CISCO-SWITCH-QOS-MIB
This MIB module extends the CISCO-CLASS-BASED-QOS-MIB by defining configuration and statistics information specific to the quality of service (QoS) features of Layer2/3 switch functionality implemented in Cisco devices. It is applicable to a device which is fully within a single QoS domain, although one or more boundaries with other QoS domains can be immediately adjacent to this device. Configuration information available through this MIB includes: + Mappings between CoS, IP Precedence, MPLS-EXP value to DSCP value and vice versa for classification purpose. + Device level QoS configuration for DSCP rewrite, policing of ACL-redirected traffic, QoS port-queueing mode, statistics collection for policy that sets a trust state. + CoS, MPLS-EXP and DSCP mutation map name and mappings. These mutations can be configured so that they change the content of packets which cross QoS boundaries, either as they enter or leave this device. + Interface QoS configuration such as default CoS value, trust state, packet assignment to queue and threshold based on CoS or DSCP value, drop algorithm and corresponding parameters, queue scheduling parameter such as WRR (Weighted Round Robin) weights, queue size allocation weight. Statistics available through this MIB includes: + Per module Multi-Layer Switching QoS statistics. + Per interface QoS queueing statistics. The following terms are used throughout this MIB: DSCP (Differentiated Services Code Point) is the six most significant bits of the ToS field in a IP packet header. DSCP Mutation: when a packet is being forwarded across an IP network, the previous hop(s) and the following hop(s) of a device may reside in a different QoS domain. A QoS domain refers to the set of QoS rules and conventions adopted by an administrative entity. For instance, a set of DSCP values may have a different meaning in different domains. DSCP mutation allows a DSCP set to be mutated or transformed in order to maintain semantic compatibility between adjacent domains. The mutation is done via mapping tables which maps the old DSCP value from one domain to a new DSCP value in the other domain. DSCP Mutation is applied to egress traffic. IP precedence is the three most significant bits of the ToS field in a IP packet header. CoS (Class of Service) is the three bits in the layer 2 header that indicates user priority value assigned to this packet. Trust state is a parameter configured at an interface to specify which QoS markings in packets arriving at that interface are acceptable as-is, rather than needing to be ignored/overwritten due to an 'untrusted' source or previous hop. BPDU (Bridge Protocol Data Unit) is used by bridges in a network to exchange information regarding their status. The Spanning Tree Protocol uses the BPDU information to elect the root switch and root port for the switched network. MPLS-EXP: MPLS experimental field in MPLS label.