D-link USB adapter question

I had a d-link dwl-122 "b" adapter connected to my TiVo and it was slow
but it worked. OfficeDepot had a D-link dwl-g120 "g" adapter on sale
for $20 after rebates so i bought one of them yesterday. It seems like
it transfers slower than the "b" adpater that I had connected. I
lookeda the box after i tried it and saw that it is version B1 and the
Tivo website says that it should be version B2. would it cause that
much of a difference between the versions? should I retrun the b1 and
try to get a b2. My other thought was to get one of the netgear wg111's
but on the internet it seems that there are several versions with
letters after the adapter. not sure which is the right one to use. any
advise would be appreciated.

thanks, Steve

I can't be 100% positive here, but I can conjecture a pretty good guess.

Presumably your current wireless network supports "b" and "g". Most
consumer model routers from Netgear, Linksys, and D-Link (esp. D-link), do
NOT perform as efficiently when running in mixed mode, i.e., support 'b" and
"g" clients concurrently. Although supported, it's with caveats (that the
vendor usually doesn't make much mention of, for obvious reasons). First,
when running both "b" and "g" clients concurrently, most routers will
DOWNGRADE the "g" clients to "b" performance, simply because it can't
actually do two things at once, it's either "b" or "g", and if a "b" client
is transmitting when a "g" client also wants to transmit, rather than wait
for all "b" transmissions to cease, the router simply forces the "g" client
to run in "b" mode (or else does make it wait). Second, in order to improve
the situation, the typical "g" router (a good one anyway, like my D-Link
DI-624) supports something called "802.11g Only Mode". It may go under some
other name w/ other products, but if it's there, its under the wireless
configuration section (e.g., w/ Belkin F5D7230-4 and F5D7231-4 routers, it's
called "54-G Only"). Why does this exist? Because when you enable this
feature, the router doesn't have to waste processing cycles to check the
channel for "b" traffic before transmitting every time! Instead, "b"
clients are simply rejected, and only "g" clients accepted, and because its
ONLY "g" clients, the router is much more efficient. Most routers level
this feature disable by default, for maximum compatibility. But if you ONLY
have "g" clients, it should be ENABLED for maximum performance. Secondarly,
it's a respectable security measure, one less class of clients that can
appropriate your wireless system!

Granted, I'm speculating here based on very little information, BUT, most
people don't appreciate these details wrt their low-cost, consumer-level
routers. These routers are definitely cheap and effective, but it comes at
a price. Yes, they support "b" and "g", but not without compromises.
Again, most vendors don't make much of it, they simply say its supports "b"
and "g", but once you start mixing modes on any given infrastructure, *then*
you start to see the limitations. If this is indeed your problem, you have
some options. For example, upgrade ALL clients to "g" and enable "g only"
mode on the router, or perhaps buy a second router, one dedicated to "b"
clients, the other "g" clients (naturally, you'll want to exercise
sufficient channel separation). But the fact "b" and "g" share the same
2.4GHz band, the situation will always be, to some degree, problematic. The
only 100% positive means to avoid interference is to use perhaps an "a/b/g"
router (e.g., D-Link DI-784), since the "a" uses the 5GHz band.

HTH

Jim



"Steve Ball" wrote in message
m...
I had a d-link dwl-122 "b" adapter connected to my TiVo and it was slow
but it worked. OfficeDepot had a D-link dwl-g120 "g" adapter on sale
for $20 after rebates so i bought one of them yesterday. It seems like
it transfers slower than the "b" adpater that I had connected. I
lookeda the box after i tried it and saw that it is version B1 and the
Tivo website says that it should be version B2. would it cause that
much of a difference between the versions? should I retrun the b1 and
try to get a b2. My other thought was to get one of the netgear wg111's
but on the internet it seems that there are several versions with
letters after the adapter. not sure which is the right one to use. any
advise would be appreciated.

thanks, Steve

Comments interspersed, please see
http://www.proxim.com/learn/library/...erformance.pdf
for one source of documentation:

Jim wrote:
I can't be 100% positive here, but I can conjecture a pretty good guess.

Well, your guesses have some bearing with reality, but fall short of the
mark in several aspects.

