Ethernet is a standard for local area computer networks that have access to the environment with CSMA/CD content (Carrier Detection Multiple Access with Collision Detection) and is a technique used to improve performance in computer networks. Its name comes from the concept of physical ether.
What is the Ethernet Port and Cable Used in Computer Networks?
Ethernet (ENET) defines the physical level signal and cabling characteristics of the OSI model and data link level data frame formats.
It is based on the preparation of the international IEEE 802.3 standard. ENET and IEEE 802.3 are often taken synonymously. The two differ in one of the fields of the data frame, and their frames can coexist on the same network.
The development of a network technology known as Experimental Ethernet began in 1972. The advanced Ethernet system, then known as the ALTO ALOHA network, was the first local area network (LAN) for personal computers (PCs). This network was first operated in May 1973 at 2.94Mb/s.
Official 10 Mb/s ENET features were jointly developed by Xerox, Digital (DEC) and Intel companies and published in 1980. These features are known as the ethernet blue book DEC-Intel-Xerox (DIX) standard. This document has made experimental Ethernet operating at 10 Mbps an open standard.
ENET technology has been adopted by the IEEE Local Networks (LAN) Committee for standardization as IEEE 802.3. The IEEE 802.3 was first published in 1985.
The IEEE 802.3 standard provides an ENET type system based on the original DIX standard but not the same. The right name for this technology is IEEE 802.3 CSMA/CD, but it is almost always called ENET. IEEE 802.3 has been adopted by the International Standardization Organization (ISO) and has become an international network standard.
ENET continued to evolve in response to changes in technology and user needs. Since 1985, the IEEE 802.3 standard has been updated to include new technologies. For example, the 10BASE-T standard was approved in 1990, the 100BASE-T standard was approved in 1995 and ENET 1998 over fiber.
ENET is a widely accepted network technology with connections for PCs, high-performance and scientific workstations, minicomputers and host systems.
ENET architecture provides error detection but does not provide error correction. There is no central control unit, all messages are transmitted to every device connected over the network. Each device is responsible for recognizing its own address and accepting messages sent to it. Access to the communication channel is controlled individually by each device using a probable access method known as contention.
Ethernet’s main objectives are consistent with those that have become the basic requirements for the development and use of LAN networks.
The original targets of Ethernet are:
Features that can make network design difficult without any significant contribution to achieving other objectives are excluded.
Technological advances will continue to reduce the total cost of connecting devices.
All these applications should be able to exchange data at the data link layer level. To avoid the possibility of incompatible variations, the feature avoids optional features.
The addressing mechanism should be able to direct data to a single device, a group of devices, or alternatively broadcast the message to all devices connected to the network.
All connected devices must have the same network access.
No device connected to the network can prevent other devices from working.
The network should work efficiently at a data rate of 10 Mbps.
At any network traffic level, there should be the lowest possible latency in data transfer.
The network must be stable under all load conditions. Forwarded messages must maintain a fixed percentage of all network traffic.
Its design should simplify network maintenance, operations, and planning.
Ethernet design should be specified as layers to separate the logical operations of the link-layer protocols from the physical communication properties of the communication channel.
There is a wide variety of IEEE 802.3 applications. A notation has been developed to distinguish between them. This notation indicates three features of the application.
Data transfer rate in Mbps.
The signaling method used.
Maximum cable segment length in hundreds of meters depending on the media type.
Some types and features of these IEEE 802.3 applications are detailed below:
1BASE-5:IEEE standard at a maximum distance of 250m for 1Mb/s baseband Ethernet over twisted pair cable. 10BASE-5: IEEE standard for 50 trunk coaxial cable and 10 Mb/s baseband Ethernet and twisted pair cable connection unit interface (AUI) at a maximum distance of 500m. 10BASE-2: IEEE standard for 10MB/s baseband Ethernet over 50 co coaxial cable with a maximum distance of 185m. 10BROAD-36: IEEE standard for 10 Mb/s broadband Ethernet over 75 Ω broadband coaxial cable with a maximum distance of 3600m. 10BASE-T: IEEE standard for 10 Mb/s baseband Ethernet over an Unshielded Twisted Pair (UTP) cable at a maximum distance of 100 m from a station to a hub following a horizontal star-shaped cable topology. 10BASE-F: IEEE standard for 10Mb/s baseband Ethernet over fiber optic with a maximum distance of 2,000 meters (2Km).
