What is 802.1p prioritization and how does it support IP Telephony?
A. The 802.1Q/p standard defines the use of the three-bit Class of Service (CoS) field in the 802.1Q tag to prioritize frames with eight classes (priorities) of traffic. The Cisco InterSwitch Link (ISL) trunk mode, which is also similar, provides the CoS field (least three significant bits in a four-bit user field). The Cisco IP phones, such as the Cisco 7960, tag the voice packets with a CoS value of five. These tagged packets are used by the Catalyst XL switches to prioritize the voice traffic by queuing them in the priority queue in the egress port. This guarantees top priority to the time critical voice packets.
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- What is 802.1p prioritization and how does it support IP Telephony?
