Network-to-Network Interface

One item of concern for a service provider is the possibility that a Frame Relay network might cross between two networks that might not be Cisco equipment. Because each vendor supports Frame Relay standards, they are also given the option of providing customizations that differentiate their product form another vendor's product.

To facilitate intervendor communication, the Network-to-Network Interface (NNI) port was defined as a bidirectional protocol to allow configuration, administration, and control information to be communicated between two networks. NNI consists of two independent unidirectional signaling protocols, one from each network, to provide bidirectional communication.

NNI supports status exchanges between the two networks, much like the exchanges between a DTE/DCE pair. The biggest difference between NNI communications and DTE/DCE pair communications is that both sides can initiate a query message exchange, and both sides can respond with either a short or long status message.

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