Our Main Tool (PingER) is Ping Based
“Universally available”, easy to understand
- no software for clients to install
Provides useful real world measures of response time, loss, reachability, unpredictability
Now monitoring from 14 sites in 8 countries monitoring > 500 links in 22 countries (> 300 sites)
Resources: 6bps/link, ~600kBytes/month/link
Notes:
The scarcest and most valuable commodity is time. Studies in late 70’s and early 80s by Walt Doherty of IBM and others showed the economic value of Rapid Response Time:
0-0.4s High productivity interactive response
0.4-2s Fully interactive regime
2-12s Sporadically interactive regime
12s-600s Break in contact regime
There is a threshold around 4-5s where complaints increase rapidly. For some newer Internet applications there are other thresholds, for example for voice a threshold appears at about 100ms - above that point, the delay causes difficulty for people trying to have a conversation and frustration grows.
Note that the TCP/IP timeout caused by a packet loss is of the order of 4-5 seconds.
For some newer Internet applications there are other thresholds, for example for voice a threshold appears at about 100ms - above that point, the delay causes difficulty for people trying to have a conversation and frustration grows
Avoid routers, they drop pings to the router if busy. Prefer lightly loaded or consistently loaded hosts, e.g. name server, mail gateway. Some sites block ping (ping o’ death attacks), others (singaren.net.sg) only allow 64 byte pings.