Alcatel Speed Touch Wireless, User Manual

Page: 145 / 362

8 Data Services - PPP & IP Routing
145 / 362
3EC 17766 AAAA TCZZA Ed. 01
8.4.7 NAPT and STWireless Transparency
As described in subsection 8.4.6, the STWireless can perform
NAPT to decouple your local IP addresses from the public IP
address negotiated during a PPP session.
However, this feature comes at the expense of the
STWireless
transparency. This because a number of protocols that are layered
on top of either TCP/IP, or UDP/IP do not adhere to the ISO/OSI
reference model.
Note : The ISO Open Systems Interconnection (OSI) reference
model promotes the layered implementation of communications
protocol stacks. Layers from protocol stacks implemented
according to this model can be changed without affecting the
upper or lower layers.
"
Consequences of NAPT on Layers
"
STWireless Solutions
"
ATMFĆ25
"
Via the PPPoAĆtoĆPPTP Relay
"
PPPĆtoĆDHCP Spoofing.
An important consequence is that changing IP addresses, or
TCP/UDP ports via NAPT affects the other layers as well.
Due to these changes, applications that are the ultimate
consumers of the protocols cannot decode the information
correctly anymore.