Download Understanding Networks II

Understanding Networks II
Objectives
• Compare client and network operating
systems
• Learn about local area network
technologies, including Ethernet, Token
Ring, FDDI, and wireless
• Use the OSI model to understand
networking
• Learn how network computers and servers
are addressed
Network Architecture Overview
• Network architecture is the overall design
of a network, including how devices and
components are connected, how devices
and components communicate, and the
network protocols needed to establish
reliable communication among nodes on
the network.
Network Architecture Overview
• A node is any device that can be
accessed by a computer on a LAN,
such as a computer, server, or printer.
• Physical topology is the physical
arrangement or shape in which
devices on a LAN are connected to
each other.
How NICs Work
• Typically, an internal NIC plugs into a
motherboard expansion slot.
• An individual NIC can be designed to support
Ethernet, Token Ring, FDDI, or wireless
architectures, but a single card will not support
multiple architectures.
• The NIC must convert the data it is transmitting
into a signal that is in a form that is appropriate
for the network.
• The component on the card responsible for this
signal conversion is called the transceiver.
How Ethernet Controls Data
Traffic
• An Ethernet network is a passive network,
meaning that the network just sits there
and waits for a computer to use it.
• A computer that wants to send packets
over Ethernet first listens on the network
for silence.
• If it hears nothing, it begins to transmit.
• As it transmits, it also listens.
How Ethernet Controls Data
Traffic (Continued)
• If it hears something other than its own data
being transmitted, it stops transmitting and
sends out a signal indicating that there has been
a collision, which occurs when two computers
attempt to send data at the same time.
• A collision can cause packets that were just sent
to be corrupted.
• Each computer waits for a random amount of
time and then tries to transmit again, first
listening for silence.
How Ethernet Controls Data Traffic
(Continued)
• This type of network technology is called a
contention-based system because each computer
must contend for an opportunity to transmit on the
network.
• Computers using Ethernet gain access to the network
using the CSMA/CD (Carrier Sense Multiple Access
with Collision Detection) method.
• Another method that can be used by a network
technology to control collisions is CSMA/CA (Carrier
Sense Multiple Access with Collision Avoidance).
Ethernet Hardware
• Three variations of Ethernet are available,
primarily distinguished from one another by
speed: 10-Mbps Ethernet, Fast Ethernet, and
Gigabit Ethernet.
• A hub is a network device that can be used to
connect devices that use a BNC or RJ-45
connector.
• A hub, like the one shown in Figure 5-20, is
generally inexpensive and is best suited for a
small, simple network.
• These devices can include computers, servers,
or printers.
Ethernet Hardware (Continued)
• Hubs are easy to configure because they
broadcast data packets to every device at once.
• A switch is used to connect computers on a
LAN.
• A switch reads the destination address at the
beginning of a data packet and sends the packet
only to the destination computer.
• Attenuation occurs when signals are weakened
due to being transmitted over long distances on
a network.
Ethernet Hardware (Continued)
• A repeater is a device that amplifies
signals on a network.
• There are two kinds of repeaters.
• An amplifier repeater simply amplifies all
incoming signals.
• A signal-regenerating repeater reads the
signal and then creates an exact duplicate
of the original signal before sending it on.
Physical Topology
• A bus topology connects each node in a
line and does not include a centralized
point of connection; cables just stretch
from one computer to the next one, and to
the next, and so on.
• A star topology connects all nodes to a
centralized hub or switch.
Physical Topology (Continued)
Wireless LAN
• Wireless LAN (WLAN) technology, as the
name implies, uses radio waves or
infrared light instead of cables or wires to
connect computers or other devices.
• Connections are made using a wireless
NIC, which includes an antenna to send
and receive signals.
• Wireless devices can communicate
directly, or they can connect to a LAN by
way of a wireless access point (AP).
Wireless LAN (Continued)
• Access points are placed so that nodes
can access at least on one access point
from anywhere in the covered area.
• The first IEEE standard that outlined
wireless LAN specifications was IEEE
802.11, published in 1990.
• Most current WLAN devices operate under
the 1999 IEEE 802.11b standard.
• This standard is also called Wi-Fi
(Wireless Fidelity).
Token Ring and FDDI
• Token Ring is an older LAN technology
developed by IBM that transmits data at 4 Mbps
or 16 Mbps.
• A Token Ring network is physically arranged
using a star topology, because each node
connects to a centralized device.
• The centralized device to which the network
nodes connect is not a hub or switch, as used in
Ethernet networks, but is called a Controlled
Access Unit (CAU), a Multistation Access
Unit (MSAU or sometimes just MAU), or a
Smart Multistation Access Unit (SMAU).
Token Ring and FDDI
(Continued)
• A token is a special series of bits used to control
which device transmits data on the network.
• Because it has a physical star topology and a
logical ring topology, a Token Ring network is
sometimes said to have a star-wired ring
topology.
• Token Ring can also use another type of
connector that has no “male” or “female”
version, known as a Universal Data Connector
(UDC) or an IBM Data Connector (IDC).
Token Ring and FDDI
(Continued)
• Fiber Distributed Data Interface (FDDI)
is a type of network that also involves a
token that travels in a ring.
• With FDDI, data frames travel on the ring
without the token, and multiple nodes can
have data on the ring at the same time.