Hello!
Today, I'd like to share with you a brief introduction to QoS.
Quality of service (QoS) refers to the expected quality of service (QoS) in terms of the packet loss rate, delay, jitter, and bandwidth.
IP QoS objectives:
1. Avoid and manage IP network congestion.
2. Reduce the IP packet loss rate.
3. Control IP network traffic.
4. Provide dedicated bandwidth for specific users or services.
5. Support real-time services on IP networks.
Bandwidth limit
BWmax = min(10M, 256k, 512k, 100M)=256 kbps
BWavail = BWmax /Flows
Maximum available bandwidth = Minimum link bandwidth
Multiple streams are transported over the same network, with the result that each application is assigned a smaller bandwidth.
E2E delay
Delay = P1 + Q1 + P2 + Q2 + P3 + Q3 + P4 = X ms
The total end-to-end delay is equal to the sum of the transmission delay, device processing time, and queue delay.
The transmission delay is fixed, and the processing and queue delay is unpredictable.
Ping...
Latency
Processing delay: Impacts of the CPU speed, CPU usage, IP switching mode, routing architecture, and configuration features on the input and output interfaces
Queuing delay: Interface bandwidth, queue depth, packet size, and queue mechanism
Propagation delay: Link bandwidth
Packet loss
The tail drop occurs when the egress queue is full. This is the most common drop mode when the link is congested.
There are many other discarding modes, such as input queue drop, ignore, overrun, and no buffer. These discarding modes are generally used in the case of router congestion.
Input queue drop: The CPU usage is too high to process these packets.
Router: The router uses up the buffer.
Overrun: The CPU is too busy to allocate buffers to new packets.
Frame errors (CRC, runt, giant): hardware detection errors
How to reduce latency
1. Increase the link bandwidth.
2. Preferentially forward important packets.
3. Compression of the payload of a Layer 2 frame
4. Compressing IP packet headers
How to Reduce Packet Loss
1. Increase the link bandwidth.
2. Provide sufficient bandwidth for sensitive services.
3. Discard packets randomly to prevent congestion.
QoS requirements of various services
Different effects of different services
This is my first time to share knowledge with you. There are many inadequacies. I will make changes later,
I hope it's helpful.
Thank you!
