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Windows Vista Security: Praxisorientierte Sicherheit für Profis by Marcus Nasarek

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Advanced Networking Concepts
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Advanced Networking Concepts
Windows Vista includes support for advanced network features, which include IPSec
and VPN. These protocols have existed for some time, but they are more readily avail-
able and usable in Windows Vista than they were in earlier releases of Windows.
Understanding the OSI Model
The Open Systems Interconnection (OSI) model defines the ways protocols operate
by breaking the different aspects of protocols into layers. The OSI model uses seven
layers with different purposes to define how protocols function. Each layer may use
the functionality of the first layer below it and export functionality to the next layer
above it. See Table 14-10 for a detailed listing of the OSI model’s layers.
OSI layer 1 covers all of the physical connectivity specifications of devices. This
includes any electrical voltage, pin-outs, connectors, cables, and hubs. Layer 1
defines all network adapters, network devices that do not work in layer 2, and host
bus adapters used in storage area networks (SANs). The main purpose of layer 1
includes establishing a connection or disconnection from a network medium. Layer 1
also covers modulation and flow control over the network medium.
OSI layer 2 controls the means of controlling data transfer among network entities.
Layer 2 also handles the control mechanism of data transferred among network enti-
ties. Bridges and switches both work within layer 2. Although there are layer 3
switches, they work on layer 2 without the use of a router.
OSI layer 3 controls the functional means of transferring data among network enti-
ties. Layer 3 handles the variable length sequences to and from destinations among
networks. It also handles QoS for the transport layer. Routing also occurs at layer 3
(in fact, routing is the most common use of layer 3).
Table 14-10. OSI layer reference
Layer level Layer name
Layer 1 Physical
Layer 2 Data Link
Layer 3 Network
Layer 4 Transport
Layer 5 Session
Layer 6 Presentation
Layer 7 Application

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