
• Unlike Classes A through C, the four octets are used to
specify a group of nodes to receive the multicast, which
consists of those nodes that are multicast subscription
members
• Class D addresses are in the range from 224.0.0.0 to
239.255.255.255
• A fifth address type, Class E, is used for
experimentation, and addresses range from 240 to 255 in
the first octet
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TCP/IP
• Besides class addressing, there are some specialpurpose IP addresses, such as 255.255.255.255, which
is a broadcast packet sent to all network locations
• A new way to ignore address class designations is by
using Classless Interdomain Routing (CIDR)
addressing that puts a slash (/) after the dotted
decimal notation
• CIDR provides more IP address options for mediumsized networks because there is shortage of Class B
and Class C addresses
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TCP/IP
• Computers and devices that use IP addressing
actually have two addresses: a physical address and
an IP address
• The use of two addresses provides better insurance
that a packet will reach the right destination, while
expending the fewest network resources
• TCP/IP works with a range of associated protocols
that make this a powerful combination for networks of
all sizes and types
Chapter 8
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Using TCP/IP Subnet Masks
Chapter 8
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TCP/IP
• Some protocols include the following:
– Routing Information Protocol (RIP)
– Simple Mail Transfer Protocol (SMTP)
– File Transfer Protocol (FTP)
– Telnet
– Hypertext Transfer Protocol (HTTP)
– Point-to-Point Protocol (PPP)
– Simple Network Management Protocol (SNMP)
– Internet Control Message Protocol (ICMP)
– Domain Name Service (DNS)
– Dynamic Host Configuration Protocol (DHCP)
Chapter 8
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AppleTalk
• AppleTalk is a network communications protocol used
between Macintosh computers
• It is designed primarily as a peer-to-peer protocol, rather
than for combined peer-to-peer and client-to-server
communications
• As a peer-to-peer protocol, AppleTalk establishes equal
communications between networked Macintosh computers,
without the need for a server
• AppleTalk performs three essential services: remote access
to files over a network, network print services, and access
to computers running MS-DOS or Windows operating
systems
Chapter 8
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Peer-to-Peer Networking
Using AppleTalk and No Server
Chapter 8
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AppleTalk
• Examples of protocols designed for use with
AppleTalk are as follows:
– AppleTalk Address Resolution Protocol (AARP)
– AppleTalk Data Stream Protocol (ADSP)
– AppleTalk Session Protocol (ASP)
– Datagram Delivery Protocol (DDP)
– Name-Binding Protocol (NBP)
– Printer Access Protocol (PAP
– Routing Table Maintenance Protocol (RTMP)
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Implementing Communications
Protocols in an Operating System
• Most computer operating systems are designed
to support one or more communications
protocols
• In general, there are two steps involved in setting
up a communications protocol in an operating
system
• The first is to install the protocol software that is
written for that operating system
• Step two is to bind the protocol with the NIC
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Implementing Communications
Protocols in an Operating System
• Binding the protocol
enables the NIC to
format data for that
protocol, and identify
the most efficient
methods for
transporting it within
Ethernet or token ring
• When two or more
protocols are used,
binding also enables
the NIC to set a priority
for which protocol to
process first
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Implementing Communications
Protocols in an Operating System
• The Mac OS up through version 9.x provides
one of the easiest methods for setting up
communications protocols
• In the Mac OS, you use a Control Panel to
designate a port for network communications
associated with the NIC
• In Mac OS X, setting up network
communications is also simplified, but with
more options than in Mac OS 9.x
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Implementing Communications
Protocols in an Operating System
• Through the Mac OS X Network panel, you can
fully configure your Mac to use TCP/IP and
TCP/IP network services, including the following:
– Manual configuration of IP address and subnet mask
– Automatic configuration of the IP address using DHCP
– Identification of the nearest router by IP address
– Identification of Domain Name Service (DNS) servers by
IP address
– Identification of search domains by IP address
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Implementing Communications
Protocols in an Operating System
• Most UNIX systems have TCP/IP networking
support built in, and some of these
automatically run a network configuration
program when you first boot the computer with
an installed NIC
• For some versions of UNIX, including Red Hat
Linux, you must configure a loopback device,
which is used to provide your computer with an
internal IP address, even when it is not
connected to the network
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Implementing Communications
Protocols in an Operating System
• In the Red Hat Linux GNOME interface, you can
configure a network connection by clicking the Start
icon on the panel, pointing to Programs, pointing to
System, and clicking Network Configuration
• Communications protocols in NetWare, such as IPX
and TCP/IP, can be set up in a window that appears
when NetWare is installed
• In Windows 3.1 and 3.111, communications protocols
are set up through the Main program group by
opening the Windows Setup icon and the Options
menu
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Implementing Communications
Protocols in an Operating System
• Communications
protocols are set
up in Windows
95/98/Me and
Windows NT 4.0
through the
Network icon in
the Control
Panel
