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Configuring DSCP Steering

When traffic is traversing an encrypted tunnel such as IPSec, every flow within that tunnel shares the same layer 3 headers, making them difficult if not impossible to disambiguate from each other.

When the tunnel endpoint encrypts traffic, it can set a DSCP value representative of the traffic within the tunnel. When the traffic reaches the SSR, the DSCP value can be used as both a representation of traffic engineering priority, and path priority.

Configuration#

DSCP traffic steering must be configured at both the service level and the network-interface.

Service Configuration#

A DSCP value or range can be configured at the Service level. DSCP aware services are configured in a hierarchy; the parent service is configured without a DSCP value, and each child service is configured with a DSCP value.

The following configuration splits the tunnel across 3 services: the traffic with dscp value 14 is handled by the high-priority service; the traffic with dscp values from 26 to 28 is handled by the low-priority service. The remaining traffic falls back into the tunnel service.

service tunnel
name tunnel
description "IPSec Tunnel"
scope public
security internal
address 5.5.5.100/0
access-policy red
source red
permission allow
exit
exit
service high-priority.tunnel
name high-priority.tunnel
description "The high priority traffic within this tunnel"
scope public
security internal
dscp-range 14
start-value 14
exit
exit
service low-priority.tunnel
name low-priority.tunnel
description "The low priority traffic within this tunnel"
scope public
security internal
dscp-range 26
start-value 26
end-value 28
exit
exit

Network Interface Configuration#

The dscp-steering option is available at the network-interface level. This allows you to enable traffic steering for DSCP traffic entering on a specific transport and port range rather than an entire interface.

Only traffic matching the dscp-steering properties configured in the service and on the network-interface will be steered using DSCP. Other traffic will be handled according to the relevant configuration.

The following example is designed to target IPSec NAT traversal traffic which is typically UDP, with a destination port 4500.

network-interface foo
name foo
global-id 12
vlan 0
dscp-steering
enabled true
transport
protocol udp
port-range
start-port 4500
exit
exit
exit
exit

Restrictions#

  • The DSCP steering transport list for a network-interface is limited to one range.
  • Any service with a dscp-range configuration must be a child service.
  • Only provisioned service-routes are supported.
  • DSCP steering ranges must not overlap.

GUI Configuration Screens#

The following screens demonstrate configuring the network interface using the GUI.

Enable DSCP Steering, and select the DSCP Steering Transport button.

DSCP Steering button

Select a protocol.

DSCP Steering Info

Enter the port or port range.

DSCP Steering Port Ranges

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