The following are some useful rules of thumb:
- Forwarding rate calculations for Ethernet
- Packets per second (pps) = link speed in bps / ((size+20)*8)
- Preamble + IFG is 20 bytes.
- Gbps x 1.5 = Mpps @ 64 bytes (actual value is 1.488).
- 1.5 Mpps @ 1 Gbps
- 15 Mpps @ 10 Gbps
- Latency
- 5 usec per km (one way).
- 10 usec per km (RTT).
- Speed of light in medium = 2x10^8 m/sec, i.e. 0.67 x c.
- 67.2 nsec @ 10G for 64 bytes (including preamble + IFG).
- Data in flight
- ~1300 bytes / 100 m @ 10 Gbps (RTT).
- Recommended default sampling rate for sflow
- 1 in (link speed in Gbps x 1000).
- 10G, 1 in 10,000
- 100G, 1 in 100,000
- 400G, 1 in 400,000
- Can use higher sampling rate if utilization is low.
- Backoff in sampling is not recommended. Instead keep track of discards and report them.
