03 IS 2639 - Lesson 3: Network Technologies and Topologies (copy)

Topology

describes the lay of the land

Network Topology

 describes how a network is physically laid out and how signals travel from one device to another

True

True or False

Physical layout of the devices and cables doesn’t describe how signals travel from one device to another

Physical and Logical Topologies

Network topologies are categorized into 2 kinds of topologies, what are these?

Physical Topology

Arrangement of cabling and how cables connect one device to another in a network is considered the network’s

Logical Topology

path data travels between computers on a network is considered the ___________

1. Bus

2. Star

3. Ring

4. Point-to-point

All network designs today are based on these basic physical topologies:

Physical bus topology

defined as a continuous length of cable connecting one computer to another in daisy-chain fashion

Physical Bus Topology

simplest and at one time the most common method for connecting computers

Electrical Pulses

________ (signals) travel the cable’s length in all directions

Signal Propagation

Signals traveling across the medium and from device to device is called __________

Terminator

Signals traveling across the medium and from device to device are called signal propagation, signal continues until it weakens or is absorbed by ________

Terminator

an electrical component called a resistor that absorbs the signal instead of allowing it to bounce back up the wire

Signal Bounce

If not terminated, the signal bounces or is “reflected” at the end of the medium

• ________ is the term used when electricity bounces off the end of a cable and back in the other direction

Physical Star Topology

Use a central device (hub or switch) to connect computers

Extended Star

most widely used in networks containing more than just a few computers

Central device

A __________ sits in the middle and instead of attached computers, other switches or hubs are connected to the central switch’s ports

Hierarchical Star

Extended Star is sometimes referred to as a __________

Extended Star

This topology is most effective when the center of the star is running at a much faster speed than other devices

Extended Star Topology Network

What kind of topology is shown in the picture?

True

True or False

How Data Travels in a Physical Star

• Details of how data travels in a physical start depend on the type of central device

• The central device determines the ‘logical’ topology

Physical Ring Topology

like a bus and devices are daisy-chained one to another. Instead of terminating each end, the cabling is brought around from the last device back to the first device to form a ring

Fiber Distributed Data Interface (FDDI)

Physical Ring Topology was most widely used to connect LANs with a technology called _______

FDDI

most often used as a network backbone, which is cabling used to communicate between LANs or between hubs and switches

Dual Ring

FDDI uses a _________, which means data travels in both directions, one ring failure doesn’t break network

Physical Ring Topology

What kind of topology is this?

Point-to-Point

• a direct link between two devices

• It is mostly used in WANs

Point-to-Multipoint Technology

an arrangement where a central device communicates with two or more other devices. All communication goes through the central device

Point-to-Multipoint Technology

often used in WANs where a main office has connections to several branch offices via a router

Mesh Topology

connects each device to every other device in a network. Multiple point-to-point connections for the purposes of redundancy and fault tolerance

To ensure that if one or more connections fail, there’s another path for reaching all devices on the network

purpose of creating a mesh topology

Large Wans, Internetwork

Mesh Topology is found in ______ and _______

Logical Topology

Describes how data travels from computer to computer

Physical Topology

Logical topology is sometimes same as ____

True

True or False

In a physical bus and physical ring, the logical topology mimics the physical arrangement of cables

Physical Star

A logical ring using a __________ implements the ring inside the central device’s electronics, which is a MAU in the token ring technology

Switched Topology

there is always an electrical connection between the computer and the switch but when no data is being transferred there is no logical connection or circuit between the devices

Network Technology

The method a network interface uses to access the medium and send data frames and the structure of these frames

• Network interface layer technologies

• Network architectures

• Data link layer technologies

Other Terms for Network Technologies

Ethernet, 802.11 Wireless

A network uses __________, ___________ wireless, or some combination of these to move data from device to device in your network

Frame Format, Media

The network technology often defines ______ and _______

Unshielded Twisted Pair

most common media type in LANs

Consists of 4 pairs of copper wires  each twisted together

True

True or False

In Unshielded Twisted Pair, the higher the number, the higher the cable’s bandwidth potential

Fiber-optic Cabling

uses thin strands of glass to carry pulses of light long distances and at high data rates

Isn’t susceptible to electrical interference

Coaxial Cable

obsolete as a LAN medium but it is used as the network medium for Internet access via cable modem

Baseband

sends digital signals in which each bit of data is represented by a pulse of electricity or light. Sent at a single fixed frequency and no other frames can be sent along with it

Broadband

uses analog techniques to encode binary 1s and 0s across a continuous range of values. Signals flow at a particular frequency and each frequency represents a channel of data

Ethernet

most popular LAN technology. Advantages include ease of installation, scalability, media support, and low cost

10 Mbps to 10 Gbps

Ethernet Networks supports a broad range of speeds

True

True or False

Ethernet can operate a in physical bus or physical star and logical bus or switched logical topology

Frame

Unit of network information that NICs and Switches work with

Media Access Method

a set of rules governing how and when the medium can be accessed for transmission

Carrier Sense Multiple Access with Collision Detection (CSMA/CD)

Ethernet uses ________

Collision Domain

extent to which signals in an Ethernet bus topology network are propagated

True

True or False

All devices in a collision domain are subject to the possibility that whenever a device sends a frame, a collision might occur

Network Protocols

Ethernet relies on _________ to ensure delivery

Cyclic Redundancy Check (CRC)

