25.02.2013 Views

TCP/IP Tutorial and Technical Overview - IBM Redbooks

TCP/IP Tutorial and Technical Overview - IBM Redbooks

TCP/IP Tutorial and Technical Overview - IBM Redbooks

SHOW MORE
SHOW LESS

You also want an ePaper? Increase the reach of your titles

YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.

4. The initiator sends back an acknowledgement upon receiving the result<br />

message.<br />

The transaction is considered complete when the responder receives the<br />

acknowledgement. If no acknowledgement is received, the responder<br />

retransmits the result message. The transaction can be aborted at any time<br />

during the sequence of events. An additional illustration of a Class 2 transaction<br />

is in Figure 18-15 on page 692.<br />

Layer-to-layer communication<br />

Service primitives are used to control the transaction traffic between the layers of<br />

the client <strong>and</strong> server. These service primitives have a similar syntax as described<br />

for WSP:<br />

X - generic name. type (parameters)<br />

Where X designates the layer providing the service. For the transaction layer, it<br />

is TR. The primitive types <strong>and</strong> their abbreviations are the same as described for<br />

WDP (see Table 18-1 on page 674).<br />

There are three primitives for the service to the upper layer:<br />

TR-Invoke Initiates a new transaction.<br />

TR-Result Sends back a result of a previously initiated transaction.<br />

TR-Abort Aborts an existing transaction.<br />

Chapter 18. Wireless Application Protocol 681

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!