IBM SNA Formats Bit Ordering is Opposite of Intel Convention

Last reviewed: April 17, 1997
Article ID: Q130861

The information in this article applies to:

Microsoft SNA Server for Windows NT, versions 2.0, 2.1, 2.11 and 3.0

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
Version : 2.0 2.1 2.11 3.0
Platform : WINDOWS

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Last reviewed: April 17, 1997
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