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Q103026: RAS Frame Format Diagram

Article: Q103026
Product(s): Microsoft Windows NT
Version(s): 3.1
Operating System(s): 
Keyword(s): kbnetwork
Last Modified: 08-AUG-2001

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The information in this article applies to:

- Microsoft Windows NT Server version 3.1 
- Microsoft Windows NT Workstation version 3.1 
- Microsoft Windows NT Advanced Server, version 3.1 
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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 
Technology        : kbWinNTsearch kbWinNTWsearch kbWinNTW310 kbWinNTSsearch kbWinNTS310 kbWinNTAdvSerSearch kbWinNTAdvServ310 kbWinNTS310search kbWinNT310Search kbWinNTW310Search
Version           : 3.1

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