Week 4.docx

**Week 4** **Physical Layer** **[Purpose of the physical Layer]** **\ -** Before any network communications can occur, a physical connection to a local network must be established. - This connection could be wired or wireless. - Generally, applies whether you are considering a corporate off...

**Week 4** **Physical Layer** **[Purpose of the physical Layer]** **\ -** Before any network communications can occur, a physical connection to a local network must be established. - This connection could be wired or wireless. - Generally, applies whether you are considering a corporate office or a home. - A Network Interface Card(NIC) connects a device to the network. - Some devices may have just one NIC, while others may have multiple NICs. - Not all physical connections offer the same level of performance. - 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 receives the bits and re-encapsulates the frame, then decides what to do with it. **Bandwidth** - 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 second. - Physical media properties, current technologies, and the laws of physics play a role in determining available bandwidth. A table with numbers and symbols Description automatically generated **\ ** **Bandwidth Terminology** - **Latency** - Amount of time, including delays, for data to travel from one given point to another - **Throughput** - The measure of the transfer of bits across the media over a given period of time. - **Goodput** - The measure of usable data transferred over a given period of time - Goodput =\> Throughput -- traffic overhead **[Cooper Cabling]** **Characteristics of Copper Cabling** - Copper cabling is the most common type of cabling used in networks today. It is inexpensive, easy to install, and has low resistance to electrical current flow. - Limitations: - Attenuation -- the longer the electrical 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(Electromagnetic Interference (EMI) and Radio Frequency Interference (RFI) and Crosstalk) - Mitigation: - 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 circuit pair wires together. **Types of Copper Cabling**  **\ ** **Unshielded Twisted Pair (UTP)** - is the most common networking media. - Terminated with RJ-45 connectors. - Interconnects hosts with intermediary network devices. - Key Characteristics of UTP 1. The outer jacket protects the copper wires from physical damage. 2. Twisted pairs protect the signal from interference. 3. Color-coded plastic insulation electrically isolates the wires from each other and identifies each pair. A diagram of a cable Description automatically generated\ **Shielded Twisted Pair (STP)** - Better noise protection than UTP - More expensive than UTP - Harder to install than UTP - Terminated with RJ-45 connectors - Interconnects hosts with intermediary network devices - Key Characteristics of STP 1. The outer jacket protects the copper wires from physical damage. 2. Braided or foil shield provides EMI/RFI protection. 3. Foil shield for each pair of wires provides EMI/RFI protection 4. Color -coded plastic insulation electrically isolates the wires from each other and identifies each pair  **\ ** **Coaxial Cable** Consists of the following: 1. Outer cable jacket to prevent minor physical damage 2. A woven copper braid, or metallic foil, acts as the second wire in the circuit and as a shiel for the inner conductor. 3. A layer of flexible plastic insulation. 4. A copper conductor is used to transmit the electronic signals. There are different types of connectors used with coax cable. Commonly used in the following situations: - Wireless installations.- attach antennas to wireless devices - Cable internet installations -- customer premises wiring. A close-up of several types of coaxial connectors Description automatically generated**\ UTP Cabling** - UTP has four pairs of color-coded copper wires twisted together and encased in a flexible plastic sheath. No shielding is used. It relies on the following properties to limit 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 fields effectively cancel each other and outside EMI/RFI. - Variation in twists per foot in each wire -- Each wire is twisted a different amount, which helps prevent crosstalk amongst the wires in the cable. **\ ** **UTP Cabling Standards and Connectors** Standards for UTP are established by the TIA/EIA. TIA/EIA 568 standardizes element like: - Cable Types - Cable Length - Connectors - Cable Termination - Testing Methods Electrical standards for copper cabling are established by the IEEE, which rates cable according to its performance - Category 3 - Category 5 and 5e - Category 6 -  Close-up of several cables Description automatically