Broadband Line Limitation

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bonkiebonks

389 posts

Ultimate Geek
+1 received by user: 7

#7252 31-Mar-2006 20:54

Hi.

I was just wondering if my line would support the new 3.5M/512k plans because from what I can see in my ADSL router settings, it shows that my DSL line DS speed is 2560k and US speed is 160k - both of which are well below the said 3.5M and 512k respectively.

It would be pointless for me to pay more than what I'm already paying to get only 2.5M down as opposed to 3.5M and only 160k as opposed to the promised 512k.

I just wanted to make sure before I sign up.

Any help would be greatly appreciated.

By the way, the DSL line in my previous house showed something along the lines of 7000+k down (can't remember the exact figure) and 300+k up.

Thanks.

Hypernova

50 posts

Geek

#31940 1-Apr-2006 00:12

I think those are bandwidth assigned to you by the exchange, they are higher because they need to factor in the ATM packet overheads.

Once upon a time everyone in Europe believed in God and his teachings on love thy neighbours and peace, historians referes to this period as THE DARK AGES.

juha

1317 posts

Uber Geek
+1 received by user: 7

Trusted

#31970 1-Apr-2006 15:03

Hypernova: I think those are bandwidth assigned to you by the exchange, they are higher because they need to factor in the ATM packet overheads.

Yep, that's correct. ATM uses small 53-byte cells (40 byte payload, 13 byte headers) whereas PPP frames are up to 1,500 bytes. These need to be chopped up into smaller units for transport over the underlying ATM link. It's known as the "ATM cell tax" and means that out of a nominally 155Mbit/s ATM STM-1 link, you can only fit around 120-125Mbit/s worth of IP traffic (depending on the frame sizes on the circuit). So, Telecom compensates for the overhead with higher linkspeeds.

Juha