Advanced Data Communication Control Procedures
In telecommunication, Advanced Data Communication Control Procedures (or Protocol) (ADCCP) is a bit-oriented data link layer protocol developed by the American National Standards Institute. It is functionally equivalent to the ISO High-Level Data Link Control (HDLC) protocol.[1]
Although the ISO and ANSI standards writers coordinated their work, so the differences between the standards are mainly editorial, there is one meaningful difference: ADCCP's definition of the basic subset required to implement balanced asynchronous mode includes the RSET frame, while HDLC makes it optional.[2]
One major difference between the two is the unnumbered (U) format. When extended (7-bit) sequence numbers are used, I and S frames have two-byte control fields. Like early versions of HDLC,[3] ADCCP specifies a 2-byte control field format with the P/F flag duplicated.[4] Later HDLC specifications, in particular ISO/IEC 13239, changed that to specify that U frames have 1-byte control fields in all cases.
| First byte | Second byte | Description | ||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | |
| 0 | N(S) | P/F | N(R) | I frame, N(S) is a 3-bit send sequence number | ||||||||||||
| 1 | 0 | type | P/F | N(R) | S frame, N(R) is a 3-bit receive sequence number | |||||||||||
| 1 | 1 | type | P/F | type | U frame | |||||||||||
| 0 | N(S) | P/F | N(R) | Extended I frame, N(S) is a 7-bit sequence number | ||||||||||||
| 1 | 0 | type | —0— | P/F | N(R) | Extended S frame, N(R) is a 7-bit sequence number | ||||||||||
| 1 | 1 | type | P/F | type | P/F | —0— | Extended U frame (ADCCP only) | |||||||||
References
- Friend et al. 1988, p. 191
- NBS 1980, p. 6, §3.0 ADCCP classes of procedures
- ISO 1984, p. 18, §7.4 Extended control fied formats
- ANSI 1979, p. 28, §5.2.2 Extended control field
- Friend, George E.; Fike, John L.; Baker, H. Charles; Bellamy, John C. (1988). Understanding Data Communications (2nd ed.). Indianapolis: Howard W. Sams & Company. ISBN 0-672-27270-9.CS1 maint: ref=harv (link)
- Guideline for implementing advanced data communication control procedures (ADCCP). National Bureau of Standards. 26 September 1980. FIPS PUB 78.
- ISO 4335:1984 Data Communication—High Level Data Link Control Procedures—Consolidation of Elements of Procedures (PDF). Archived from the original on 12 September 2013.
- ANSI X3.66-1979: American National Standard for advanced data communication procedures (ADCCP). American National Standards Institute. 9 January 1979. FIPS PUB 71-1980.
