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More than 2 ad-hoc nodes?

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Anonymous
a b F Wireless
July 7, 2004 6:23:22 PM

Archived from groups: alt.internet.wireless,microsoft.public.windows.networking.wireless (More info?)

I have a question about 802.11g ad-hoc mode. Everything I read refers to
ad-hoc mode as point-to-point, implying that only 2 computers can be so
networked. But I've also seen diagrams implying that an ad-hoc network can
be expanded beyond 2 nodes (no AP), using more than 2 ad-hoc nodes.

So what happens if there are 3 computers with a 802.11g ad-hoc, all
configured with the same SSID? Will all 3 be able to see and talk to each
other without having to disconnect from one and connect with the other? A
with B with C?

Or is 3 computers (one adhoc device per computer) with the same ad-hoc SSID
(within range of each other and on the same channel) illegal?

Thanks,
Bruce.

More about : hoc nodes

Anonymous
a b F Wireless
July 7, 2004 6:23:23 PM

Archived from groups: alt.internet.wireless,microsoft.public.windows.networking.wireless (More info?)

Hi

There is some Wireless Client Hardware that can do more than two.

However the resultant Network is Quirky.

Given that Wireless Cable DSL Router is close to the price of Client card,
it make much more sense to connect one computer to a Router via cable the
rest can be Wireless.



Jack (MVP-Networking).





"Bruce Chastain" <bchastain@XNOSPAMXhyperfeed.com> wrote in message
news:uHTGc.5018$sD4.3113@newsread3.news.atl.earthlink.net...
> I have a question about 802.11g ad-hoc mode. Everything I read refers to
> ad-hoc mode as point-to-point, implying that only 2 computers can be so
> networked. But I've also seen diagrams implying that an ad-hoc network
can
> be expanded beyond 2 nodes (no AP), using more than 2 ad-hoc nodes.
>
> So what happens if there are 3 computers with a 802.11g ad-hoc, all
> configured with the same SSID? Will all 3 be able to see and talk to each
> other without having to disconnect from one and connect with the other? A
> with B with C?
>
> Or is 3 computers (one adhoc device per computer) with the same ad-hoc
SSID
> (within range of each other and on the same channel) illegal?
>
> Thanks,
> Bruce.
>
>
July 7, 2004 7:44:59 PM

Archived from groups: alt.internet.wireless (More info?)

Ad-hoc networks can have as many stations as the bandwidth will support.
These networks are called point-to-point to distinguish them from the usual
infrastructure network, which is a hub. The difference is that, in ad-hoc,
each station transmits directly to the receiver - therefore point-to-point,
although the receiver could be any station in the net - while in the
infrastructure (hub) network, all stations transmit to the AP, which
retransmits to the receiver.

"Bruce Chastain" <bchastain@XNOSPAMXhyperfeed.com> wrote in message
news:uHTGc.5018$sD4.3113@newsread3.news.atl.earthlink.net...
> I have a question about 802.11g ad-hoc mode. Everything I read refers to
> ad-hoc mode as point-to-point, implying that only 2 computers can be so
> networked. But I've also seen diagrams implying that an ad-hoc network
can
> be expanded beyond 2 nodes (no AP), using more than 2 ad-hoc nodes.
>
> So what happens if there are 3 computers with a 802.11g ad-hoc, all
> configured with the same SSID? Will all 3 be able to see and talk to each
> other without having to disconnect from one and connect with the other? A
> with B with C?
>
> Or is 3 computers (one adhoc device per computer) with the same ad-hoc
SSID
> (within range of each other and on the same channel) illegal?
>
> Thanks,
> Bruce.
>
>
Related resources
Anonymous
a b F Wireless
July 7, 2004 8:00:12 PM

Archived from groups: alt.internet.wireless (More info?)

> Ad-hoc networks can have as many stations as the bandwidth will support.
> These networks are called point-to-point to distinguish them from the usual
> infrastructure network, which is a hub. The difference is that, in ad-hoc,
> each station transmits directly to the receiver - therefore point-to-point,
> although the receiver could be any station in the net - while in the
> infrastructure (hub) network, all stations transmit to the AP, which
> retransmits to the receiver.