generated **Straight-through and Crossover UTP Cables**  **Cable Type** **Standard** **Application** ------------------------------------------------------------------------------------------------ -------------------------------- --------------------------------------------------------------------- Ethernet Straight-through Both ends T568A or T568B Host to Network Device Ethernet Crossover One end T568A, other end T568B Host-to-Host, Switch-to-Switch, Router-to-Router Considered Legacy due to most NICs using Auto-MDIX to sense cable type and complete connection Rollover Cisco Proprietary Host serial port to Router or Switch Console Port, using an adapter **\ 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 susceptible to attenuation, and completely immune to EMI/RFI - Made of flexible, extremely thin strands 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. - Very small core - Uses expensive lasers - Long-distance applications **Multimode Fiber** A diagram of a metal tube Description automatically generated with medium confidence - Larger core - Uses less expensive LEDs - LEDs transmit at different angles - Up to 10 Gbps over 550 meters Dispersion refers to the spreading out of a light pulse over time. Increased dispersion means increased loss of signal strength. MMF has greater dispersion than SMF, with the maximum cable distance for MMF is 550 meters. **Fiber-Optic Cabling Usage** Fiber-optic cabling is now being used in four types of industry: - **Enterprise Networks** - Used for backbone cabling applications and interconnection infrastructure devices - **Fiber-to-the-Home(FTTH)** - Used to provide always-on broadband service to homes and small businesses - **Long-Haul Networks** - Used by service providers to connect countries and cities - **Submarine cable Networks** - Used to provide reliable high-speed, high capacity solutions capable of surviving in harsh undersea environments at up to transoceanic distances. Our focus in this course is the use of fiber within the enterpirse. **Fiber-Optic Connectors**  **Fiber Patch Cords** A close-up of a patch cord Description automatically generated A yellow jacket is for single-mode fiber cables and orange(or aqua) for multimode fiber cables. **Fiber versus Copper** Optical fiber is primarily used as backbone cabling for high-traffic, point-to-point connections between data distribution facilities and for the interconnection of buildings in multi-building campuses. **Implementation Issues** **UTP Cabling** **Fiber-Optic Cabling** -------------------------------- -------------------------------- ------------------------------------- Bandwidth supported 10 Mb/s - 10 Gb/s 10 Mb/s -- 100 Gb/s Distance Relatively short(1-100 meters) Relatively long (1- 100,000 meters) Immunity to EMI and RFI Low High (Completely Immune) Immunity to electrical hazards Low High (Completely Immune) Media and connectors costs Lowest Highest Installation skills required Lowest Highest Safety precautions Lowest Highest **Wireless Media** **Properties of Wireless Media** **It carries electromagnetic 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:** - **Coverage area -- Effective coverage can be significantly impacted by the physical characteristics of the deployment location.** - **Interference --** Wireless is susceptible to interference and can be disrupted by many common devices. - **Security --** Wireless communication coverage requires no access to a physical strand of media, so anyone can gain access to the transmission. - **Shared medium --** 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 **Types of Wireless Media** The IEEE and telecommunications industry standards for wireless data communications cover both the data link and physical layers. In each of these standards, physical layer specifications dictate: - Data to radio signal encoding methods - Frequency and power of transmission - Signal reception and decoding requirements - Antenna design and construction Wireless Standards: - **Wi-Fi** - Wireless LAN (WLAN) technology - **Bluetooth** - Wireless Personal Area network (WPAN) standard - **WiMax** - Uses a point-to-multipoint topology to provide broadband wireless access. - **Zigbee** - Low data-rate, low power-consumptions communications, primarily for Internet of Things (IoT) applications **Wireless LAN** In general, a Wireless LAN (WLAN) requires the following devices: - **Wireless Access Point (AP)** - **Wireless NIC Adapters** There are a number of WLAN standards. When Purchasing WLAN equipment, ensure compatibility, and interoperability. Network Administrators must develop and apply stringent security policies and processes to protect WLANs from unauthorized access and damage.