Page 151 - Computer_Science_F5

Computer Science 2. Evaluate the impact of different Data Link layer protocols on network
performance. How do protocols like Ethernet and Wi-Fi manage access to
the shared communication medium, and which is more efficient in various
scenarios?

3. Explain why is it necessary for organisation to use VLANs?
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Network layer
The Network layer, also known as layer 3 in the OSI model, handles device addressing,
tracks device locations on the network, and determines the most efficient way to
transport data. It is responsible for facilitating communication between devices that
are not directly connected. In cases where there is a direct point-to-point link between
stations, the Network layer may not be necessary as the data link layer can handle the
link management. Routers, which are layer 3 devices, are specifically designed for the
Network layer and provide routing services within the internetwork. The Network layer
divides messages into data packets and adds a customized header containing the IP
destination and source addresses. There are two types of packets used at the Network
layer: data packets and route update packets. Data packets are used to transport user
data across the internetwork. The protocols that support data traffic are known as routed
protocols, with examples including IP and IPX. On the other hand, route update packets
are used to inform
neighbouring
routers about the
networks connected
to all routers within
the internetwork.

The protocols that
send route update
packets are called
routing protocols,
such as RIP, EIGRP,
and OSPF. Route
update packets

assist in building
and maintaining
routing tables on
each router. Figure 3.10: The network layer (to be redrawn)

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for Advanced Secondary Schools

Computer Science Form 5.indd 142 23/07/2024 12:33