Hello All,
While Phillip's answer is
correct, I'd say it's not optimal.
The SAP should group together
all the primitives that are required
for one instance of a
particular entity to provide services to an instance
of another entity.
If each entity is providing
services to the other, I'd respectfully
suggest that two SAPs should
be provided. This should make the
description of the purpose of
the SAP clearer.
Also, architecturally, it
also makes it possible to reroute the
communications, e.g. to
insert a new
entity that relates to just
one SAP and has no effect on the other
such as a new
fragmentation/reassembly sublayer.
Best Regards,
Adrian
My quick answer is 'Yes'.
The SAP is just a focal point
for communications in the model.
While for any specific message
exchange through a SAP the roles of the participants are set, the roles
of the participants may change from message exchange-to-message
exchange. In one exchange the MS may be a service user. In another
exchange the MS may be a service provider.
Thanks,
Phillip Barber
Chief Scientist
Broadband Wireless Solutions
Huawei Technologies Co., LTD.
----- Original Message -----
Sent:
Sunday, September 03, 2006 8:31 PM
Subject:
Re: [802.21] SAP semantics
Phil, as the 802.16g SAP expert, what is your take on the following?
Can an entity (MIHF 802.21 in this case) that provides services through a SAP (MIH_SAP)
also obtain services (transport and delivery of commands to a remote MIHF)
through the same SAP?
Andrea wrote: I always thought that at the two ends of a SAP the roles of service user and
service provider are fixed. Is this not the case? Can the same entity (the MIHF
in our case) be at the same time a service provider and a service user with
respect to the same SAP?
Peretz Feder
On 9/3/2006 12:56 AM, Andrea Francini wrote:
Hello Everyone,
I have a very basic question from reading the latest 802.21 draft
(P802-21-D01-09):
In section 5.6 (page 29, line 34 through 40) I find the following statement:
"The MIH_SAP and associated primitives provide the interface from MIHF to the
upper layers of the mobility-management stack. Upper layers need to register
with MIHF as users to receive MIHF generated events and also for link layer
events that originate at layers below the MIHF but may be passed on to upper
layers through MIHF. Upper layers may directly send commands to MIHF. Similarly
MIHF entity may also send commands to another remote (peer) MIHF entity.
Primitives corresponding to all these services described above are within the
scope of MIH_SAP."
The statement indicates that MIHF provides services to a number of upper layers
(MIH users) through the MIH_SAP. Then the statement also seems to indicate (the
wording is not totally explicit) that MIHF can use MIH_SAP to send commands to a
remote MIHF entity.
My question is about the general SAP semantics:
Can an entity (MIHF in this case) that provides services through a SAP (MIH_SAP)
also obtain services (transport and delivery of commands to a remote MIHF)
through the same SAP?
I always thought that at the two ends of a SAP the roles of service user and
service provider are fixed. Is this not the case? Can the same entity (the MIHF
in our case) be at the same time a service provider and a service user with
respect to the same SAP?
Thanks a lot,
Andrea