This counts instances where the BAsize field in a SIP3 header fell entirely outside the range of valid SMDS-defined buffer sizes, a stricter check than lportSmdsCntSip3BasizeIncorrects which flags a mismatch against the actual payload rather than an out-of-range value on its own. An admin distinguishes the two: BasizeInvalids means the size field itself is nonsensical per the SMDS spec, which usually points to gross frame corruption or a fundamentally broken sender, rather than a minor calculation bug. For example, a BAsize value outside the handful of standard SMDS buffer-size options would register here, suggesting either severe corruption in transit or a completely non-conformant sending device.