Does that mean that in infrastructure mode, an 11Mb/s link can only
transfer a maximum of about 500KB/s between two nodes (vs 1MB/s between
the hub and any other node) ?


Stefan
Anonymous
a b F Wireless
July 7, 2004 8:19:19 PM

Archived from groups: alt.internet.wireless (More info?)

"gary" <pleasenospam@sbcglobal.net> wrote in message
news:%TUGc.11795$C76.7901@newssvr24.news.prodigy.com...
> Ad-hoc networks can have as many stations as the bandwidth will support.
> These networks are called point-to-point to distinguish them from the
usual
> infrastructure network, which is a hub. The difference is that, in ad-hoc,
> each station transmits directly to the receiver - therefore
point-to-point,
> although the receiver could be any station in the net - while in the
> infrastructure (hub) network, all stations transmit to the AP, which
> retransmits to the receiver.

Interesting. Thanks for the helpful answer!

One more thing confuses me. If A and B are in range, and B and C are in
range, but A is not in range of C, will A and C automatically use B as a
relay point? Or is ad-hoc limited to direct connections with no hops?

Thanks again!
Bruce.
Anonymous
a b F Wireless
July 7, 2004 8:19:20 PM

Archived from groups: alt.internet.wireless (More info?)

On Wed, 07 Jul 2004 16:19:19 GMT, "Bruce Chastain"
<bchastain@XNOSPAMXhyperfeed.com> wrote:

>One more thing confuses me. If A and B are in range, and B and C are in
>range, but A is not in range of C, will A and C automatically use B as a
>relay point? Or is ad-hoc limited to direct connections with no hops?

Direct only. B cannot be used as a repeater to get from A to C.
There's also no access point to use as a client to client repeater.
Clients that can't see each other can't communicate.

You can setup a dedicated repeater to extend the range and coverage
for peer to peer, but it will need to be configured with all the MAC
addresses involved, which could grow quite large. Store-n-forward
will also cut your thruput in half. There are also some client radios
that can act as repeaters, which are the basis of a mesh network.

Peer-to-peer also has some collision issues as there is no access
point to arbitrate transmission times with flow control packets.

Incidentally, 802.11g does NOT officially support peer-to-peer
communications at the faster speed and is limited to 802.11b speeds
for peer-to-peer.


--
Jeff Liebermann jeffl@comix.santa-cruz.ca.us
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 AE6KS 831-336-2558
July 7, 2004 8:26:17 PM

Archived from groups: alt.internet.wireless (More info?)

Yes, an infrastructure network cuts station-station throughput in half. It's
half-duplex - the same antenna can't be used to transmit and receive
concurrently.

"Stefan Monnier" <monnier@iro.umontreal.ca> wrote in message
news:jwvn02bn725.fsf-monnier+alt.internet.wireless@gnu.org...
> > Ad-hoc networks can have as many stations as the bandwidth will support.
> > These networks are called point-to-point to distinguish them from the
usual
> > infrastructure network, which is a hub. The difference is that, in
ad-hoc,
> > each station transmits directly to the receiver - therefore
point-to-point,
> > although the receiver could be any station in the net - while in the
> > infrastructure (hub) network, all stations transmit to the AP, which
> > retransmits to the receiver.
>
> Does that mean that in infrastructure mode, an 11Mb/s link can only
> transfer a maximum of about 500KB/s between two nodes (vs 1MB/s between
> the hub and any other node) ?
>
>
> Stefan
Anonymous
a b F Wireless
July 7, 2004 8:52:28 PM

Archived from groups: alt.internet.wireless (More info?)

In an ad-hoc network, all stations are supposed to be within range of every
other station. This differs from an infrastructure network, in which all
stations must be within range of the access point, but not each other.

Ron Bandes, CCNP, CTT+, etc.