100BASE-TX: IEEE standard for 100 Mbps baseband Ethernet over two pairs of UTP cables (Category 5 pairs or more each) or two pairs of STP cables. 100BASE-T4: IEEE standard for 100 Mbps baseband Ethernet over 4 category 3 (or higher) UTP cable pairs. 100BASE-FX: 62.5 / 125 μm is the IEEE standard for 100Mb/s baseband Ethernet over two fiber optic cabling systems. 100BASE-T2: IEEE standard for 100Mb/s baseband Ethernet over a pair of UTP cables of category 2 or 3 higher.
1000BASE-SX: IEEE standard for 1000Mb/s (1Gb/s) baseband over 2 multimode fiber (50/125 μm or 62.5 / 125 μm) fiber optic cabling. 1000BASE-LX: IEEE standard for 1000Mb/s (1Gb/s) baseband for 2 single-mode or multi-mode (50/125 μm or 62.5 / 125 μm) fiber optic cabling. 1000BASE-CX: IEEE standard for 1000 Mb/s (1 Gb/s) baseband over 150 balanced shielded copper wiring. It is a special cable with a maximum length of 25m. 1000BASE-T: IEEE standard for ENET 1000Mb/s (1Gb/s) baseband ENET on 4 category 5 or higher UTP cable pairs with a maximum category 100m wiring distance.
Differences Between Ethernet and IEEE 802.3
Although IEEE 802.3 and Ethernet are similar, they are not the same. The differences between them are so important that they make them incompatible.
All versions of Ethernet are similar in that they share the same Carrier Sense Multiple Access with Collision Detection (CSMA/CD). However, the IEEE 802.3 standard has evolved over time, so it now supports multiple environments, including 50 75 and 75 75 coaxial cable in the physical layer, Unshielded Twisted Pair (UTP) cable, twisted pair cable, Shielded Twisted Pair or STP and fiber optics. Other differences between the two include transmission speed, signaling method, and cable length.
The main difference between the original ENET technology and the IEEE 802.3 standard is the difference between the formats of its frames. This difference is important enough to make the two versions incompatible.
One of the differences between the formats of the two frames (preamble) is in the initial suffix. The purpose of the starter is to announce the framework and allow all recipients on the network to synchronize with the incoming framework. The length of the ENET entry is 8 bytes, but in IEEE 802.3 its length is 7 bytes, the last one is the beginning of the eighth frame delimiter.
The second difference between the frame format is the frame type field. A type of field is used to indicate the protocol carried in the frame. This allows many protocols to be carried in the frame. The type field was replaced by a frame length field in the IEEE 802.3 standard used to specify the number of bytes in the data field.
The third difference between the formats of both frames is found in both the destination and the starting point address fields. The IEEE 802.3 format allows the use of both 2 and 6-byte addresses, while the ENET standard allows only 6-byte addresses. The frame format currently valid in network environments is IEEE 802.3, but network technology continues to be referred to as Ethernet.
Some of the defining features of Ethernet are as follows: Its features (IEEE 802.3) are also adopted by ISO and are found in the international 8802-3 standard. It is based on the logic of the bus topology. Initially, the bus was a single cable length to which network devices were connected. In existing applications, the bus has been miniaturized and placed in a hub to which stations, servers, and other devices are connected.
It uses a method of contention to access the environment. Transmissions are broadcast on the shared channel for listening by all connected devices, only the intended target device accepts transmission. This type of access is known as CSMA/CD.
Various environments have evolved to operate at multiple transmission speeds on coaxial cable, twisted pair, and fiber optics. All applications can work together and simplify the transition to new versions of Ethernet.
Multiple segments can be connected to create a large LAN network using repeaters. The correct operation of a LAN depends on the segment of media created according to the rules of that particular environment. Complex LAN networks created with multiple media types should be designed according to the multipart configuration guidelines provided in the ENET standard. The rules include the total segment and repeater count limits that can be used to make a LAN.
