Which of the following are Data Link Layer standards? 1. Ethernet 2. HSSI 3.…

Concept

The OSI reference model classifies a networking standard by the function it performs, not by its name. A Data Link layer (Layer 2) standard defines framing, media access control, and station addressing over a link, while a Physical layer (Layer 1) standard defines only the electrical, mechanical, or cabling specification used to carry raw bits and defines no framing or addressing.

Application

• Ethernet (IEEE 802.3) defines the MAC frame format and station addressing used on a LAN, so it is a Data Link layer standard.

• HSSI (High-Speed Serial Interface) defines only the electrical and connector specification between a router and a CSU/DSU on a high-speed serial line, so it is a Physical layer specification, not Data Link.

• Frame Relay (ITU-T Q.922 / ANSI T1.618) defines framing and virtual-circuit addressing between the two ends of a link, so it is a Data Link layer standard.

• 10-Base-T denotes the twisted-pair cabling and signalling variant defined within IEEE 802.3, so it is a Physical layer specification, not Data Link.

• Token Ring (IEEE 802.5) defines the token-passing access method and frame format on a ring LAN, so it is a Data Link layer standard.

Of the five, only Ethernet, Frame Relay, and Token Ring (items 1, 3, 5) define Data Link layer functions.

Cross-check

IEEE naming gives an independent check: a “BASE” suffix (10BASE-T, 100BASE-TX) always names a Physical-layer transmission variant, and interface standards named after their connector or electrical specification (HSSI, RS-232, V.35) are always Physical layer by definition. This confirms HSSI and 10-Base-T sit at Layer 1, leaving Ethernet, Frame Relay, and Token Ring (items 1, 3, 5) as the Data Link layer standards.