On the Backbone VLAN Identifier (BVID) Allocation in 802.1Qay Provider Backbone Bridged — Traffic Engineered Networks

Abstract

Carrier Ethernet is rapidly being deployed in the metropolitan and core segments of the transport network. One of the emerging flavors of Carrier Ethernet is the IEEE 802.1Qay PBB-TE or Provider Backbone Bridging—Traffic Engineering standard. PBB-TE relies on the assignment of a network-specific Virtual Local Area Network (VLAN) tag, called the Backbone VLAN ID or BVID that is used in conjunction with a backbone Media Access Control (MAC) address for forwarding. The 12-bit BVID along with 48-bit Backbone MAC address are used to forward an Ethernet frame. The assignment of BVIDs in a network is critical, given that there are only 4094 possible assignments, especially for those paths that are overlapping in the network graph and incident at the same destination. While the only way to scale is to reuse BVIDs, this method can lead to a complication if the same BVID is allocated to an overlapping path. To the best of our knowledge, this is the first instance of isolating this problem of limited BVID availability which rises only due to graphical overlap between services. We formulate and solve this as a constrained optimization problem. We present optimal and heuristic algorithms to solve the BVID problem. The optimal approach solves the `static' case, while the heuristic can solve both the `static' and the `dynamic' cases of the BVID allocation problem. Results show that the developed heuristics perform close to the optimal and can be used in commercial settings for both the static and dynamic cases.