Peter Ashwood-Smith

Provider link state bridging

Wide area communications technology has been challenged to virtualize large numbers of Ethernet LAN segments. This is a consequence of a mismatch between the broadcast nature of the LAN segment and the extremely constrained connectivity implied by the p2p connections or tunnels available in the WAN environment, which have been combined to create virtual LAN segments. PBB-TE has been a practical demonstration of how filtering applied to a broadcast media can result in a connection. This article introduces provider link state bridging (PLSB), which adds a control plane to the PBB data plane in order to extend the techniques for manipulation of Ethernet bridges for unicast paths pioneered by PBB-TE. PLSB solves the problem of largescale virtualization of LAN segments over an Ethernet infrastructure by applying advances in computation performance to the multicast capabilities inherent in the Ethernet data plane. The result is that the fundamental primitives of connectivity today, the broadcast LAN segment and the connection, can be virtualized in a scalable manner on a common (but substantially larger and better utilized) Ethernet-based infrastructure.

Multiple abstraction schemes for generalized virtual private switched networks

An IP-VPN overlay over traditional L1/L2 transport networks has serious problems with scaling, not only with respect to routing but also the time it takes to provision these services. GVPN is a service that uses GMPLS as the common control plane to address these issues with features like client initiated signaling and auto-discovery. It allows routing over the access links, eliminating the O(n¿2) client routing adjacency issue. In todays deployment, routing enables exchange of reachability information, which is not very useful for dynamic edge nodes requiring services on demand. Also a major obstacle to exploiting routing to its full potential is the providers reluctance to expose the internals of the core network. In this piece, we try to explore the idea of enabling traffic-engineering capability to the edge routers using the concept of topology abstraction, which involves no preset resources. The study shows the different forms of abstractions that are possible with their pros and cons. We end our discussion prototyping two different abstraction schemes discussed in this article using a real lab setup. Our discussion for the most part is generic and could be applied to any L1 or L2 switched transport networks.