In Ethernet terminology, I hit the word Lane, this speed is 4 Lanes or 2 lanes ?
I searched google, but I didn't get any useful results ? Can any one explain what's a lane, its width and its relation to speeds ?
Some Ethernet flavors use multiple lanes within a link. E.g. 10BASE-T and 100BASE-TX use one dedicated lane (one twisted pair) in each direction while 1000BASE-T and 2.5/5/10/25/40GBASE-T use four lanes bidirectionally.
Each lane transports its fraction of the total data rate - for 1000BASE-T, each lane/pair effectively transports 250 Mbit/s. Due to PHY encoding, this doesn't match the physical signal rate (e.g. 125 MBd for 1000BASE-T).
For copper cables, each lane is represented by a twisted pair. With fiber cables, a lane can be a separate fiber pair, a wavelength (WDM), or a combination of both.
Usually, the number of lanes is fixed for a given PHY but some PHYs can be split very commonly, e.g. 40GBASE-R into 4x 10GBASE-R.