Error-checking code in an frame’s trailer is __________

Half-duplex Communication

works like a two-way radio; you can talk and listen but not both at the same time

Full-Duplex Communication

means NIC/switch can transmit/receive simultaneously

True

True or False
CSMA/CD is not used because a collision cannot occur in full-duplex mode

True

True or False

Most switches operate in full-duplex

1. Using the IEEE document number defining the standard (IEEE 802.3)

2. XBaseY – 10BaseT, 100BaseT, 100BaseFX

Ethernet standards are expressed in one of two ways:

10BaseT Ethernet

Uses two of the four wire pairs

Runs over Category 3 or higher UTP cabling

Highly susceptible to collisions and is obsolete

100BaseTX Ethernet

Most common Ethernet variety

Runs over Category 5 or higher UTP

Uses two of four wire pairs

Also sometimes called “Fast Ethernet”

100BaseFX Ethernet

Runs over two strands of fiber optic cabling

Typically used as backbone cabling between hubs or switches

Also used to connect clients or servers when immunity to noise and eavesdropping is required

1000BaseT Ethernet

Usually called “Gigabit Ethernet”

Runs over Category 5e or higher UTP and uses all four wire pairs

To support full-duplex transmission over a single pair of wires:

1000BaseT uses hybrid and canceller technology, which combines multiple signals and cancels interference

2.5GBaseT and 5GBaseT

This specification was largely in response to increasing Wi-Fi speeds

Faster wired Ethernet speeds are needed as uplink ports from new 802.11ac APs

Runs over Cat 5e/6 cabling

10GBaseT Ethernet

Runs over four pairs of Category 6A or 7 UTP

Operates only in full-duplex mode

No hubs, only switches support 10GBaseT

Still considered an expensive option, although prices are dropping

Good for network servers so they can keep up with desktop systems that commonly operate at 1 Gbps

100BaseT4

Uses all four pairs of wires in UTP Category 3 cable

Obsolete

1000BaseLX

Uses fiber-optic media

“L” stands for “long wavelength” laser

Supports a maximum cable segment length of 5,000 meters

Some manufacturers have extended it by using specialized and proprietary optical transceivers

1000BaseSX

Uses fiber-optic media

“S” stands for “short wavelength” laser

Can’t cover as much distance as long-wavelength lasers, but are less expensive

1000BaseCX

Uses specially shielded, balanced, copper jumper cables

Might also be called “twinax” or “short-haul” copper cables

10 Gigabit Ethernet IEEE 802.3ae Standards

Much like the others in frame formats and media access

Defined to run only on fiber-optic cabling and specifies a maximum distance of 40 kilometers

Primarily used for network backbones

Varieties:

10GBaseSR, 10GBaseLR, 10GBaseER, 10GBaseSW, 10GBaseLW, and 10GBaseEW

40 Gigabit and 100 Gigabit Ethernet

Very high cost is still prohibitive

Adoption has been slow

Fiber-optic cabling is primary medium

Although there are provisions to use special copper assemblies over short distances

802.11 wireless

also referred to as Wireless Fidelity (Wi-Fi)

Hotspot

In most towns you can usually find a public Wi-Fi network, called a _____

Airwaves

802.11 is essentially an extension to Ethernet. Using _______ instead of cabling as the medium

1. Infrastructure mode use a central access point (AP)

2. Ad hoc mode is a mode of operation where there is no central device

Wi-Fi can operate in one of two modes

Infrastructure mode use a central access point (AP)

Stations connect through a wireless AP before they can communicate with other devices

Ad hoc mode is a mode of operation where there is no central device

Data travels from device to device like a bus

Sometimes called “peer-to-peer mode”

2.4GHz and 5.0 GHz

Wi-Fi networks operate at one of two radio frequencies:

2.4 GHz

actually 2.412 thru 2.484 divided into 14 channels spaced 5 MHz apart

5.0 GHz

actually 4.915 thru 5.825 GHz divided into 42 channels of 10, 20, or 40 MHz each

TV Channel

A wireless channel works like a _______:

You must tune to the correct channel to connect

True

True or False

If you are configuring several Wi-Fi networks:

Choose channel five apart from other known APs

Transmitted, Receiver

The antenna on a Wi-Fi device is both ____and ____

Characteristics and placement determine how well a device transmits or receives Wi-Fi signals

Omnidirectional antennas

signals radiate out from the antenna with equal strength in all directions

Unidirectional antenna

signals are focused in a single direction

Ideal for placement at one end of long, narrow spaces

Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA)

Wi-Fi devices use __________

Absorption

solid objects absorb radio signals, causing them to attenuate (weaken)

Refraction

the bending of a radio signal as it passes from a medium of one density through a medium of a different density

Diffraction

the altering of a wave as it tries to bend around an object

Reflection

occurs when a signal hits a dense, reflective material, resulting in signal loss

Scattering

when a signal changes direction in unpredictable ways, causing a loss in signal strength

Signal-to-noise ratio

the amount of noise compared with the signal strength, Noise can come from equipment, other wireless devices, and other wireless networks

Throughput

the actual amount of data transferred

Not counting errors and acknowledgements

Goodput

actual application-to-application data transfer speed

Overhead

Packet frame headers, acknowledgements, and retransmissions are collectively known as

802.11a

requires more power and has a shorter indoor range, transfers data at 54 Mbps

802.11b

was the most widely accepted standard because of its low cost and good indoor range