"gary" <pleasenospam@sbcglobal.net> wrote in message
news:%TUGc.11795$C76.7901@newssvr24.news.prodigy.com...
> Ad-hoc networks can have as many stations as the bandwidth will support.
> These networks are called point-to-point to distinguish them from the
usual
> infrastructure network, which is a hub. The difference is that, in ad-hoc,
> each station transmits directly to the receiver - therefore
point-to-point,
> although the receiver could be any station in the net - while in the
> infrastructure (hub) network, all stations transmit to the AP, which
> retransmits to the receiver.
>
> "Bruce Chastain" <bchastain@XNOSPAMXhyperfeed.com> wrote in message
> news:uHTGc.5018$sD4.3113@newsread3.news.atl.earthlink.net...
> > I have a question about 802.11g ad-hoc mode. Everything I read refers
to
> > ad-hoc mode as point-to-point, implying that only 2 computers can be so
> > networked. But I've also seen diagrams implying that an ad-hoc network
> can
> > be expanded beyond 2 nodes (no AP), using more than 2 ad-hoc nodes.
> >
> > So what happens if there are 3 computers with a 802.11g ad-hoc, all
> > configured with the same SSID? Will all 3 be able to see and talk to
each
> > other without having to disconnect from one and connect with the other?
A
> > with B with C?
> >
> > Or is 3 computers (one adhoc device per computer) with the same ad-hoc
> SSID
> > (within range of each other and on the same channel) illegal?
> >
> > Thanks,
> > Bruce.
> >
> >
>
>
July 7, 2004 11:05:16 PM

Archived from groups: alt.internet.wireless,microsoft.public.windows.networking.wireless (More info?)

On Wed, 07 Jul 2004 14:23:22 GMT, "Bruce Chastain"
<bchastain@XNOSPAMXhyperfeed.com> wrote:

>I have a question about 802.11g ad-hoc mode. Everything I read refers to
>ad-hoc mode as point-to-point, implying that only 2 computers can be so
>networked. But I've also seen diagrams implying that an ad-hoc network can
>be expanded beyond 2 nodes (no AP), using more than 2 ad-hoc nodes.
>
>So what happens if there are 3 computers with a 802.11g ad-hoc, all
>configured with the same SSID? Will all 3 be able to see and talk to each
>other without having to disconnect from one and connect with the other? A
>with B with C?
>
>Or is 3 computers (one adhoc device per computer) with the same ad-hoc SSID
>(within range of each other and on the same channel) illegal?
>
>Thanks,
>Bruce.

Bruce,

You can indeed have more than two computers on a peer-to-peer (ad hoc) wireless
network. But remember, all computers must share the same channel, so with more
computers connected, the throughput drops for each. Worse yet, channel
throughput drops as the chances of collisions (two computers transmitting
simultaneously) increases.

All computers will have to have the same SSID, which you manually configure,
along with channel number.

And try to make sure all computers can see each other. A hidden node situation
(where computer A sees computers B and C, but B and C can't see each other) will
increase the probability of collisions even more.

It is point-to-point, just with more than two it becomes
multipoint-to-multipoint.

<http://www.microsoft.com/technet/prodtechnol/winxppro/m...;

Cheers,
Chuck
Paranoia comes from experience - and is not necessarily a bad thing.
July 7, 2004 11:17:03 PM

Archived from groups: alt.internet.wireless (More info?)

"Jeff Liebermann" <jeffl@comix.santa-cruz.ca.us> wrote in message
news:19aoe0l4qc53qhareu0n8ge4qc748d37ko@4ax.com...
> On Wed, 07 Jul 2004 16:19:19 GMT, "Bruce Chastain"
> <bchastain@XNOSPAMXhyperfeed.com> wrote:
>
> >One more thing confuses me. If A and B are in range, and B and C are in
> >range, but A is not in range of C, will A and C automatically use B as a
> >relay point? Or is ad-hoc limited to direct connections with no hops?
>
> Direct only. B cannot be used as a repeater to get from A to C.
> There's also no access point to use as a client to client repeater.
> Clients that can't see each other can't communicate.
>
> You can setup a dedicated repeater to extend the range and coverage
> for peer to peer, but it will need to be configured with all the MAC
> addresses involved, which could grow quite large. Store-n-forward
> will also cut your thruput in half. There are also some client radios
> that can act as repeaters, which are the basis of a mesh network.
>
> Peer-to-peer also has some collision issues as there is no access
> point to arbitrate transmission times with flow control packets.
>
> Incidentally, 802.11g does NOT officially support peer-to-peer
> communications at the faster speed and is limited to 802.11b speeds
> for peer-to-peer.

