This question was cobbled together from several common e-mails this week.
Hey, Inetdaemon, Doesn’t bandwidth solve all network problems with [Skype, Facetime, Vonage, NetFlix, Hulu, YouTube, World of Warcraft (WoW)...], and push my frame rates through the roof in [choose any FPS/MMORPG]?
Answer: Not so!
Engineers use a measurement called “latency” to measure delay between endpoints in communications systems, including the Internet. High latency is bad, low latency is good. High latency indicates a problem between endpoints. This could be you and a friend across Skype, Facetime, Vonage or anything else. Problems with ‘delay’ are the real causes of ‘slowness’ and communications problems. More bandwidth will only solve are issues of congestion and over-subscription and only if you can add more bandwidth along the entire path from end-to-end. It can’t do anything about the actual delay from the communications system and the infrastructure supporting it or from the server. Moreover, if the “internet pipe” at the far end serving the person or site you’re trying to reach is full, or the equipment that pipe is connected to are busy, there’s no benefit to upgrading your service to higher bandwidth. Given the nature of the Internet, everyone else would also have to upgrade thier Internet connection to make your services faster.
Sources of Latency
Latency is the measure of end-to-end delay. Delay is caused by the distance and by the air, fibers and wires, by the network components and network devices, and by the computers and terminals at each end. Sources of latency include:
- Physcial distance
- Propagation delay of the physical media
- Media Converters (Conversion and Transcoding)
- Network device packet & frame forwarding delay
- Application delay: Encryption and Compression
- Server CPU time & interrupts
- Network Device CPU time & interrupts
- and more…
You cannot ‘drive down’ latency with more bandwidth, but you CAN reduce it with:
- Reducing the physical distance (reduce cable-length, eliminate back-hauls to common switchpoints)
- Installing faster equipment
- Eliminating encryption and compression
Why “More Speed” (Bandwidth) Doesn’t Help
The time it takes a that first single bit (a zero or one) to move from one end of the communications path to the other. The total end-to-end delay is called ‘latency’. Bandwidth will shorten the time between when the first bit and the very last bit of your YouTube video arrive, but the time it takes any given bit within the video stream to travel over the entire end-to-end path is unaffected by more-bits-per-second speed or “bandwidth”.
Things that can reduce the delay and thus the latency:
- Reducing the total distance between the endpoints
- Switching from a relatively slow electrical transmission to a faster fiber transmission
- Eliminating equipment between the endpoints
- Upgrading network equipment between the endpoints
- Upgrading the endpoints themselves
Latency and Video Display Frame Rates
Network Latency has zero impact on local Frame Rates on your computer. It does have an impact on how quickly the server can inform your computer that something that triggers a screen update… Continue reading