4 ms·
That quote has always bugged me. It's dimensionally wrong: a station wagon doesn't have bandwidth. Bandwidth (in the sense intended here) is measured in bits/
by waqf 16y ago
That quote has always bugged me. It's dimensionally wrong: a station wagon doesn't have bandwidth.
Bandwidth (in the sense intended here) is measured in bits/second: how do you measure that from a station wagon [full of mag tapes]?
Now a freeway full of station wagons ... that has bandwidth.
- RodgerTheGreat 16y agoIf it takes an hour to copy a terabyte of data to a tape, put it in a car, drive to a location and read the tape, you just transported 8796093022208 bits in 3600 seconds, or about 2443359173 bits/second. edit: I always understood the quote as "the [potential] bandwidth"- the bandwidth that can be available using the station wagon as physical infrastructure.
- waqf 16y agoFirstly, that number is a function of how far apart your particular origin and destination are, so it's not intrinsic to the station wagon. And secondly, you just measured latency there, not bandwidth.
- redthrowaway 16y agoUnless I'm wrong, they've measured both: Latency is 1 hour (time it takes a packet to go from source to destination), bandwidth is that number they quoted.
- regularfry 16y agoLatency is greater than 1 hour, if it takes an hour to copy the data to the tapes. You've got to get them to the destination and copy them off after that.
- redthrowaway 16y ago>If it takes an hour to copy a terabyte of data to a tape, put it in a car, drive to a location and read the tape That's 1 hr latency, unless I'm mistaken. Latency doesn't include disk operations on the client side, does it? Is latency time between a signal being sent and received, or between sent, received, and acknowledgement sent/received? ie, is latency time(client->SYN->server->SYNACK->client->ACK->server), or time(client->SYN->server)?
- regularfry 16y agoBah. My reading comprehension not so good.
- waqf 16y agoLatency is 1 hour, but to get bandwidth you need to divide not by 1 hour but by the time between successive station wagon departures. For example if you only have one station wagon and driving back after copying the tapes takes a further 30 minutes, then the denominator is 5400 seconds and so the system bandwidth is 50% less than the number quoted.