Term
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Definition
| family of technologies that provides data-link and physical specifications for controlling access to a shared network medium. |
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Term
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Definition
| Institute of Electrical and Electronic Engineers |
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Term
| 4 main benefits of using Ethernet? |
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Definition
• Simple to install and manage
• Inexpensive
• Flexible and scalable
• Easy to interoperate between vendors |
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Term
| What are the 3 types of Ethernet Cabling Types? |
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Definition
• Coaxial cabling – almost entirely deprecated in Ethernet networking
• Twisted-pair cabling
• Fiber optic cabling |
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Term
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Definition
| consists of a single wire surrounded by insulation, a metallic shield, and a plastic sheath. The shield helps protect against electromagnetic interference (EMI), which can cause attenuation, a reduction of the strength and quality of a signal. |
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Term
| What is Coaxial Cabling used for? |
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Definition
| Coax is commonly used to deploy cable television to homes and businesses. |
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Term
| What is thicknet/thinnet cabling? |
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Definition
| Thicknet has a wider diameter and more shielding, which supports greater distances. However, it is less flexible than the smaller thinnet, and thus more difficult to work with. A vampire tap is used to physically connect devices to thicknet, while a BNC connector is used for thinnet. |
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Term
| What is a twisted-pair cable? |
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Definition
| consists of two or four pairs of copper wires in a plastic sheath. Wires in a pair twist around each other to reduce crosstalk, a form of EMI that occurs when the signal from one wire bleeds or interferes with a signal on another wire. Twisted-pair is the most common Ethernet cable. |
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Term
| What is the different between shielded and unshielded twisted pairs? |
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Definition
| Shielded twisted- pair is more resistant to external EMI; however, all forms of twisted-pair suffer from greater signal attenuation than coax cable. |
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Term
| How are ethernet twisted-pair cables identified? |
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Definition
| They are identified by the amount of twists per inch of the copper pairs |
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Term
| What are the 4 types of ethernet Categories? |
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Definition
• Category 3 or Cat3 - three twists per inch.
• Cat5 - five twists per inch.
• Cat5e - five twists per inch; pairs are also twisted around each other.
• Cat6 – six twists per inch, with improved insulation. |
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Term
| How does fiber optic ethernet work? |
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Definition
| Fiber optic ethernet works by sending light to transmit a signal |
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Term
| What are the two types of fiber optics ethernet? |
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Definition
• Singlemode fiber – consists of a very small glass core, allowing only a single ray or mode of light to travel across it. This greatly reduces the attenuation and dispersion of the light signal, supporting high bandwidth over very long distances, often measured in kilometers.
• Multimode fiber – consists of a larger core, allowing multiple modes of light to traverse it. Multimode suffers from greater dispersion than singlemode, resulting in shorter supported distances. |
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Term
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Definition
| both the physical and logical structure of a network. |
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Term
| What are 4 types of topology configurations in use today? |
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Definition
• Bus
• Star
• Ring
• Full or partial mesh |
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Term
| What 2 types of topology does ethernet support today? |
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Definition
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Term
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Definition
| all hosts share a single physical segment (the bus or the backbone) to communicate |
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Term
| What are 3 disadvantages to using a bus topology? |
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Definition
• Both ends of the bus must be terminated, otherwise a signal will reflect back and cause interference, severely degrading performance.
• Adding or removing hosts to the bus can be difficult.
• The bus represents a single point of failure - a break in the bus will
affect all hosts on the segment. Such faults are often very difficult to troubleshoot. |
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Term
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Definition
| each host has an individual point-to-point connection to a centralized hub or switch |
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Term
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Definition
| Hub forwards data frames through every port |
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Term
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Definition
| builds a hardware address table, allowing it to make intelligent forwarding decisions based on frame (data-link) headers. A frame can then be forwarded out only the appropriate destination port, instead of all ports |
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Term
| What are two disadvantages of using a star topology? |
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Definition
• The hub or switch represents a single point of failure.
• Equipment and cabling costs are generally higher than in a bus
topology. |
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Term
| What is a preamble in an Ethernet Frame? |
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Definition
Size: 7 bytes or 56 bits
Synchronizes communication on an ethernet network
NOT CALCULATED WITHIN TOTAL FRAME SIZE |
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Term
| What is the Start of Frame Delimiter? |
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Definition
Size: 1 Byte
indicates a valid frame is about to begin
NOT CALCULATED WITHIN TOTAL FRAME SIZE |
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Term
| What is the MAC source of a frame? |
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Definition
Size: 48 bit
used for hardware addressing
First 24 bits are used for manufacturer
Second 24 bits are used to identify unique host |
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Term
| What is the MAC Destination of a frame? |
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Definition
Size: 6 Bytes
The destination MAC address identifies who is to receive the frame - this can be a single host (a unicast), a group of hosts (a multicast), or all hosts (a broadcast). The source MAC address indentifies the host originating the frame. |
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Term
| What is the 802.1Q tag in a frame? |
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Definition
| The 802.1Q tag is an optional field used to identify which VLAN the frame belongs to. |
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Term
| What is the Ethertype/Length Field of a frame? |
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Definition
| With 802.3, the field identifies the length of the payload. The length of a frame is important – there is both a minimum and maximum frame size. |
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Term
| What is the absolute minimum frame size for Ethernet? |
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Definition
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Term
| What happens if a frame is smaller than 64 bytes? |
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Definition
| A frame that is smaller than 64 bytes will be discarded as a runt. |
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Term
| What is the minimum REQUIRED Ethernet Header size for a frame? |
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Definition
| The required fields in an Ethernet header add up to 18 bytes – thus, the frame payload must be a minimum of 46 bytes, to equal the minimum 64-byte frame size. If the payload does not meet this minimum, the payload is padded with 0 bits until the minimum is met. |
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Term
| What is an optional 4-byte 802.1Q size? |
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Definition
| If the optional 4-byte 802.1Q tag is used, the Ethernet header size will total 22 bytes, requiring a minimum payload of 42 bytes. |
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Term
| What is the MAXimum frame size for Ethernet? |
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Definition
| 1518 Bytes OR 18 bytes of header fields and 1500 bytes of payload OR 1522 bytes with the 802.1Q tag used |
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Term
| What is the 32-bit Cycle Redundancy Check Field (CRC) used for? |
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Definition
| field is used for error- detection. A frame with an invalid CRC will be discarded by the receiving device. This field is a trailer, and not a header, as it follows the payload. |
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Term
| What is the 96-bit Interframe Gap used for? |
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Definition
| is a required idle period between frame transmissions, allowing hosts time to prepare for the next frame. |
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Term
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Definition
CSMA/CD utilizes Carrior Sense Multiple Access with Collision Detect to control media address.
Carrier sense specifies that a host will monitor the physical link, to determine whether a carrier (or signal) is currently being transmitted. The host will only transmit a frame if the link is idle, and the Interframe Gap has expired |
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