Page 147 - Computer_Science_F5

Computer Science on the same network, it Ethernet switches. These devices operate at the data
uses ARP to find out the link layer (Layer 2) of the OSI model. Switches
MAC address associated
receive incoming frames on one port and forward
with the target IP address.
them to the appropriate output port based on the
The device broadcasts an
FOR ONLINE READING ONLY
ARP request packet on the
tables to make forwarding decisions, which they
network, and the device destination MAC address. They use MAC address
build by learning the source addresses of incoming
with the matching IP frames. Switches reduce collisions and improve
address responds with its network performance by creating separate collision
MAC address.
domains for each connected device. Figure 3.9 shows
(b) Ethernet switch incoming forwarding frame.

Ethernet is a widely used
technology for wired
LANs. It defines wiring
and signaling standards for Src: A
Frame 1
the physical layer and a data Dst: B Frame 1
frame format and protocols Fa0/1 B
for the data link layer. A Fa0/2
Ethernet frames consist of
a preamble, destination and Fa0/3
source MAC addresses, an Mac address Port
EtherType field, payload, Frame 1
and frame check sequence aaaa.aaaa.aaaa Fa0/1
(FCS).
C
The standards that ethernet Figure 3.9: Switch’s incoming forwarding frame
follows include common
Ethernet standards such
as 10BASE-T (10 Mbps), (d) VLANs (Virtual Local Area Networks)
Fast Ethernet (100 Mbps), VLANs allow network administrators to segment
Gigabit Ethernet (1 Gbps), a physical network into multiple logical networks.
and 10 Gigabit Ethernet (10 Devices on different VLANs cannot directly
Gbps). communicate with each other without a router or Layer

3 switch. VLANs provide improved security, reduce
(c) Link-Layer Switches
The Link-Layer switches broadcast traffic, and allow for better management of
sometimes are known as network resources.

138
for Advanced Secondary Schools

Computer Science Form 5.indd 138 23/07/2024 12:33