3 ms·
Disclaimer: I've been designing and troubleshooting networks at ISPs for about 12 years. Below are my observations of the problem given what I know to be true
by smutticus 16y ago
Disclaimer:
I've been designing and troubleshooting networks at ISPs for about 12 years. Below are my observations of the problem given what I know to be true from experience. I do not fully understand the problem as described but I will do my best to drop some knowledge.
I would be very surprised if any ISP is still using routers and switches that buffer anything in software. Even modern store and forward switches only use a very small hardware buffer for packets. All major vendors use layer-3 hardware switching on their carrier platforms. The ASICs and TCAM are designed to run at a high enough clock rate so that buffering in SW isn't necessary.
That said, wireless routers almost always use software buffers. And so do most home CPE devices like DSL routers or something like DLink, Netgear or Linksys.
This article is strictly talking about buffering at the end-point. Or host buffering.
There are a few quick and dirty solutions that involve TCP windowing.
http://en.wikipedia.org/wiki/TCP_tuning http://en.wikipedia.org/wiki/TCP_tuning
But bear in mind most protocols that need very low latency are UDP so this might not help.
It's really really really hard to do any kind of latency testing without a hardware based packet sender and analyzer. Without it you never really know if the problem is your OS or the network device you're testing.
If the problem really is because your CPE device has too bigbuffers than build your own. Get a *NIX box and make the network buffer really small in the kernel. If you no longer have bad latency than you found the problem. If you still have bad latency then look for something else to replace.
- wmf 16y agoI don't see how it matters whether the buffering is implemented in software or hardware; it's still there and it's too big. If the problem really is because your CPE device has too bigbuffers than build your own. I think Gettys wants to solve the problem for everyone, not just ubergeeks.
- adestefan 16y agoWhat he's saying is that you can make custom hardware that's fast enough so you don't need any buffering.
- smutticus 16y agoThat's right. But this hasn't trickled down to the consumer market yet. Maybe there is a market for a pro-sumer home router or cable modem? It would cost more than your typical Best Buy Netgear or whatever. But it would implement L3 forwarding in hardware and have advanced congestion control and QOS. My guess is the market research has been done and consumer router manufacturers have determined that not enough consumers are willing to pay for things they don't understand.
- wmf 16y agoNo. In any router with different-speed interfaces, buffering is necessary on the slow interface. On any router with more than two ports, buffering is needed to absorb possible congestion.