1
Scope
1.1 General
1.2 Requirements for error-correcting
procedures
1.3 A DCE employing data compression
2 References
3 Definitions
4 Abbreviations
5 Functional description of a DCE
5.1 General
5.2 DTE/DCE interchange circuits
5.3 Signal converter
5.4 Control function
5.5 Error-control function
5.6 Data compression function
6 Procedures of the data compression
function
6.1 Overview of the data compression
function
6.2 Dictionary structure
6.2.1 Encoder dictionary
6.2.2 Decoder dictionary
6.3 Encoding
6.3.1 String-matching procedure
6.3.2 String-extension procedure
6.3.3 Creating string-segments
6.3.4 Encoding summary
6.4 Decoding
6.4.1 Processing codes
6.4.2 Creating new strings
6.5 Transparent mode
6.5.1 Transition from compressed mode to transparent mode
6.5.2 Transition from transparent mode to compressed mode
6.6 Transfer
6.6.1 Transfer of control codes, ordinals, and codewords
6.6.2 Transfer of string-extension length
6.6.3 Code prefixes
6.6.4 Example of Transfer
7 Operations of data compression
7.1 Communication between the control
and data compression functions
7.2 Communications between peer data
compression functions
7.3 Negotiation of V.44 capability
7.4 Negotiation of data compression
parameters
7.4.1 Negotiation through XID
7.4.2 Negotiation after link establishment
7.5 Initialization of the data
compression function
7.5.1 Initial state of the encoder dictionary
7.5.2 Initial state of the decoder dictionary
7.6 Establishment of error-controlled
connection
7.7 Transfer of data between the
DTE/DCE interface and the data compression function
7.8 Encoding
7.9 Transfer of data between the data
compression function and the error-control function
7.10 Decoding
7.11 Autonomous adjustments
7.11.1 Ordinal size and STEPUP
7.11.2 Codeword size and STEPUP
7.11.3 Node-tree full
7.11.4 History full
7.11.5 Data compressibility monitoring
7.12 Dictionary reinitialization
7.13 Expedited data transfer and FLUSH
7.14 ESCAPE command sequence
7.15 Action on detection of C-ERROR
8 Parameters
Annex A - XID
information field for negotiating V.44 capability when used with V.42
Annex B - Operation
of V.44 in Packet Networks
B.1 Packet method operation of V.44
B.1.1 General description
B.1.2 Default values of data compression parameters for packet method
B.2 Multi-packet method of operation
of V.44
B.2.1 General description
B.2.2 Default values of data compression parameters for multi-packet method
Appendix I - Notes on Implementation
I.1 Selection of N2: the total number of codewords
I.2 Selection of N7: maximum string length
I.3 Selection of N8: data structures and length of
history
I.4 Efficient compression of Unicode
data
I.5 Applicability of transparent mode
I.6 Calculation of compression
performance
I.7 Differences between V.44 and V.42 bis
Appendix II -
Illustration of operation of V.44 algorithm
II.1 Compression and decompression of
"ABCDEXABCDEYABCDE FFH AC"
II.2 Compression & decompression of
"CCCCCCCCCCX"