Module 4 Flashcards
NIC
Network Interface Card - computer hardware component that connects the computer to a network
Some devices may have just one NIC, while others may have multiple NICs (Wired
and/or Wireless, for example)
Purpose of the Physical Layer (4tk)
1) Transports bits across the network media 2) Accepts a complete frame from the Data Link Layer and encodes it as a series of signals that are transmitted to the local media 3) The last step in the encapsulation process. 4) The next device in the path to the destination receives the bits and re-encapsulates the frame, then decides what to do with it.
Encoding
Encoding converts the stream of
bits into a format recognizable by
the next device in the network
path.
Signaling
The signaling method is how the bit
values, “1” and “0” are represented on
the physical medium (media).
Bandwidth
Bandwith - 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
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
Types of copper cabling (3tk)
1) Unshielded Twisted Pair (UTP)
2) Shielded Twisted Pair (STP)
3) Coaxial Cable
Characteristics of copper cabling
Copper cabling is the most common type of cabling used in networks today. It is
inexpensive, easy to install, and has low resistance to electrical current flow.
Limitations:
• Attenuation – the longer the electrical signals have to travel, the weaker they get.
• The electrical signal is susceptible to interference from two sources, which can distort and corrupt
the data signals (Electromagnetic Interference (EMI) and Radio Frequency Interference (RFI) and
Crosstalk).
Characteristics of UTP cabling
UTP is the most common networking media. • Interconnects hosts with intermediary network devices. • The outer jacket protects the copper wires from physical damage. • Twisted pairs protect the signal from interference. • Color-coded plastic insulation electrically isolates the wires from each other and identifies each pair.
Characteristics of Fiber-Optic Cabling
• Not as common as UTP because of the expense involved
• 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
Fiber-Optic Cabling Usage (4 types of industry)
- Enterprise Networks - Used for backbone cabling applications and interconnecting
infrastructure devices - Fiber-to-the-Home (FTTH) - Used to provide always-on broadband services to
homes and small businesses - Long-Haul Networks - Used by service providers to connect countries and cities
- Submarine Cable Networks - Used to provide reliable high-speed, high-capacity
solutions capable of surviving in harsh undersea environments at up to transoceanic
distances.
Wireless media
• Carries electromagnetic signals representing binary digits using radio or
microwave frequencies.
Limitations of wireless media (4tk)
• Coverage area - Effective coverage can be significantly impacted by the physical
characteristics of the deployment location.
• Interference - Wireless is susceptible to interference and can be disrupted by many
common devices.
• Security - Wireless communication coverage requires no access to a physical strand
of media, so anyone can gain access to the transmission.
• Shared medium - WLANs operate in half-duplex, which means only one device can
send or receive at a time. Many users accessing the WLAN simultaneously results in
reduced bandwidth for each user.
