N10-009 Networking Concepts Study Guide for the CompTIA Network+

Transmission Media and Transceivers

Transmission media and transceivers refer to how data is sent and through which type of connection device. You should be able to compare and contrast different types of transmission media and transceivers.

Wireless

Wireless standards govern wireless device usage and their frequencies, specifications, and frequency spectrums. Given a scenario, you will need to be able to identify, install, and configure the appropriate wireless standard and technology for a given scenario.

802.11 Standards

The 802.11 standards, also known as Wi-Fi standards, were created and are maintained by the Institute of Electrical and Electronics Engineers (IEEE). They specify the architecture, protocols, and limitations used by 802.11-enabled devices for wireless LAN communications. 802.11 was the original standard, which has been built upon by subsequent committees and subcommittees, with each new development indicated by an added character, such as 802.11a or 802.11g. All 802.11-enabled WLAN devices and products have the ability to data rate shift or automatically move from one transmission speed to another, such as from 11 Mbps to 5.5 Mbps, without interrupting communications.

Cellular

Cellular communications is a wireless communication method that creates a wireless network over large geographical areas using two-way communications between mobile devices and interconnected networking devices. Cellular technology, like other wireless communication technologies, has developed in response to vulnerabilities and usage demand.

Satellite

A satellite link creates a connection via a satellite signal from an orbital satellite to an earthbound receiver. Satellite links tend to be slower than physical links but can offer the ability to send and receive data from remote areas.

Wired

The cable and connectors are the physical media that are used to create a wired connection for data transmission and connection of end devices. You should be familiar with each cable and the connector type each can use, as well as which solution would be appropriate for specific situations.

802.3 Standards

Ethernet is a connection method that shares bandwidth between all hosts on a link. Ethernet standards refer to the physical and data link layer specifications as defined in IEEE 802.3 for Ethernet connections. The IEEE developed a standardization for different Ethernet media and their corresponding properties, functions, and implementations.

Single-Mode vs. Multimode Fiber

Fiber (or fiber-optic) cables transmit data via light pulses sent over a glass or plastic core. The core glass or plastic is surrounded by a glass or plastic cladding that reflects the light pulses back into the core cable. This is then wrapped in a flexible plastic buffer. The entire cable can then be wrapped in another protective layer, commonly Kevlar, which can also be sheathed with PVC or FEP.

Fiber cables can be either single or multimode. A single-mode fiber-optic (SMF) cable consists of a single glass fiber (sometimes two) that transmits data from the light source, either light-emitting diodes (LEDs) or lasers, via a pulsed light. SMF can transmit data extremely quickly over long distances, up to 40 kilometers. Multimode fiber-optic (MMF) cable can be either glass or plastic and uses the light source to disperse multiple signals across multiple paths within the core. MMF has an effective distance of only around 500 meters.

Direct Attach Copper (DAC) Cable

A DAC cable is a common medium for data transmission through a copper twinaxial (or a single twisted pair) cable with a factory-installed terminating transceiver on each end. Each individual copper wire is sheathed in a plastic coating to prevent the copper components from touching other wires. DAC cables are more cost-effective and are commonly used in data centers for high speed transmissions over a short distance.

Note: The term DAC cable may also be used to refer to a direct attach cable using a fiber medium.

Twinaxial Cable

A twinaxial cable is similar to traditional coax except that it contains two copper conductors in a twisted pair instead of one. Twisted pairs can be either a shielded twisted pair (STP), meaning they are encased in a protective metallic shield, or an unshielded twisted pair (UTP), meaning they are not encased. Twinaxial cable can deliver up to 10 GbE connections over a short distance at a lower cost than fiber.

Coaxial Cable

Coaxial, commonly referred to as coax cable, is a solid strand of copper surrounded by a plastic jacket with a braided shield over the top of the entire cable. The most commonly used type of coax cable is radio-grade 6 (RG-6), which is designed for cable TV and cable modem transmissions but is not suitable for direct Ethernet connections. An RG-6 cable typically uses an F-type connector.

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Cable Speeds

The cable speed is the transmission capabilities of a particular wired connection with different cabling types providing different speeds over different maximum lengths, with copper’s maximum distance being up to 100 meters and fiber’s maximum distance being up to 100 kilometers. The IEEE 802.3 standards for copper are as follows:

10BASE-T—10BASE-T (defined in IEEE 802.3i) provides 10 Mbps over a Cat 3 UTP cable using an RJ45 connector (also known as an eight-pin modular connector) with a physical star topology or logical bus topology.

100BASE-TX—100BASE-TX (defined in IEEE 802.3u and known as Fast Ethernet) provides 100 Mbps over a Cat 5, 5e, or 6 STP or UTP cable using an RJ45 connector with a physical star or logical bus topology.

1000BASE-T—1000BASE-T (IEEE 802.3ab) provides 1,000 Mbps over a Cat 5 or higher UTP cable using an RJ45 connector.

10GBASE-T—10GBASE-T (IEEE 802.3an) provides 10 Gbps over a Cat 5e and up UTP cable with an RJ45 connector.

