Some terms frequently used in networking

To be continuously added in study

 

RTS (Request To Send) : signal that a device sends to another device to request permission to transmit data.

 

CTS (Clear To Send) : signal that a device sends back to the requesting device to indicate that the channel is clear and the requesting device can now transmit data.

 

ACK (Acknowledgement) : signal that a receiving device sends to a transmitting device to confirm that it has received and processed the data sent to it.

 

CIFS(Collision Avoidance Inter-Frame Space) : This is the shorter interframe space, used by nodes that have successfully transmitted a packet. The duration of the CIFS is determined by the lowest data rate supported by the wireless network. It is designed to reduce the chances of collision by giving priority to the sender of the previous frame.

 

DIFS(Distributed Coordination Function Inter-Frame Space): This is the longer interframe space, used by nodes that are contending for the wireless medium. The DIFS duration is calculated as the sum of the SIFS (Short Inter-Frame Space) and two times the slot time. It is used to ensure that the channel is idle before transmission and to avoid collisions when multiple nodes try to transmit simultaneously. Nodes must wait for DIFS before attempting to transmit a frame, and if the channel is busy, they will choose a random backoff period before trying again.

 

NAV(Network Allocation Vector): virtual countdown timer used in CSMA/CA wireless networks to reserve airtime for the ongoing transmission. It is an important mechanism that enables collision avoidance in wireless networks. It is measured in time units called slots.

 

MAC(Media Access Control): unique identifier assigned to network interfaces for communications on a physical network segment. A MAC address is usually represented as a sequence of six groups of two hexadecimal digits separated by colons, such as 01:23:45:67:89:ab.

 

NAC(Negative Acknowledgement): message sent by a receiver to a sender indicating that data has been received with errors or has not been received at all. Nak is a way for the receiver to request the sender to retransmit the data.

 

Poll: process of a network device actively requesting another device to transmit data. This is done to avoid having the network being idle and waiting for the next transmission.

 

FDMA(Frequency Division Multiple Access): A channel access method where frequency bands are divided into multiple channels, and each channel is assigned to one user.

 

TDMA(Time Division Multiple Access): A channel access method where time is divided into multiple slots, and each slot is assigned to one user.

 

CDMA(Code Division Multiple Access): A channel access method where multiple users can transmit data simultaneously over the same frequency band by using unique codes.

 

Fequency: the number of cycles of a periodic waveform that occur in a unit of time. It is typically measured in hertz (Hz), which represents one cycle per second.

 

Bandwidth: the range of frequencies over which an electronic or communication signal can be transmitted. In other words, it refers to the maximum amount of data that can be transmitted through a communication channel over a given amount of time, usually measured in bits per second (bps).

 

DLC(Data Link Control: a layer in the OSI model that provides error control, flow control and synchronization for the data exchanged between two nodes.

 

CRC (Cyclic Redundancy Check):  an error-detecting code commonly used in computer networking to ensure the integrity of transmitted data by detecting errors caused by noise or other forms of interference.

 

FSM(Finite State Machine): mathematical model used to describe the behavior of a system that can be in one of a finite number of states at any given time, commonly used in software and control systems engineering. 

 

ARQ(Automatic Repeat reQuest): a protocol used in data transmission to ensure error-free data delivery by retransmitting damaged or lost packets until they are received correctly. It is commonly used in telecommunications and computer networks.

 

LLC(Logical Link Control): a sublayer of the Data Link layer in the OSI model that handles the communication between the Network layer and the MAC (Media Access Control) layer, providing error control, flow control, and addressing.

 

PCF(Point Coordination Function): an alternative medium access method used in wireless networks that utilizes a centralized access point to coordinate the access of multiple devices to the shared wireless medium.

 

DCF(Distributed Coordination Function): a medium access method used in wireless networks to manage the access of multiple devices to the shared wireless medium.

 

Comparison of DCF and PCF

Contention-Free: a method of accessing a shared communication medium where nodes or devices are guaranteed access to the medium without any contention or competition.

 

PIFS(PCF Interframe Space): a type of interframe space in wireless networking protocols that is shorter than DIFS and longer than SIFS. It is used in the PCF (Point Coordination Function) access method to reserve the wireless medium for a predetermined time.

 

SIFS(Short Interframe Space: the shortest interframe space in wireless networking protocols and is used for high-priority messages, such as acknowledgments, to reduce latency and improve network efficiency. It is typically shorter than the other interframe spaces, including PIFS and DIFS (DCF Interframe Space).

 

AP(Access Point): a wireless networking device that connects wireless devices to a wired network. It serves as a central hub for wireless communication, providing a connection point and managing the flow of data between wireless devices and the wired network.

Poll: a medium access method used in wireless networks where a central device (such as an Access Point) controls the communication between devices by polling them for data transmission, reducing contention and improving network efficiency.

 

eCPRI(enhanced Common Public Radio Interface): a standardized protocol for connecting radio equipment controllers and radio equipment to support 5G networks, enabling remote radio heads to connect with a central unit using high-speed Ethernet connectivity.

 

Beamforming: a signal processing technique used in wireless communication systems that focuses the transmission of radio signals towards a specific direction, improving signal strength, quality, and range of the wireless link, while reducing interference and noise.

 

MIMO(Multiple Input Multiple Output): a wireless communication technology that uses multiple antennas on both the transmitter and receiver sides to improve data speed, capacity, and reliability by creating multiple signal paths, enhancing signal quality, reducing interference, and increasing network coverage.

 

Overhead: the extra time, effort, or resources needed to manage a system, protocol, or process beyond its core function. It affects efficiency, performance, and resource utilization.

 

SYN(Synchronize): a flag in the TCP header used to initiate a connection between two devices. It signals the start of a three-way handshake, synchronizing sequence numbers before data transmission begins.

 

PSH(Push): a flag in the TCP header that indicates the data in the packet should be immediately pushed to the receiving application. It ensures prompt data delivery, bypassing any buffering mechanisms in the receiving device's TCP stack.

 

ESC(Escape Character): a special character that is used to indicate the start of a control sequence or a special command. The ESC character is represented by the ASCII code 27 (0x1B in hexadecimal) and is typically used in conjunction with other characters to form an escape sequence that is recognized and acted upon by a terminal or a network device.