IBM SNA Formats Bit Ordering is Opposite of Intel Convention

Article translations Article translations
Article ID: 130861 - View products that this article applies to.
This article was previously published under Q130861
This article has been archived. It is offered "as is" and will no longer be updated.
Expand all | Collapse all


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).


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
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.


Article ID: 130861 - Last Review: February 23, 2014 - Revision: 4.1
  • Microsoft Host Integration Server 2000 Standard Edition
  • Microsoft SNA Server 2.0
  • Microsoft SNA Server 2.1
  • Microsoft SNA Server 3.0
  • Microsoft SNA Server 3.0 Service Pack 4
  • Microsoft SNA Server 4.0
kbnosurvey kbarchive kbinterop kbnetwork KB130861

Contact us for more help

Contact us for more help
Connect with Answer Desk for expert help.
Get more support from