Connection information passed on the CINIT control vector 64

During session establishment, a VTAM® session initiation record called a CINIT is created and sent to the primary application. Attached to the CINIT is a control vector 64 (CV64) that is created by Telnet to provide additional information about the Telnet connection. The CV64 control vector contains four sub-vectors. The CV64 control vector and the four sub-vectors are all defined as key/length vectors.

• CV64 - Start of control vector
  • Key/Length (2 bytes)

    X'64mm', where mm is (ii + 2) + 4 + (hh +2 (if SBV85 present)) + 19 (if SBV86 present)

• SBV81 - Flags and IP address
  • Key/Length (2 bytes)

    X'81ii', where ii is 06 for IPv4, 18 for IPv6

  • IP address type (1 byte)
    • 04 - IPv4
    • 06 - IPv6
  • Flags (1 byte)
    • 80 - Reserved for future use
    • 40 - Reserved for future use
    • 20 - On if secure connection
    • 10 - On if secure connection flag is valid
    • 08 - On if takeover of the connection is possible
    • 04 - On if the TCP/IP stack supports IPv6 addresses and the client has an IPv4 address
    • 02 - On if the Telnet server is the z/OS® Communications Server TN3270E Telnet server
    • 01 - On if the client is a TN3270E client and supports definite response
  • IP address (4 bytes if IPv4, 16 bytes if IPv6)
• SBV82 - Port number
  • Key/Length (2 bytes)

    X'8202'

  • Port (2 bytes)
• SBV85 - Host name of the client (SBV85 is not always present)
  • Key/Length (2 bytes)

    X'85hh', where hh is 1 + DNS name length

  • Flags (1 byte)
    • 80 - On if DNS name is truncated to 128 bytes
  • DNS name (Maximum 128 bytes)
• SBV86 - Zone ID if specified for a client IPv6 address (SBV86 is not always present)
  • Key/Length (2 bytes)

    X'8611'

  • Flags (1 byte)
    • 80 - On if zone is truncated
  • Zone ID (16 bytes)