Actually, I can't find support anywhere in the 802.11g standard for this
claim. It is true that many, if not most, vendors limit ad-hoc to 802.11b
mode, and the reason is understandable. An ad-hoc network cannot be hybrid.
If you have an ad-hoc net of all "g" devices, and a "b" device tries to
join, all clients must detect this and switch to 802.11b mode. This would be
complex and expensive to do correctly, although it's fairly easy for an AP
to do it in an infrastructure setting.

As I read the standard, it simply does not require clients to support ERP in
ad-hoc - it doesn't prohibit it. In fact clause 7 devotes a lot of time to
describing how to handle non-ERP stations joining an all-ERP IBSS. See
7.3.2.13, for example, about setting the nonERP_Present bit in an IBSS when
a beacon from a non-ERP station is received.

>
>
> --
> Jeff Liebermann jeffl@comix.santa-cruz.ca.us
> 150 Felker St #D http://www.LearnByDestroying.com
> Santa Cruz CA 95060 AE6KS 831-336-2558
Anonymous
a b F Wireless
July 7, 2004 11:22:31 PM

Archived from groups: alt.internet.wireless (More info?)

"Jeff Liebermann" <jeffl@comix.santa-cruz.ca.us> wrote in message
news:19aoe0l4qc53qhareu0n8ge4qc748d37ko@4ax.com...
> Direct only. B cannot be used as a repeater to get from A to C.
> There's also no access point to use as a client to client repeater.
> Clients that can't see each other can't communicate.

Thanks for the info!

> Incidentally, 802.11g does NOT officially support peer-to-peer
> communications at the faster speed and is limited to 802.11b speeds
> for peer-to-peer.

Thanks. That clears up another question I had!

Bruce.
Anonymous
a b F Wireless
July 8, 2004 10:02:42 AM

Archived from groups: alt.internet.wireless (More info?)

On Wed, 07 Jul 2004 19:17:03 GMT, "gary" <pleasenospam@sbcglobal.net>
wrote:

>"Jeff Liebermann" <jeffl@comix.santa-cruz.ca.us> wrote in message
>news:19aoe0l4qc53qhareu0n8ge4qc748d37ko@4ax.com...

>> Incidentally, 802.11g does NOT officially support peer-to-peer
>> communications at the faster speed and is limited to 802.11b speeds
>> for peer-to-peer.

>Actually, I can't find support anywhere in the 802.11g standard for this
>claim. It is true that many, if not most, vendors limit ad-hoc to 802.11b
>mode, and the reason is understandable. An ad-hoc network cannot be hybrid.
>If you have an ad-hoc net of all "g" devices, and a "b" device tries to
>join, all clients must detect this and switch to 802.11b mode. This would be
>complex and expensive to do correctly, although it's fairly easy for an AP
>to do it in an infrastructure setting.

Would this notice by DLink help?

http://support.dlink.com/faq/view.asp?prod_id=1482&ques...
"D-Link wireless products follow the IEEE 802.11 standards. The
802.11b and 802.11g standards specify that Ad-Hoc mode only needs to
support up to 11Mbps. For best results, use an access point or
wireless router and set your adapters to Infrastructure (station)
mode."

I'll dig through the 802.11g addendum and see if I can find anything
on the topic.

>As I read the standard, it simply does not require clients to support ERP in
>ad-hoc - it doesn't prohibit it. In fact clause 7 devotes a lot of time to
>describing how to handle non-ERP stations joining an all-ERP IBSS. See
>7.3.2.13, for example, about setting the nonERP_Present bit in an IBSS when
>a beacon from a non-ERP station is received.

I'll reserve comment until I've re-read it and when I've gotten 8.0
hrs of sleep.


--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831.336.2558 voice http://www.LearnByDestroying.com
# jeffl@comix.santa-cruz.ca.us
# 831.421.6491 digital_pager jeffl@cruzio.com AE6KS
Anonymous
a b F Wireless
July 8, 2004 7:02:15 PM

Archived from groups: alt.internet.wireless,microsoft.public.windows.networking.wireless (More info?)

