Determine the technology and media access control method for Ethernet networks

Exam: Cisco 200-120 - Interconnecting Cisco Networking Devices: Accelerated (CCNAX)

LAN uses Ethernet networking that allows all hosts on a network to use the same bandwidth. Ethernet infrastructure can be easily upgraded to a fast Ethernet infrastructure by using new technologies. It is easy to implement and troubleshoot Ethernet. It uses both Data Link and Physical layer specifications.

The traditional Ethernet was designed to use coaxial cable as a shared medium and token ring and token bus technologies.Now the Ethernet has started using CSMA/CD (Carrier Sense Multiple Access with Collision Detection) protocol to take care of the collisions on the network while sharing the bandwidth evenly among the network devices. The CSMA/CD was simpler than token ring and token bus technologies.

The host with CSMA/CD protocol implemented checks the cable for any existing signal. If there is no signal, it proceeds with transmission of data. During transmission, if the host detects another signal, it sends an extended jam signal, which causes all the nodes on the network to stop sending signals for some time and then try again after a short duration

Ethernet at the Physical Layer

With advanced networking and use of switches and routers many new improvements were made to Ethernet and many new standards came into existence. Ethernet physical layer has evolved from coaxial cables to twisted pair cables and from twisted pair cables to fiber optic cables. The speed of Ethernet now ranges from 10 Mbps to 1 Gbps with different cable types.

Among all the cable types the fiber optic cables are best till date. The fiber optic cables are not susceptible to electromagnetic interference (EMI) and provide high speed.

The high speed Ethernet is very costly and should be used only when required. In addition each cable type that is specified to be used on Ethernet by the EIA/TIA suffers from loss of signal strength as the signal travels through the cable. This loss of signal strength is called attenuation. The quality of cables is measured in categories such as category 3, 4, or 5. The high rated cables have low attenuation and high category.

Let us look into various Ethernet 802.3 standards defined by IEEE:

• 10Base2: The 10Base 2 standard is also called thinnet. The 10 in 10Base 2 standard stands for 10Mbps speed and Base stands for baseband technology, which is a signalling method for communication on the network. The 10Base 2 standard uses a physical and logical bus with AUI connectors and can be up to 185 meters in length supporting 30 workstations on a single segment. The 10Base 2 standard Ethernet cards use BNC (Bayonet Nut Connector) and T-connectors to connect to a network.
• 10Base5: The 10Base 2 standard is also called thicknet. The 10Base5 standard uses a physical and logical bus with AUI connectors and can be up to 500 meters in length. It can support up to 2,500 meters in length with repeaters and 1,024 users for all segments. Just as The 10Base 2 standard, 10Base 5 standard also uses Ethernet cards use BNC (Bayonet Nut Connector) and T-connectors to connect to a network.
• 10BaseT: The 10BaseT standard uses category 3 UTP wiring. This standard allows only one host per segment and requires each network device to connect to a hub or switch. The 10BaseT standard uses RJ45 connector and allows you to use a physical star topology and a logical bus.

Latest Ethernet Standards

The following standards are the expanded IEEE Ethernet 802.3 standards for Fast Ethernet:

• 100Base-TX: The 100Base-TX is IEEE 802.3u standard and is also known as Fast Ethernet. This standard allows only one user per segment. The segment can be up to 100 meters long. The 100Base-TX standard uses RJ45 connector and allows you to use a physical star topology and a logical bus. The 100Base-TX uses two-pair wirings of EIA/TIA 5, 5E, or 6 UTP categories.
• 100Base-FX: The 100Base-FX is IEEE 802.3u standard that uses fiber cabling of 62.5/125-micron multimode fiber. The segment made of this standard can be up to 412 meters long. The 100Base-FX uses media-interface connectors such as ST and SC connectors.
• 1000Base-CX: The 100Base- CX is IEEE 802.3z standard that uses twinax, a Copper twisted-pair cable, which is a balanced coaxial pair. The segment made of this standard can be up to 25 meters long. The 100Base-CX uses 9-pin HSSDC(High-Speed Serial Data Connector) connector.
• 1000Base-T: The 1000Base-T is IEEE 802.3ab standard that uses Category 5, four-pair UTP wiring. The segment made of this standard can be up to 100 meters long and can support up to 1Gbps speed.
• 1000Base-SX:The 1000Base-SX is IEEE 802.3z standard that uses multimode fiber-optic cable and short wavelength laser. The segment made of this standard can support up to 1Gbps speed and 220 meters of length by using 62.5- and 50-micron core. It can go up to 550 meters with 50-micron.
• 1000Base- LX:The 1000Base-LX is IEEE 802.3z standard that uses multimode fiber-optic cable and short wavelength laser. The segment made of this standard can support up to 1Gbps speed and from 3 kilometres of length to 10 kilometres of length by using a 9-micron core and 1300nm laser.
• 1000Base- ZX:The 1000Base-XX is Cisco standard for Gigabit Ethernet communication that uses single mode fiber-optic cable. The segment made of this standard can span up to 70 kilometres.
• 10GBase-T: 10GBase-T is IEEE 802.3ae standard that provides 10Gbps connections over conventional UTP cables (category 5e, 6, or 7 cables). This standard allows you to use RJ45 connector for Ethernet LANs. The segment made of this 10GBase-T standard can support up to signal transmission at the full 100-meter distance specified for LAN wiring.

The IEEE 802.3ae standard consists of following standards

• 10GBase-Short Range (SR): This is a 10 Gigabit Ethernet standards that uses multimode fiber-optic cable and short wavelength laser at 850nm. The segment made of this standard can support between 2 meters to 300 meters of distance depending on the size and quality of the fiber.
• 10GBase-Long Range (LR):This is a 10 Gigabit Ethernet standards that uses single mode fiber-optic cable and long wavelength laser at1,310nm.The segment made of this standard can support between 2 meters to 10 kilometres of distance depending on the size and quality of the fiber.
• 10GBase-Extended Range (ER):This is a 10 Gigabit Ethernet standards that uses single mode fiber-optic cable and extra long wavelength laser at1,550nm.The segment made of this standard can support the longest distance possible on 10-Gigabit technologies, which isbetween 2 meters to 40 kilometres of distance depending on the size and quality of the fiber.
• 10GBase-Short Wavelength (SW): 10GBase-SW is uses multimode fiber-optic cable with an 850nm laser transceiver with a bandwidth of 10Gbps. It is a mode of 10GBase-S, as defined by IEEE 802.3ae. The segment made of this standard can support upto 300 meters of cable length. This standard is designed to connect to SONET equipment.
• 10GBase-Long Wavelength (LW): 10GBase-LW is a mode of 10GBase-Lstandard that uses single mode fiber-optic cable(G.652).This standard is designed to connect to SONET equipment. The segment made of this standard can support upto 10 kilometres of distance.
• 10GBase- Extra Long Wavelength (EW): 10GBase-EW is a mode of 10GBase-Estandard that uses optical wavelength1,550nm based on G.652.This standard is designed to connect to SONET equipment. The segment made of this standard can support upto 10 kilometres of distance.

Exam question

The 1000Base-LX (long range) can go

• upto 3 kilometers of range
• upto 10 kilometers of range
• upto 7 kilometers of range
• From 3 kilometers up to 10 kilometers of range

Answer: D

The 1000Base-LX (long range) can go from 3 kilometers up to 10 kilometers.

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