What is double tagging (QinQ)? Introducing the application of network technology

Explanation of IT Terms

What is Double Tagging (QinQ)? Introducing the Application of Network Technology

In the realm of network technology, Double Tagging, also known as QinQ (pronounced “Q-in-Q”), refers to a method of encapsulating Ethernet frames within other Ethernet frames. It is primarily employed in service provider networks to allow for the transmission of multiple virtual LAN (VLAN) customer networks over a single physical network infrastructure.

Understanding Double Tagging (QinQ)

In traditional VLAN networks, a single VLAN tag is used to distinguish and segregate different networks. VLAN tagging allows network administrators to partition a physical network into smaller, logical networks. However, this approach has its limitations, especially in scenarios where service providers need to carry multiple VLANs from multiple customers over their network infrastructure.

This is where Double Tagging or QinQ comes into play. With QinQ, an additional layer of VLAN tags is added to the original VLAN tag, creating a nested structure. This allows for the identification and separation of multiple customer VLANs within the service provider’s infrastructure, enabling the simultaneous transmission of multiple customer networks over a single physical network interface.

The additional VLAN tags serve as a means of encapsulating the customer’s VLAN tags. Each layer of the VLAN tags consists of a VLAN ID and a priority value. The priority value is used to prioritize different customer traffic within the network.

Application of Double Tagging (QinQ)

Double Tagging finds its primary application in service provider networks, where multiple customers need to transport their VLANs over a shared network infrastructure. By using Double Tagging, service providers can effectively carry and deliver traffic from different customer networks while preserving the VLAN information at each hop in the network.

The benefits of Double Tagging (QinQ) in service provider networks include:

1. Enhanced Scalability: By allowing the transmission of multiple VLANs over a single physical interface, service providers can efficiently utilize their network infrastructure and accommodate a larger number of customers.

2. Improved Security and Isolation: Double Tagging enables the separation of customer VLANs, ensuring that traffic from one customer cannot access another customer’s network. This helps maintain the security and privacy of each customer’s data.

3. VLAN Translation: Double Tagging facilitates VLAN translation, allowing service providers to map VLANs from different customers to a shared VLAN when necessary. This translation mechanism enables seamless communication between different customer networks.

In conclusion, Double Tagging (QinQ) is a network technology that addresses the limitations of traditional VLAN tagging by enabling the transmission of multiple customer VLANs over a shared network infrastructure. Its application in service provider networks provides enhanced scalability, improved security and isolation, and VLAN translation capabilities. Double Tagging plays a vital role in enabling service providers to efficiently and securely deliver their services to multiple customers over a single network.

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