Re:An OSI model for the 21st century (2014)
by Hikikomori on Monday August 21, 2017 @03:18AM
(#15062563)
Switching = forwarding by looking at l2 headers
Routing = forwarding by looking at l3 headers
It does not matter one bit if above is done in software or an ASIC/FPGA/NPU, what the device looks at to perform it's forwarding decision is what matters, so one device may not just fit neatly into one OSI layer.
Layer 3 switch is mainly a marketing term, it's nonsense really. The devices that fits into that category are what would classically be switches (many ethernet ports, small buffers, cheap) but with full routing capabilities.
Routers can be either software or hardware based. Software routers mainly make up the low-end offers from vendors, rich in features and cheap. Hardware routers that use ASIC/NPU's make up low-ish end to the very high end. Any router that ISP's use in their backbone will be the very high end and do all forwarding in hardware, have all QoS features in hardware, etc.
Routing = forwarding by looking at l3 headers
It does not matter one bit if above is done in software or an ASIC/FPGA/NPU, what the device looks at to perform it's forwarding decision is what matters, so one device may not just fit neatly into one OSI layer.
Layer 3 switch is mainly a marketing term, it's nonsense really. The devices that fits into that category are what would classically be switches (many ethernet ports, small buffers, cheap) but with full routing capabilities. Routers can be either software or hardware based. Software routers mainly make up the low-end offers from vendors, rich in features and cheap. Hardware routers that use ASIC/NPU's make up low-ish end to the very high end. Any router that ISP's use in their backbone will be the very high end and do all forwarding in hardware, have all QoS features in hardware, etc.