Thursday, May 23, 2013

You visit a website and it is slow today (it is not slow everyday). What could be the cause(s) of the slowness?


of 4vote
At a high level there are 3 things one or more of which may be slow:
01. Your computer, 02. internet connection, 03. the server
01. Your computer it can be slow because of some anti virus scan, some process using high processor/network, HDD may be full, your computer may be virus infected, and thousands other possible reasons.
02. Internet: Your proxy setting may be using a slow proxy, your ISP may be slow, the server may have failed over to a different Geo so it is taking long time to route the calls, etc.
03. Slow server: Server might be under DOS attack, All the instances may not be up, because of festival season/deal/new offering much more than usual # of people are using the site, servers running out of space, Networking issue in data center, slow or dead partner servers, etc. to name a few.
First I'd ask for more clarification: Is the specific website is slow or all the websites that you're visiting that day is slow?
If yes, then it could be the computer, the browser, and/or any other nodes between you and your ISP (e.g., the routers, DNS server, your network equipment, etc.). In this case it's hard to tell if there is a server latency. You can still use traceroute command to see the latency between the routers/gateways between your computer and the web server.

If no, then there is a a server latency and/or network latency between your ISP and the server. Then you can discuss the possible reasons for server latency and/or network latency.

It's also a good idea to discuss the networks tools, such as ping, traceroute/tracert, etc., that you can use to pinpoint the specific issue.