[wplug] DSL speed
Patrick Wagstrom
patrick at wagstrom.net
Wed Feb 27 09:31:12 EST 2008
Zach wrote:
> The speed test at dslreports.com is showing my download speed as 625
> Kb/s. This seems a lot less than the 768 Kb/s I'm supposed to have. My
> latency to their test server in NY was 50ms. Is there anything I can
> do to to increase my download speed? I'm using Ubuntu 7.04 Live CD
> until I can buy a new computer. Running 2.6.18 kernel and
> Debian/Ubuntu.
That actually sounds pretty good. You've got two layers of overhead going
on in your connection: encapsulation to PPPoE and then TCP/IP. For most
packets, these numbers are both small (8 octets for PPPoE, 20 octets for
IP, 20 octets for TCP). In that case you're losing about 4% right off the
bat to overhead. However, depending on the way data is transmitted it
could be far worse. Telnet usually transmits single octets, which means
that on a DSL you're sending 49 octets of which 1 octet is data. Yay for
98% overhead.
Another issue is that there is inherent noise in the DSL line. This causes
some data to retransmit, lowering your throughput even more. Noise is
present on most lines (cable too), but the nature of the phone network
means its slightly more susceptible.
This is normal. Getting 625Kb/s on a 768Kb/s is great. If you were around
400Kb/s that would be an issue.
--Patrick
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