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<concept id="GUID-BAFF62FA-55D9-5CEE-8747-FF4E4BEC4042" xml:lang="en"><title>PPP
Compression Plugins Overview</title><shortdesc>This topic describes the Point-to-Point Protocol (PPP) Compression
Plugins collection. </shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>
<section id="GUID-D4738F9B-3C83-47A8-A4E2-042E75A55457"><title>Purpose</title> <p>This collection contains the three compression
control protocols available for use with the <xref href="GUID-602026AB-ABD6-5937-A8FB-EFB21EBEEEC3.dita">Point-to-Point
Protocol</xref> component. </p> </section>
<section id="GUID-1A342A77-AA6C-44C1-893A-E42E103B9B04"><title>Architecture</title> <p>After a Point-to-Point Protocol link
has been established, optional facilities such as data compression may be
negotiated. Compression is used over a point-to-point link to increase throughput.
Increasing the throughput is important when low bandwidth transport media
is used. An example of low bandwidth transport media is GSM data at 9.6kbit/s. </p> <p>The
Point-to-Point Protocol includes the Compression Control Protocol (CCP) to
handle the negotiation of the compression on the link. The Compression Control
Protocol is defined by RFC1962. </p> <p>The interface between the Symbian
platform implementation of PPP and the compression plugins is not published.
New compression plugins cannot be created. </p> <p>Plugins are loaded when
a <i>config request</i> packet is received which requests the plugin as part
of the Compression Control Protocol. Each direction on the link can have zero
or one plugins loaded. A different plugin can be used in each direction. </p> <p>The
plugins are configured in the <filepath>ccp.ini</filepath> file. The Point-to-Point
Protocol component reads the <filepath>ccp.ini</filepath> file on startup
and checks that the plugins exist. The Point-to-Point Protocol component does
not load the plugins on startup. </p> </section>
<section id="GUID-63A9C70B-380A-4296-9730-AECFB830D1EE"><title>Components</title> <p>Symbian platform provides three compression
plugins for use with the Point-to-Point Protocol component: </p> <ul>
<li id="GUID-52E0A1C0-E43B-5960-BBEA-BD0C6CDFB6F3"><p>Predictor-1 PPP compressor </p> <p>This
compression control is used for high speed data and implements RFC 1978. </p> </li>
<li id="GUID-725A7F96-BD81-5E08-B0AC-AEDF5BD32042"><p>Microsoft Point-To-Point
Compression (MPPC) </p> <p>This compression control implements RFC 2118. </p> </li>
<li id="GUID-6B1A4C56-C5EC-5B49-8D29-2A7DC70A1B1F"><p>Stac LZS Compression </p> <p>This
compression control is optimised to compress efficiently and implements RFC
1974. The Symbian platform implementation does not include the <i>multiple
history buffers</i> feature of the protocol. </p> </li>
</ul> </section>
<section id="GUID-78E5697B-23D5-4425-970C-ECCB44CA9D20"><title>Using PPP Compression Plugins</title> <p>The components in
this collection are not used directly by client application software. The
components are loaded as part of the negotiation of the Point-to-Point protocol. </p> </section>
</conbody></concept>