intro to networks ch 4

Single-mode fiber (SMF) Multimode fiber (MMF)

Fiber-optic cables are broadly classified into two types:

Enterprise Networks, Fiber-to-the-Home (FTTH) Long-Haul Networks Submarine Cable Networks

Fiber-optic cabling is now being used in four types of industry:

integrated service routers

(ISRs)

small plastic cap when not in use.

Fiber cables should be protected with a

4412

4412

Rollover

A Cisco proprietary cable used to connect a workstation to a router or switch console port.

Ethernet Crossover Cable

A cable used to interconnect similar devices. For example to connect a switch to a switch, a host to a host, or a router to a router. (ends are different)

1) The properties of the physical media 2)The technologies chosen for signaling and detecting network signals

A combination of factors determines the practical bandwidth of a network:

Wireless Access Point (AP) & Wireless NIC adapters

A common wireless data implementation is enabling devices to connect wirelessly via a LAN. In general, a wireless LAN requires the following network devices:

wireless connection using radio waves.

A physical connection can be a wired connection using a cable or a

wireless devices to connect as well.

Additionally, many ISRs also include an AP, which allows

Wire map Cable length Signal loss due to attenuation Crosstalk

After installation, a UTP cable tester, like the one shown in the figure, should be used to test for the following parameters:

Wireless installations & Cable Internet installations

Although UTP cable has essentially replaced coaxial cable in modern Ethernet installations, the coaxial cable design is used in:

Accepts a frame from a medium De-encapsulates the frame Re-encapsulates the packet into a new frame Forwards the new frame appropriate to the medium of that segment of the physical network

At each hop along the path, a router:

kilobits per second (kb/s), megabits per second (Mb/s), or gigabits per second (Gb/s).

Bandwidth is typically measured in

Cable Internet installations

Cable service providers provide Internet connectivity to their customers by replacing portions of the coaxial cable and supporting amplification elements with fiber-optic cable. However, the wiring inside the customer's premises is still coax cable.

100BASE-TX Fast Ethernet installations.

Category 5 (Cat5) cable is used commonly in

Wireless installations

Coaxial cables attach antennas to wireless devices. The coaxial cable carries radio frequency (RF) energy between the antennas and the radio equipment.

Multimode fiber (MMF)

Consists of a larger core and uses LED emitters to send light pulses.

Single-mode fiber (SMF)

Consists of a very small core and uses expensive laser technology to send a single ray of light

electrical pulses

Data is transmitted on copper cables as

Cancellation

Designers now pair wires in a circuit. When two wires in an electrical circuit are placed close together, their magnetic fields are the exact opposite of each other. Therefore, the two magnetic fields cancel each other and also cancel out any outside EMI and RFI signals.

physical layer standards

Each type of connection and the accompanying devices has cabling requirements stipulated by

light pulses and convert them to voltages.

Electronic semiconductor devices called photodiodes detect the

Institute of Electrical and Electronics Engineers (IEEE) International Telecommunication Union (ITU) International Organization for Standardization (ISO) American National Standards Institute (ANSI)

Engineering organizations that define open standards and protocols that apply to the network access layer include:

Topology

How the connection between the nodes appears to the data link layer.

Media sharing

How the nodes share the media. The media sharing can be point-to-point, such as in WAN connections, or shared such as in LAN networks.

the shield may act as an antenna and pick up unwanted signals.

If the cable is improperly grounded,

Data to radio signal encoding Frequency and power of transmission Signal reception and decoding requirements Antenna design and construction

In each of these standards, physical layer specifications are applied to areas that include:

single-mode and multimode patch cords. A yellow jacket is for single-mode fiber cables and orange (or aqua) for multimode fiber cables.

The use of color distinguishes between

Lasers & Light emitting diodes (LEDs)

Light pulses representing the transmitted data as bits on the media are generated by either:

10BASE-T. Ethernet 100BASE-X family uses 4B/5B encoding and 1000BASE-X uses 8B/10B encoding.

Manchester encoding is used in older Ethernet standards such as

inexpensive, easy to install, and has low resistance to electrical current. However, copper media is limited by distance and signal interference.

Networks use copper media because it is

Optical Time-Domain Reflectometer is a type of specialized cable tester that allows for locating faults and breaks in fiber-optic cabling.

