What is Ethernet

Ethernet refers to the baseband LAN specification created by Xerox and jointly developed by Xerox, Intel and DEC. It is the most common communication protocol standard used in today's existing LANs. Ethernet uses CSMA/CD (Carrier Supervisory Multiple Access and Conflict Detection) technology and operates at a rate of 10M/S over many types of cables. Ethernet is similar to the IEEE802-3 family of standards. I. Standard Ethernet

Beginning Ethernet had only 10Mbps throughput and used the CSMA/CD (Carrier Listening Multiple Access with Collision Detection) access control method, and this early 10Mbps Ethernet is called Standard Ethernet. There are two main transmission media for Ethernet, and those are twisted pair and fiber optics. All Ethernet networks follow the IEEE 802.3 standard. Below is a list of some of the IEEE 802.3 Ethernet standards, in which the first number indicates the transmission speed in "Mbps", the last number indicates the length of a single segment of cable (the base unit is 100m), and "Base" means "baseband". The last number indicates the length of a single cable (the base unit is 100 meters), Base means "baseband", and Broad stands for "bandwidth".

-10Base-5 uses thick coaxial cable with a maximum segment length of 500m, the baseband transmission method;

-10Base-2 uses thin coaxial cable with a maximum segment length of 185m, the baseband transmission method;

-10Base T using twisted-pair cable with a maximum segment length of 100m;

- 1Base-5 using twisted-pair cable with a maximum segment length of 500m and a transmission speed of 1Mbps;

-10Broad-36 using coaxial cable ( RG-59/U CATV), the maximum span of the network is 3600m, the maximum network segment length of 1800m, is a broadband transmission mode;

-10Base-F using fiber-optic transmission media, the transmission rate of 10Mbps;

Second, Fast Ethernet

< p>With the development of the network, the traditional standard Ethernet technology has been difficult to meet the growing network data traffic speed requirements. Prior to October 1993, for LAN applications requiring more than 10Mbps of data traffic, only the Fiber Distributed Data Interface (FDDI) was available, but it was a very expensive, 100Mpbs fiber-optic cable-based LAN.In October 1993, Grand Junction introduced the world's first Fast Ethernet hubs In October 1993, Grand Junction launched the world's first Fast Ethernet hub, Fastch10/100, and the network interface card FastNIC100, making Fast Ethernet technology officially available. Subsequently, Intel, SynOptics, 3COM, BayNetworks and other companies have launched their own Fast Ethernet devices. At the same time, the IEEE802 engineering group also conducted research on various standards for 100Mbps Ethernet, such as 100BASE-TX, 100BASE-T4, MII, repeater, full-duplex, etc. In March 1995, the IEEE announced the IEEE802.3u 100BASE-T Fast Ethernet standard (Fast Ethernet), and thus began the era of Fast Ethernet.

Fast Ethernet and the original work in the 100Mbps bandwidth FDDI compared to it has many advantages, mainly reflected in the Fast Ethernet technology can effectively protect the user in the implementation of cabling infrastructure investment, which supports 3, 4, 5 twisted-pair cable as well as fiber optic connections, can effectively use the existing facilities. The shortcomings of Fast Ethernet is also the shortcomings of Ethernet technology, that is, Fast Ethernet is still based on CSMA / CD technology, when the network load is heavier, it will cause a reduction in efficiency, of course, this can be compensated for the use of switching technology. The 100Mbps Fast Ethernet standard is subdivided into three subcategories: 100BASE-TX, 100BASE-FX, and 100BASE-T4.

- 100BASE-TX: is a Fast Ethernet technology that uses Category 5 data-grade unshielded twisted pair or shielded twisted pair. It uses two pairs of twisted pairs, one pair for transmitting and one pair for receiving data. It uses 4B/5B encoding for transmission at a signal frequency of 125 MHz and complies with the EIA586 Category 5 cabling standard and the IBM SPT Category 1 cabling standard. It uses the same RJ-45 connector as 10BASE-T. Its maximum segment length is 100 meters. It supports full-duplex data transmission.

