4-1-3 Role of the Data Link Layer · ITPEC FE Textbook

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4-1-3 Role of the Data Link Layer

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ARP resolves IP addresses to MAC addresses2 Ethernet and IP packet addressing1

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4-1-3 Role of the Data Link Layer

The main role of the data link layer is to deliver data to the devices (e.g., computers) that are connected directly by using the communication medium (e.g., cables). In the data link layer, a MAC address is used to identify the individual device. The MAC address is a device (i.e., hardware) specific identifier. (However, since it is not managed in a consolidated manner, it is not guaranteed to be absolutely unique.) If the destination MAC address of a packet flowing across the communication channel matches the MAC address of a device that is connected to the network, the device acquires that packet. The flow of the communication using an IP address and a MAC address is as shown below. The MAC address corresponding to the destination IP address is acquired by ARP (Address Resolution Protocol). · 2 questions

Original Role of the Data Link Layer source table or explanation box, preserving its complete original arrangement, labels and values. Source text: (1) [Terminal X] In order to send a packet to terminal Y, set the IP address (i.e., I4) of terminal Y in the destination IP address. However, since terminal Y is not a directly connected device, set the MAC address (i.e., M2) of the directly connected router α in the destination MAC address to send the packet. (2) [Router α] Since the destination MAC address (i.e., M2) is addressed to self, the packet is acquired. However, since the destination IP address (i.e., I4) is not addressed to self, the packet is sent by setting the MAC address (i.e., M3) of the router β that is connected to the network of the destination IP address in the destination MAC address. (3) [Router β] Since the destination MAC address (i.e., M3) is addressed to self, the packet is acquired. However, since the destination IP address (i.e., I4) is not addressed to self, the packet is sent by setting the MAC address (i.e., M4) of the device (i.e., terminal Y) of the directly connected destination IP address in the destination MAC address. (4) [Terminal Y] Since the destination MAC address (i.e., M4) is addressed to self, — p. 335 · Enlarge

Ethernet and IP packet addressing · 1 practice questions

p. 336

Original Role of the Data Link Layer source table or explanation box, preserving its complete original arrangement, labels and values. Source text: the packet is acquired. Moreover, since the destination IP address (i.e., I4) is also addressed to self, the packet is processed in an upper layer. — p. 336 · Enlarge

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Practice arp resolves ip addresses to mac addresses (2) Practice ethernet and ip packet addressing (1)

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New FE Textbook Vol.1 · IT Fundamentals · First Edition, April 2015