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Microsoft KB Archive/103026

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Knowledge Base


RAS Frame Format Diagram

Article ID: 103026

Article Last Modified on 11/1/2006



APPLIES TO

  • Microsoft Windows NT Advanced Server 3.1
  • Microsoft Windows NT Workstation 3.1
  • Microsoft Windows NT Advanced Server 3.1



This article was previously published under Q103026

Below is a diagram indicating the format of Remote Access Service (RAS) frames:

                  +---+---+---+---+------  --------+---+---+---+
        



   RAS 1.0 frame  |SYN|SOH| LENGTH| <--> Data <--> |03h|  CRC  |
   asybeui frame  +---+---+---+---+------  --------+---+---+---+
        



                       ^
                       |--SOH_BCAST or SOH_DEST
        



                  +---+---+---+---+---+------  --------+---+---+---+
        
   RAS 2.0 frame  |SYN|SOH| LENGTH|COH| <--> Data <--> |ETX|  CRC  |
   asybeui frame  +---+---+---+---+---+------  --------+---+---+---+
   with compress       ^
        



                       |--(SOH_BCAST|SOH_COMPRESS)
                          or (SOH_DEST|SOH_COMPRESS)
        



                  +---+---+---+---+---+------  --------+---+---+---+
        



   RAS 2.0 frame  |SYN|SOH| LENGTH|COH| <--> Data <--> |ETX|  CRC  |
   asybeui frame  +---+---+---+---+---+------  --------+---+---+---+
   with compress   ^   ^
   with XON/XOFF   |   |--(SOH_BCAST|SOH_COMPRESS)
        
                   |      or (SOH_DEST|SOH_COMPRESS)
                   |
                   +-------(SYN | SYN_XONXOFF)
        





                  +---+---+---+---+---+---+-----  -------+---+--+--+
        



   RAS 2.0 frame  |SYN|SOH| LENGTH| E-TYPE|<--> Data <-->|ETX| CRC |
   with TCP/IP    +---+---+---+---+---+---+-----  -------+---+--+--+
   no compress         ^
        



                       |--(SOH_BCAST|SOH_TYPE) or (SOH_DEST|SOH_TYPE)
        



                  +---+---+---+---+---+---+---+----  ------+---+--+--+
        



   RAS 2.0 frame  |SYN|SOH| LENGTH| E-TYPE|COH|<-> Data <->|ETX| CRC |
   with TCP/IP    +---+---+---+---+---+---+---+----  ------+---+--+--+
   and compress        ^
        



                       |--(SOH_BCAST|SOH_TYPE|SOH_COMPRESS)
                          or (SOH_DEST|SOH_TYPE|SOH_COMPRESS)
        



   NOTE: Compression is performed after COH and before ETX. This does
   mean that E-TYPE is not compressed. Also, when CRC is performed,
   SOH through ETX (inclusive) is checked. ETX is included because RAS
   1.0 also checked ETX.
        



   SYN          = 0x16
   SOH_BCAST    = 0x01
   SOH_DEST     = 0x02
   SOH_TYPE     = 0x80
   SOH_COMPRESS = 0x40
   SYN_XONXOF   = 0x20
   CRC          = 16 bit CRC polynomial (Big-Endian format)
   LENGTH       = length of Data part of frame (two-byte Big-Endian)
        

Keywords: kbnetwork KB103026