Advanced Data Communication Control Procedures
Computer networking protocol
In telecommunications, 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.
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.
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, ADCCP specifies a 2-byte control field format with the P/F flag duplicated. 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) | |||||||||
Sources and credits
This article is adapted from the Wikipedia article “Advanced Data Communication Control Procedures”, written by its contributors and licensed under CC BY-SA 4.0. Fathomly has changed the layout, removed citation markers, navigation and maintenance notices, and adjusted punctuation. This adapted version is shared under the same license. For references, see the original article.
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