Ethernet is designed to be easily expanded. The use of interconnection devices, such as bridges, routers, and switches, allows individual LAN networks to be interconnected. Each LAN continues to operate independently, but can easily communicate with other connected LANs.
Each device operates independently from other devices on the network and does not use a controller. All devices are connected to a shared signal communication channel.
Signals are transmitted serially, one bit is transmitted at a time. Transfers are made over the shared signal channel, where all connected devices can listen to the transmission. Before starting a transmission, a device listens for the transmission channel to see if it is independent of the transmission channel. If the channel is empty, the device can transmit its data in the form of an ENET frame.
Once a frame is transmitted, all devices on the network compete for the next opportunity to transmit a frame. The dispute over the opportunity to transmit between devices cannot block other devices to ensure fair access to the communication channel.
Access to the shared communication channel is determined by the MAC substrate. This media access control is known as CSMA/CS.
Address fields in the ENET framework carry 48-bit addresses for both destination and source addresses. The IEEE standard manages part of the address space by assigning control to a 24-bit identifier known as the OUI (Enterprise Specific Identifier). Each organization that wants to create network interfaces (NICs) is assigned a unique 24-bit OUI that is used as the first 24-bit of the NIC’s 48-bit address. A 48-bit address is called a physical address, hardware address, or MAC address.
Using unique pre-assigned addresses makes it easy to set up and grow an ENET network.
The logical topology of a network determines how signals are transmitted in the network. The logical topology of the ENET network provides a single communication channel that carries signals from all connected devices. This logical topology may differ from the physical topology or actual order of the environment. For example, if the middle sections of an ENET network are physically connected after a star topology, the logical topology continues to be that of a single communication channel carrying signals from all connected devices.
Multiple segments can be linked together using repeaters to create a larger LAN network. Each media segment is part of the entire signal system. This interlocking segment system is never connected to a loop, so each segment must have two ends.
The signal produced by a device is put in the middle segment to which it is connected. The signal is repeated in all other connected segments so that it can be heard by all other stations. Regardless of the physical topology, there is only one signal channel to transmit frames from all segments to all connected devices.
For the media access control method to work properly, all network interfaces must be able to respond to signals within a certain period of time. The duration of the signal depends on the duration of a signal from one end of the network to the other and back (Round Trip Time).
Despite the middle segment combination used in the construction of the network, the Round Trip Time limit should be reached. Configuration guidelines provide rules for combining segments with repeaters to maintain signal timing. If these rules are not followed, stations may not hear broadcasts on time and signals from these stations interact with each other, causing late collisions and network congestion.
Media segments should be created according to the configuration guidelines for the selected media type and network transmission speed (high-speed networks require a smaller network size). Local networks created by multiple media types should be designed by following the guidelines for multi-part configurations of the standard.
Components of 10 Mbps
Original IEEE 802.3 specifications were for 10 Mbps Ethernet over thick coaxial cable. Today, there are four types of Ethernet running at 10Mb/s speed, and each of them operates in a different environment. These are summarized below:
10BASE-5 > Thick Coaxial Cable
10BASE-2 > Thin Coaxial Cable
10BASE-T > Twisted Pair Cable
10BASE-F > Fiber Optic Cable
AUIs, PMAs, and MDIs can be inside or outside the network device.
Data Terminal Equipment (DTE)
In the IEEE standard, network devices are called data terminal equipment (DTE). Every DTE connected to the Ethernet network must be equipped with an Ethernet network interface (NIC). It provides a link to the NIC communication channel. This includes the electronic components and software required to perform the functions required to send an ethernet frame over the network.
Attachment Unit Interface (AUI)
AUI provides a way for signals and power between Ethernet network interfaces (NICs) and PMA. In the original DIX standard, this component is called a radio cable.
Physical Medium Attachment (PMA) Connection
PMA is the part of the physical layer responsible for transmission control, collision detection, clock recovery, and Spread Delay (Skew) alignment.
