Configuring interface delay

The delay represents the unidirectional link delay from the local router to the remote router (that is, the forward-path latency). The interface delay is a link property and is typically calculated as the combination of speed of light versus fiber length versus fiber composition. Typically, these delay components are not subject to sudden change in a network. If a change occurs, it may be caused by fiber cuts (such as light out) or Layer 1 reroute events.

If delay is configured for all links in the network, the attribute can be used as a feasible metric for SR flex-algo applications.

The static delay represents a forward-path metric, in microseconds, between two routers. It is not possible to configure a delay on a loopback or system interface; the delay IGP extension TLVs (specified in RFC 8570) are not defined for stub links. The delay is encoded in IGP application-specific attributes (for example, for IS-IS, see draft-ietf-isis-te-app-14.txt). The delay can be configured upon other interface links.

The default setting is no delay, which means that IGP (for example, IS-IS) does not add a link delay metric TLV. The lack of this TLV in flex-algo causes the link with the no delay TLV setting to be pruned from the topology.

config>router
     interface interface-name
          if-attribute
               delay
                   static microseconds
                   no static

The static delay can be configured within the range 1 to 16777214 microseconds.