Explains how DiffServ tunneling modes define the interpretation of inner and outer QoS markings as packets traverse a network core. It describes the behavior of Uniform, Pipe, and Short-Pipe modes in maintaining or isolating service differentiation across network domains.
A DiffServ tunneling mode is a QoS packet-handling model that
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defines how inner and outer traffic markings are interpreted as packets traverse a network core
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specifies which header drives classification and queuing decisions, and
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influences how end-to-end service differentiation is maintained or isolated across domains.
Uniform mode
Uniform mode enables a consistent QoS model across interconnected domains. When a packet enters a tunnel, the marking from the inner header is copied to the outer header. When the packet exits the tunnel, the marking is restored to the inner header. This ensures that classification uses the same QoS value end-to-end, regardless of whether the packet is encapsulated.
Pipe mode
Pipe mode provides QoS isolation between domains. Within the tunnel, only the outer header marking is used for classification and queuing. The inner marking is preserved for use at the tunnel edge but is not used inside the core unless a policy explicitly copies or rewrites it.
Short-pipe mode
Inside the tunnel, forwarding uses the outer header marking. When the packet exits the tunnel, classification and queuing decisions at the egress device are based on the inner header marking, not the outer one. This mode is useful when customer or application markings must be honored at the network edge.
Short-pipe mode is not supported in all releases. See Short-pipe mode for support details.
DiffServ tunneling modes may preserve or expose QoS marking fields, but they are not marking mechanisms. Marking is performed only when explicit policy‐map commands, such as set dscp , set cos , or set mpls experimental , are used. To learn about marking commands and how they are applied, see Packet marking.