Modular QoS Configuration Guide for Cisco 8000 Series Routers, Cisco IOS XR Release
Modular QoS Configuration Guide for Cisco 8000 Series Routers, Cisco IOS XR Release
Introduces how QoS markings are preserved, mapped, or redefined when packets undergo encapsulation across GRE, MPLS, or Segment Routing tunnels.
This topic introduces how QoS markings are preserved, mapped, or redefined when packets undergo encapsulation across GRE, MPLS, or Segment Routing tunnels.
QoS marking on Generic Routing Encapsulation (GRE) tunnels is a QoS traffic differentiation feature that
preserves or maps DSCP and Type of Service (ToS) values between inner and outer IP headers when packets are encapsulated or decapsulated
ensures consistent QoS treatment for tunneled traffic by maintaining class-of-service information across GRE boundaries, and
coordinates with other encapsulation types, such as MPLS, to copy or derive appropriate QoS field values when MPLS labels coexist with GRE headers.
Generic Routing Encapsulation (GRE)
GRE is an IP tunneling protocol that encapsulates a wide variety of network layer packets inside IP tunnels. It allows one network to transport packets across another network by adding an outer IP header. GRE is commonly used to create logical point-to-point links between routers, enabling the transport of traffic types that are not natively routable across intermediate networks.
For more information on GRE tunnels, refer to the Interfaces Configuration Guide for Cisco 8000 Series Routers.
Type of Service (ToS)
ToS is an eight-bit field in the IPv4 header that specifies how an IP packet should be handled during transmission. The ToS field includes bits for DSCP and Explicit Congestion Notification (ECN), which together determine packet priority and congestion handling.
| Feature Name |
Release Information |
Feature Description |
|---|---|---|
| QoS Behavior for Generic Routing Encapsulation (GRE) Tunnels: Default Marking |
Release 25.4.1 |
Introduced in this release on: Fixed Systems (8010 [ASIC: A100])(select variants only*) *This feature is supported on:
|
| QoS Behavior for Generic Routing Encapsulation (GRE) Tunnels: Default Marking |
Release 25.1.1 |
Introduced in this release on: Fixed Systems (8700 [ASIC: K100], 8010 [ASIC: A100])(select variants only*) *This feature is supported on:
|
| QoS Behavior for Generic Routing Encapsulation (GRE) Tunnels: Default Marking |
Release 24.4.1 |
Introduced in this release on: Fixed Systems (8200 [ASIC: P100], 8700 [ASIC: P100])(select variants only*); Modular Systems (8800 [LC ASIC: P100])(select variants only*) *This feature is now supported on:
|
| QoS Behavior for Generic Routing Encapsulation (GRE) Tunnels: Default Marking |
Release 7.3.1 | With the support for GRE encapsulation and decapsulation tunnel interfaces, there are some important updates to QoS behavior for GRE tunnels. These updates are applicable for default packet marking and involve Type of Service (ToS) and MPLS experimental bits. |
During encapsulation of IPv4/IPv6 payload inside the GRE header, QoS behavior is as follows:
Ingress: QoS supports classification on the payload Layer 3 fields or EXP and remarking payload IP header DSCP.
Egress: QoS supports setting outer GRE IP header DSCP. It doesn’t overwrite the Tunnel Type of Service (ToS) configuration and doesn’t remark GRE IP header DCSP.
During decapsulation of the outer GRE header (in which the inner IPv4/IPv6/MPLS payload is forwarded to the next-hop router), QoS behavior is as follows:
Ingress: QoS supports classification on Layer 3 fields of outer GRE using the set qos-group command. Setting DSCP on the ingress interface sets DSCP for the inner headers.
Egress: QoS supports classification using qos-group to set DSCP or EXP for egress packets.
Explicit QoS marking for SRv6 encapsulation is a QoS traffic differentiation feature that
sets DSCP or Traffic Class values in the outer IPv6 header during SRv6 encapsulation, and
ensures consistent QoS treatment across SRv6 transport paths by aligning encapsulated markings with class-based policy actions.
Explicit QoS marking feature is also known as packet marking.
| Feature Name |
Release Information |
Feature Description |
|---|---|---|
| Set IP Marking for SRv6 Encapsulation |
Release 26.1.1 | Introduced in this release on: Centralized Systems (8400 [ASIC: K100]) (select variants only*) *This feature is now supported on the Cisco 8404-SYS-D routers. |
| Set IP Marking for SRv6 Encapsulation |
Release 25.4.1 | Introduced in this release on: Fixed Systems (8010 [ASIC: A100])(select variants only*) *This feature is supported on:
|
| Set IP Marking for SRv6 Encapsulation |
Release 25.1.1 | Introduced in this release on: Fixed Systems (8010 [ASIC: A100])(select variants only*) *This feature is supported on Cisco 8011-4G24Y4H-I routers. |
| Set IP Marking for SRv6 Encapsulation |
Release 24.4.1 |
Introduced in this release on: Fixed Systems (8200 [ASIC: P100], 8700 [ASIC: P100, K100])(select variants only*); Modular Systems (8800 [LC ASIC: P100])(select variants only*) *This feature is now supported on:
|
| Set IP Marking for SRv6 Encapsulation |
Release 24.2.11 | With this feature support for IP marking for SRv6 packets that are encapsulated, there are some important updates to the QoS behavior. This is an explicit packet marking feature that applies only to ingress QoS policies. CLI: This feature introduces the set ip encapsulation command. |
The explicit packet marking feature is supported only on ingress QoS policies.
The set ip encapsulation class-of-service command is supported only in ingress QoS policies.
The set qos-group configuration cannot be used together with the set ip encapsulation class-of-service command.
The set ip encapsulation class-of-service and set mpls experimental commands are mutually exclusive and cannot coexist in the same policy configuration.
The encapsulation marking behavior applies exclusively in pipe mode.
In uniform mode or propagate mode, the CoS value from the inner header is automatically copied to the outer header, regardless of the QoS policy encapsulation settings.
Default QoS marking for VXLAN encapsulation is a QoS traffic differentiation feature that
assigns a DSCP value of 0 (Class Selector 0) to the outer IP header when a Provider Edge (PE) device encapsulates IP traffic into a VXLAN tunnel,
ensures VXLAN transport packets are treated with best-effort service across the underlay network.
VXLAN (Virtual eXtensible LAN) tunnels encapsulate Layer 2 Ethernet frames in UDP/IP packets. When the PE performs this encapsulation, the system must decide what value to place in the outer IP header’s DSCP field, which determines per-hop QoS treatment for the VXLAN packet itself.
The default behavior is to clear or reset that field to DSCP 0 (Class Selector 0, best effort).
| Feature Name |
Release Information |
Feature Description |
|---|---|---|
| Set VXLAN Outer IP Header DSCP Value to 0 |
Release 24.4.1 | Introduced in this release on: Fixed Systems (8200 [ASIC: P100], 8700 [ASIC: P100, K100])(select variants only*); Modular Systems (8800 [LC ASIC: P100])(select variants only*) *This feature is now supported on:
|
| Set VXLAN Outer IP Header DSCP Value to 0 |
Release 24.2.11 | When a PE device transports IP traffic over a VXLAN tunnel that originates on the device, it automatically sets the DSCP value in the VXLAN outer IP header to 0 (CS0). |