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Implementing Communications
Protocols in an Operating System
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Integrating Different Operating
Systems on the Same Network
• The key to implementing multiple operating systems
on one network is to select a transport protocol and
communications protocols that are supported in all of
the operating systems that must be connected
• Ethernet is particularly well suited to a network that
has different operating systems
• In situations where TCP/IP is not supported by all
operating systems, then multiple protocols can be
configured, such as a combination of AppleTalk,
TCP/IP, and IPX/SPX
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Bridging and Routing
• One or more networks or segments can be linked by
using internetworking devices such as bridges and
routers
• Bridges are used to link segments that are close
together, such as on different floors in the same
building
• Another use for bridges is to extend segments, such
as when more stations must be added, but the
primary segment already contains the maximum
length of cable or number of stations permitted by
network standards
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Bridging and Routing
• Bridges operate in what network administrators
call promiscuous mode, which means that they
examine the physical destination address of
every frame that passes through them
• Bridges are protocol independent, a
characteristic that permits them to forward all
kinds of frame formats
• Bridges are not designed to route packets from
one network to another because they ignore
routing information
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Using a Bridge Filter to Direct
Segment A Frames to Segment D
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Bridging and Routing
• Switches operate in promiscuous mode like bridges, but
they provide additional logic that enables them to move
network traffic more efficiently than the old-style bridges
• Routers are used to join networks, either locally or
remotely
• Unlike bridges, routers are designed to look at routing
information in packets before forwarding those packets
to another network
• Routers also make excellent firewalls because networks
connected to a router can be divided into subnets as a
way to control incoming and outgoing traffic to each
subnet
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Router Linking Different
Types of Networks and Protocols
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Local and Wide Area Networks
• A local area network (LAN) is one in which the service area
is relatively small, such as a network in an office area, or
one spread through a floor in a building
• A wide area network (WAN) is one that offers networking
services over a long distance, such as between cities,
states, or countries
• There are several interrelated elements that can be used to
determine the intersection of a LAN with a WAN
• One element is that the network topology may change
between the two, such as a LAN that uses a ring topology
and a WAN that uses a star
• Another factor is a change in cable type
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Using Operating
Systems for Dial-Up Access
• Windows NT/2000/.NET Server offer a similar
option for dialing into a LAN through a Remote
Access Services (RAS) server
• RAS is a set of network services that can be
installed on any Windows NT/2000/.NET server
connected to one or more modems
• Besides setting up a RAS server, there must be
a way to set up remote access capability on
client workstations
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Using Operating
Systems for Dial-Up Access
• Windows 95/98/Me and Windows
NT/2000/XP all have a dial-up networking
service that can be configured to access a
remote network
• Security for dial-up remote access is a
very important topic because of potential
threats from viruses or hackers
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Using Operating
Systems for Dial-Up Access
• Two ways to enhance the security
surrounding the use of remote access is with
authentication and encryption
• Authentication is the way you identify and
validate who you are to the server
• Encryption is the encoding of the data
between you and the server so that only you
and the server can decode the information
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Summary
• A network is a system of information resources and
productivity tools that facilitates our human need to
communicate
• Networks were invented because they enable users to
share information and information resources over short
and long distances
• Networks are designed in standardized topologies (bus,
star, and ring) and use standardized communication means,
such as frames, packets, and protocols, with the end result
that a network in Jackson, Wyoming can be connected to
another in Denver, Colorado or Montreal, Canada
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Summary
•
Protocols are particularly important to networking because they act as a
common language for communications
•
Modern computer operating systems use a variety of network protocols
for communications, such as TCP/IP, IPX/SPX, and NetBEUI
•
Table 8-1, 8-2, and 8-3 provide a summary of the transport,
communications, and remote protocols introduced in this chapter, and the
operating systems that support those protocols
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Summary
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Summary
• Bridges, switches, and routers can be employed for
network security and to control network traffic patterns
• LANs are smaller networks that run throughout an office
area or a floor in a building
• WANs are long-distance networks that can span states and
continents to join LANs and individual users
• Also called dial-up access, modem communications with a
LASN are made possible through remote communications
protocols, such as SLIP and PPP
• PPP is most commonly used because it can transport a
combination of protocols, such as TCP/IP and IPX/SPX
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