Cisco CCNA Exam: IP Packet Traffic Marking Location

Which Byte of an IP Packet Can Traffic Be Marked?

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In which byte of an IP packet can traffic be marked?



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In an IP packet, traffic can be marked in the ToS (Type of Service) byte. The ToS byte is a single byte field located in the IPv4 header and is used to specify the quality of service (QoS) for the IP packet.

The ToS byte has 8 bits, and the first 6 bits are used to specify the Differentiated Services Code Point (DSCP), which is a way to mark packets to indicate their priority. The last 2 bits are used to specify the Explicit Congestion Notification (ECN), which is used to indicate network congestion to the sender of the packet.

The DSCP value can be used by network devices to determine the priority of a packet and apply the appropriate QoS policy to it. Different DSCP values correspond to different levels of priority and can be used to prioritize certain types of traffic, such as voice or video, over other types of traffic, such as web browsing or file transfers.

Overall, the ToS byte plays an important role in QoS and can be used to ensure that critical traffic is given priority over less important traffic in a network.