This read-write integer sets the Maximum Burst Size, in cells, for a VBR connection set up under PNNI control, defining how large a burst above the sustained rate the connection may send, and defaults to 1024 on MGX release 3.0.0.0 and above. Admins tune this the same way as the per-channel ingrUpcCBS but specifically in the PNNI/VBR connection-setup context, balancing burst tolerance against buffer/queue impact. For example, a PNNI-routed VBR connection expected to send large occasional bursts would have its ausmConnMBS raised above the 1024 default to accommodate those bursts without early discard.