Karl Fife wrote:
On Wed, 29 Oct 2008 10:01:31 +0000, "Paul Mansfield"
I think you mean "asymmetric" rather than "half duplex".
Hi Paul.
I do make mistakes, but I did in fact mean to say BOTH asymmetric AND
half-duplex. In other words:
ADSL is Asymetric AND ALSO half-duplex
SDSL @1.5mbs is Symmetirc but only HALF-duplex
ON THE OTHER HAND, a T1 is fully symmetric BUT it is also FULL-duplex.
In other words, A 1.544 mbs T1 can actually transfer 3.88 mbs - 1.544 in
EACH direction. Compare that to SDSL @1.544 mbs which can transfer at
most 1.544 mbs total. 1.544 up OR 1.544 down OR some combination
thereof where up + down <= 1.544 mbs.
People who talk about full-duplex SDSL are usually talking about 768k
(or slower) SDSL which CAN be full-duplex (because the 1.5 mbs data link
layer can divide its total wire line capacity between the 2 legs)
Again, to my original point, someone with an expensive 1.5mbs sdsl
circuit can only be assured of proper shaping if they always cap their
bandwidth at 768k. Otherwise their traffic shaper would naturally give
for example 1.2mbs to an outbound stream, fully expecting easily meed
the demand of .9 mbs to an inbound stream. In fact it will be
dropping 600k of RTP packets on the floor because it's over
capacity. See what I mean? I have experienced this phenomenon first
hand, and it is worthy of attention.
YES, I could limit the shaper to 768k in each direction, but that means
one has to leave HALF of your available bandwidth sitting idle to be
confident that the shaper does not make assumptions that result in
dropped RTP packets.
I see that as a problem worthy of attention, especially as VOIP and
other RTP traffic continues to gain traction as killer apps.
I'm hoping you developers out there will weigh in on this.
Keep up the great work!
-Karl
---------------------------------------------------------------------
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
Usually you can force full-duplex operation on most DSL devices by
setting full-duplex on the device it is connected to - for instance if
you are plugging the computer running pfsense directly into the DSL
modem, manually set the interface on the pfsense box to full duplex
(usually with ifconfig from the command line, not sure if this can be
done from the gui).
- Joel
---------------------------------------------------------------------
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
