Irlmp; Link Management-Information Access Service (Lm-Ias) - DCA Intertel s’print BT User Manual

types of frames and is also used to count frames. Frames can carry status,
data, or commands. The IrLAP protocol has a command syntax of it's own,
and these commands are part of the control byte. Lastly, IrLAP frames carry
data. This data is the information or "I" field. The integrity of the frame is
ensured with a 16-bit CRC, referred to as the Frame Check Sequence
(FCS). The end of the frame is marked with an EOF character which is
always a 0xC1. The frame structure described here is used for all versions
of IrDA protocols used for serial wire replacement for speeds up to 38400
baud.
In addition to defining the frame structure, IrLAP provides the
"housekeeping" function of opening and closing connections, and
maintaining connections once they' re open. The critical parameters that
determine the performance of the link are part of this function.
These parameters control how many BOFs are used, identify the speed of
the link, how fast either party may change from receiving to transmitting, etc.
IrLAP has the responsbility of negotiating these parameters to the highest
common set so that both sides can communicate as fast and as reliably as
possible.

2.3.1.3 IrLMP

The IrLMP protocol provides:
• Multiplexing of the IrLAP layer. This allows multiple channels above an
IrLAP connection.
• Protocol and service discovery. This is via the Information Access
Service (IAS).
When two devices that contain the IrDA standard feature are connected,
there is generally one device that has something to do, and the oder device
has the resource to do it. For example, a laptop may have a job to print and
an IrDA standard compatible printer has the resources to print it. In IrDA
standard terminology, the laptop is a Primary device and the printer is the
Secondary device. When these two devices connect, the Primary device
must determine the capabilities of the Secondary device to determine if the
Secondary device is capable of doing the job. This determination is made by
the Primary device asking the Secondary device a series of questions.
Depending on the answers to these questions the Primary device may or
may not elect to connect to the Secondary device.
The queries from the Primary device are carried to the Secondary device
using IrLMP. The responses to these queries can be found in the
Information Access Service (IAS) of the Secondary device.
The IAS is a list of the resources of the Secondary device. The Primary
device compares the IAS responses with its requirements and then makes
the decision if a connection should be made.

2.3.1.4 Link Management-Information Access Service (LM-IAS)

Each LM-IAS entity maintains an information data base to provide:
• Information on service for other devices that contain the IrDA standard
feature (Discovery)
• Information on service for the device itself
• Remote accessing of another device's information base
This is required so that clients on a remote device can find configuration
information needed to access a service.
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