[LINK] 1.5 Mbps limit lifted from Telstra's ADSL DSLAMs?

Robin Whittle rw at firstpr.com.au
Thu Jan 11 21:48:52 AEDT 2007

I have a fixed IP address Internode ADSL service, which uses Telstra's
DSLAM at the local exchange building.  My current plan is 1500 kbps
downstream and 256 kbps upstream (although real rates are a little below
this due to protocol overhead) with a 10 GB/month download limit.  This
costs $79.95 and has been very reliable, since May.  The two outages
were server or router problems which affected the whole of Internode.

Until now, I understood that Telstra capped the rate of its ADSL
services - the ones it retailed and those it wholesales to Internode
etc. - to 1.5Mbps, even though the DSLAM and modem might be able to go
to 6 or 8 Mbps.

Does anyone know the politics of this?  I guess the old limit was to
stop people downloading videos too fast and competing with Foxtel - or
maybe as part of jockeying for the need to do VDSL (AKA Fibre to the Node).

Now those limits are gone.


My old plan seems to be represented by "SOHO-1500-Power10" and is $10
cheaper.  For $10 more ($89.95) I can get the same 10 GB/month limit
with speeds up to 8 Mbps downstream and 384 kbps upstream:
"SOHO-High-Power10".  Extra 10 Gigs per month cost about $10, so this is
0.1 cents per Megabyte.

I won't get 8Mbps, since the exchange building is quite a few km away,
but I recall the modem (D-Link DSL 502T, based on an impressive Texas
Instruments chip) was reporting a speed well above 1.5 Mbps when I
initialised it.  I don't think I can do that with the modem in its
current configuration.

SFTP from my server in San Francisco runs at about 85kBps (680kbps).
The limit there might be the long distance and TCP taking a while to
adapt to the large window of data in transit - but I didn't see it
moving much faster as time went on.

Downloading a bz2 file from http://mirror.aarnet.edu.au runs at about
137 kBps with Mozilla on Windows and 155 kbps with wget on a Linux
machine.  Running two such processes, on the same file, on two machines
leads to about the same total download rate split between them.

Running one mirror.aarnet.edu.au wget process and one SFTP process from
the San Francisco server, it was clear that one affected the other, with
the total speed being around 155kB/s.  This is 1.24Mbps, which is not
bad considering TCP protocol overhead and the ADSL modem protocols of
PPP over Ethernet, using ATM within the ADSL system.  So it seems this
limit is that of the ADSL link, presumably set in Telstra's DSLAM.

I signed up for the "up to 8 Mbps downstream and 384 kbps upstream"
plan.  Supposedly the new speed will be available in an hour.  I will
unplug the ADSL modem to be sure.

   - Robin

More information about the Link mailing list