The OSI Model and Encapsulation Flashcards
(26 cards)
Open Systems Interconnection (OSI) reference Model
A seven layer model that categorizes various network technologies. It is commonly referred to as the OSI model or the OSI stack
What are the 7 Layers
All People Seems To Need Data Processing
7-Application, 6-Presentation, 5-Session, 4-Transport, 3-Network, 2-Data Link, 1-Physical.
protocol data unit (PUD)
Data at different layers of the OSI model. Specifically, a Layer 4 PDU is a segment, Layer 3 PDU is a packet, a Layer 2 PDU is a frame, and a Layer 1 PDU is a bit.
IP (Internet Protocol) header
Information at the beginning of an Internet Protocol (IP) packet that enables proper addressing and routing
TCP (Transmission Control Protocol) header
a data packet header that contains 10 mandatory fields totaling 20 bytes (or octets). the header holds information about the connection and data currently being sent.
UDP (User Datagram Protocol) header
In a UDP datagram, a header that contains four fields (source port, destination port, length, and checksum) totaling 8 bytes.
TCP flag
A field in a TCP header that is used to indicate a particular connection state or provide additional information. It is often used for troubleshooting purposes or to control how a particular connection is handled.
Payload
Way to describe data itself, which is separate and distinct from any of the other information required for proper transmission.
(MTU)- Maximum transmission unit
The largest packet size supported on an interface.
Current state modulation
A way to electrically or optically represent binary digits by using a binary 1 for the presence of voltage on a copper cable or the presence of light on a fiber-optic cable and using a binary 0 for the absence of light or voltage.
State transition modulation
An approach of representing binary digits in which the transition between a voltage level (for example, going from a state of no voltage to a state of voltage, or vice versa, on a copper cable) or the transition of having light or no light on a fiber-optic cable is represented as a binary 1; having no transition in a voltage level or light level from one time period to the next is represented as a binary 0.
Cyclic redundancy check (CRC)
A mathematical algorithm that is executed on a data string by both the sender and the receiver of the data string. If the calculated CRC values match, the receiver can conclude that the data string was not corrupted during transmission.
Physical Layer
Layer 1- of the OSI model, Which is concerned with the transmission of bits on a network.
Data Link Layer
Layer 2 of the OSI model, which is packaging data into frames and transmitting those frames on a network, performing error detection/correction, uniquely identifying network devices with an address, and handling flow control.
Network Layer
Layer 3 of the OSI model, which is forwarding data based on logical addresses.
Transport Layer
Layer 4 of the OSI model, which acts as a dividing line between the upper layers and the lower layers. Specifically, messages are taken from the upper layers (Layers 5–7) and encapsulated into segments for transmission to the lower layers (Layers 1–3). Similarly, data streams coming from lower layers are decapsulated and sent to Layer 5 (the session layer) or some other upper layer, depending on the protocol.
Session Layer
Layer 5 of the OSI model, which is responsible for setting up, maintaining, and tearing down sessions.
Presentation Layer
Layer 6 of the OSI model, which is responsible for the formatting of data being exchanged and securing the data with encryption.
Application Layer
Layer 7 of the OSI model, which provides applications access to network services
Network interface layer
The layer of the TCP/IP stack (also known as the network access layer) that encompasses the technologies addressed by Layers 1 and 2 (that is, the physical and data link layers) of the OSI model.
Internet layer
The layer of the TCP/IP stack that maps to Layer 3 (the network layer) of the OSI model. Although multiple routed protocols (for example, IPv4 and IPv6) may reside at the OSI model’s network layer, the Internet layer of the TCP/IP stack focuses on IP as the protocol to be routed through a network.
transport layer (TCP/IP stack)
Layer 3 of the TCP/IP stack that maps to Layer 4 (the transport layer) of the OSI model. The two primary protocols found at the TCP/IP stack’s transport layer are TCP and UDP.
application layer (TCP/IP stack)
In software-defined networking, the logical layer that presents the applications to the network manager. These applications allow simple control over the environment, permitting the engineer to configure and monitor the network as needed.
time-division multiplexing (TDM)
A method of transmitting different communication sessions (for example, different telephone conversations in a telephony network) on the same physical medium by allowing sessions to take turns. For a brief period of time, defined as a time slot, data from the first session is sent, followed by data from the second session. This continues until every session has had a turn, and the process repeats.
