Ethernet At the end of 1970, PARC (Palo Alto Research Center) work was done in the work.According to the computer computers and air communication was used as the media and communication satellites. Ethernet name comes from here. The server is 3 Mbps. The ethernet we use now supports 10/100 Mbps speed. Ethernet has fast speeds such as fast ethernet and giga ethernet.This standard is 802.x (second month of 1980). It has almost the same structure as 802.2 with the 802.2 standard. Only the frame structures are different.
802.x Family and Protocols
The model that corresponds to the IEEE LAN standards began in the second month of 1980, and this family was called the 802.x family. In this family of standards 8023 is known as Ethernet technology. Jenny ring 802.5, fast ethernet 802.3u, gigabit ethernet 802.3z, 802.4 is used for the toll road.
Ethernet –IEEE 802.3
Ethernet was first used at PARC in the communication of computers via satellite. The transmission speed was 2.94 Mbps. Currently, the types used are 10Mbps or 10 / 100Mbps in general. 95% of the LANs in the world use ethernet.It is easy to install, simplicity and plenty of parts are important factors in the selection of these types of networks. As a technology, a weak and insecure method, broadcast (broadcast) is used. In the case of a packet, when a packet arrives, all the network bandwidth is used and two way data transmission is not allowed. one is CSMA / CD.
CSMA / CD-protocol is a protocol based on broadcast which is the basic communication of ethernet. This protocol is used to detect collision, not to interfere. CSMA / CD protocol, Ethernet and some kind of media access control mechanism used by 802.3 networks. In other words, it specifies how to place the information pack in the communication line.
CSMA / CD `Carrier Sense is an abbreviation of Multiple Access / Collision Detect. Before a unit leaves its information on the network line, the other party listens to the line to see if it has even left the information. When the device that wants to send information decides that the line is empty, it abandons its knowledge and continues to listen to another device to make sure that it does not even leave information at this time. If another device at this time thinks that the line is empty and also stops its knowledge, it will collide. In order for the crusher to be seated, the whole of the data must be felt without crossing the computer.
There is a conflict between the first end and the last end. a certain time is passed to feel the situation. By the time the computer has to continue to generate packets and 64bit data is generated in these 10Mbps networks. 640bit data is generated in 100Mbps networks. If the data to be generated is 64bytes or 640bytes smaller, fill bits are used to complete these numbers. For example, in a 10 / 100Mbps network, a computer must send a bit of data to the other side, even if it needs to fill in 640 bytes to fill in.
What happens when a collision is detected? The nodes (computers) that detected the collision wait for a random period of time. This is a random number that is selected from a certain number of clusters for which the number of clusters is selected. The number cluster is the result of some mathematical calculations (nothing in engineering is left to chance). I will not bother telling you how to calculate this number set. In the event that there is a conflict between the two computers in the same count, the conflicting computers will again score a number. If there are 16 consecutive conflicts, the red light on the ethernet card is steadily lit and the error message is sent to the upper layer. The first remaining node is a special node called “jamming” broadcast messages.
Ethernet topologies
Because it communicates with Ethernet broadcast, it is based on a common path as the topology. Today, ethernet is common with hubs. Hub devices have a fairly simple structure. It provides a common way for ethernet, which can be used in more functional but more expensive devices called switches.
The physical layer of the Ethernet technology uses the base band, so it uses one sign at the same time on the path and the bandwidth can be used by the sign that uses it. Hub physical as it appears in the star topology, it uses the common path technology as a rationale.
data goes to all the computers. The computer that owns the packet gets the package. The digitals are listening. If the two computers extract data at the same time, they will be used as the base band. they will interfere and they will be degraded to such an extent that they can not be corrected. Hub-connected knots (computers)
Computers connected to each other via Ethernet. The hub’s function is to provide a common way to use computers only if it appears to be connected to the star topology as a view through the hub.
Ethernet Framework Formation
The ethernet is converted into various frames and sent to the other computers. The header information is added by various protocols before the physical entity is removed. Finally, the ethernet frame format is almost same as the ethernet frame structure.
The following structure is the frame structure of 802.3. The difference between Ethernet and Ethernet is only in the header part, and the ethernet header part is prefixed with + prefixed prefix and is not further defined as 8 bytes.
Ethernet: prefix 8 bytesPrefix: Used for synchronization in the 802.3 standard. It allows the sender clock to synchronize with the sender clock. The prefix and start separator are used together, and the 8 bit prefix is used.
Recipient address: MAC address (Media Access Control): A hexadecimal number that can be recognized by Ethernet network devices, and a serial number that is no longer unique in the world. MAC address (MAC address) can be specified as a group, group or broadcast address. It is given. These numbers are given by the manufacturer in the factory. 6 bytes are written to the ROM on the ethernet card (some networks provide security using these numbers).
