1. What does OSI stand for?: Open Systems Interconnection, which is a seven-
layer network model
2. What does TCP/IP stand for?: Transmission Control Protocol/Internet Protocol
3. Name the 7 layers of the OSI model in order (# & name): 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."
4. What is UTP?: Unshielded Twisted Pair cable. Usually contains four pairs of
wires that can transmit and receive data
5. Define the Physical Layer of OSI: 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).
6. What is a MAC address?: 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.
, CompTIA Network+ Certification (Exam N10-007)
7. What are 2 other ways to refer to the MAC address?: 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.
8. How do NICs read computer data?: 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.
9. How does the network get the right data to the right system?: 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.
10. What is a "frame"?: 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.
11. Name the parts of a frame & describe each part.: 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).
12. What is FCS?: 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.
13. What is MAC addressing?: CompTIA calls the use of the MAC address to
get frames to the proper computer or node MAC addressing.
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