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Virtual Concatenation (VCAT)
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VCAT is an inverse multiplexing technique that supports the bundling of multiple independent lower-rate channels (STS-1/VC-3, VT1.5/VC-11) into a higher rate channel. Unlike traditional SDH/SONET's contiguous concatenation method, VCAT allows an arbitrary number of either low-order or high-order SDH/SONET channels to be combined logically into one, known as a Virtual Concatenation Group (VCG).
VCAT will support a much more flexible Ethernet services model than is available today over traditional transport networks. With VCAT in place, a network operator can provide their business customer with a Gigabit Ethernet interface to the network and allocate as much bandwidth as the customer requires to that interface, in 51 Mbps increments. The customer may begin by requesting only 200 Mbps. Later, the customer may find they need to increase that allocation or add additional services to that interface. The operator has the flexibility to either increase the size of the VCG associated with that interface, or create additional, unique VCGs (Virtual Concatenation Groups), such as one for dedicated Internet access, one for a corporate Ethernet VPN and yet another for packetized voice transport. This ability to support multiple service flows from a single interface will be a key to unlocking new revenue opportunities for carriers.
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