DSL speeds

[UnfixedMidget]

i might be switching the address of where i get my DSL while i take care of my grandparents, since im there 6-7 days a week.

thing is tho that AT&T only offers the 756kbps in his area...

im not overly worried about dwnld speed since i dont dwnld much anymore... but i am wondering about what kind of ping (latency) i could expect from this type of service?

thanks

[ThaMan]

Latency is not effected by bandwidth. You should see the same "ping" as the 6M DSL.

[Kamui]

ping shouldn't be an issue. It isn't affected by distance from the line card in the same way bandwidth is.

In general, nearly any distance of wire shouldn't add even 1ms of latency. modems add about as much as the final miles of copper. switches add 1 to 2 ms*. routers add up to 5 ms*.

*Depending on forwarding scheme (full read vs store and forward, etc)

Obviously, there are a lot of other variables (link balancing, flow consolidation, QOS, overloaded links, etc etc etc). Long story short, traffic and devices add latency. Not distance.
A connection out in the boonies does not have considerably more devices behind it than a urban connect.

[ThaMan]

And Nam thinks I ramble :tongue:

[Namoric]

yeah, I lost Kamui at "ping"

[UnfixedMidget]

i knew distance didnt really affect ping... i was more concerned about the slower speed... i thought it would add a considerable amount of ms's to my ping... seems i was mistaken though.

tyvm all

[Savistik]

Electricity flows at about 1,000,000,000 feet per second or roughly the speed of light through regular copper wire, so every 186 miles of wire takes an extra millisecond to traverse. Odds are there's not that much extra wire between you and the wiring center.

[Kamui]

ping is a measure of how long it takes data to get from A to B, and be processed (and returned). Analogy: the length of a garden hose, and how many nozzles there are in it.
Bandwidth is a measure or how much information can be sent at a time. Analogy: how wide the hose is.

These two metrics are mostly unrelated.
(for the sake of argument, the water pressure is always the same)

As for the flow of electricity, there's more to ping-through-a-wire than that. Transmitting a minimum size packet takes as long as it takes for the first voltage spike on the wire to reach the far end (of a maximum length cable), so for the full data packet to move from A to B takes at least twice the time Sav was speaking about (too lazy to do the calculation right now).
But yes, still much less than one ms. All the real lag is in the smart boxes.

[Walterus]

A normal ping is, I believe, a package of data 32 bit long. What you can do is sending a larger package. What this does is to tell you something about the load on the line. Ping -l 512 would send a 512 bit package. Most routers/switches has a max size of a single package (think it's around 512), so making the size of the ping larger than that doesn't realy have an affect. I remember we had a problem with our line to Singapore some years back. I did some testing and after confronting MCI they finaly acknowledged that they had a problem with the line (they had sold more bandwidth than the line could take. Normaly you oversell by a factor, since not all users are online at the same time, but their factor was probably way off). I might be wrong in this, so please feel free to correct.