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VLAN: Definition, Uses and Importance

VLAN stands for Virtual Local Area Networks (VLANs). Virtual network within a global network allowing certain machines to be isolated from one another in the global network.

A VLAN, for Virtual Local Area Network, describes a type of local network. The VLAN logically and independently groups together a set of computer machines. We can find several of them coexisting simultaneously on the same network switch.

As for the advantages, the VLAN improves the management of the network by providing more flexibility in its administration. It brings more security by requiring, for example, the passage through a router for communication between two machines.

Finally, it optimizes bandwidth, separates flows and reduces traffic diffusion.

There are three different types of VLANs: Tier 1 (also known as per-port VLAN), Tier 2 (per-MAC address VLAN), and Tier 3 (per-IP address VLAN).

VLANs allow the administrator to partition their networks to meet system operational and security requirements without installing additional cables or making major changes to current network infrastructure.

The IEEE 802.1Q standard defines VLANs. The VLAN tag or identifier counts 12 bits in the Ethernet frame, thus inducing a limit of 4,096 VLANs on a single LAN.

Benefits of VLANs

  • VLANs offer several advantages. But most fundamental is the ability for network managers to move devices from one VLAN to another without having to rewire the network.
  • Another benefit: VLANs help enterprises overcome bottlenecks by reducing traffic at Layer 2. VLANs also enhance security by limiting which devices can access a given VLAN.
  • VLANs can also be used to isolate groups of users. For example, one can create a VLAN to provide guest access on a WiFi network, isolating contractors and other third parties in a resource-constrained subnet. Or, a network manager can create a VLAN for a particular department, such as HR or finance.
  • A VLAN improves network management by increasing security.
  • A VLAN improves network management by enhancing security levels.

History of VLANs

Virtual LANs (VLANs) have been around for decades. They were invented by W. David Sincoskie in the 1980s while working for Bellcore.

After Bell System was broken up in 1982 under antitrust laws, Bell Communications Research (now iconectiv) was established to create a new company from the assets of New Jersey-based Bell Labs.

Better known as Bellcore, this “Baby Bell” recruited most of its early collaborators from former Bell Labs employees. In 1984 W. David Sincoskie, a former computer engineer from Bell Labs, joined Bellcore to work on IP telephony.

It was at Bellcore that he implemented the first Ethernet LAN and it was while looking for a solution to eliminate bottlenecks and increase capacity that Mr. Sincoskie developed the first VLANs.

The problem that the computer engineer had to solve with Ethernet was that this broadcast medium transmitted the signal from the host to all the devices on the network, which then had to process the frames received, whether they were relevant or not for the device.

This modality creates a significant overhead on the CPU of each device, while clogging the network with unnecessary traffic. Also, at the time, there was no proven way to connect multiple Ethernet networks.

IP routing was a possible solution, but the downside was that IP routing was slow and expensive. So Sincoskie looked for a fast, cheap alternative with low CPU overhead, which led him to transparent bridging.

Unfortunately, this approach created new problems, including turning core switches into bottlenecks that limited scalability. W. David Sincoskie invented VLANs to solve the bottleneck problem.

His concepts were eventually included in Ethernet standards, such as the IEEE 802.1Q standard in 1998, which describes the concept of Ethernet VLANs.

Later additions to the standard (IEEE 802.1ad IEEE 802.1ah) added other mechanisms, such as nested VLAN tags, to facilitate bridging and improve scalability.

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Mehmet is one of the administrator of Teknonel. As a software developer, he loves to share his knowledge in related topics. He is highly familiar with the editorial process from the inception of an article idea, through the iterative process, publishing, and performance analysis as well as product reviews.

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