Darrin Johnson's Weblog: Need for speed...

Alas it is time to step out of the shadows as a blog lurker and draft my inaugural blog entry. The topic is simply "What is real networking performance?".

What does the word "performance" mean to you? Some may use words like endurance, speed, reliability, etc. as synonyms. In the networking world, most would see performance as how fast we can push data over the wire, often using descriptors such as 10 megabit, 100 Mb, 1 Gigabit, or even 10 Gigabit. Others may use less precise language such as dial-up, DSL, cable modem, satalite, T1, T3, etc. Networking performance however is not just a simple matter of how fast data can be pushed over a particular networking media.

Networking performance is a combination of three factors -- throughput, latency and utilization. Throughput is the classical speed of the network with 10 Gigabit being faster than 1 Gb, 100 Mb, and 56 Kb). Clearly this is in import part of the performance equation. Latency however is also critical part of the equation because the overhead can have a significant impact on the networking performance. One need only use the "ping" command to see the packet latency between two machines over different types of distances, network media, through various types of networking gear, with packet loss, jitter, etc. Just think of talking to somebody face to face versus talking to that same person deep in the Amazon forest over a bad phone connection.

Utilization is also an imporant measure of performance although it may be a bit controversial. Utilization in this case is simply the resource costs required to achieve the performance. We can use CPU utilization as a simple measure on the impact of performance. Not so long ago it would take a 100% of a CPU to saturate (e.g. run at full throughput)a 1 Gigabit connection but today we have measured CPU utilization as low as 8% to saturate the same connection. The utilization (and there performance) improvement is the result of a better network stack, faster CPUs, improved NIC technology, etc. Keeping throughput and latency constant the utilization improvement yields a positive performance increase.

Remember: Performance = Throughput + Latency + Utilization

Don't want to be too long winded so I will save deeper discussions on each of these for later blogs.

- Darrin