a QOS scheduler can use the COS filed to qualify the traffic in to different QOS queues. L3 - QOS-----L3 QOS is required for IP level classification. Classification can be achieved by Diffserv implementations that takes many IP parameters in to consideration in prioritizing traffic. This priority can be set in TOS field of IP header.
Dears. I have a questions , I'm making tests in some routers using QoS, I configure to mark the packets with ip precedence=5, then I have to put in a equipment that send traffic the type of service (ToS) on the header IP , in order that the router can mark the packets, but i dont know what numer I should put in the ToS , I guess is A0, but the router doesn't mark the packets, also can you QOS DSCP Marking - Cisco 6 bits are used only with dscp, as was historically with tos the last 2 have never been used the takeaway is the 3 bit shift right repurposing those from tos for dscp, keeping the first 3 aligned for compatibility with Cos, Ip prec, tos and now dscp as in the above diagram Quality of service - Wikipedia Quality of service (QoS) is the description or measurement of the overall performance of a service, such as a telephony or computer network or a cloud computing service, particularly the performance seen by the users of the network. To quantitatively measure quality of service, several related aspects of the network service are often considered, such as packet loss, bit rate, throughput
ToS Header of IP Packet Used for DSCP Marking. The above diagram depicts an IP packet, with a close-up on the ToS portion of the header. The ToS bits were originally used for Precedence and ToS (delay, throughput, reliability, and cost) settings, but were later repurposed by RFC2474 for the more versatile DSCP settings.
The type of service (ToS) field is the second byte of the IPv4 header. It has had various purposes over the years, and has been defined in different ways by five RFCs. Prior to the redefinition, the ToS field could specify a datagram's priority and request a route for low-delay, high-throughput, or highly-reliable service. For the customer service-oriented term, see service quality. Quality of service ( QoS) is the description or measurement of the overall performance of a service, such as a telephony or computer network or a cloud computing service, particularly the performance seen by the users of the network. To quantitatively measure quality of service, several related aspects of the network service are often considered, such as packet loss, bit rate, throughput, transmission delay, availability, jitter, etc. Quality of Service (QoS) In general, QoS defines standard ways to prioritize traffic in a network where different types of packets should be assigned different priorities, based on their type. It is often used to classify VoIP, SIP, Video Streaming, gaming, and other types of priority traffic to improve user experience. The IPv4 header defined in RFC 791 contains a 1 byte field called the Type of Service or ToS. The intent was to use this 1 byte field to mark packets for preferential treatment in conjunction with QoS. The ToS field was further divided into a high order 3 bits called IP Precedence or IPP.
MPLS and Quality of Service | Network World
Jun 30, 2020 CCNA 200-125 Exam: QoS Questions With Answers