![]() ![]() In scenarios where the payload is an IPv4 packet (for example, 元VPNv4 over SRv6):.When the ingress performs SRv6 encapsulation for different services, the path MTU processing mechanism is as follows: The ingress generates a path MTU entry based on the message and performs SRv6 encapsulation based on this entry. In an SRv6 BE forwarding scenario, if a transit node finds that the packet length exceeds the IPv6 MTU of physical interfaces, it performs the standard IPv6 path MTU processing and replies with an ICMPv6 Too Big message. Verification State : - SuppressTimeRemain :. Template ID : 0 Path Verification : DisableĭelayTimerRemain : - Segment-List Count : 1 Policy State : UP State Change Time : 11:45:30Īdmin State : UP Traffic Statistics : Disableīackup Hot-Standby : Disable BFD : Disable TunnelType : SRv6-TE Policy DelayTimerRemain :. # After the configuration is complete, check the path MTU configuration of the SRv6 TE Policy. Run the commit command to commit the configuration. ![]() Run the segment-list list-name path-mtu mtu-value command to configure a path MTU for a segment list. ![]() Run the candidate-path preference preference command to enter the candidate path view of the SRv6 TE Policy. Run the srv6-te policy name-value endpoint endpoint-ip color color-value command to create an SRv6 TE Policy and enter its view. The ingress sends packets using the smaller value of either the active path MTU or the IPv6 MTU of physical interfaces. For a segment list, the configured path MTU minus the reserved value is the active path MTU, which must be greater than or equal to 1280 bytes. (Optional) Configure a path MTU for a segment list.Īn SRv6 path MTU configured for a segment list overrides the global SRv6 path MTU. (Optional) Run the path-mtu reserved reserved-value command to configure a globally reserved path MTU.īy default, the globally reserved path MTU is 72 bytes. Run the path-mtu mtu-value command to configure a global path MTU for an SRv6 TE Policy. Run the segment-routing ipv6 command to enable SRv6 and enter the SRv6 view. Run the system-view command to enter the system view. Configure a path MTU for an SRv6 TE Policy. As a result, the default reserved path MTU increases. For example, when In-situ Flow Information Telemetry (iFIT) detection is performed for SRv6 services, iFIT detection adds extra iFIT header encapsulation to service packets. Other scenarios are also considered for the default reserved path MTU. This means that the default reserved path MTU (72 bytes) is sufficient in an SRv6 TI-LFA FRR scenario. In this case, the reserved path MTU is 40 bytes (2 x 16 bytes + 8 bytes). Based on the preceding analysis, TI-LFA on an SRv6 network uses two SIDs to protect services in 100% of failure scenarios. When the SRv6 forwarding plane is used, End.X SIDs have the routable attribute and do not need to use End SIDs as preambles, resulting in one fewer SID in the SRv6 scenario than in the SR-MPLS scenario. This active path MTU is then compared with the IPv6 MTU of physical interfaces, and the smaller of the two is the MTU that the SRv6 ingress uses for forwarding based on the segment list.īy default, the globally reserved path MTU is 72 bytes, which is approximately equal to the length of four SRv6 SIDs plus the fixed SRH (4 x 16 bytes + 8 bytes = 72 bytes).Īccording to the evaluation of the IETF draft "Topology Independent Fast Reroute using Segment Routing" on the SR-MPLS scenario, the TI-LFA repair list uses two SIDs to protect services in 99.9% of failure scenarios and three SIDs in 100% of failure scenarios. The SRv6 path MTU of the segment list minus the globally configured reserved value is the active path MTU of the segment list. If an SRv6 path MTU is set to a value other than 1600 bytes for a segment list, this segment list uses the newly configured value. The involved segment list uses the configured SRv6 path MTU, and other segment lists use the global default value of 9600 bytes.įor example, if an SRv6 path MTU is set to 1600 bytes globally, the SRv6 path MTU of all segment lists is 1600 bytes by default. The involved segment list uses the configured SRv6 path MTU, and other segment lists use the global configuration. Table 1-1 Effective SRv6 path MTU for segment lists in an SRv6 TE Policy scenarioĮffective SRv6 Path MTU for Segment ListsĪll segment lists use the global default value of 9600 bytes.Īll segment lists use the global configuration. ![]()
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