OTDR

connecting media

On the receiving end, the physical layer receives signals across the

dispersion

One of the highlighted differences between multimode and single-mode fiber is the amount of

(core and cladding) and a protective outer shield (jacket)

Optical fiber is composed of two kinds of glass

Multimode Fiber (MMF)

Popular in LANs because they can be powered by low-cost LEDs. It provides bandwidth up to 10 Gb/s over link lengths of up to 550 meters.

Single-mode fiber (SMF)

Popular in long-distance situations spanning hundreds of kilometers, such as those required in long haul telephony and cable TV applications.

radio waves and electromagnetic devices, such as fluorescent lights or electric motors.

Potential sources of EMI and RFI include

media access control sublayer.

Regulating the placement of data frames onto the media is controlled by the

duplex connector

Some fiber connectors accept both the transmitting and receiving fibers in a single connector known as a

Category 7 Cable

Some manufacturers are making cables exceeding the TIA/EIA Category 6a specifications and refer to these as

True

T OR F ? Unlike copper wires, fiber-optic cable can transmit signals with less attenuation and is completely immune to EMI and RFI. Optical fiber is commonly used to interconnect network devices.

True

T or F ? Each wired device has a separate communications channel over its Ethernet cable.

True

T or F ? In an internetwork or network with multiple segments, throughput cannot be faster than the slowest link in the path from source to destination.

True

T or F ? the IETF does not define the functions and operation of that model's network access layer.

data link and physical layers.

The IEEE and telecommunications industry standards for wireless data communications cover both the

Node

The Layer 2 notation for network devices connected to a common media is called a

Topology, media sharing

The actual media access control method used depends on:

Logical Link Control (LLC) Media Access Control (MAC)

The data link layer is divided into two sublayers:

-Allowing the upper layers to access the media -Accepting Layer 3 packets and packaging them into frames -preparing network data for the physical network -Controlling how data is placed and received on the media -Exchanging frames between nodes over a physical network media, such as UTP or fiber-optic -Receiving and directing packets to an upper layer protocol -Performing error detection

The data link layer of the OSI model (Layer 2), is responsible for:

Ethernet straight-through cable

The most common type of networking cable. It is commonly used to interconnect a host to a switch and a switch to a router. (both ends the same)

signaling method in use.

The nature of the actual signals representing the bits on the media will depend on the

Institute of Electrical and Electronics Engineers (IEEE). IEEE rates UTP cabling according to its performance.

The electrical characteristics of copper cabling are defined by the

end device or an intermediate device.

The encoded bits that comprise a frame are received by either an

Misalignment

The fiber-optic media are not precisely aligned to one another when joined.

Ethernet Straight-through, Ethernet Crossover, Rollover

The following are the main cable types that are obtained by using specific wiring conventions:

End gap

The media does not completely touch at the splice or connection.

End finish

The media ends are not well polished, or dirt is present at the termination.

Physical Components, Encoding, Signaling

The physical layer standards address three functional areas:

software designed by software engineers and computer scientists.

The protocols and operations of the upper OSI layers are performed in

the rules for access to different media. These media access control techniques define if and how the nodes share the media.

The protocols at the data link layer define

Internet Engineering Task Force (IETF).

The services and protocols in the TCP/IP suite are defined by the

media access control method.

The technique used for getting the frame on and off the media is called the

Unshielded Twisted Pair (UTP) Shielded Twisted-Pair (STP) Coaxial

There are three main types of copper media used in networking:

Goodput

There is a third measurement to assess the transfer of usable data that is known as

Unshielded Twisted Pair (UTP) Shielded Twisted-Pair (STP) Coaxial

These cables are used to interconnect nodes on a LAN and infrastructure devices such as switches, routers, and wireless access points.

Manchester encoding

This is similar to the signaling method used in Morse code, which may use a series of on-off tones, lights, or clicks to send text over telephone wires or between ships at sea.

OSI Physical Layer

This layer accepts a complete frame from the data link layer and encodes it as a series of signals that are transmitted onto the local media.

Media Access Control (MAC) address

This lower sublayer defines the media access processes performed by the hardware. It provides data link layer addressing and access to various network technologies.

