1. Rate
Rate is data rate (data rate) or data transmission rate or bit rate
The amount of information (bits) transmitted per unit time (seconds)
The most important performance indicator in computer networks
Unit: bps, kbps, Mbps
k = 10^3、M = 10^6、G = 10^9
Rate often refers to rated rate or nominal rate, ideal data transfer rate
2. Bandwidth
- "Bandwidth" originally refers to the frequency bandwidth of a signal, that is, the difference between the highest frequency and the lowest frequency, in Hz
- The bandwidth of a network refers to the highest data rate that a digital channel can transmit, in bps
- Commonly used bandwidth units: kb/s, Mb/s, Gb/s, Tb/s
3. Delay/delay
Why does packet loss and delay occur in packet switching?
Packets are queued in the router buffer when the packet arrival rate exceeds the capacity of the output link
Packets are queued, waiting for the output link to be available
Four types of packet delays:
(1) Node processing delay (d_proc): error detection; determining output link; usually less than ms
(2) Queuing delay (d_queue): waiting for the output link to be available; depends on the router congestion level
(3) Transmission delay (d_trans): packet length (bits), link bandwidth (bps), d_trans = L/R
(4) Propagation delay (d_prop): physical link length, signal propagation speed
4. Delay bandwidth product
Delay-bandwidth product = propagation delay * bandwidth = d_prop * R
Delay-bandwidth product of a link: link length in bits
5. Packet loss (packet loss) - packet loss rate
- Queue cache capacity is limited
- Packets arriving in a queue that is full will be discarded
- Dropped packets may be retransmitted by the preceding node or source.
6. Throughput
Indicates the data rate transmitted between the sender and receiver
Instant throughput, average throughput
On the end-to-end path, the link that limits the end-to-end throughput