40GBASE-T—40GBASE-T (IEEE 802.3bq) provides 40 Gbps over a Cat 8 UTP cable and is commonly used in data centers.

The IEEE 802.3 standards for fiber are as follows:

100BASE-FX—100BASE-FX (IEEE 802.3u) provides 100 Mbps over an MMF fiber-optic cable in a point-to-point topology with ST and SC connectors.

1000BASE-SX—1000BASE-SX (IEEE 802.3z) provides 1,000 Mbps over an MMF fiber-optic cable using short wavelength lasers and SC connectors.

1000BASE-LX—1000BASE-LX (IEEE 802.3z) provides 1,000 Mbps over either an MMF or SMF fiber-optic cable using longer wavelength lasers and SC or LC connectors.

10GBASE-SR—10GBASE-SR (IEEE 802.3 Clause 49) provides 10 Gbps over an MMF fiber-optic cable and an 850 nm laser.

10GBASE-LR—10GBASE-LR (IEEE 802.3 Clause 49) provides 10 Gbps over an SMF fiber-optic cable and a 1,310 nm laser over a distance of 10 kilometers.

Plenum vs. Non-Plenum Cable

The most commonly used plastic sheathing for copper cabling is polyvinyl chloride (PVC) and fluoroethylene propylene (FEP). FEP, commonly known as Teflon™, is plenum-rated because it resists fire and does not release hazardous chemicals into the air if burnt. Safety requirements specify that cable running in the plenum, the space between building floors, must be plenum-rated.

Transceivers

A transceiver, as relates to physical connection types, is a device that both transmits and receives signals in a single housing or by using common circuitry. Transceivers commonly refer to wireless connection devices but may also be used when referring to copper or fiber connections. Transceivers come in different configurations with different capabilities.

Protocol

The protocol of a transceiver refers to the method of communication that is used to transmit data between devices.

Fibre Channel (FC)

FC is a communication method used primarily to connect servers to storage devices in a SAN. An FC protocol is the traditional SAN protocol used for high-speed data transfer using Small Computer System Interface (SCSI) commands via an optical network that is not inherently compatible with TCP/IP. FC connects dedicated storage hardware and switches through fiber-optic cables. FC connections provide more isolation to the SAN, which increases the security of the SAN but also requires specialized hardware, which may be costly to install and maintain.

Ethernet

Ethernet is a method for media access that provides network connection over a shared bandwidth using a predefined set of communication rules and protocols, including the TCP/IP protocol. Ethernet can also be used for Fibre Channels over Ethernet (FCoE). An FCoE connects a SAN to a network via Ethernet cabling and encapsulates Fibre Channel traffic within Ethernet frames. This allows for FC traffic to be sent on pre-established Ethernet lines via TCP/IP while still maintaining the isolation of a traditional FC.

Form Factors

The form factor of a transceiver is the physical specifications of a transceiver device, including the size of the device, the connection type, and the shape of the device. The form factor determines device compatibility and is standardized.

Small Form-Factor Pluggable (SFP)

An SFP transceiver is a compact pluggable hot-swappable optical receiver used with 100BSE or 1000BASE applications over long distances. SFPs can accommodate either copper or fiber and allow for connections to a switch or other networking device. SFPs support two bidirectional links on one interface. An enhanced form-factor pluggable (SFP+) is similar to an SFP but supports up to 16 Gbps transmissions over a shorter distance.

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Quad Small Form-Factor Pluggable (QSFP)

A QSFP is a compact pluggable hot-swappable optical receiver that can accommodate four links on one interface at gigabit speeds. An enhanced quad small form-factor pluggable (QSFP+) is similar to the QSFP but supports 10-gigabit speeds over a shorter distance.

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Connector Types

The connector type refers to the attachment on the termination point of a cable, which allows for connection to an end device. Connector types differ depending on the type of cable used.

Subscriber Connector (SC)

An SC is a fiber connection type that uses a push pull latching device to secure a fiber to a device.

Local Connector (LC)

An LC, also known as a Lucent connector, is similar to an SC, but much smaller in size. The LC also uses a clip-like latch to stabilize the connection.

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Straight Tip (ST)

An ST connector is a fiber connection type, developed by AT&T, that uses the Bayonet Neill-Concelman (BNC) attachment method to secure a fiber to a device. The BNC attachment method allows for a quick connection that secures itself through an insert-and-twist design.

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Multi-Fiber Push On (MPO)

An MPO is a connection type that is used to connect multiple fiber optics into a single interface.

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Registered Jack (RJ) and RJ11

An RJ connector is a standardized connection method used most commonly for Ethernet connections. An RJ11 connector is commonly used for telephone transmissions and uses a four-pinout layout (how the wires are placed within the connector).

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RJ45

An RJ45 connector houses four pairs of wires and is commonly used with Ethernet twisted pair cables in an eight-pinout layout.

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F-Type

An F-type connector (or F connector) is a connection method that houses the wire inside a connector that can be screwed onto the receiving device to ensure a secure connection. F-type connectors are commonly used with coax cabling and RG-6 connectors.

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