Manchester encoding

This type of encoding is used in 10 b/s Ethernet.

Logical Link Control (LLC) sublayer

This upper sublayer communicates with the network layer. It places information in the frame that identifies which network layer protocol is being used for the frame. This information allows multiple Layer 3 protocols, such as IPv4 and IPv6, to utilize the same network interface and media.

Misalignment End gap End finish

Three common types of fiber-optic termination and splicing errors are:

metallic shielding and require proper grounding connections.

To counter the negative effects of EMI and RFI, some types of copper cables are wrapped in

opposing circuit wire pairs twisted together, which effectively cancels the crosstalk.

To counter the negative effects of crosstalk, some types of copper cables have

data link layer and the physical layer.

Two layers of the OSI model are so closely tied, that according to the TCP/IP model they are in essence one layer. Those two layers are the

Cancellation Varying the number of twists per wire pair

UTP cable does not use shielding to counter the effects of EMI and RFI. Instead, cable designers have discovered that they can limit the negative effect of crosstalk by:

TIA/EIA

UTP cabling conforms to the standards established jointly by the

Request for Comments (RFCs).

Unlike the protocols of the upper layers of the TCP/IP suite, data link layer protocols are generally not defined by

Long-Haul Networks

Used by service providers to connect countries and cities.

Enterprise Networks

Used for backbone cabling applications and interconnecting infrastructure devices.

Fiber-to-the-Home (FTTH)

Used to provide always-on broadband services to homes and small businesses.

Submarine Cable Networks

Used to provide reliable high-speed, high-capacity solutions capable of surviving in harsh undersea environments up to transoceanic distances.

Shared medium

WLANs operate in half-duplex, which means only one device can send or receive at a time. The wireless medium is shared amongst all wireless users. The more users needing to access the WLAN simultaneously, results in less bandwidth for each user. Half-duplex is discussed later in this chapter.

physical connection to a local network must be established.

Whether connecting to a local printer in the home or a web site in another country, before any network communications can occur, a

Security

Wireless communication coverage requires no access to a physical strand of media. Therefore, devices and users, not authorized for access to the network, can gain access to the transmission. Network security is a major component of wireless network administration.

Coverage area

Wireless data communication technologies work well in open environments. However, certain construction materials used in buildings and structures, and the local terrain, will limit the effective coverage.

Coverage area Interference Security Shared medium

Wireless does have some areas of concern, including:

Interference

Wireless is susceptible to interference and can be disrupted by such common devices as household cordless phones, some types of fluorescent lights, microwave ovens, and other wireless communications.

crosstalk interference

a disturbance caused by the electric or magnetic fields of a signal on one wire to the signal in an adjacent wire.

Physical media properties, current technologies, and the laws of physics

all play a role in determining the available bandwidth.

MAC sublayer

also communicates with wireless technologies such as Wi-Fi and Bluetooth to send and receive frames wirelessly.

Fiber patch cords

are required for interconnecting infrastructure devices

Nodes

build and forward frames

Optical Time Domain Reflectometer (OTDR)

can be used to test each fiber-optic cable segment. This device injects a test pulse of light into the cable and measures backscatter and reflection of light detected as a function of time.

MAC sublayer

communicates with Ethernet LAN technology to send and receive frames over copper or fiber-optic cable.

Serial links

consist of a direct connection between only two devices.

In LANs, UTP cable

consists of four pairs of color-coded wires that have been twisted together and then encased in a flexible plastic sheath that protects from minor physical damage. The twisting of wires helps protect against signal interference from other wires.

TIA/EIA-568 standard

describes the wire color codes to pin assignments (pinouts) for Ethernet cables.

WLAN NIC and must use a wireless connection.

devices, such as tablets and smartphones, might only contain a

A wired device

does not need to share its access to the network with other devices.

When terminated improperly,

each cable is a potential source of physical layer performance degradation.

Cat 6 cable (UTP)

each pair has an added separator around it, allowing it to function at higher speeds. supports 1000 mb/s-10 Gb/s, through 10 Gb/s is not RECOMMENDED

Data Link Layer

effectively separates the media transitions that occur as the packet is forwarded from the communication processes of the higher layers.