- 100BASE-FX: It is a Fast Ethernet technology that uses fiber optic cables and is available in single-mode and multimode fibers (62.5 and 125um) The maximum distance for multimode fiber connection is 550 meters. The maximum distance for a single-mode fiber connection is 3,000 meters. The 4B/5B coding method is used in transmission with a signal frequency of 125 MHz. it uses MIC/FDDI connectors, ST connectors or SC connectors. Its maximum segment length is 150m, 412m, 2000m or longer up to 10km, depending on the type of fiber used and the mode of operation, and it supports full-duplex data transmission. 100BASE-FX is particularly suitable for use in environments where there are electrical interferences, for connections over larger distances, or for high-security environments.

- 100BASE-T4: is a Fast Ethernet technology that can be used with Category 3, 4, or 5 unshielded twisted pair or shielded twisted pair. 100Base-T4 uses four pairs of twisted pairs, three of which are used to transmit data at 33MHz, with each pair operating in half-duplex mode. The fourth pair is used for CSMA/CD conflict detection. The 8B/6T coding method is used in transmission with a signaling frequency of 25 MHz, in compliance with the EIA586 structured cabling standard. It uses the same RJ-45 connector as 10BASE-T and has a maximum segment length of 100 meters.

Third, Gigabit Ethernet

Gigabit Ethernet technology, as the latest high-speed Ethernet technology, brings users to improve the core network of effective solutions, the biggest advantage of this solution is the inheritance of the traditional advantages of cheap Ethernet technology. Gigabit technology is still Ethernet technology, which uses the same frame format, frame structure, network protocols, full/half-duplex mode of operation, flow control mode, and cabling system as 10M Ethernet. Since this technology does not change the traditional Ethernet desktop applications, operating systems, it works well with 10M or 100M Ethernet. Upgrading to Gigabit Ethernet maximizes investment protection by eliminating the need to change network applications, network management components, and network operating systems. Gigabit Ethernet supports shorter distances in order to detect collisions with 64Bytes frames. The types of networks supported by Gigabit Ethernet are listed in the following table:

Transmission Media Distance

1000Base-CX Copper STP 25m <

1000Base-T Copper Cat 5 UTP 100m

1000Base-SX Multi-mode Fiber 500m

1000Base-LX Single -mode Fiber 3000m

There are two standards for Gigabit Ethernet technology: IEEE802.3z and IEEE802.3ab. IEEE802.3z establishes standards for fiber and short-haul copper connectivity solutions. IEEE802.3ab establishes standards for longer-haul connectivity solutions over Category 5 twisted-pair cable.

1. IEEE802.3z

The IEEE802.3z working group is responsible for developing standards for full-duplex links over optical fiber (singlemode or multimode) and coaxial cable.IEEE802.3z defines 1000Base-X based on fiber optics and short-range copper cables using 8B/10B coding technology, with a channel transmission speed of 1.25Gbit/ s, after decoupling to achieve 1000Mbit/s transmission speed. IEEE802.3z has the following Gigabit Ethernet standards:

- 1000Base-SX only supports multi-mode fiber, can use multi-mode fiber with a diameter of 62.5um or 50um, the working wavelength is 770-860nm, and the transmission distance is 220-550m.

- 1000Base-LX multi-mode fiber: can use multi-mode fiber with a diameter of 62.5um or 50um. Multimode fiber with diameter of 62.5um or 50um, working wavelength range of 1270-1355nm, transmission distance of 550m.

Single-mode fiber: It can support single-mode fiber with diameter of 9um or 10um, working wavelength range of 1270-1355nm, transmission distance of about 5km.

- 1000Base-CX uses 150-ohm shielded twisted pair (STP), and the transmission distance is 25m.

2. IEEE802.3ab

The IEEE802.3ab working group is responsible for developing the Gigabit Ethernet standard for half-duplex links based on UTP, which produces the IEEE802.3ab standard and protocol. IEEE802.3ab defines the 1000Base-T standard based on Category 5 UTP, which aims to transmit 100m at 1000Mbit/s rate over Category 5 UTP. The significance of the IEEE802.3ab standard is twofold:

(1) Protecting the user's investment in a Category 5 UTP cabling system.

