DRAFT
Ethernet is a standard which defines how devices in a local area network (LAN) communicate with each other. Ethernet can be transmitted over various physical media, including twisted-pair copper cables (such as Cat 5e and Cat 6), fiber optic cables, and wireless connections (Wi-Fi).
The standard defines both the physical layer and Data Link Layer of the OSI model. It describes how everyone can take the carrier, in an asynchronous system. The communication must be synchronized every time. Ethernet uses CSMA/CD (Carrier Sense Multiple Access with Collision Detection) to handle collisions on shared networks. Collisions occur when two devices transmit data simultaneously on the same Ethernet segment. The system works in unconnected mode, the host talks whether the other is listening or not and the communication is accepted or refused, but is not validated with the sender. There may therefore be lost frames.
Ethernet provides a method for devices to address each other at the MAC address level and transfer data frames between them. Ethernet uses ARP to discover MAC addresses and map them to IP addresses.
Ethernet defines the frame Format, including preamble, destination MAC address, source MAC address, EtherType (indicating the type of data carried in the frame), data payload, and a frame check sequence (FCS) for error detection.
Ethernet Standards:
Ethernet has evolved over the years, with various standards defining different data rates and physical media. Some common Ethernet standards include:
10BASE-T: Ethernet over twisted-pair copper cables at 10 Mbps.
100BASE-TX: Fast Ethernet over twisted-pair cables at 100 Mbps.
1000BASE-T: Gigabit Ethernet over twisted-pair cables at 1 Gbps.
10GBASE-T: 10 Gigabit Ethernet over twisted-pair cables at 10 Gbps.
1000BASE-SX and 1000BASE-LX: Gigabit Ethernet over fiber optics.
10GBASE-SR and 10GBASE-LR: 10 Gigabit Ethernet over fiber optics.
Ethernet RJ45 cable and plugs (UTP unshielded, FTP global shielding, STP shielding of each pair, SFTP global shielding and of each pair, SSTP Super STP).
- UTP Cat.3 (2 individually twisted pairs) for voice communications (most often for telephone lines). Cable abandoned since 2006 must be replaced by 5e.
- UTP Cat.5 (4 twisted pairs 100Mb/s (1000Mb/s possible if TSB-95 tested)
- UTP Cat.5e Class D 100Mb/s and 1000Mb/s
- UTP Cat.6e Class E 1000Mb/s (10Gb/s possible but not recommended)
- STP Cat.6e Class E 1000Mb/s (10Gb/s possible but not recommended) - shielded pairs + cable shield
- STP Cat.6a Class EA 10Gb/s (SFTP)
- STP Cat.7 Class F 10Gb/s
- STP Cat.7a Class Fa 40Gb/s
Mechanical errors to avoid: stretching the wire, twisting it, bending it too much
Shielding type
UTP (U/UTP) Twisted pair no shielding
FTP (F/UTP) Twisted pairs, overall shielding by aluminum foil
STP (U/FTP) Twisted pairs, each pair shielded by aluminum foil
SFTP (SF/UTP) Twisted pairs, double shielded with foil and braid
FFTP (F/FTP) General foil and foil shielding per pair
SSTP (S/FTP or SF/UTP) General foil and braid per pair (better)
SFTP provides better electromagnetic isolation than UTP.
For shielded cables, connect the shield on one side only to avoid a ground loop.
Do not use shielded cable if the cable comes from outside, as this acts as an antenna and causes interference.
The cord has 4 pairs. The middle pair is not used as it is historically reserved for the telephone.
Looking at the connector from the front, tab down, the first pair from the left (8-7) is either :
- brown/white-brown, followed by orange/white-orange wires in positions 3 and 6, blue/white-blue in the middle in 4-5, green/white-green in 1-2
- brown/white-brown, followed by green/white-green in position 3 and 6, blue/white-blue in position 4-5, orange/white-orange in 1-2)
The important thing is that in both connectors the wires are in the same order.
If the wires are not in the same order on both sides the cable is crossed.
Should you have a Data Link issue (the switch led does not light up) check the cable. It can be either functional, damaged, or crossed.
PoE is a technology that allows both data and electrical power to be delivered over Ethernet cables. Want to discover more about PoE, click here.
Structured cabling.
We understand by vertical cabling all the links connecting the telecom rooms between them, as well as the buildings and the external networks.
Horizontal cabling is defined as all links between the telecom rooms and each individual connector in the offices.
Normally Class E Cat 6 (distribution panel, cable and plug). If one of these elements is of lower category the whole chain decreases in performance.
Attention, if the standard says 100m. It is 100m for the patch cable (max 6m) the horizontal cabling (max 90m) and the user cable (max 3m). Officially the length of a patch cord is 5m. The patch cable and the connection cable must never exceed 10 meters. Avoid the proximity of disturbing elements (motor, radio, wi-fi-gsm), distance 3m. Cross the power cables at 90° and separate them by at least 5 cm. Single strand (more rigid) is used for backbone cabling and multi-strand for patch cords and links.
It is considered that each splitter (local) covers a diameter of about 60 meters. For an estimate, on each cable we count 10m more for the rise under the ceiling and the descent under the false floor in the info room and the rise in the wiring closet.
Here are some training videos that might interest you
Introduction to Ethernet
Network Types
Network Cables
Cable Management
Copper Connectors
Copper Cabling
568A and 568B Colors
Optical Fiber
Fiber Connectors
Straight-Through and Crossover Cables