Microsoft KB Archive/103026

= RAS Frame Format Diagram =

Article ID: 103026

Article Last Modified on 11/1/2006

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APPLIES TO


 * Microsoft Windows NT Advanced Server 3.1
 * Microsoft Windows NT Workstation 3.1
 * Microsoft Windows NT Advanced Server 3.1

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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       ^

<pre class="fixed_text">                      |--(SOH_BCAST|SOH_TYPE|SOH_COMPRESS) or (SOH_DEST|SOH_TYPE|SOH_COMPRESS)

<pre class="fixed_text">  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.

<pre class="fixed_text">  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

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