Sender address: The frame contains the sender’s address.
Kind: This two byte type field specifies which upper layer protocol or function to send the received frames (ftp, telnet, etc.)
Data: It can be between 46-1514 bytes. For 10 Mbps ethernet networks, it should be at least 46 bytes. The reason is related to the 64 bytes described above.
Frame Check Sequence (FSC): A CRC of 32 bits is inserted (CRC is a kind of error checking algorithm). The error test is done for all bits of the frame except the prefix.
Ethernet Logic Coding System
There are a wide variety of digital sign coding formats. NRZ-L, NRZI, Manchester, differential Manchester and 4B5B.
They use Manchester or 4B5B encoding as the logic encoding system provided in the Ethernet. The basic principle of Manchester encoding is that the transmission is done in a way that the vibration is generated so that it is easy to understand whether the line is used or not. The use of this type of transport requires ethernet.
Cabling Technologies
10base-2 Thin coaxial
10base-5 thick coaxial
10base-T UTP, STP (twisted pair) cables.
Ethernet networks have three types of cabling as standard:
UTP unshield twited pair, STP shield twisted pair, thin Ethernet, coaxial, and thick Ethernet.
The network-based bandwidth and speed determine the selected cabling technology.
Twisted pair: A cable used in network communication systems and high-grade telephone lines. There are two types: Protected (STP) and unprotected (UTP). The protected one has a protective sheath to prevent the data from being influenced by the outside. It is costly compared to the one that is used in very noisy and sensitive environments. Used in 10BaseT / 100BaseTX standards. RJ-45 terminated with connectors. 8 pairs of wires are used in pairs.
Thin Ethernet Coaxial: Network coaxial, named 10Base 2. They use BNC connectors.
Thick Ethernet: It is called Standard Ethernet. Used in 10 Mbps bandwidth networks. It is a heavy, hard and expensive wiring method of installation. They use BNC connectors.
Fast Ethernet: It is a system capable of carrying 100 Mbps data. Known as 100 BaseTX. It is similar to 10Base-T Ethernet, but it is 10 times faster.
Category 3 (10Base-T for 10 Mbps networks) and Category 5 (100Base-TX for 100 Mbps Fast Ethernet Networks).
It is thin, flexible and easy to install and use with RJ-45 connectors. It is very difficult to prepare these types of connector cables for a medium-sized computer with a pair of pliers. Color sequencing is important. One of the major advantages is the ease of fault detection, and if the connection between the hub and a node goes away, then only that node can take advantage of the network features, which can not affect the entire network.
If you want to extend your network, it will be quite easy to grow your network as it is possible to connect your hub or switch to other hubs or switches with “crossover” cabling. You should know the color pairs you are using for crossover cabling and you should make adjustments like 1-3, 2-6.
Cable Quality Standards
Network standards specify cable types for 10 Mbps and 100 Mbps Ethernet networks. Category indicates quality grade or ability to carry data. Elevation of the category increases the reliability of the assignment.
In our homes, the cable we use as a phone cable uses Category 1 cable and RJ-11 connectors. Some commercial agencies use Category 3 cabling on their telephone lines. Category 1 cable can not be used in network connections, only Category 3 and 5 are used.
Category 3 UTPCategory 3 is used in networks with 10 Mbps bandwidth. Can not be used on 100 Mbps networks.
Category 5 UTPCategory 5 is used in networks that can transfer data at 100Mbps bandwidth. It works fine on 10 Mbps networks, but is slightly more expensive than Category 3. Networks that want to move to 100 Mbps in the future can already use Category 5 cabling.
Coaxial CablingCoaxial cable is similar to cable TV or known antenna cable, but allows higher data transfer rates. There are two types of coaxial cables used in networks. These are 10BASE 2 and 10BASE 5. 10BASE 5. Thick coaxial is widely used today.
10BASE 2It uses BNC connectors. It is used in small and medium sized networks. It is reliable but quite expensive. BUS structure is used in networks.
Connectors and Ports
RJ-45 Connectors
10 BASET and 100BASETX cables are terminated with RJ-45 connectors.
It provides a reliable connection by plugging in the port on the hub or switch.
BNC Coaxial ConnectorsThe BNC cable connection does not allow you to monitor the status between your computer and the network through the LEDs. The open ends of the cable are terminated with a resistance of 50 Ohms.
RJ-45 Straight PortsThese are standard ports on Hubs and Switches. The connection between the hub (or switch) and the node is provided by these ports.
RJ-45 Crossover PortsIn network connections, flat cable is used between the central connection point and the connected equipment. But in case of network expansion, we need to use crossover connection when we connect two hubs together. Some hubs or switches have an extra port that does not require a “crossover” connection.
BNC Ports10 BASE2 is used for coaxial cable connections.
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