ITU-T V.150.1

For the error controlled and asymmetric non-error controlled configurations, Raw octet compressed
may not be used; the only choice from the mandatory set is octet without format. For symmetric
non-error corrected configurations, both octet without formatting and Raw octet compressed may
be chosen. If the configuration is symmetric non-error controlled octet without format is treated as
an optional data type in the data type selection procedures.
14.5.1 Octet without formatting
This data type may be used for Error Controlled Data or character data mode. When used in
character data mode, it shall not include start-stop bits. This data type may include DLCI. The use
of the DLCI is indicated by a code-point in the IP-TLP CONNECT message.
14.5.2 Raw Octet Compressed
This data type has application with synchronous data streams. This Raw data type shall preserve all
bits received from the DCE interface. The amount of data exchanged may be reduced by use of
simple compression. Repeated octet patterns are coded and removed by the transmitter from the
data stream. The receiver decodes the stream and restores it to original form.
14.6 Optional Modem Relay Data Types
Gateways shall indicate the capability and support of their receivers for the optional data types
defined in this Recommendation. Gateway packet transmitters shall not use an optional data type if
the peer Gateway receiver does not support it and there is no obligation of the transmitter of an
optional data types to use a capability indicated by a receiver.
14.6.1 Character with formatting Data Type
This data type allows for the transport of Start-Stop characters of different formats. The characters
are transmitted unpacked (i.e. one character per octet, one octet per character. This data type shall
use the same format rules as defined in Annex B/V.42. The mandatory Start-Stop character
capabilities a Gateway shall support are Data plus Parity shall equals eight bits and one stop-bit.
There are two forms of this data type; both are indicated as separate options. The first allows for the
changing of character format during a MR session and the second does not. Each type has a unique
message ID.
14.6.2 Raw bit compressed Data Type
This data type is used in the same application as the Raw octet compressed type. This format codes
and decodes N-bit repeated patterns. N may have the value of 8.
14.6.3 Framed Data Type
This optional data type is for use by a pair of consenting Gateways if a Gateway is able to
determine that the data format is Framed data consistent with ISO/IEC 3309 and 4335. If this data
type is selected by the Gateways, it may transmit the data with the framing elements removed.
These elements if removed shall be replaced by the receiver such that the data remains consistent
with ISO/IEC 3309 and 4335. The means and method by which a Gateway determines the data type
is beyond the scope of this Recommendation.
This data type shall not be used when either or both Gateways have negotiated V.42 or Annex A/
V.42 (1996).
ITU-T Rec. V.150.1 (01/2003) – Prepublished version 24