Terminology

Term	Definition
Layer 2 Switching	Networks that operate at the Data Link layer (Layer 2) of the OSI model. Packets are sent to a specific switch port based on the destination MAC address.
Layer 3 Routing	Networks that operate at the Network layer (Layer 3) of the OSI model. Packets are sent to a specific next-hop IP address based on the destination IP address.
Leaf Switch	A switch that connects servers to the network. In a multitier fabric, it also connects to spine switches to enable communication with servers on other leaf switches.
Spine Switch	A switch that connects multiple leaf switches together in a multitier fabric.
Fabric Tier	Refers to the leaf, spine, or trunk (not defined in this specification) switches within a multitier fabric.
Fabric Rail or Ply	In the context of Gaudi 3, refers to a separate switch network for each of the three NICs on a Gaudi card. Each of the 8 Gaudi cards in a server connects to all three separate rails (plies).
Megapod (MP)	A group of 64 Gaudi cards connected to the same leaf switch in a two-tier accelerator fabric topology.