Presumably your current wireless network supports "b" and "g". Most
consumer model routers from Netgear, Linksys, and D-Link (esp. D-link), do
NOT perform as efficiently when running in mixed mode, i.e., support 'b" and
"g" clients concurrently.

This is true, though I want to point out (and will back up further down)
that you are overstating the effects.

Although supported, it's with caveats (that the
vendor usually doesn't make much mention of, for obvious reasons).

Mostly because the issue is much too complex to the casual user, and
doesn't really matter that much to them.

First,
when running both "b" and "g" clients concurrently, most routers will
DOWNGRADE the "g" clients to "b" performance, simply because it can't
actually do two things at once, it's either "b" or "g", and if a "b" client
is transmitting when a "g" client also wants to transmit, rather than wait
for all "b" transmissions to cease, the router simply forces the "g" client
to run in "b" mode (or else does make it wait).

This is sort-of true. It *is* true that only 1 device on a given 802.11
collision domain can broadcast at once, so that when your "g" device is
broadcasting, your "b" device must wait. But this happens even if you
have all "b" devices or all "g" devices. What is *not* true is that
your "g" devices are forced to transmit in "b" mode. The only change
that your "g" device has to do is use a longer "slot" time (20
microseconds vs. 9 microseconds) to be compatible w/ the "b" device slot
times. This has an effect, but it's probably about a 20% penalty, not
the 80% penalty that would be incurred from going from 54 Mbps to 11 Mbps.

The one situation where you *may* see such a high penalty is where you
have *2* overlapping mixed wireless collision domains (i.e. 2 wireless
routers) on overlapping or identical channels, but this is not the
typical residential wireless scenario, it's more of a problem for
corporate networks.

Second, in order to improve
the situation, the typical "g" router (a good one anyway, like my D-Link
DI-624) supports something called "802.11g Only Mode". It may go under some
other name w/ other products, but if it's there, its under the wireless
configuration section (e.g., w/ Belkin F5D7230-4 and F5D7231-4 routers, it's
called "54-G Only"). Why does this exist? Because when you enable this
feature, the router doesn't have to waste processing cycles to check the
channel for "b" traffic before transmitting every time! Instead, "b"
clients are simply rejected, and only "g" clients accepted, and because its
ONLY "g" clients, the router is much more efficient. Most routers level
this feature disable by default, for maximum compatibility. But if you ONLY
have "g" clients, it should be ENABLED for maximum performance.

I don't think I can agree that it's *much* more efficient. The shorter
slot time does improve throughput, but your *maximum* gain is
theoretically about 33%. While this is significant, it certainly
doesn't explain why his "g" adapter is *slower* than his "b" adapter
was. Also, if you look at past threads, maximum Tivo throughput is
nowhere near what 802.11g can support, but is instead throttled by
internal processes in the DVR (most likely encryption duties).

Secondarly,
it's a respectable security measure, one less class of clients that can
appropriate your wireless system!

Calling it a *respectable* security measure is a stretch. Since most
new devices use 802.11g I'd say it's pretty much a *marginal* security
measure, i.e. it doesn't hurt, but it doesn't do much good either.

snip

My views on this would be buy "g" equipment when you buy new stuff, but
don't spend money on upgrading existing equipment if it works fine now.
Mixed mode networks have some penalty involved but it isn't likely
something that will impact you greatly.

The *real* speed gains on Tivo DVR transfers are gained by hacking the
box and removing the encryption processes totally. Others here can tell
you more about that, but it's not nearly as simple as upgrading a
wireless adapter.

Also, "g" won't be the fastest wireless protocol on the block for very
much longer. 802.11n (touted mostly as "MIMO" right now) has not been
ratified yet, but pre-ratification products are already coming out.
These devices are basically very similar to 802.11g (and are backward
compatible, fortunately) but use multiple receivers and multiple
transmitters in order to increase range and reduce deadspots. They
reportedly work very well, I'd definitely recommend getting them when
they become widely available.

Randy S.

