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The Dial-up Networking profile defines the
requirements for Bluetooth devices necessary to support the Dial-up
networking use case. Essentially the Headset profile defines the protocols
and procedures that shall be used by devices implementing the usage model
called ‘Internet Bridge'. The most common examples of such devices are
modems and cellular phones.
Two main scenarios are implemented: the Usage of a
cellular phone or modem by a computer as a wireless modem for connecting
to a dial-up internet access server, or using other dial-up services , and
Usage of a cellular phone or modem by a computer to receive data calls
For more details : Download the K7
Specification from the SIG website, or visit the Documents
Page.
The figure below shows the protocols and entities
used in this profile.
*Diagram Source: Courtesy of Bluetooth SIG, K7 Profile,
Figure 2.1 , p 226
The Baseband, LMP and L2CAP are the OSI layer 1 and
2 Bluetooth protocols. RFCOMM is the Bluetooth adaptation of GSM TS 07.10,
used for providing serial port emulation. SDP is the Bluetooth Service
Discovery Protocol. Dialling and control is the commands and procedures
used for automatic dialling and control over the asynchronous serial link
provided by the lower layers.
The modem emulation layer shown above is the entity
emulating the modem, and the modem driver is the driver software in the
data terminal.
For the shaded protocols/entities shown above, the Serial
Port Profile is used as base standard. For these protocols, all
requirements stated in the Serial Port Profile apply except in those cases
where this profile explicitly states deviations.
Two roles are defined for Bluetooth devices in this
profile, Gateway (GW) and Data Terminal (DT):
- Gateway (GW) – This is the device that provides access to
the public network. Typical devices acting as gateways are cellular
phones and modems
- Data Terminal (DT) – This is the device that uses the
dial-up services of the gateway. Typical devices acting as data
terminals are laptops and desktop PCs.
In the rest of this document, these terms are only
used to designate these roles.
For purposes of mapping the Dial-up Networking
profile to the conventional modem system architecture, the GW is
considered Data Circuit Endpoint (DCE), and the DT is considered Data
Terminal Endpoint (DTE).
The scenarios covered by this profile are the following:
- Usage of a GW by a DT as a wireless modem for connecting to a
dial-up internet access server or using other dial-up services
- Usage of a GW by a DT to receive data calls
The following restrictions apply to this profile:
- The modem is not required to be able to report and/or discriminate
between different call types for incoming calls.
- This profile requires support for one-slot packets only. This means
that this profile ensures that data rates up to 128 Kbps can be used.
Support for higher rates are optional.
- Only one call at a time is supported.
- The profile only supports point-to-point configurations.
- There is no way defined in this profile to discriminate between two
SCO channels originating from the same device. It is therefore
manufacturer-specific as to how to deal with the situation where there
are multiple applications requiring the use of multiple SCO channels
originating from the same device.
- Before a cellphone or modem can be used with a PC/Laptop for the
first time, an initialization procedure must be performed. This
typically involves manually activating initialization support, and
entering a PIN code on the PC/Laptop keyboard. This procedure may have
to be repeated under certain circumstances.
- This profile does not support multiple instances of its
implementation in the same device.
Security is ensured by authenticating the other
party upon connection establishment, and by encrypting all user data. The
baseband and LMP mechanisms for authentication and encryption are used.
Before a DT can use the services of a GW for the
first time, the two devices have to initialise. Initialization includes
exchanging a PIN code, creation of link keys and service discovery.
A link has to be established before calls can be
initiated or received. This requires paging of the other device. Link
establishment is always initiated by the DT.
There are no fixed master/slave roles.
The GW and DT provide serial port emulation. For the
serial port emulation, the serial port profile is
used. The serial port emulation is used to transport the user data, modem
control signals and AT commands between the GW and the DT. AT-commands are
parsed by the GW and responses are sent to the DT.
An SCO link is used to transport audio.For security
purposes, authentication is used, and all user data is encrypted. For
this, the baseband/LMP mechanisms are used.
Support for Data call without audio feedback
is mandatory for both the DT and GW. Support for Data call with audio
feedback is optional for both DT and GW. Support for Fax services
without audio feedback, Fax services with audio feedback and
Voice call is not available.
The support of data calls is mandatory for both GWs
and DTs. Optionally, audio feedback may be provided.
The GW shall emulate a modem connected via a serial
port. The Serial Port Profile is used for RS-232 emulation, and a modem
emulation entity running on top of the serial port profile provides the
modem emulation.
The support of fax is not covered by this profile
(see Fax Profile), nor is the support of voice
calls covered by this profile (see Cordless Telephony
Profile).
To guarantee that basic functionality can always be
provided, it is required that a GW device supports the commands and
responses as defined in the supported fax class of service(s):
- Fax Class 1
TIA-578-A and ITU T.31
- Fax Class 2.0
TIA-592 and ITU T.32
- Fax Service Class 2
No industry standard exists
(manufacturer specific).
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- Command syntax, Protocols and Result Codes: Refer to each
specific implemented fax service class document for a description of
the required commands, protocols and result codes.
- Fax Service Class selection procedure: This profile does not
require a specific service class of fax. This profile supports 2
standards-based fax ‘classes’ – fax class 1 and fax class
2., 0 and a third manufacturer-specific pseudo-standard, fax class 2
(no industry reference standard exists).
The DT shall check the GW SDP or perform an ‘AT+FCLASS"
command to discover the fax class of service(s) supported by the
GW.Bluetooth devices implementing this profile must support a minimum of
one fax service class, but may support any or all fax services classes.
The GW or DT may optionally be able to provide audio
feedback during call establishment. This clause applies only to
gateways/data terminals that are able to provide audio feedback.
SCO links are used to transport the digitized audio
over the Bluetooth link. The GW shall take all initiatives for SCO link
establishment. The setting of the M parameter controls whether the GW
provides audio feedback.
If a GW provides audio feedback for a call, the GW
shall use the ‘initiate SCO link’ procedure (see Link
Manager protocol) to establish the audio link when the DCE goes
off-hook.
Depending on the setting of the M parameter, the GW
releases the audio link when the DCE has detected a carrier or when the
DCE goes on-hook. The ‘remove SCO link’ procedure (see Link
Manager protocol) shall be used for audio link release.
If SCO link establishment fails, the call
establishment shall proceed without the audio feedback.
This profile assumes that the DT is not active in
any other profile that uses SCO links while it is operating in the Fax
profile. Therefore, behaviour is not defined for a situation where
multiple SCO links are established simultaneously.
This profile requires compliance with the Serial
Port Profile. For the purposes of reading the Serial Port Profile, the
GW shall always be considered to be Device B and the DT shall always be
considered to be Device A.
- For the RFCOMM & L2CAP layer, no additions to the requirements
as stated in the Serial Port Profile shall apply
- For the SDP layer, a number of service records are defined for the
gateway and the data terminal respectively. They can be found on page
256 of the Dial-up Networking Profile
- In addition to the requirements for the Link Manager as stated in
the Serial
Port Profile , Section 5.6, this profile mandates support for SCO
links, in both the GW and DT. The support is conditional upon the
ability to provide audio feedback.
This profile requires compliance with the Generic
Access Profile
Note , the above text contains excerpts from the Bluetooth
SIG's Specification, as well as various interpretations of the Specs. For
complete details of the various sections, consult the actual Bluetooth
Specification.
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