Chapter 4 - Physical Layer

Physicsl layer specifications are applied to areas that include the following:

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

Limitations to Copper Cabling

-Attenuation: the longer the elecrical signals have to travel, the weaker they get. -The electrical signal is susceptible to interference from two sources, which can distort and corrupt the data signals (Electomagnetic Interference (EMI) and Radio Frequency Interference (RFI) and Crosstalk).

Shielded Twisted Pair STP

-Better noise protection than UTP -More expensive than UTP -Harder to install than UTP -Terminated w/ RJ-45 connectors -Interconnects hosts w/ intermediary network devices Key Characteristics of STP: 1.The outer jacket protects the copper wires from physical damage 2.Braided or foil shiel provides EMI/RFI protection 3.Foil shield for each pair of wires does same 4.Color-coded plastic insulation electrically isolates the wires from each other and identifies each pair.

Rollover

-Cisco proprietary -Connects a workstation serial port to a router console port, using an adapter

The physical connection NOT vocab

-Connection between devices could be wired or wireless -Some devices may have one or multiple NIC cards -Not all physical connections offer the same level of performace.

Unshielded twisted-pair UTP

-Is the most common networking media -Terminated w/ RJ-45 connectors -Interconnects hosts w/ intermediary network devices. Key Characteristics: 1.The outer jacket protects the copper wires from physical damage. 2.Twisted pairs protect the signal from interference. 3. Color-coded plastic insulation electircally isolates the wires from each other & identifiees each pair

Multimode Fiber

-Larger core -Uses less expensive LEDs -LEDs transmit at different angles -Up to 10 gbps over 550 meters

Properties of fiber-optic cabling

-Not as common as UTP because of the expense involved -Ideal for some networking scenarios -Transmits data over longer distances at higher bandwidth than any other networking media -Less susceptibla to attenuation, and completely immune to EMI/RFI -Made of flexible, extremly thin starnds of very pure glass -Uses a laser or LED to encode bits as pulses of light -The fiber-optic cable acts as a wave guide to transmit light between the two ends with minimal signal loss. -Two types of fiber: Single-mode and multimode

Ethernet Crossover

-One end T568A, other end T568B -Connects two network hosts Connects two network intermediary devices (switch to switch or router to router)

The physical layer standards address three functional areas:

-Physical Components -Encoding -Signaling

Mitigation for Copper Cabling

-Strict adherence to cable length limits will mitigate attenuation -Some kinds of copper cable mitigate EMI and RFI by using metallic shielding and grounding -Some kinds of copper cable mitigate crosstalk by twisting opposing circuit pair wires together.

Encoding

-This converts the stream of bits into a format recognizable by the next device in the network path. -This 'coding' provides predictable patterns that can be recognized by the next device.

Bandwidth

-This is the capacity at which a medium can carry data. -Digital bandwidth measures the amount of data that can flow from one place to another in a given amount of time; how many bits can be transmitted in a secound. -Physical media properties, current technologies, and the laws of physics play a role in determning available bandwidth.

Signaling

-This method is how the bit values, 1 and 0 are represented on the physical medium. -The mthod of signaling will vary based on the typ of medium being used.

The Physical layer- What it essentially does Not Vocab

-Transports BITS across the network media -Accepts a complete frame from the Data Link Layer and encodes it as a series of signals that are transmitted to the local media. -This is the last step in the encapsulation process -The next device in the path to the destination recieves the bits and re-encapsulates the frame, then decides what to do with it.

Single-mode Fiber

-Very small core -Uses expensive lasers -Long-distance applications

Types of Wirelss Media Wireless standars:

-WI-FI (IEEE 802.11) Wireless Lan (WLAN) technology -Blutooth (IEEE 802.15) Wireless Personal Area Network (WPAN) standard devices communicate in distance from 1 to 100 meters -WiMAX (IEEE 802:16) Uses a point-to-multipoint topology to provide broadband wireless access. Known as Worldwide Interoperability for Microware Access -Zigbee (IEEE 802.15.4) Low data-rate, low power-consuption communications, primarily for Internet of Things (loT) applications

Crosstalk

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

Fiber Patch Cords

A yellow jacket is for single-mode fiber cables and orange or aqua for mulitmode fiber cables

Ethernet Straight-through

Both ends T568A or both ends T568B -Connects a network host to a network device such as a switch or hub

Coaxial Cable

Cosists of the following: 1. Outer cable jacket to prevent minor physical damages 2. A woven copper braid, or metallic foil, acts as the secound wire in the circuit and as shiel for the inner conductors. 3. a Layer of flexible plastic insulation 4. A copper conductor is used to transmit the electrical signals. -Different types of connectors used such as BNC, N type & F type EX. of situations used: -Wireless installation- attaches antennas to wireless devices - Cable internet installation

Covereage area *For wireless media

Effective coverage can be significantly impacted by the physical characteristics of the deployment location.

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

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

Properties of wireless Media

It carries electormagnetic signals representing binary digits using radio or microwave frequencies. This provides the greatest mobility option, WIreless connection numbers continue to increase. -Some of the limitations of wireless: Covereage area, Interference, Security, Shared medium. -Great for home and enterprise network

UTP cabling standards and Connectors

Standards for UTP are established by the TIA/EIA. standarized elements like: -Cable types, Cable lengths, Connectors, Cable termination, Testing Methods. Ex of cables according to its performance: Category 3, 5, 5e, 6 (the higher the category the better)

Fiber-optic Connectors

Straight-tip ST connector -Lucent Connector LC Simplex COnnectors -Subscriber Connector SC connectors -Duplex multimode LC Connectors

Goodput

The measurement of usable data transferred over a given period of time. Goodput= Throughput - traffic overhead

Physical Components

These are the hardware devices, media, and other connectors that transmit the signals that represent the bits. -Hardware components like NICs, interfaces and connectos, cable materials, and cable designs are all specified in standars associated with the physical layer.

Bandwidth Terminology

These are used to measure the quality of bandwdth -Latency -Throughput -Goodput

Wireless Access Point (AP)

These concentrate the wireless signals from users and connect to the existing copper-based network infrastructure

Wireless NIC adapters

These provide wirless commnication capability to network hosts.

Electromagnetic interference EMI and Radio frequency interference RFI

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

Properties of UTP cabling

UTP cable does not use shielding to counter the effects of EMI and RFI. Instead, cable designers have discovered other ways that they can limit the negative effect of crosstalk: -Cancellation: Each wire in a pair of wires uses opposite polarity. One wire is negative, the other wire is positive. They are twisted together and the magnetic field s effectively cancel each other and outside EMI/RFI. -Variation in twists per foot in each wire

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 *For wireless media

WLANs operate in half-duplex, which means only one device can send or receive at a time. Many users accessing the WLAN simultaneously results in reduced bandwidth for each user.

Security *For wireless media

Wireless communication coverage require no access to a physical strand of media, so anyone can gain access to the transmission.

Interference *For wireless media

Wireless is susceptible to interference and can be disrupted by many common devices.

Characteristics of Copper Cabling

is most common type of cabling used in networks today. It is inexpensive, easy to install, and has low resistance to electical current flow.

Throughput

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

Latency

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