Home > Articles > Networking > Routing & Switching

  • Print
  • + Share This
From the author of

Ethernet Allows for Layer 2 VPNs (VPLS)

VPNs can operate at layer 2 or layer 3 (IP). There are advantages and disadvantages to both technology types. An attempt was made in IEEE 802.1Q to provide an Ethernet VPN mechanism in the form of a 12-bit field in the MAC header. This is in addition to the 3-bit IEEE 802.1p priority field. The problem was that 12 bits only give scope for 212 or 4,096 distinct VPNs (or VLANs). This is simply not enough to make this a scalable carrier-grade service—imagine a service provider that wants to support tens of thousands of VPNs. The problem is that the VPN ID must be unique throughout the service provider network and the allowed range of 4,096 is insufficient. A new approach was needed to solve this problem, and has taken the form of virtual private LAN service (VPLS). The merit of VPLS is that it leverages the MPLS cores that so many service providers are deploying.

  • + Share This
  • 🔖 Save To Your Account