IBM SNA Formats Bit Ordering is Opposite of Intel Convention

ID: Q130861

The information in this article applies to:

Microsoft SNA Server, versions 2.0, 2.1, 2.11, 3.0, 4.0

SUMMARY

In conventional Intel bit ordering, the most significant bit (MSB) is numbered 7 and the least significant bit (LSB) is numbered 0:


MSB                         LSB
 7   6   5   4   3   2   1   0

In Systems Network Architecture (SNA), IBM defined the LSB and MSB to be the opposite of the Intel convention. The MSB is numbered 0 and the LSB is numbered 7:


 MSB                         LSB
  0   1   2   3   4   5   6   7

You need to consider the difference in the Intel and IBM conventions when interpreting SNA Server traces using the IBM SNA Formats Guide (part number: GA27-3136-10).

MORE INFORMATION

The following is a sample message in an SNA Server SNA Formats trace:


---------------------------------------------- 13:51:52.71
                      >>SEND>> EXCHANGE ID

TH: 0d0000000600

---- Data ----
                    Byte 10
                      |
                      V
326605DF FFFF0000 B0041000 00000000     <2f..............>
00010B40 00100900 00000007 00103700     <...@..........7.>
27110C08 04F0F2F0 F0F0F00F 06D4E240     <'....020000..MS@>
E2D5C140 E2C5D9E5 C5D90908 F0F0F0F0     <SNA@SERVER..0000>
F0F0F013 11031000 10F0F0F0 F0F0F0F0     <000......0000000>
F0F0F0F0 F0F00E0E F4C1D7D5 C5E34BC3     <000000..4APNETKC>
D7D6C9D5 E3C3                           <POINTC          >

Byte 10 (=0x10) above in binary is: 0001 0000. It is read from left to right.

Additional query words: prodsna

Keywords : kbinterop kbnetwork ntgeneral snadlc snasdlc snawinnt sna211 sna3 sna4 sna2 sna21
Version : WINDOWS:2.0,2.1,2.11,3.0,4.0
Platform : WINDOWS
Issue type :