Specifications

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2.7.6 Application Layer
The application layer is that which network applications operate at. Applications
that operate at this layer are, for example, HTTP, FTP, SMTP, DHCP, NFS,
Telnet, SNMP, POP3, NNTP and IRC. The function of this layer is that it
provides services to programs that want to use the network and to issue the
appropriate commands to properly use the services provided by the lower levels.
2.7.7 Microchip TCP/IP Stack
Microchip provides a freely available TCP/IP stack for use with their
microprocessors. Figure 15 below shows how it is implemented and compares it
to the TCP/IP Reference Model.
Figure 15 Comparing the Microchip TCP/IP stack structure to the TCP/IP
reference model (Reprinted with Permission from Microchip)
Unlike the Reference model, some layers in the Microchip TCP/IP Stack have
direct access layers which are not immediately below it. The decision for when a
layer would bypass its adjacent module was made based on the amount of
overhead and whether a given service needs intelligent processing before it can
be passed to the next layer or not.
With Microchip‟s design, they depart from traditional TCP/IP Stack
implementation by adding StackTask and ARPTask. StackTask manages the
operations of the stack and all of its modules, while ARPTask manages the
services of the Address Resolution Protocol Layer.
Microchip‟s TCP/IP stack is a live stack; some of the layers must be able to
perform timed operations asynchronously. To meet the requirement, Microchip‟s