Hardware Reference
In-Depth Information
Execute Write Request/Response
Execute all pending queued write operations, the server then reports the success
or failure to the client.
Server Initiated
Used by the server to asynchronously
push
attribute values to the client, they in‐
clude:
Handle Value Indication/Confirmation
Asynchronous server update of an attribute's value and identified by its handle,
expects an acknowledgement in the form of a confirmation from the client.
Handle Value Notification
Asynchronous server update of an attribute's value and identified by its handle,
without acknowledgment. This operation does not follow the request/response
sequencing and can be sent at any time.
All operations except the ones in the
server initiated
category (and a few select others)
are grouped into request/response pairs. Requests are always sent by the client and
responses are issued by the server as a reply to a request.
Chapter 4
provides more information on ATT itself and how it enables the Generic
Attribute Profile (GATT).
Security Manager (SM)
The Security Manager (SM) is both a protocol and a series of security algorithms de‐
signed to provide the Bluetooth protocol stack with the ability to generate and exchange
security keys, which then allow the peers to communicate securely over an encrypted
link, to trust the identity of the remote device, and finally, to hide the public Bluetooth
Address if required to avoid malicious peers tracking a particular device.
The Security Manager defines two roles:
Initiator
Always corresponds to the Link Layer master and therefore the GAP central.
Responder
Always corresponds to the Link Layer slave and therefore the GAP peripheral.
Although it is always up to the initiator to trigger the beginning of a procedure, the
responder can asynchronously request the start of any of the procedures listed in
“Se‐
curity Procedures”
. There are no guarantees for the responder that the initiator will
actually heed the request, serving more as a hint than a real, binding request. This
security request
can logically be issued only by the slave or peripheral end of the con‐
nection.