"Chuck" <none@example.net> wrote in message
news:p b3pe09mncr1k442r9gu7o99ibq61qp2k4@4ax.com...
> You can indeed have more than two computers on a peer-to-peer (ad hoc)
wireless
> network. But remember, all computers must share the same channel, so with
more
> computers connected, the throughput drops for each. Worse yet, channel
> throughput drops as the chances of collisions (two computers transmitting
> simultaneously) increases.

Thanks for the help Chuck, and the informative link!

Bruce.
July 8, 2004 8:06:59 PM

Archived from groups: alt.internet.wireless (More info?)

"Jeff Liebermann" <jeffl@comix.santa-cruz.ca.us> wrote in message
news:lkope0disbb61fup7c418qd9aer978vcch@4ax.com...
> On Wed, 07 Jul 2004 19:17:03 GMT, "gary" <pleasenospam@sbcglobal.net>
> wrote:
>
> >"Jeff Liebermann" <jeffl@comix.santa-cruz.ca.us> wrote in message
> >news:19aoe0l4qc53qhareu0n8ge4qc748d37ko@4ax.com...
>
> >> Incidentally, 802.11g does NOT officially support peer-to-peer
> >> communications at the faster speed and is limited to 802.11b speeds
> >> for peer-to-peer.
>
> >Actually, I can't find support anywhere in the 802.11g standard for this
> >claim. It is true that many, if not most, vendors limit ad-hoc to 802.11b
> >mode, and the reason is understandable. An ad-hoc network cannot be
hybrid.
> >If you have an ad-hoc net of all "g" devices, and a "b" device tries to
> >join, all clients must detect this and switch to 802.11b mode. This would
be
> >complex and expensive to do correctly, although it's fairly easy for an
AP
> >to do it in an infrastructure setting.
>
> Would this notice by DLink help?

It confirms what I thought. The standard fully supports ad-hoc for rates up
to 54 Mbps. D-Link is merely saying that they are not required to offer
speeds over 11 Mbps, which is common. Ad-hoc itself is optional. The only
reason I brought this up was that your comment suggested the standard
doesn't support it. From what I've read, some chipsets in fact support the
higher rates for ad-hoc, but the vendors choose not to use the
functionality. That doesn't mean the chipsets are not standard-compliant, or
that vendors couldn't change their minds in the future. For now, the
decision makes perfect sense. You don't really want a hybrid ad-hoc network.

>
>
http://support.dlink.com/faq/view.asp?prod_id=1482&ques...
> "D-Link wireless products follow the IEEE 802.11 standards. The
> 802.11b and 802.11g standards specify that Ad-Hoc mode only needs to
> support up to 11Mbps. For best results, use an access point or
> wireless router and set your adapters to Infrastructure (station)
> mode."
>
> I'll dig through the 802.11g addendum and see if I can find anything
> on the topic.
>
> >As I read the standard, it simply does not require clients to support ERP
in
> >ad-hoc - it doesn't prohibit it. In fact clause 7 devotes a lot of time
to
> >describing how to handle non-ERP stations joining an all-ERP IBSS. See
> >7.3.2.13, for example, about setting the nonERP_Present bit in an IBSS
when
> >a beacon from a non-ERP station is received.
>
> I'll reserve comment until I've re-read it and when I've gotten 8.0
> hrs of sleep.
>
>
> --
> # Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
> # 831.336.2558 voice http://www.LearnByDestroying.com
> # jeffl@comix.santa-cruz.ca.us
> # 831.421.6491 digital_pager jeffl@cruzio.com AE6KS
Anonymous
a b F Wireless
July 8, 2004 8:07:02 PM

Archived from groups: alt.internet.wireless,microsoft.public.windows.networking.wireless (More info?)

> You can indeed have more than two computers on a peer-to-peer (ad hoc)
> wireless network. But remember, all computers must share the same
> channel, so with more computers connected, the throughput drops for each.
> Worse yet, channel throughput drops as the chances of collisions (two
> computers transmitting simultaneously) increases.

> All computers will have to have the same SSID, which you manually configure,
> along with channel number.

But that applies to infrastructure mode just as well.

> And try to make sure all computers can see each other. A hidden node
> situation (where computer A sees computers B and C, but B and C can't see
> each other) will increase the probability of collisions even more.

It doesn't increase the probability of collision, but it creates the
possibility of undetected and unrepairable collisions.


Stefan
!