Coaxial cable (coax)

gets its name from the fact that there are two conductors that share the same axis.

Encoding or line encoding

is a method of converting a stream of data bits into a predefined "code".

Cat5e

is now the minimally acceptable cable type

the OSI data link layer

is responsible for the exchange of Ethernet frames between source and destination nodes over a physical network media.

Media access control

is the equivalent of traffic rules that regulate the entrance of motor vehicles onto a roadway.

UTP cable

is usually terminated with an RJ-45 connector. This connector is used for a range of physical layer specifications, one of which is Ethernet.

Internet Engineering Task Force (IETF)

maintains the functional protocols and services for the TCP/IP protocol suite in the upper layers

Digital bandwidth

measures the amount of data that can flow from one place to another in a given amount of time.

physical layer standards

must define what type of signal represents a "1" and what type of signal represents a "0"

Physical Layer

must generate the electrical, optical, or wireless signals that represent the "1" and "0" on the media.

All wireless devices

must share access to the airwaves connecting to the wireless access point.

The OSI physical layer

provides the means to transport the bits that make up a data link layer frame across the network media.

Data Link Layer

receives packets from and directs packets to an upper layer protocol, in this case IPv4 or IPv6. This upper layer protocol does not need to be aware of which media the communication will use.

Latency

refers to the amount of time, to include delays, for data to travel from one given point to another.

Dispersion

refers to the spreading out of a light pulse over time. The more there is, the greater the loss of signal strength.

Manchester encoding

represents a 0 bit by a high to low voltage transition, and a 1 bit is represented as a low to high voltage transition.

checking that the device connections are correct

should be the first troubleshooting action if connectivity is not achieved.

Layer 2 protocols

specify the encapsulation of a packet into a frame and the techniques for getting the encapsulated packet on and off each medium.

CAT5e (UTP)

supports 1000 mb/s RECOMMENDED!

Bandwidth

the capacity of a medium to carry data.

LLC and MAC sublayers

the data link layer is separated into the

signal attenuation

the longer the signal travels, the more it deteriorates. This is referred to as

Goodput

the measure of usable data transferred over a given period of time.

the method or pattern used to represent digital information. Similar to how Morse code encodes a message using a series of dots and dashes.

the method or pattern used to represent digital information. Similar to how Morse code encodes a message using a series of dots and dashes.

Each time copper cabling is terminated

there is the possibility of signal loss and the introduction of noise into the communication circuit.

Optical fiber cable

transmits data over longer distances and at higher bandwidths than any other networking media.

Networking media

use modular jacks and plugs to provide easy connection and disconnection.

CAT5 (UTP)

used for data transmission, supports 100 mb/s and can support 1000 mb/s, BUT NOT RECOMMENDED

Cat3 (UTP)

used for voice communication, most often used in phone lines

Optical Time Domain Reflectometer (OTDR)

will calculate the approximate distance at which these faults are detected along the length of the cable.

a wired connection

will not degrade in performance.

Wireless Access Point (WAP)

wireless device will experience degradation in performance based on its distance from a

carry higher bandwidth rates.

Cables are placed into categories based on their ability to

sender and receiver

Codes are groupings of bits used to provide a predictable pattern that can be recognized by both the

control how that data accesses the physical media.

On the sending device, it is the role of the data link layer to prepare data for transmission and

True

T or F ? Even if all or most of the segments have high bandwidth, it will only take one segment in the path with low throughput to create a bottleneck to the throughput of the entire network.

True

T or F ? In telephone circuits, crosstalk can result in hearing part of another voice conversation from an adjacent circuit. Specifically, when an electrical current flows through a wire, it creates a small, circular magnetic field around the wire, which can be picked up by an adjacent wire.

True

T or F ? a single type of physical connector may be used for multiple types of connections. For example, the RJ-45 connector is widely used in LANs with one type of media and in some WANs with another media type.

Cable types Cable lengths Connectors Cable termination Methods of testing cable

TIA/EIA-568 stipulates

signaling method

The method of representing the bits is called the

Switch devices and wireless access points

are often two separate dedicated devices within a network implementation.