Sorry, I was at work and just saw the replies, which i greatly
appreciate. Jim, I have the DI-624 same as you and I found the option
to trun on "g" only and I see what you mean about that. Like I said in
my origianl post witht he d-link "b" adapter iwas using I think it was
about 1 1/2 hours to transfer a 1 hour show. does this sound right?
with the new dwl-g120 adapter it says that it is goignto take 3 hours.
My big questionwas that on the TiVo website they said the dwl-g120
version B2 was compatible. after i got it home i saw on the box that it
was a B1. It looks the same as the B2. does the hardware version make
that much difference to where the speed would be that much slower? all
I did when I connected it to my TiVo was plug it in the USB port and
then the Tivo restarted itself. Should I have done something different?
Is there a way to tell which device the Tivo thinks is conneceted so i
can make sure it is using the right driver?

Thanks for all the replies I greatly appreciate it. Steve.


Randy S. wrote:

Comments interspersed, please see
http://www.proxim.com/learn/library/...erformance.pdf
for one source of documentation:

Jim wrote:

I can't be 100% positive here, but I can conjecture a pretty good guess.


Well, your guesses have some bearing with reality, but fall short of the
mark in several aspects.

Presumably your current wireless network supports "b" and "g". Most
consumer model routers from Netgear, Linksys, and D-Link (esp.
D-link), do
NOT perform as efficiently when running in mixed mode, i.e., support
'b" and
"g" clients concurrently.


This is true, though I want to point out (and will back up further down)
that you are overstating the effects.

Although supported, it's with caveats (that the
vendor usually doesn't make much mention of, for obvious reasons).


Mostly because the issue is much too complex to the casual user, and
doesn't really matter that much to them.

First,
when running both "b" and "g" clients concurrently, most routers will
DOWNGRADE the "g" clients to "b" performance, simply because it can't
actually do two things at once, it's either "b" or "g", and if a "b"
client
is transmitting when a "g" client also wants to transmit, rather than
wait
for all "b" transmissions to cease, the router simply forces the "g"
client
to run in "b" mode (or else does make it wait).


This is sort-of true. It *is* true that only 1 device on a given 802.11
collision domain can broadcast at once, so that when your "g" device is
broadcasting, your "b" device must wait. But this happens even if you
have all "b" devices or all "g" devices. What is *not* true is that
your "g" devices are forced to transmit in "b" mode. The only change
that your "g" device has to do is use a longer "slot" time (20
microseconds vs. 9 microseconds) to be compatible w/ the "b" device slot
times. This has an effect, but it's probably about a 20% penalty, not
the 80% penalty that would be incurred from going from 54 Mbps to 11 Mbps.

The one situation where you *may* see such a high penalty is where you
have *2* overlapping mixed wireless collision domains (i.e. 2 wireless
routers) on overlapping or identical channels, but this is not the
typical residential wireless scenario, it's more of a problem for
corporate networks.

Second, in order to improve
the situation, the typical "g" router (a good one anyway, like my D-Link
DI-624) supports something called "802.11g Only Mode". It may go
under some
other name w/ other products, but if it's there, its under the wireless
configuration section (e.g., w/ Belkin F5D7230-4 and F5D7231-4
routers, it's
called "54-G Only"). Why does this exist? Because when you enable this
feature, the router doesn't have to waste processing cycles to check the
channel for "b" traffic before transmitting every time! Instead, "b"
clients are simply rejected, and only "g" clients accepted, and
because its
ONLY "g" clients, the router is much more efficient. Most routers level
this feature disable by default, for maximum compatibility. But if
you ONLY
have "g" clients, it should be ENABLED for maximum performance.


I don't think I can agree that it's *much* more efficient. The shorter
slot time does improve throughput, but your *maximum* gain is
theoretically about 33%. While this is significant, it certainly
doesn't explain why his "g" adapter is *slower* than his "b" adapter
was. Also, if you look at past threads, maximum Tivo throughput is
nowhere near what 802.11g can support, but is instead throttled by
internal processes in the DVR (most likely encryption duties).

Secondarly,
it's a respectable security measure, one less class of clients that can
appropriate your wireless system!


Calling it a *respectable* security measure is a stretch. Since most
new devices use 802.11g I'd say it's pretty much a *marginal* security
measure, i.e. it doesn't hurt, but it doesn't do much good either.

snip

My views on this would be buy "g" equipment when you buy new stuff, but
don't spend money on upgrading existing equipment if it works fine now.
Mixed mode networks have some penalty involved but it isn't likely
something that will impact you greatly.

