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bgcm12

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Contention - in real terms?

I have just migrated from an ISP that gave me only a 512k connection but guarenteed no contention.

For the same price per month, my new ISP allows me 2mb connection (altough I can only use 1Mb on my phone line) for the same price as my old ISP.  However, there is a 1:30 contention on the line.

What does this mean to me in real-terms?  How will I be impacted?  Does the extra bandwidth more than compensate for the amount of contention on the line?   Which is the better deal (bearing in mind they are the same price per month)?

Thanks very much.
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CajunBill

So, what does 1:30 contention mean - does it mean there are 30 other potential contenders?

Were you using the entire 512K bandwidth before? How much of the 1Mb are you using?

If you were using a lot of bandwidth a lot of the time, and there are 30 others possibly contending for the line, sounds like you better hope they don't use it much.

But I must admit, I don't really have that expperience.
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yes I believe that 30 people share that resource.  But I think that only applies the ISP connection to the backbone - the BT backbone is set at a contention of 50:1 anyway apparently.  I realy am not sure how much contention is an issue if someone could clarify for me.

I was getting connection speeds of 470k on my old ISP - I get similar results with the new ISP as it hasn't yet been upgraded to 1mb (you have to migrate from one ISP to another at the same connection speed)- yet things seem slower.  This could be psycological tho...
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CajunBill

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1:30 contention means that they have oversold the capacity.  This isn't bad, it's quite normal.

Say they have a 2 Mbps connection from their site to "the internet".

if they sell ONE customer the entire 2 Mbps, well, 99.9% of the time it's going to sit idle.  Right?  You'll be surfing along, grab a few KB or MB for a page and then read it for a few seconds, click some where, grab another MB, etc......

Instead they sell 30 customers that 2 Mbps.  For normal surfing, you'll never notice it.  Occasionally there is a tiny (unnoticable) delay when somebody else is grabbing their MB page using 'your' bandwidth.  The technical term here is 'jitter'.  It always takes 72ms to get the reply from the remote site, except every few seconds it takes 92ms.

BUT: The whole thing is based upon the assumption of that bursty traffic pattern.  So that on average (over a period of 1-2 seconds), the bandwidth gets evenly shared and nobody notices the delay.

The kicker is that today's access patterns don't always work like that.  Streaming music and VoIP services require low jitter.  That next packet HAS to arrive on time or there is nothing to play on the speaker.   So streaming players and VoIP phones are programmed to recover - various ways, irrelevant here - and mostly you won't notice.  Could be a little 'static' or a pop, but people have amazing tollerance for these little glitches.


Still, as more and more of your 30 close friends (ie bandwidth sharers) use these kinds of time critical services, the worse things get.  Until one day...  ("Sorry, the internet is busy.  Try again later").


-----Burton

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Hmmm - thanks for that Burton.  I now have worrying visions of an engaged tone when i click on my browser icon!!!

One last point to clear up please...

The BT line that my ISP uses has a 1:50 contention.  The ISP sells the bandwidth on a 1:30 contention.  How do these figures interact?

Thanks again.
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I agree with Burton that you have swapped a guaranteed 512Mbps for for an unguaranteed but sometimes possible 2Mbps (1Mbps for yo since your phone line limits you)

Like I said in that previous post
"So then, the effect will depend on...
2. what the other people who share your connection are doing."
Bill