WLAN (Wireless Local Area Network) NICs

are used for wireless.

bits that are transmitted per second

Bandwidth is sometimes thought of as the speed that bits travel, however this is not accurate. For example, in both 10Mb/s and 100Mb/s Ethernet, the bits are sent at the speed of electricity. The difference is the number of

-The amount of traffic -The type of traffic -The latency created by the number of network devices encountered between source and destination

Due to a number of factors, throughput usually does not match the specified bandwidth in physical layer implementations. Many factors influence throughput, including:

*********UTP cable relies solely on the cancellation effect produced by the twisted wire pairs to limit signal degradation and effectively provide self-shielding for wire pairs within the network media.

Notice in the figure that the orange/orange white pair is twisted less than the blue/blue white pair. Each colored pair is twisted a different number of times.**********

acceptance and processing

On the receiving end, the physical layer receives signals across the connecting media. After decoding the signal back into data, the physical layer passes the frame to the data link layer for

1- The user data is segmented by the transport layer, placed into packets by the network layer, and further encapsulated into frames by the data link layer. 2- The physical layer encodes the frames and creates the electrical, optical, or radio wave signals that represent the bits in each frame. 3- These signals are then sent on the media, one at a time. 4- The destination node physical layer retrieves these individual signals from the media, restores them to their bit representations, and passes the bits up to the data link layer as a complete frame.

The process that data undergoes from a source node to a destination node is:

Copper cable

The signals are patterns of electrical pulses.

Fiber-optic cable

The signals are patterns of light.

Wireless

The signals are patterns of microwave transmissions.

-Selecting the cable type or category most suited to a given networking environment. -Designing a cable infrastructure to avoid known and potential sources of interference in the building structure. -Using cabling techniques that include the proper handling and termination of the cables.

The susceptibility of copper cables to electronic noise can also be limited by:

Electromagnetic interference (EMI) or Radio frequency interference (RFI) or Crosstalk

The timing and voltage values of the electrical pulses are also susceptible to interference from two sources:

Varying the number of twists per wire pair

To further enhance the cancellation effect of paired circuit wires, designers vary the number of twists of each wire pair in a cable. UTP cable must follow precise specifications governing how many twists or braids are permitted per meter (3.28 feet) of cable.

special shielded STP data connectors.

To gain the full benefit of the shielding, STP cables are terminated with

wireless access point (AP).

To offer wireless capability, devices on a wireless network must be connected to a

network hosts with intermediate networking devices, such as switches and routers.

Unshielded twisted-pair (UTP) cabling is the most common networking media. UTP cabling, terminated with RJ-45 connectors, is used for interconnecting

EMI and RFI signals

can distort and corrupt the data signals being carried by copper media.

STP cables

combine the techniques of shielding to counter EMI and RFI, and wire twisting to counter crosstalk.

significantly more expensive and difficult to install & Like UTP cable, uses an RJ-45 connector.

compared to UTP cable, STP cable is

Throughput

is the measure of the transfer of bits across the media over a given period of time.

Modulation

is the process by which the characteristic of one wave (the signal) modifies another wave (the carrier).

Goodput

is throughput minus traffic overhead for establishing sessions, acknowledgments, and encapsulation.

integrated service routers (ISRs)

offer a switching component with multiple ports, allowing multiple devices to be connected to the local area network (LAN) using cables

Physical Layer

produces the representation and groupings of bits as voltages, radio frequencies, or light pulses.

Shielded Twisted Pair (STP)

provides better noise protection than UTP cabling.

Different physical layer standards

specify the use of different connectors. These standards specify the mechanical dimensions of the connectors and the acceptable electrical properties of each type.

-Type of copper cabling used -Bandwidth of the communication -Type of connectors used -Pinout and color codes of connections to the media -Maximum distance of the media

standards for copper media are defined for the:

TIA/EIA 568 standard

stipulates the commercial cabling standards for LAN installations and is the standard most commonly used in LAN cabling environments.

encoding the binary digits that represent data into signals.

the physical layer controls how the data is transmitted onto the physical media by

(ISO) (TIA/EIA) (ITU) (ANSI) (IEEE) (FCC) in the USA and the European Telecommunications Standards Institute (ETSI)

the physical layer hardware, media, encoding, and signaling standards are defined and governed by the:

Cat6

the recommended type for new building installations.