1. Attribute Protocol(ATT)
실시간 시스템 연구실
서재희

2. Contents
ATT
Attribute
Attribute Protocol
Methods

3. ATT Discovering attributes Reading the attributes
Bluetooth Radio (also called Physical Layer)
Link Layer
L2CAP
Attribute Protocol(ATT)
Generic Attribute Profile(GATT)
Generic Access Profile(GAP)
GATT Based Profiles
Security Manager(SM)
Host Controller Interface(HCI)
Discovering attributes
Reading the attributes
Writing the attributes
Client Server model
Attribute : data

4. Attribute Attribute Type Attribute Handle Access Permissions
Attribute Value
Attribute Structure
Attribute Handle(2 octets)
Attribute Type (2 octets or 16 octets)
Attribute Value (Fixed or Variable length)
Attribute Permissions (Established by GATT profile)

5. Attribute Type
Attribute Type is identified by a Universally Unique Identifier(UUID).
128bit : Bluetooth SIG has defined a single 128-bit UUID, called Bluetooth Base UUID
Ex) F9B34FB
16bit : In general.
128-bit UUID = 16-bit UUID * 2^96 + Bluetooth_Base_UUID
Ex) 0x2A01 => full 128-bit UUID : 00002A F9B34FB
Service UUIDs : 0x1800 ~ 0x26FF
Units : 0x2700 ~ 0x27FF
Attribute Types : 0x2800~0x28FF
Characteristic Descriptors : 0x2900~0x29FF
Characteristic Types : 0x2A00~0x2AFF

6. Attribute Handle
Attribute Handle is used by the client in all operations with the server to identify the attribute.
Unique
0x0000 is reserved, and shall not be used.
0xFFFF is known as the maximum.

7. Attribute Permissions
Each attribute has a set of permissions associated with it which determines the level of access that is permitted for that particular attribute.
Access Permissions : Readable, Writable, Readable and Writable
Authentication Permissions : clients to access attribute, server has to send notification or indication
Authorization Permissions : client needs to be authorized before accessing an attribute value
Error code is returned.
Read Not Permitted
Write Not Permitted
Insufficient Authentication
Insufficient Authorization
Insufficient Encryption Key Size
Insufficient Encryption

8. Attribute Value Fixed Length / Variable Length
ATT does not allow multiple attribute values to be transmitted in a single PDU. A PDU contains only one attribute value and if the attribute value is too long to transmit in a single PDU, it can be split across multiple PDUs.

9. The Others Control Point Attributes Grouping of Attribute Handles
Be written, notified, or indicated : control the behavior of a device
Grouping of Attribute Handles
The clients can request the first and the last handle associated with the group of attributes.
Read By Group Type
Atomic Operations
Multiple clients may be connected to a server.
The server treats each operation from the client as an atomic operation which is not impacted by any other client initiating an operation at the same time.
Prepare Write Request, Execute Write Request

10. Attribute Protocol Role : Attribute Server, Attribute Client Request
Response
Client
Server
Indication
Confirmation
Client
Server
Command
Client
Server
Notification

11. PDU(Protocol Data Unit) Format
Security
Opcode
(1 octect)
Attribute Parameters
(Variable Length)
Authentication signature
(Optioanl – 12 octets)
Method
(6-bit)
Command Flag
(1-bit)
Auth Signature Flag

12. Methods : Request and Response Type
Message
Request Parameters
Response Parameters
Error
Opcode in Error, Handle in Error, Error Code
Exchange MTU
Client Rx MTU
Server Rx MTU
Find Information
Starting Handle, Ending Handle
(Handle, Type)
Find By Type Value
Starting Handle, Ending Handle, Type, Value
(Found Handle, End Group Handle)
Read By Type
Starting Handle, Ending Handle, Type
Length, (Handle, Value)
Read
Handle
Value
Read Blob
Handle, Offset
Part Value
Read Multiple
(Handle)*
(Value)
Read By Group Type
Starting Handle, Ending Handle, Group Type
(Handle, End Group Handle, Value)
Write
Handle, Value -
Prepare Write
Execute Write
Flags

13. Methods : Command Type PDU Command Parameters Write Command
Handle, Value
Signed Write Command
Handle, Value, Authentication Signature

14. Methods : Notification Type
PDU
Notification Parameters
Handle Value Notification
Handle, Value

15. Methods : Indication and Confirmation Type
PDU
Indication Parameters
Confirmation Parameters
Handle Value Indication
Handle, Value

16. Bluetooth Analyze : BPA600
CC2540
Type, Value
Message
Request Parameters
Response Parameters
Error
Opcode in Error, Handle in Error, Error Code
Find By Type Value
Starting Handle, Ending Handle, Type, Value
(Found Handle, End Group Handle)
Read By Type
Starting Handle, Ending Handle, Type
Length, (Handle, Value)
Read
Handle
Value
Write
Handle, Value -

17. Bluetooth Analyze : BPA600 (Cont.)
Read, Write
Write Command
Handle Value Notification
Handle Value Indication