Image Processing Reference
In-Depth Information
Local service user
Remote service user
1
3
2
(N)_service.req
(N)_service.con
(N)_service.ind
Local layer N
Remote layer N
(N - 1)_service.req
(N - 1)_service.con
(N - 1)_service.ind
Local service provider
Remote service provider
FIGURE .
Locally confirmed service.
.
Locally confirmed service
. A locally confirmed service (Figure .) comprises a request,
an indication, and a confirmation. In this case, layer N of the sender then receives a
confirmation from local layer N
. Based on the parameters transmitted, the service
provider can tell whether its underlying layer was able to accept and process the request
accordingly. After a brief preprocessing, this local confirmation is also made known to
the service user by means of a confirmation service primitive. As the name suggests, a
locally confirmed service gives no guarantee that the remote user receives the informa-
tion transmitted. he confirmation can be omitted at all, which leads to an unconfirmed
service.
.
Confirmed service
. This type of service also consists of a request, an indication and a
confirmation. With a confirmed service, however, the peer layer generates an acknowl-
edgment immediately after receiving the indication (Figure .). .).The acknowledgment is
returned to the sender via a service primitive of the remote layer N
−
−
andsignaledtothe
service provider via an indication of local layer N
. Note that contrary to the procedure
outlined in point above, the transmitted parameters and data come from the partner
−
Local service user
Remote service user
4
2
1
(N)_service.req
(N)_service.con
(N)_service.ind
Local layer N
Remote layer N
3
(N - 1)_service.req
(N - 1)_service.ind
(N - 1)_service.req
(N - 1)_service.ind
Local service provider
Remote service provider
FIGURE .
Confirmed service.