Medium Dependent Interface (MDI)
MDI provides PMA with a physical and electrical connection to the transmission medium. For example, in the case of 10BASE-T Ethernet, MDI is an 8-position modular connector that matches the 8-position modular plug connected to 4 double UTP cables.
The medium carries signals between the connected devices. Thin or thick coaxial cable, twisted pair cable or fiber optic cable can be used.
Components of 100 Mbps
Increasing the speed ten times results in a reduction factor of ten times the time it takes to transmit a little in the network. The frame format, amount of data carried, and media access control method remain unchanged. There are four types of Ethernet operating at 100Mb/s. These are summarized below:
100BASE-T2 > 2 pairs of UTP (Category 3 or higher)
100BASE-T4 > 4 pairs UTP (Category 3 or higher)
100BASE-TX > 2 double twisted pair data cables (UTP or STP category 5 or higher)
100BASE-FX > Fiber Optic Cable
The 100BASE-TX and 100BASE-FX standards are called 100BASE-X together. These standards adopt physical environment standards for FDDI and TP-PMD developed by ANSI. The 100BASE-T2 and 100BASE-T4 standards have been developed to ensure the use of lower quality UTP cables.
The functions performed by DTE and MDI are the same as 10Mb/s Ethernet. However, Fast Ethernet specifications include an auto-negotiation mechanism. This makes it possible to provide dual-speed network interfaces (NICs) that can run automatically at both 10 and 100Mb/s.
Media Independent Interface (MII)
MII is a set of optional electronic components designed to make the signaling differences required for different environments transparent to the Ethernet chips located in the NICs of the network devices. MII electronics and the corresponding 40-pin connector and cable make it possible to connect a network device to one of several media types for greater flexibility.
Physical Layer Device (PHY)
The role of this device is similar to the 10Mb/s Ethernet transceiver. This unit can be inside or outside the network device. It is usually part of the network interface and the hub that contains the circuits necessary to transmit and receive data on the cable.
It can use 100 Mbps Ethernet, UTP, STP or fiber optic cable (coaxial cable is not supported).
Components of 1000 Mbps
Gigabit Ethernet (GE) further increases the transfer speed to 1000 Mb/s (1 Gb/s). It uses the same frame format, runs full-duplex, and uses the same flow control methods as other versions of Ethernet. In half-duplex mode, GE uses the same method to access CSMA/CD media to resolve conflicts over shared media.
There are four types of Ethernet operating at 1Gb/s. These are summarized below.
SX, LX and CX standards are collectively called 1000BASE X (IEEE 802.3z). These standards adopt physical environment standards developed by ANSI for fiber optics. The T standard (IEEE 802.3ab) was developed to enable the use of UTP cable.
Components used in 1 Gb/s ENET networks perform the same functions as Fast Ethernet. However, the Media Independent Interface (MII) is now called the Gigabit Media Independent Interface (GMII).
Introduction ENET networks usually consist of multiple separate sections that are connected by repeaters. The sections are connected by following what is called a rootless tree pattern. Each segment is a separate branch of the entire network.
Interconnected segments are considered rootless as they can grow in any direction.
Historically, each media type requires a different arrangement of cable physics. Currently, the physical topology recommended for installations is the star topology specified in ANSI / TIA / EIA-568-A. The use of star topology made it possible to limit network interruptions caused by wiring problems.
When using a thin coaxial cable, the physical topology of the network can only be a bus topology. In this design, all devices are connected to a single cable length. This cable provides a way for electrical signals common to all connected devices and carries all transmissions between devices.
A problem with the cable bus design is that a fault in any part of the thin coaxial cable interrupts the electrical path. As a result, the operation of all connected devices will be interrupted.
Devices connected to a thin coaxial cable segment follow a topology known as a daisy chain. In this topology, a thin coaxial cable connected to a BNC T connector on one device connects to another T connector on the next device. The T connectors on the opposite ends of the segment are the terminals.
In a daisy chain topology, if any thin coaxial cable is incorrectly removed from the T-connector, the entire segment will not be functional for all connected devices. If the T connector is removed from the network interface, the segment continues to operate as the coaxial cable is not disconnected.
