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IP precedence


I'm quite new to QoS technology. Can you please let me know what is IP precedence , DSCP vales ...



Re: IP precedence

IP header has some bits which can be used to mark the packets with some values (called as precedence or DSCP) so that they can be classified into different classes. Once they are classified into different classes based on these values, each class can be provided different level (quality) of service. Like for example, you can have a voice and data existing in your network. If you do not have QoS implemented for voice ,it will experience delay and performance will suffer. (dropped calls, one way voice). So using the bits in the IP headers, first the packets are marked (data with precedence of 0, voice with precedence of 5). Once they are marked, the routers on the path of voice packets can be configured to service or give more priority to voice packets compared to data.

IP precedence uses 3 bits, which creates eight different classes 000(0) through 111(7). While DSCP stands for differential services code point, which supercedes IP precedence. It uses 6 bits, which creates 64 different classes, helps in more granular control on QoS traffic marking.

You can read more here.

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