Chapter 3.pdf

Module 4: Physical Layer Introduction to Networks v7.0 (ITN) Module Objectives Module Title: Physical Layer Module Objective: Explain how physical layer protocols, services, and network media support communications across data networks. Topic Title Topic Obje...

Module 4: Physical Layer Introduction to Networks v7.0 (ITN) Module Objectives Module Title: Physical Layer Module Objective: Explain how physical layer protocols, services, and network media support communications across data networks. Topic Title Topic Objective Purpose of the Physical Layer Describe the purpose and functions of the physical layer in the network. Physical Layer Characteristics Describe characteristics of the physical layer. Copper Cabling Identify the basic characteristics of copper cabling. UTP Cabling Explain how UTP cable is used in Ethernet networks. Fiber-Optic Cabling Describe fiber optic cabling and its main advantages over other media. Wireless Media Connect devices using wired and wireless media. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 2 4.1 Purpose of the Physical Layer © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 3 Purpose of the Physical Layer The Physical Connection Before any network communications can occur, a physical connection to a local network must be established. This connection could be wired or wireless, depending on the setup of the network. This 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 (Wired and/or Wireless, for example). Not all physical connections offer the same level of performance. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 4 Purpose of the Physical Layer The Physical Layer 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. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 5 4.2 Physical Layer Characteristics © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 6 Physical Layer Characteristics Signaling The signaling method is how the bit Light Pulses Over Fiber-Optic Cable values, “1” and “0” are represented on the physical medium. The method of signaling will vary based on the type of medium being used. Electrical Signals Over Copper Cable Microwave Signals Over Wireless © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 7 Physical Layer Characteristics Bandwidth 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. Unit of Bandwidth Abbreviation Equivalence Bits per second bps 1 bps = fundamental unit of bandwidth Kilobits per second Kbps 1 Kbps = 1,000 bps = 103 bps Megabits per second Mbps 1 Mbps = 1,000,000 bps = 106 bps Gigabits per second Gbps 1 Gbps – 1,000,000,000 bps = 109 bps Terabits per second Tbps 1 Tbps = 1,000,000,000,000 bps = 1012 bps © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 8 Physical Layer Characteristics 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 © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 9 4.3 Copper Cabling © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 10 Copper Cabling Types of Copper Cabling © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 11 Copper Cabling Unshielded Twisted Pair (UTP) 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. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 12 Copper Cabling 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 © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 13 Copper Cabling 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 shield 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 © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 14 4.4 UTP Cabling © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 15 UTP Cabling Properties of UTP Cabling UTP has four pairs of color-coded copper wires twisted together and encased in a flexible plastic sheath. No shielding is used. UTP 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. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 16 UTP Cabling UTP Cabling Standards and Connectors Standards for UTP are established by the TIA/EIA. TIA/EIA- 568 standardizes elements like: Cable Types Cable Lengths Connectors Cable Termination Testing Methods Electrical standards for copper cabling are established by the IEEE, which rates cable according to its performance. Examples include: Category 3 Category 5 and 5e Category 6 © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 17 UTP Cabling UTP Cabling Standards and Connectors (Cont.) RJ-45 Connector Poorly terminated UTP cable Properly terminated UTP cable RJ-45 Socket © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 18 UTP Cabling 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 Host-to-Host, Switch-to-Switch, T568B 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 © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 19 4.5 Fiber-Optic Cabling © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 20 Fiber-Optic Cabling 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 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 © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 21 Fiber-Optic Cabling Types of Fiber Media Single-Mode Fiber Multimode Fiber Larger core Very small core Uses less expensive LEDs Uses expensive lasers LEDs transmit at different angles Long-distance applications 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 a the maximum cable distance for MMF is 550 meters. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 22 Fiber-Optic Cabling Fiber-Optic Connectors Lucent Connector (LC) Simplex Connectors Straight-Tip (ST) Connectors Subscriber Connector (SC) Connectors Duplex Multimode LC Connectors © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 23 Fiber-Optic Cabling Fiber Patch Cords SC-SC MM Patch Cord LC-LC SM Patch Cord ST-LC MM Patch Cord ST-SC SM Patch Cord A yellow jacket is for single-mode fiber cables and orange (or aqua) for multimode fiber cables. © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 24