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Fixed markup. 

Binh.
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binh 2005-02-19 14:26:51 +00:00
parent f555925a89
commit 26e9cba67f
1 changed files with 48 additions and 18 deletions
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66
LDP/guide/docbook/Linux-Networking/Layering.xml
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@ -120,19 +120,36 @@ to recognise implementation and design issues and pertaining to interfaces of la
and their respective functions and services.
</para>
- entity: in software, it is sometimes called a process; in hardware in hardware it
could mean in pratice an I/O chip
- peer enties: entities at the same layer in different machines/devices
- service provider: eg. layer n, a layer that provides a service
- service receiver: eg. layer n + 1, a layer that receives a service
- service access point (SAP): a point where service is accessed, for example a
function call in software, or the telephone for a telephone company
- protocol data unit (PDU): a data unit that is communicated between peer entities
- service data unit (SDU): the PDU from the serice receiver
- protocol control information (PCI): is appended by a service receiver to an SDU
in order to indicated the type of service required and forms the IDU
- interface data unit (IDU): the data unit that is given from a service receiver to
a service provider.
<para><variablelist>
<varlistentry><term>entity:</term>
<listitem><para>in software, it is sometimes called a process; in hardware in hardware it could mean in pratice an I/O chip</para></listitem></varlistentry>
<varlistentry><term>peer enties:</term>
<listitem><para>entities at the same layer in different machines/devices</para></listitem></varlistentry>
<varlistentry><term>service provider:</term>
<listitem><para>eg. layer n, a layer that provides a service</para></listitem></varlistentry>
<varlistentry><term>service receiver:</term>
<listitem><para>eg. layer n + 1, a layer that receives a service</para></listitem></varlistentry>
<varlistentry><term>service access point (SAP):</term>
<listitem><para>a point where service is accessed, for example a function call in software, or the telephone for a telephone company</para></listitem></varlistentry>
<varlistentry><term>protocol data unit (PDU):</term>
<listitem><para>a data unit that is communicated between peer entities</para></listitem></varlistentry>
<varlistentry><term>service data unit (SDU):</term>
<listitem><para>the PDU from the serice receiver</para></listitem></varlistentry>
<varlistentry><term>protocol control information (PCI):</term>
<listitem><para>is appended by a service receiver to an SDU in order to indicated the type of service required and forms the IDU</para></listitem></varlistentry>
<varlistentry><term>interface data unit (IDU):</term>
<listitem><para>the data unit that is given from a service receiver to a service provider.</para></listitem></varlistentry>
</variablelist></para>
<para>
The term "service" can be deemed to mean a number of things. These are outlined
@ -167,11 +184,24 @@ the service interface. The primitives differ for different services. As a simple
example, a service may provide the following primitives:
</para>
1. LISTEN: listen for an incoming communication request
2. CONNECT: make a communication request
3. RECEIVE: receive data of a communication
4. SEND: send data of a communication
5. DISCONNECT: disconnect or discontinue a communication
<para><orderedlist>
<varlistentry><term>LISTEN:</term>
<listitem><para>listen for an incoming communication request</para></listitem></varlistentry>
<varlistentry><term>CONNECT:</term>
<listitem><para>make a communication request</para></listitem></varlistentry>
<varlistentry><term>RECEIVE:</term>
<listitem><para>receive data of a communication</para></listitem></varlistentry>
<varlistentry><term>SEND:</term>
<listitem><para>send data of a communication</para></listitem></varlistentry>
<varlistentry><term>DISCONNECT:</term>
<listitem><para>disconnect or discontinue a communication</para></listitem></varlistentry>
</orderedlist></para>
<para>
As discussed before, each layer has specfic functions and offers certain services