Question about bits and bytes for ADSL

[Jorden]

How fast is fast these days?

Asking these questions for a friend of mine, but also for me once I get my ADSL.

1. If I have a 1Mbit download connection at maximum, how long does a 1.5Gigabyte file take to download then?
2. Are all downloads measured in Kbits or Kbytes per second?
3. Will my PCI NIC be a bottleneck when downloading (from an external ADSL modem), as it only runs at 33Mb/s ?
4. Will ADSL-downloadspeed matter on an ISDN line?

Jord.

[The PIT]

I'm in the UK so I can only say BT and if you're lucky and overpriced.

[Dr Mordrid]

You most often don't get the full tilt speed from either an ADSL or cable connection. How fast it runs at any given time depends on how busy your ISP's node is. Generally the downloads are much faster than uploads.

Today my cable does: 800 kbps down, 350 kbps up. Some late nights the download bitrate actually exceeds 1 mbps because I'm the only one up

Your PCI/33 bus doesn't run at 33 mbytes/s. It runs at 33 MHZ. The bandwidth of PCI/33 bus is actually 133 mbytes/s. Your connection shouldn't even come close to that.

As for the NIC...a 10 mbit NIC can transfer 10x the bandwidth of your connection so no problem there either.

Someone else will have to speak to ISDN's specifics, but the test site I use lists the typical dual channel ISDN throughput at about 130 kbps.

Test site: http://www.dslreports.com/stest

Dr. Mordrid

[Helevitia]

DSL is measured in bits so to get the true throughput you would take your bandwidth/8. In your case it would be 1Mb/8 = 125KB/s.

Your 10Mb nic card can handle your bandwidth. You will never get full 10Mb/s though. With overhead, and other factors, you will, at best, get 3.5-4Mb/s.

Your last question doesn't make any sense.


For comparison, I have cable through @home. They claim 1.5-2Mb/s(probably the average speed). I actually get up to 6Mb/s which equals to 6Mb/8 = 750KB/s. I have seen sustained speeds of 600+ on webistes such as EA.

So to break it down

Your ADSL = 125KB/s (125000 Bytes a second) download speeds

My cable = up to 750KB/s (750000 Bytes a second) download speeds

Hope this helps.

Dave

[Guru]

Jorden if you wnat to test your conection speed I would recomed http://webservices.cnet.com/bandwidt...lt.asp?Start=1 since you live in Europe

[borat]

if your last question is how fast is isdn compared to ADSL the answer is very slow
i had bt's isdn in the uk for a year running at 64k for most of the time and although it was about twice as fast as a normal modem it still wasn't quick enough to browse the web properly. on the odd occasion that i used it at 128k web browsing was acceptable but file downloads still took too much time.
now i have a cable modem which runs at between 350kb/s and 500kb/s depending on the time of day.
the only thing is it is supplied by a company called telewest who are the biggest bunch of legal cowboys out there and the service usually goes down for about 30mins - 1hour once a day on average
still its nice when it works.

[Wombat]

I'm not an expert, but doesn't DSL use ATM protocols? That's roughly 8/10 isn't it? (8 bits of data you're interested in, 2 bits of protocol).

[Kosh Naranek]

Yes DSL use ATM cards , but so does most nodes !
( CableModem Nodes does use ATM cards ... of course this is ISP dependant ...)
Some DSL connections use routers and ATM cards and DSL Modems ..... !

[Kosh Naranek]

However .....

If the connection isn't tweaked properly it can end up giving as little as 256 kpbs on a 1024 kpbs connection !

[Wombat]

I was just thinking that Cable uses PPPoE, which will cut into effective bandwidth even further.

[Jorden]

Thanks to you who have answered already.

But I don't have ADSL yet. A friend of mine got his package in today and he asked me these questions. Sorry to disappoint you who thought this was the 'other' "a friend of mine wants to know" question

He has ISDN, he has option of dual dialup, he has got the 512Kbps/128kps package of ADSL.

Full speed I know won't be in the package, but for that after you were online for 10 minutes you will get the full speed here in Holland. So, for me, that means I will have approximately 1Mbit speed after 10 minutes.
I've got a normal telephone line, my friend has ISDN. I can just hang the adsl modem inbetween my phoneline to the PC room and my NIC. No problem there.

However, NORMAL ISDN uses a phonecentral, giving options of up to 4 seperate telephone lines. With all their different numbers if you want to. And 2 of those lines can call in to your provider, if your ISP has that option.
Now, if you want to put an ADSL modem on that system, you sure want to have you 2 phonelines free plus the other 2 understanding that they are a dataline.

Meaning Dave, that it does matter and makes sense

Jord.

[WayneHu]

There are two types of protocols currnet DSL modem uses:

PPPoA -> PPP over ATM
PPPoE -> PPP over Ethernet

I have no idea about the Cable network protocol. But it should be something like PPP, too.

In ATM network,
Each cell is 53 bytes ( 5byte header + 48 bytes payload)
Thus its overhead is about 9% during ATM cell transmission.

In the 48 bytes payload, its have 5 modes in AAL layer, which has another header. The current defined ones are AAL 1, 2, 3/4, 5.

If you are using IP over ATM, it uses AAL5.
Thus you have to count the AAL layer header overload, too.

In the IP packet, it also has IP header and TCP/UDP header. Don't you need to count them to get the actual maximum effective data bandwidth?

[xortam]

Righto Wayne. I was going to point out earlier that their ain't much data getting through after all of those layers of headers. Kinda like OSes taking over the machine so there's nothing left for the apps.

[DentyCracker]

I have 512kbps down 256kbps up ADSL here at work (which is why I'm still here instead of at home) and get download speeds of 52-54 kbps

[Jorden]

Fun thing you called there Wayne. I didn't understand a bit of it, I hope my friend did

But for: we're using PPPoE... anything you can enlighten us about that?

Jord.