A Non-Broadcast Multiple Access Network (NBMA network) allows only data transfer from one computer to another over a virtual circuit or across a switching device. The NBMA network is the opposite of a broadcast network, on which multiple computer devices are connected through a shared cable. All frames are broadcasted on the network but only the device to which the frames are addressed can receive the frames.

The typical NBMA networks are Frame Relay, ATM and X.25 networks. In an NBMA network, intersubnet routing involves forwarding packets hop-by-hop through intermediate routers. The Next Hop Resolution Protocol (NHRP) is used to determine the NBMA subnetwork addresses of the NBMA next hop to an IP address. Multiprotocol over ATM (MPOA) enables the fast routing of internetwork-layer packets across a nonbroadcast multi-access (NBMA) network. MPOA replaces multi-hop routing with point-to-point routing using a direct virtual channel connection (VCC) between ingress and egress edge devices or hosts. An ingress edge device or host is defined as the point at which an inbound flow enters the MPOA system; an egress edge device or host is defined as the point at which an outbound flow exits the MPOA system.

Nonbroadcast Multiple Access (NBMA) Network:

NBMA: Non-Broadcast Multiple Access Network

Related Terms: ATM, Frame Relay, X.25, NHRP, MPOA