B TAG (Backbone VLAN Tag)

Introduction

The Backbone VLAN Tag (B TAG) is a protocol used in computer networking to provide a scalable and flexible way to manage and prioritize traffic on a network. It is a tagging mechanism that is used to identify and classify different types of traffic on a network. In this article, we will explain what the B TAG is, how it works, and why it is important in modern computer networking.

What is a B TAG?

A B TAG is a tagging mechanism that is used to identify and classify different types of traffic on a network. It is a 32-bit tag that is inserted into the Ethernet frame header, which identifies the VLAN that the frame belongs to. The B TAG is a proprietary protocol that is used by some vendors, such as Brocade, to manage and prioritize traffic on a network.

How does the B TAG work?

The B TAG works by inserting a tag into the Ethernet frame header, which identifies the VLAN that the frame belongs to. The tag is a 32-bit value that is inserted between the source MAC address and the type/length field in the Ethernet frame header. The tag contains several fields that are used to identify and classify the traffic on the network.

The B TAG contains the following fields:

• Priority field: This field is used to prioritize traffic on the network. It is a 3-bit field that allows up to 8 different levels of priority to be defined.

• CFI field: This field is used to identify frames that are carrying control information. It is a 1-bit field that is set to 1 for control frames and 0 for data frames.

• VLAN ID field: This field is used to identify the VLAN that the frame belongs to. It is a 12-bit field that allows up to 4096 different VLANs to be defined.

The B TAG is inserted into the Ethernet frame header by the network switch when the frame enters the switch. When the frame leaves the switch, the B TAG is removed from the frame header. This process is known as tagging and untagging.

Why is the B TAG important?

The B TAG is important in modern computer networking for several reasons. First, it provides a way to manage and prioritize traffic on a network. By assigning different levels of priority to different types of traffic, network administrators can ensure that critical traffic, such as VoIP traffic, is given priority over less important traffic, such as file transfers.

Second, the B TAG provides a way to segment a network into multiple VLANs. VLANs are used to isolate traffic on a network, which improves security and performance. By using the B TAG to identify the VLAN that a frame belongs to, network administrators can ensure that frames are only forwarded to devices that are members of the same VLAN.

Third, the B TAG provides a scalable and flexible way to manage traffic on a network. By allowing up to 4096 different VLANs to be defined, the B TAG allows network administrators to segment their networks into as many VLANs as they need. This provides a way to manage large, complex networks that have many different types of traffic.

Conclusion

The B TAG is a tagging mechanism that is used to identify and classify different types of traffic on a network. It is a 32-bit tag that is inserted into the Ethernet frame header, which identifies the VLAN that the frame belongs to. The B TAG is important in modern computer networking because it provides a way to manage and prioritize traffic on a network, segment a network into multiple VLANs, and provide a scalable and flexible way to manage traffic on a network.