Bluetooth Logical Link Control and Adaptation Protocol (btl2cap)

BTL2CAP is a protocol that sits directly ontop of BTHCI_ACL and which prodives signalling and sessions between applications on two Bluetooth devices.

Protocol dependencies

Some protocols implemented ontop of BTL2CAP are. These protocols are called "profiles"

Example traffic

No.     Time        Source                Destination           Protocol Info
     77 146.955458                                              SDP      Rcvd SDP_ServiceSearchAttributeRequest

Frame 77 (13 bytes on wire, 13 bytes captured)
Bluetooth HCI H4 Rcvd ACL Data
Bluetooth HCI ACL Packet
    .... 0000 0010 1010 = Connection Handle: 0x002a
    ..01 .... .... .... = PB Flag: Continuing Fragment (1)
    00.. .... .... .... = BC Flag: Point-To-Point (0)
    Data Total Length: 8
    This is a continuation to the PDU in frame: 76
Bluetooth L2CAP Packet
    Length: 21
    CID: 0x0040
    PSM: SDP (0x0001)
Bluetooth SDP: SDP_ServiceSearchAttributeRequest (0x6)
    PDU: SDP_ServiceSearchAttributeRequest (0x06)
    TransactionID: 0x0001
    ParameterLength: 16
    ServiceSearchPattern UUID:Headset (0x1108)
        Headset(0x1108)
    MaximumAttributeByteCount: 672
    AttributeIDList
        0x0000 - 0xffff
    ContinuationState

Wireshark

The BTL2CAP dissector is fully functional and supports fragment reassembly through the BTHCI_ACL layer.

Preference Settings

There are no preference settings for BTL2CAP.

Example capture file

Display Filter

A complete list of BTL2CAP display filter fields can be found in the display filter reference

Capture Filter

You cannot directly filter BTL2CAP protocols during capturing since captureing is not yet possible.

See Bluetooth for example captures and links.

Discussion

BTL2CAP (last edited 2008-04-12 17:51:49 by localhost)