Computer Network LAN Technologies

Network LAN Technologies (Fully Explained)

In the diagram, various VLANs are illustrated using different color codes. Hosts within the same VLAN, even when connected to the same switch, cannot see or communicate with hosts in different VLANs. VLAN is a Layer-2 technology that operates closely with Ethernet. To route packets between two different VLANs, a Layer-3 device, such as a Router, is necessary.

Let's take a brief look at different LAN technologies:

Ethernet

Ethernet is a commonly used LAN technology. This technology was created by Bob Metcalfe and D.R. Boggs in 1970 and was standardized in IEEE 802.3 in 1980.

Ethernet operates on shared media. Networks that utilize shared media have a high chance of data collisions. To manage these collisions, Ethernet employs Carrier Sense Multi Access/Collision Detection (CSMA/CD) technology. When a collision occurs, all hosts in the Ethernet network back off, wait for a random period, and then attempt to retransmit the data.

The Ethernet connector is a network interface card that comes with a 48-bit MAC address. This feature allows other Ethernet devices to recognize and communicate with remote devices within the Ethernet network.

Traditional Ethernet adheres to the 10BASE-T specifications. The number 10 indicates a speed of 10MBPS, BASE refers to baseband, and T signifies Thick Ethernet. 10BASE-T Ethernet can achieve transmission speeds of up to 10MBPS and utilizes coaxial cable or Cat-5 twisted pair cable with an RJ-45 connector. Ethernet operates on a star topology with a segment length of up to 100 meters, where all devices connect to a hub or switch in a star configuration.

Fast-Ethernet

To meet the demands of rapidly advancing software and hardware technologies, Ethernet has evolved into Fast-Ethernet. This version can operate on UTP, optical fiber, and even wirelessly. It offers speeds of up to 100 MBPS. This standard is referred to as 100BASE-T in IEEE 803.2 and uses Cat-5 twisted pair cable. For wired media sharing among Ethernet hosts, it employs the CSMA/CD technique, while for wireless Ethernet LAN, it uses the CSMA/CA (Collision Avoidance) technique.

Fast Ethernet on fiber is specified under the 100BASE-FX standard, which provides speeds of up to 100 MBPS on fiber. Ethernet over fiber can extend up to 100 meters in half-duplex mode and can reach a maximum of 2000 meters in full-duplex mode over multimode fibers.

Giga-Ethernet

Since its introduction in 1995, Fast-Ethernet held its high-speed title for just three years until Giga-Ethernet came onto the scene. Giga-Ethernet offers speeds of up to 1000 mbits per second. The IEEE802.3ab standard governs Giga-Ethernet over UTP using Cat-5, Cat-5e, and Cat-6 cables. Meanwhile, IEEE802.3ah specifies Giga-Ethernet over Fiber.

Virtual LAN

LAN operates on Ethernet, which relies on shared media. This shared media in Ethernet creates a single Broadcast domain and a single Collision domain. The introduction of switches into Ethernet has resolved the issue of a single collision domain, allowing each device connected to a switch to function within its own collision domain. However, switches still cannot separate a network into distinct Broadcast domains.

Virtual LAN serves as a solution to partition a single Broadcast domain into multiple ones. A host in one VLAN cannot communicate with a host in another VLAN. By default, all hosts are assigned to the same VLAN.