Valid RU sizes

The actual transmission RU size for SNA NJE buffer can be further limited (rounded down) by the SNA architecture which only allows RU sizes that can be described by the formula

M * 2**E

where M (mantissa) and E (exponent) are integers between 1 and 15.

For NJE connections, the actual transmission data buffer size used is equal to the smaller buffer size of the two adjacent nodes. This is negotiated independently for each NJE session through the functional management header (FMH-4) records. Some NJE systems require that a valid RU size be used in the negotiation. Therefore, you should pick an acceptable RU sizes within the range 512–32512 (in increments of 128).