Various questions

Bluez-users Christoph Torens 3 participants 3 messages Oct 19, 2004 Bluetooth drivers

lore

Share & tools

lore

Christoph Torens

author

2004-10-19 01:08 UTC #0 lore raw

Hi BlueZ List,

I'm just very confused about quite a few things.

At first, I believed ACL stands for 'Asynchronous Connection Less' But I just read the BT_Core_v1_2 Specification that sais ACL is Asynchronous Connection Oriented (page 118 of 1200 / Architecture page 42 of 82) So, what is it? I have read books and internet articles that said ACL is connection less. Are they all wrong or am I totally messing up something?

PAN uses the bnep protocol layer. Is bnep based on rfcomm?
I think not, because I don't need to load rfcomm.o when using pand. But looking at the figure from
http://www.rvs.uni-bielefeld.de/~heiko/bluetooth/bluetooth.pdf
(page 6) you can get this idea. (From http://www.holtmann.org/linux/bluetooth/)
(There are some other sources, too)

What about the three error connection modes. Is it right that they are determined by packet type and so there is no way to turn it on / off ? (using pand for example / which paket types does pand use?) Because some papers speak about optionally error correction (ARQ)

Data rate:
Whats the data rate of a pand connection?
I measured a data rate of 60-65 kbyte/s one way
30-35 kbyte/s the other way.

The way I understand the Spec. (page 274 of 1200) that would be above the limits. 60 kbyte/s = 480 kbit/s is greater than the symmetric rate of 433 kbit/s but 30 kbyte/s = 180 kbit/s is greater any of the asymetric data rates.

Whats my failure?

Thanks for any clarity and de-confusion.

Signature · 13 lines

Regards,
Christoph Torens


-------------------------------------------------------
This SF.net email is sponsored by: IT Product Guide on ITManagersJournal
Use IT products in your business? Tell us what you think of them. Give us
Your Opinions, Get Free ThinkGeek Gift Certificates! Click to find out more
http://productguide.itmanagersjournal.com/guidepromo.tmpl
_______________________________________________
Bluez-users mailing list
[email protected]
https://lists.sourceforge.net/lists/listinfo/bluez-users

Peter Stephenson

2004-10-19 09:24 UTC #1 lore raw

Quoted 6 lines · Christoph Torens

At first, I believed ACL stands for 'Asynchronous Connection Less' But I just read the BT_Core_v1_2 Specification that sais ACL is Asynchronous Connection Oriented (page 118 of 1200 / Architecture page 42 of 82)
So, what is it? I have read books and internet articles that said ACL is connection less. Are they all wrong or am I totally messing up something?

It's "connection-less", but I never heard anybody use the full form. (It's a slightly odd meaning of "connection", since of course the devices are connected. It really means "without a reserved chunk of air time".)

Quoted 1 line

PAN uses the bnep protocol layer. Is bnep based on rfcomm?

No, it's straight on top of L2CAP.

Quoted 4 lines

What about the three error connection modes. Is it right that they are determined by packet type and so there is no way to turn it on / off ? (using pand for example / which paket types does pand use?) Because some papers speak about optionally error correction (ARQ)

I'm not quite sure what the question is, but I think you're asking if a higher level profile such as PAN is affected by the details of what goes over the air. The answer is no, the baseband will use such packets as it thinks are appropriate whatever ACL data it is transferring. It will, for example, pick packets with or without error correction (FEC, not ARQ; the ARQ scheme is mandatory for acknowledgements) depending on the quality of the radio link.

Quoted 4 lines

Data rate:
Whats the data rate of a pand connection?
I measured a data rate of 60-65 kbyte/s one way
30-35 kbyte/s the other way.

It will vary depending on the devices, the connection to the host, and the host stack. There's nothing in principle to stop you getting up to the full 721 kbps. The device will adapt to the presence of data in both directions, limiting you to 433 kbps if the channel is full both ways.

pws

**********************************************************************
This email and any files transmitted with it are confidential and intended solely for the use of the individual or entity to whom they are addressed. If you have received this email in error please notify the system manager.

This footnote also confirms that this email message has been swept by MIMEsweeper for the presence of computer viruses.

www.mimesweeper.com
**********************************************************************

-------------------------------------------------------
This SF.net email is sponsored by: IT Product Guide on ITManagersJournal Use IT products in your business? Tell us what you think of them. Give us Your Opinions, Get Free ThinkGeek Gift Certificates! Click to find out more
http://productguide.itmanagersjournal.com/guidepromo.tmpl
_______________________________________________
Bluez-users mailing list
[email protected]
https://lists.sourceforge.net/lists/listinfo/bluez-users

Marcel Holtmann

maintainer

2004-10-19 10:59 UTC #2 lore raw

In reply to Christoph Torens

Hi Christoph,

Quoted 7 lines

PAN uses the bnep protocol layer. Is bnep based on rfcomm? I think not, because I don't need to load rfcomm.o when using pand. But looking at the figure from
http://www.rvs.uni-bielefeld.de/~heiko/bluetooth/bluetooth.pdf
(page 6) you can get this idea. (From
http://www.holtmann.org/linux/bluetooth/)
(There are some other sources, too)

this graphic is wrong. The BNEP layer is on top of L2CAP and not on top of RFCOMM. Take a look at my slides from www.bluez.org/talks.html for a correct protocol stack overview.

Regards

Marcel