What does OSI stand for? CORRECT ANSWER -Open Systems Interconnection, which is a seven-layer network model
What does TCP/IP stand for? CORRECT ANSWER
... [Show More] -Transmission Control Protocol/Internet Protocol
Name the 7 layers of the OSI model in order (# & name) CORRECT ANSWER -Layer 7 Application, Layer 6 Presentation, Layer 5 Session, Layer 4 Transport, Layer 3 Network, Layer 2 Data Link, Layer 1 Physical
Bottom-up mnemonic: "Please Do Not Throw Sausage Pizza Away."
Top-down mnemonic: "All People Seem To Need Data Processing."
What is UTP? CORRECT ANSWER -Unshielded Twisted Pair cable. Usually contains four pairs of wires that can transmit and receive data
Define the Physical Layer of OSI CORRECT ANSWER -Layer 1 of the OSI model defines the method of moving data between computers, so the cabling and central box are part of the Physical layer (Layer 1). Anything that moves data from one system to another, such as copper cabling, fiber optics, even radio waves, is part of the OSI Physical layer. Layer 1 doesn't care what data goes through; it just moves the data from one system to another system. NOTE: The NIC is NOT considered part of the Physical Layer, but usually is part of Layer 2 (Data Link).
What is a MAC address? CORRECT ANSWER -Inside every NIC, burned onto some type of ROM chip, is special firmware containing a unique identifier with a 48-bit value called the media access control address, or MAC address.
No two NICs ever share the same MAC address—ever. Any company that makes NICs must contact the Institute of Electrical and Electronics Engineers (IEEE) and request a block of MAC addresses, which the company then burns into the ROMs on its NICs. Many NIC makers also print the MAC address on the surface of each NIC.
Represented in hex, each hex being 4 bits, hence, 12 hex chars make up the 48-bit MAC address value.
E.g. 00-40-05-60-7D-49
The first six digits, in this example 00-40-05, represent the number of the NIC manufacturer. Once the IEEE issues those six hex digits to a manufacturer—referred to as the Organizationally Unique Identifier (OUI)—no other manufacturer may use them. The last six digits, in this example 60-7D-49, are the manufacturer's unique serial number for that NIC; this portion of the MAC is often referred to as the device ID.
What are 2 other ways to refer to the MAC address? CORRECT ANSWER -Most techs just call them MAC addresses, as you should, but you might see MAC-48 or EUI-48 on the CompTIA Network+ exam.
The Institute of Electrical and Electronics Engineers (IEEE) forms MAC addresses from a numbering name space originally called MAC-48, which simply means that the MAC address will be 48 bits, with the first 24 bits defining the OUI, just as described here. The current term for this numbering name space is EUI-48. EUI stands for Extended Unique Identifier.
How do NICs read computer data? CORRECT ANSWER -NICs send and receive the computer's binary data as pulses of electricity, light, or radio waves. The NICs that use electricity to send and receive data are the most common, so let's consider that type of NIC.
Just think of a charge on the wire as a one and no charge as a zero.
How does the network get the right data to the right system? CORRECT ANSWER -All networks transmit data by breaking whatever is moving across the Physical layer (files, print jobs, Web pages, and so forth) into discrete chunks called frames.
What is a "frame"? CORRECT ANSWER -A frame is basically a container for a chunk of data moving across a network. The NIC creates and sends, as well as receives and reads, these frames.
A number of different frame types are used in different networks. All NICs on the same network must use the same frame type, or they will not be able to communicate with other NICs.
Name the parts of a frame & describe each part. CORRECT ANSWER -Recipient's MAC | Sender's MAC | Type | Data | FCS
The frame starts with the MAC address of the NIC to which the data is to be sent, followed by the MAC address of the sending NIC.
Type: indicates the specific network technology of the frame.
Data: the payload. Note, NICs don't care at all what the data is; it just passes it along unaware. Special software will take care of what data gets sent and what happens to that data when it arrives. Different types of networks use different sizes of frames, but the frames used in most networks hold at most 1500 bytes of data.
FCS: special bit of checking information called the frame check sequence (FCS).
What is FCS? CORRECT ANSWER -Frame Check Sequence. The FCS uses a type of binary math called a cyclic redundancy check (CRC) that the receiving NIC uses to verify that the data arrived intact.
What is MAC addressing? CORRECT ANSWER -CompTIA calls the use of the MAC address to get frames to the proper computer or node MAC addressing.
What happens when the data to be sent is larger than the frame size? CORRECT ANSWER -The sending system's software must chop the data up into nice, frame-sized chunks, which it then hands to the NIC for sending. As the receiving system begins to accept the incoming frames, the receiving system's software recombines the data chunks as they come in from the network.
What is a hub? CORRECT ANSWER -In the early days of networking, the central box was called a hub. A hub was a dumb device, essentially just a repeater. When it received a frame, the hub made an exact copy of that frame, sending a copy of the original frame to every other system on the network.
The interesting part of this process was when the copy of the frame came into all the other systems. Only the NIC to which the frame was addressed would process that frame—the other NICs simply erased it when they saw that it was not addressed to their MAC address. This is important to appreciate: with a hub, every frame sent on a network was received by every NIC, but only the NIC with the matching MAC address would process that particular frame. Wasteful.
Give a brief description of a switch CORRECT ANSWER -Switches filter traffic by MAC address. Rather than sending all incoming frames to all network devices connected to it (like a hub), a switch sends the frame only to the recipient MAC address.
Give a brief overview of CRC CORRECT ANSWER -Most FCSs are only 4 bytes long, yet the average frame carries at most 1500 bytes of data. How can 4 bytes tell you if all 1500 bytes in the data are correct? That's the magic of the math of the CRC. Think of the CRC as just the remainder of a division problem. The NIC sending the frame does a little math to make the CRC. Using binary arithmetic, it works a division problem on the data using a divisor called a key. The result of this division is the CRC. When the frame gets to the receiving NIC, it divides the data by the same key. If the receiving NIC's answer is the same as the CRC, it knows the data is good. [Show Less]