| 单词 | SDLC (Synchronous Data Link Control) |
| 释义 | SDLC (Synchronous Data Link Control) A bit-oriented, synchronous data communications proto- col. SDLC supports high-speed transmission (56 kbps or better) over dedicated circuits in point-to-point or point-to-multipoint network configurations and operates in either half-duplex (HDX) or full duplex (FDX) mode. SDLC uses a cyclic redundancy check (CRC) error detection mechanism, specifically known as Frame Check Sequence (FCS) in this case. SDLC allows as many as 128 frames to be sent in a string, with each frame containing up to 7 blocks, each up to 512 characters. Each block within each frame is checked individually for errors. Errored blocks must be identified as such to the transmitting device within a given time limit, or they are assumed to have been received error-free.The SDLC frame consists of synchronizing bits, data bits, and control characters sent in a continuous data stream, frame-by-frame. The SDLC protocol was developed by IBM in the mid-1970s as a key element of its System Network Architecture (SNA). SDLC corresponds the Layer 2, the Data Link Layer of the OSI Reference Model. Figure S-1 illustrates the SDLC frame and its component fields.The same frame format applies to High-level Data Link Control (HDLC) frames and X.25 packets. A C D O F F D N FRAME L L R T |
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