Which of the following protocols was developed in the mid197

Which of the following protocols was developed in the mid-1970s for use in Systems Network Architecture (SNA) environments?

A. SDLC

B. ISDN

C. LAP-B

D. X.25

Solution

A. The Synchronous Data Link Control (SDLC) protocol was developed in the mid-1970s for use in Systems Network Architecture (SNA) environments. SDLC is unique in that it was the first synchronous, link layer, bit-oriented protocol. The ISO modified SDLC to create the High-Level Data Link Control (HDLC) protocol and release it as a standard. Answer B is incorrect because ISDN is an end-to-end telephone service that is digital in nature. Answer C is incorrect because Link Access Procedure–Balanced (LAP-B) is a subset of HDLC and is not used by SNA. Answer D is incorrect because X.25 is an efficient protocol developed in the 1970s for packet-switched networks.