The *real* speed gains on Tivo DVR transfers are gained by hacking the
box and removing the encryption processes totally. Others here can tell
you more about that, but it's not nearly as simple as upgrading a
wireless adapter.

Also, "g" won't be the fastest wireless protocol on the block for very
much longer. 802.11n (touted mostly as "MIMO" right now) has not been
ratified yet, but pre-ratification products are already coming out.
These devices are basically very similar to 802.11g (and are backward
compatible, fortunately) but use multiple receivers and multiple
transmitters in order to increase range and reduce deadspots. They
reportedly work very well, I'd definitely recommend getting them when
they become widely available.

Randy S.

Steve Ball wrote:
Sorry, I was at work and just saw the replies, which i greatly
appreciate. Jim, I have the DI-624 same as you and I found the option
to trun on "g" only and I see what you mean about that. Like I said in
my origianl post witht he d-link "b" adapter iwas using I think it was
about 1 1/2 hours to transfer a 1 hour show. does this sound right?
with the new dwl-g120 adapter it says that it is goignto take 3 hours.
My big questionwas that on the TiVo website they said the dwl-g120
version B2 was compatible. after i got it home i saw on the box that it
was a B1. It looks the same as the B2. does the hardware version make
that much difference to where the speed would be that much slower?

Somewhat unlikely, but certainly possible.

all
I did when I connected it to my TiVo was plug it in the USB port and
then the Tivo restarted itself. Should I have done something different?
Is there a way to tell which device the Tivo thinks is conneceted so i
can make sure it is using the right driver?

When adding a USB wireless adapter to your Tivo, always restart it
afterwards. I don't think Linux is quite as plug and play (or plug and
pray ;-) ) as Windows is.

But I would guess you may be running into interference issues. Try
setting your router to use a different channel. If it's on 1, try 11.
If it's at 11 try 1. If it's at 6 try either 1 or 11. The rest of the
channels overlap, so 1, 6, and 11 are probably the best ones to try.

Randy S.

D-link is awful in respect to their internals.
They will keep the same product model number, but change the understand in
the process make them not compatible with previous drivers.
The B1 and B2 are very different.

If you go to their web site and try to download drivers for it. the driver
version is different for each Sub-release.

This problem spans their product line.

--
Steven BerkHolz
Send to Domain TESCOGroup dot com, username SB

Note: you may also want to know that you should never send mail to:







"Steve Ball" wrote in message
m...
I had a d-link dwl-122 "b" adapter connected to my TiVo and it was slow but
it worked. OfficeDepot had a D-link dwl-g120 "g" adapter on sale for $20
after rebates so i bought one of them yesterday. It seems like it
transfers slower than the "b" adpater that I had connected. I lookeda the
box after i tried it and saw that it is version B1 and the Tivo website
says that it should be version B2. would it cause that much of a
difference between the versions? should I retrun the b1 and try to get a
b2. My other thought was to get one of the netgear wg111's but on the
internet it seems that there are several versions with letters after the
adapter. not sure which is the right one to use. any advise would be
appreciated.

thanks, Steve

Thanks for all the repiles. I think I am going to retuontrn the
dwl-g120 and just stay with the "b" adapter i have right now. To verify
what i was saying i tried to move a 1 hour show with the dwl-g120
attached and tivo desktop said it was going to take over 3 hours to
transfer the show. I disconnected the dwl-g120 and reconnected the
dwl-122 i had before and tried it again. With the "b" adapter connected
it said it was only going to take a little under 2 hours to transfer the
same show. I tried all the things i could such as setting my router for
"g" only and it didnt make a difference. the only thing i can think of
is the version of the card being 1 off from what tivo says is supported.
oh well. maybe they'll add some drivers later for faster devices that
wll actually work.

thanks for all the help.

Steve

BerkHolz, Steven wrote:
D-link is awful in respect to their internals.
They will keep the same product model number, but change the understand in
the process make them not compatible with previous drivers.
The B1 and B2 are very different.

If you go to their web site and try to download drivers for it. the driver
version is different for each Sub-release.

This problem spans their product line.