(2) 1000Base-T is a natural extension of 100Base-T and is fully compatible with 10Base-T and 100Base-T. However, to reach 1000Mbit/s transmission rate on Category 5 UTP need to solve the problem of crosstalk and attenuation of Category 5 UTP, thus making the development task of the IEEE802.3ab working group a bit more complex than the IEEE802.3z

Fourth, 10 Gigabit Ethernet

10 Gigabit Ethernet specification is included in the complementary standards of the IEEE 802.3 standard IEEE 802.3ae, which extends the IEEE 802.3 protocol and MAC specifications to support 10Gb/s transmission rates. In addition, 10 Gigabit Ethernet can also be scaled to lower transmission rates, such as 9.584640 Gb/s (OC-192), via the WAN interface sublayer (WIS: WAN interface sublayer), which allows 10 Gigabit Ethernet devices to be compatible with the Synchronous Optical Networking (SONET) STS-192c transport format.

- The 10GBASE-SR and 10GBASE-SW primarily support shortwave (850 nm) multimode fiber (MMF) over fiber distances from 2m to 300 m. The 10GBASE-SR and 10GBASE-SW support shortwave (850 nm) multimode fiber (MMF) over fiber distances from 2m to 300m.

10GBASE-SR primarily supports "dark fiber", which is fiber that has no light propagation and is not connected to any device.

10GBASE-SW is primarily used to connect SONET devices, which are used for remote data communications.

- 10GBASE-LR and 10GBASE-LW mainly support longwave (1310nm) single-mode fiber (SMF) with a fiber distance of 2m to 10km (about 32808 feet).

10GBASE-LW is primarily used when connecting to SONET devices,

10GBASE-LR is used to support "dark fiber".

- 10GBASE-ER and 10GBASE-EW primarily support ultra-longwave (1550nm) single-mode fiber (SMF) over distances ranging from 2m to 40km (~131,233 feet).

10GBASE-EW is primarily used to connect SONET devices,

10GBASE-ER is used to support "dark fiber".

- The 10GBASE-LX4 uses wavelength-division multiplexing (WDM) technology to send signals at four times the optical wavelength over a single pair of cables. The system operates at 1310nm in either multimode or singlemode dark fiber. The system is designed for multimode fiber mode from 2m to 300m or singlemode fiber mode from 2m to 10km.

△ Ethernet connection [edit paragraph] Topology Bus type: less cable required, cheap, high management cost, not easy to isolate the point of failure, using **** enjoy the access mechanism, easy to cause network congestion. Early Ethernet mostly used bus-type topology, the use of coaxial cable as a transmission medium, the connection is simple, usually in a small-scale network does not require special network equipment, but because of its inherent defects, has been gradually replaced by hubs and switches as the core of the star-type network.

Star: Easy to manage, easy to expand, requires specialized network equipment as the core node of the network, requires more network cables, and requires high reliability of the core equipment. The use of dedicated network equipment (such as hubs or switches) as the core node, through the twisted-pair cable to connect each host in the LAN to the core node, which forms a star structure. Although a star network requires more cables than a bus type, the cabling and connectors are cheaper than those of a bus type. In addition, a star topology can easily expand the network to a large size by cascading, and is therefore widely used and adopted by the vast majority of Ethernet networks. [edit]Transmission media Ethernet can use a variety of connection media, including coaxial cable, twisted pair and optical fiber. Among them, twisted pair is mostly used for connections from hosts to hubs or switches, while optical fiber is mainly used for cascading between switches and point-to-point links between switches and routers. Coaxial cable has been gradually phased out as the primary connection medium in the early days.

Note the distinction between straight-through and crossover wiring in twisted-pair cables.

Straight-through cables should be used for the following connections:

Switch to router Ethernet port

Computer to switch

Computer to hub

Crossover cables are used for direct connections to the following devices on the LAN:

Switch to switch

Switch to hub

Hub to hub

Router to router's Ethernet port connection

Computer to computer

Computer to router's Ethernet port