Physical Layer Protocols Features & Characteristics

Physical Layer Protocols Features & Characteristics

This article of Network Access will describe the Physical Layer Protocols their functions and protocols that manage data transmission.

NETWORK CONNECTIONS

Whether it is a connection to a local printer at home or to a website in another country, in order for any network communication to occur, a connection to a local network must first be established . A physical connection can be a cable connection or a wireless connection using radio waves. The type of physical connection used depends entirely on the network configuration. For example, it may be that a desktop or laptop PC physically connects, via cables, to a shared switch. This type of configuration is called a wired network . Data is transmitted through a physical cable.

Or, it may also be the case of wireless connections for laptops, tablets and smartphones. In the case of wireless devices, data is transmitted by radio waves; where the devices that are in a wireless network must be connected to a wireless access point (AP - Access Point).

NETWORK INTERFACE CARD (NIC)

Network interface cards (NICs) connect a device to the network . Ethernet NICs are used for wired connections, while wireless local area network (WLAN) NICs are used for wireless connections. Devices for end users can include one type of NIC or both.

It is worth mentioning that cable-connected devices do not need to share network access with other devices (each device connected by cable has a separate communication channel through its own Ethernet cable), unlike wireless devices (where several devices they access the network simultaneously and consequently the performance may be slower).

PURPOSE OF THE PHYSICAL LAYER

The physical layer of the OSI model provides the means of transporting the bits that make up a frame of the data link layer through the network means. As well as:

• Accept a full frame from the data link layer
• It encodes it as a series of electrical, optical or radio wave signals that represent the bits in each frame that are transmitted to local media.

PHYSICAL LAYER MEDIA

There are three basic formats of network media:

• Wired Media : the signals are patterns of electrical pulses.
• Fiber optic cable : the signals are light patterns.
• Wireless Media: signals are patterns of microwave transmissions.

 PHYSICAL LAYER STANDARDS

The physical layer consists of electronic circuits, media and connectors developed by engineers. That is why the main organizations specialized in electrical engineering and communications define the standards that govern this hardware, for example, some of them are:

• International Telecommunications Union (ITU)
• International Organization for Standardization (ISO)

• Commission (FCC) of the United States and the European Telecommunications Standards Institute (ETSI)

• American National Standards Institute (ANSI)
• Association of Telecommunications Industries (TIA) and Association of Electronic Industries (EIA)
• Institute of Electrical and Electronic Engineers (IEEE)
• National telecommunications regulatory authorities, including the Federal Communication

FUNCTIONS OF THE PHYSICAL LAYER

The physical layer standards cover three functional areas:

• Physical components
• Coding
• Signaling

 PHYSICAL COMPONENTS

They are the electronic devices of hardware, media and connectors that transmit and transport the signals to represent the bits. All hardware components, such as NICs, interfaces and connectors, materials and cable design, are specified in the standards associated with the physical layer.

CODING

Encoding is a method used to convert a transmission of data bits into a predefined "code." In the case of networks, the coding is a voltage or current pattern used to represent the bits; 0 and 1. In addition to creating codes for the data, the physical layer coding methods can also provide control codes, such as identifying the beginning and end of a frame.Network coding methods include:

• Manchester coding
• No return to zero (NRZ)

 SIGNALING

The physical layer must generate the wireless, optical or electrical signals that represent the "1" and the "0" in the media. The bit representation method is called the signaling method .

The signals can be transmitted in two ways:

• Asynchronous: data signals are transmitted without an associated clock signal. Therefore, the frames require start and stop indicators.
• Synchronous: data signals are sent together with a clock signal that occurs in uniformly spaced time duration called "bit time."

CHARACTERISTICS OF THE PHYSICAL LAYER

Within the transfer of data in the physical layer we handle two important terms:

•  Bandwidth : Ability of a medium to transport data is generally measured in kilobits per second (kbps), megabits per second (Mbps) or gigabits per second (Gbps)

Occasionally, bandwidth is thought of as the speed at which the bits travel, however, this is not adequate. For example, in 10 Mbps and 100 Mbps Ethernet, the bits are sent at the speed of electricity. The difference is the number of bits that are transmitted per second.

• Performance : is the measure of bit transfer through the media for a certain period of time. Many factors influence performance: The amount of traffic, the type of traffic, the latency created by the number of network devices found between origin and destination.
• Latency : refers to the amount of time, including delays, that it takes data to transfer from one point to another.