QoS Design Notes for CCDE
Trying to get my CCDE studies going again. I’ve finished the End to End QoS Design book (relevant parts) and here are my notes on QoS design.
Basic QoS
Different applications require different treatment, the most important parameters are:
- Delay: The time it takes from the sending endpoint to reach the receiving endpoint
- Jitter: The variation in end to end delay between sequential packets
- Packet loss: The number of packets sent compared to the number of received as a percentage
Characteristics of voice traffic:
- Smooth
- Benign
- Drop sensitive
- Delay sensitive
- UDP priority
One-way requirements for voice:
- Latency ≤ 150 ms
- Jitter ≤ 30 ms
- Loss ≤ 1%
- Bandwidth (30-128Kbps)
Characteristics for video traffic:
- Bursty
- Greedy
- Drop sensitive
- Delay sensitive
- UDP priority
One-way requirements for video:
- Latency ≤ 200-400 ms
- Jitter ≤ 30-50 ms
- Loss ≤ 0.1-1%
- Bandwidth (384Kbps-20+ Mbps)
Characteristics for data traffic:
- Smooth/bursty
- Benign/greedy
- Drop insensitive
- Delay insensitive
- TCP retransmits
Quality of Service (QoS) – Managed unfairness, measured numerically in latency, jitter and packetloss
Quality of Experience (QoE) – End user perception of network performance, subjective and can’t be measured
Tools
Classification and marking tools: Session, or flows, are analyzed to determine what class the packets belong to Continue reading