Data Link Speeds

sometimes you can't go 30 over because traffic

When troubleshooting a link, learn to differentiate between the expected performance and actual performance.

speed vs. throughput

at the physical layer, a signal transmitted over a link consists of a stream of events called symbols. a symbol can be anything, from a pulse of higher voltage over an electrical current or the transition in an electromagnetic wave between the peak and the trough.

the number of symbols that can be transmitted in a second is called the baud rate, usually measured in hertz (MHz or GHz).

at the datalink layer, the bandwidth of the link is the amount of information that can be transmitted, usually measured in bits per second (bps). signal encoding allows for the transmission of multiple bits per symbol, resulting in a higher bitrate than the baud rate. for Ethernet, the expected performance ranges from 10 Mbps to 1Gbps and more.

throughput is the average rate of transfer for real-world conditions. it factors in losses at the physical and datalink layers. latency is the delay between receiving packets, and it measures the speed of the network. it's measured as a unit of time (usually milliseconds).

can't go too far now

each type of media can consistently support a given bitrate over a defined distance. after that, attenuation and interference are too much and the signal is unusable.