It is also possible to have point-to-point segments in a thin coaxial cable environment. Using a multi-port repeater, you can connect a segment directly to a device. This limits the number of devices that can be affected by damage to a particular cable.
Twisted pair and fiber optic segments are arranged in a star physical topology. In this topology, individual devices are connected to a central hub that forms a partition. Signals from each connected device are sent to the hub and then broadcast to all other connected devices. This design allows Ethernet to function logically as a bus, but physically the bus only exists on the hub.
The star topology simplifies network management and troubleshooting because each cable operation connects only two devices, one at each end of the cable. If a device cannot successfully communicate with the network, it can be physically moved to another location to determine if the malfunction is in the cable or on the device. This type of isolation is much more difficult in a daisy chain or bus topologies.
What is Fast Ethernet?
Fast Ethernet, also known as 10BASE-T, has been developed in response to the need for an ENET-compliant LAN with a higher transfer rate that can operate over UTP cabling. 100BASE-T was developed by IEEE802.3 and is fully 10BASE-T compatible. 100BASE-T features are found in the IEEE802.3u standard.
At 100BASE-T, the time parameters increase tenfold to achieve a 10-fold increase in transfer speed. However, the rest of the CSMA/CD mechanism has not changed. The difference in performance level is associated with how often frames are delivered. The frame format, length, error handling, and information management are almost the same as those found in 10BASE-T. This provides an improvement in performance using familiar technology.
However, there are several changes to 100BASE-T:
Additional error control functions.
There is no support for any coaxial cable environment.
Automatic negotiation support. This is the technique that allows 10BASE-T and 100BASE-T devices to recognize each other and automatically switch at a transfer rate accepted by both.
Fast Ethernet specifies four types of transceivers, 100BASE-T2, 100BASE-T4, 100BASE-TX and 100BASE-FX. All four are similar in terms of component requirements, mode of operation, and topology. All operate within the wiring distance limitations specified in the ANSI/TIA/EIA-568-A, and ISO/IEC 11801 standards for wiring.
Three of the Fast Ethernet transceiver types, 100BASE-T4, 100BASE-TX and 100BASE-FX, are described in the IEEE 802.3u supplement published in 1995. 100BASE-T2 is defined in the IEEE 802.3 annex and published in 1997. 100BASE-T4, 100BASE-TX and 100BASE-FX are the most widely used versions of Fast Ethernet.
T4 type segments operate on the UTP category 3 or higher. To allow the use of Category 3 UTP, the signal scheme uses four pairs of cables. All four pairs are used in parallel, which reduces the signal bandwidth required for each pair. This translates to simpler data recovery circuit requirements and a more robust system.
In 1995, the IEEE 802.3y working group was created to examine the probability of 100 Mbps transmission on two pairs of category 3 UTP. In 1997, the 100BASE-T2 standard was completed.
It works on all currently used UTP media types for the new transceiver 100BASE-T4 and 100BASE-TX. While it is possible to obtain a 100Mb/s data rate over two Category 3 UTP cables, this is the cost of complex digital signaling techniques. Near-End Crosstalk Cancellation (NEXT) and Adaptive Digital EQ are required for 100BASE-T2 transceivers to function.
Fast Ethernet 100BASE-FX standard covers 100BASE-TX and 100BASE-FX. Both use physical media standards developed by ANSI for FDDI. The X standard combines the ENET and FDDI standards. Uses CSMA/CD media access control method and FDDI transceiver type.
The 100BASE-X contains two types of transceivers, copper twisted pair, and multimode fiber optic. The TX segment type operates on two twisted pair data class pairs, namely UTP category 5 or higher, or STP-A 150W. FX type FX operates on two 62.5 / 125 μm multimode optical fibers. 100BASE-X does not provide a bridging mechanism between ENET and FDDI networks.
The signaling technique in 100BASE-X transmits data in two signal paths, one in each direction. Each signal path provides a full data transfer rate of 100Mb/s.
The 100BASE-X architecture preserves the full-duplex nature of the basic communication channel. Any 100BASE-X transceiver can be used for full-duplex transfers.
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