Editing Bluetooth (section)

=== Bluetooth protocol stack ===
{{Main|List of Bluetooth protocols}}
[[File:Bluetooth protokoly.svg|thumb|250px|right|Bluetooth protocol stack]]

Bluetooth is defined as a layer protocol architecture consisting of core protocols, cable replacement protocols, telephony control protocols, and adopted protocols.<ref name="autogenerated2">{{cite book|last=Stallings|first=William|year=2005|title=Wireless communications & networks|location=Upper Saddle River, NJ|publisher=Pearson Prentice Hall|isbn=9788132231561}}</ref> Mandatory protocols for all Bluetooth stacks are LMP, L2CAP and SDP. In addition, devices that communicate with Bluetooth almost universally can use these protocols: [[Bluetooth protocols#Host Controller Interface (HCI)|HCI]] and RFCOMM.{{citation needed|date=November 2023}}

==== Link Manager ====
The Link Manager (LM) is the system that manages establishing the connection between devices. It is responsible for the establishment, authentication and configuration of the link. The Link Manager locates other managers and communicates with them via the management protocol of the LMP link. To perform its function as a service provider, the LM uses the services included in the Link Controller (LC).
The Link Manager Protocol basically consists of several PDUs (Protocol Data Units) that are sent from one device to another. The following is a list of supported services:
* Transmission and reception of data.
* Name request
* Request of the link addresses.
* Establishment of the connection.
* Authentication.
* Negotiation of link mode and connection establishment.

==== Host Controller Interface ====
The Host Controller Interface provides a command interface between the controller and the host.

==== Logical Link Control and Adaptation Protocol ====
The ''Logical Link Control and Adaptation Protocol'' (L2CAP) is used to multiplex multiple logical connections between two devices using different higher level protocols.
Provides segmentation and reassembly of on-air packets.

In ''Basic'' mode, L2CAP provides packets with a payload configurable up to 64&nbsp;kB, with 672 bytes as the default [[Maximum transmission unit|MTU]], and 48 bytes as the minimum mandatory supported MTU.

In ''Retransmission and Flow Control'' modes, L2CAP can be configured either for isochronous data or reliable data per channel by performing retransmissions and CRC checks.

Bluetooth Core Specification Addendum 1 adds two additional L2CAP modes to the core specification. These modes effectively deprecate original Retransmission and Flow Control modes:
; Enhanced Retransmission Mode (ERTM): This mode is an improved version of the original retransmission mode. This mode provides a reliable L2CAP channel.
; Streaming Mode (SM): This is a very simple mode, with no retransmission or flow control. This mode provides an unreliable L2CAP channel.

Reliability in any of these modes is optionally and/or additionally guaranteed by the lower layer Bluetooth BDR/EDR air interface by configuring the number of retransmissions and flush timeout (time after which the radio flushes packets). In-order sequencing is guaranteed by the lower layer.

Only L2CAP channels configured in ERTM or SM may be operated over AMP logical links.

==== Service Discovery Protocol ====
The ''Service Discovery Protocol'' (SDP) allows a device to discover services offered by other devices, and their associated parameters. For example, when you use a mobile phone with a Bluetooth headset, the phone uses SDP to determine which [[Bluetooth profile]]s the headset can use (Headset Profile, Hands Free Profile (HFP), [[Advanced Audio Distribution Profile|Advanced Audio Distribution Profile (A2DP)]] etc.) and the protocol multiplexer settings needed for the phone to connect to the headset using each of them. Each service is identified by a [[Universally unique identifier]] (UUID), with official services (Bluetooth profiles) assigned a short form UUID (16 bits rather than the full 128).

==== Radio Frequency Communications ====
''Radio Frequency Communications'' (RFCOMM) is a cable replacement protocol used for generating a virtual serial data stream. RFCOMM provides for binary data transport and emulates [[EIA-232]] (formerly RS-232) control signals over the Bluetooth baseband layer, i.e., it is a serial port emulation.

RFCOMM provides a simple, reliable, data stream to the user, similar to TCP. It is used directly by many telephony related profiles as a carrier for AT commands, as well as being a transport layer for OBEX over Bluetooth.

Many Bluetooth applications use RFCOMM because of its widespread support and publicly available API on most operating systems. Additionally, applications that used a serial port to communicate can be quickly ported to use RFCOMM.

==== Bluetooth Network Encapsulation Protocol ====
The ''Bluetooth Network Encapsulation Protocol'' (BNEP) is used for transferring another protocol stack's data via an L2CAP channel.
Its main purpose is the transmission of IP packets in the Personal Area Networking Profile.
BNEP performs a similar function to [[Subnetwork Access Protocol|SNAP]] in Wireless LAN.

==== Audio/Video Control Transport Protocol ====
The ''Audio/Video Control Transport Protocol'' (AVCTP) is used by the remote control profile to transfer AV/C commands over an L2CAP channel. The music control buttons on a stereo headset use this protocol to control the music player.

==== Audio/Video Distribution Transport Protocol ====
The ''Audio/Video Distribution Transport Protocol'' (AVDTP) is used by the advanced audio distribution ([[A2DP]]) profile to stream music to stereo headsets over an [[List of Bluetooth protocols#Logical link control and adaptation protocol (L2CAP)|L2CAP]] channel intended for video distribution profile in the Bluetooth transmission.

==== Telephony Control Protocol ====
The ''Telephony Control Protocol{{nbsp}}– Binary'' (TCS BIN) is the bit-oriented protocol that defines the call control signaling for the establishment of voice and data calls between Bluetooth devices. Additionally, "TCS BIN defines mobility management procedures for handling groups of Bluetooth TCS devices."

TCS-BIN is only used by the cordless telephony profile, which failed to attract implementers. As such it is only of historical interest.

==== Adopted protocols ====
Adopted protocols are defined by other standards-making organizations and incorporated into Bluetooth's protocol stack, allowing Bluetooth to code protocols only when necessary. The adopted protocols include:
;[[Point-to-Point Protocol]] (PPP): Internet standard protocol for transporting [[IP datagram]]s over a point-to-point link.
;[[TCP/IP]]/UDP: Foundation Protocols for TCP/IP protocol suite
;[[OBject EXchange|Object Exchange Protocol]] (OBEX): Session-layer protocol for the exchange of objects, providing a model for object and operation representation
;[[Wireless Application Protocol|Wireless Application Environment/Wireless Application Protocol]] (WAE/WAP): WAE specifies an application framework for wireless devices and WAP is an open standard to provide mobile users access to telephony and information services.<ref name="autogenerated2" />