We've been measuring the impact to user traffic for link failures on the ACX2200 when the router has learned a fairly large number of routes (~11600 FIB routes) and finding that it is larger than we had anticipated. This is since moving to Junos 21.2 With little in the way of route load, we're seeing times around the 500-600 ms mark. This is already larger than expected as we were seeing times around 100-300 ms when running Junos 19.4. All LSPs have fast-reroute enabled so we were really expecting more around the 100 ms mark really. When we increase the number of routes were seeing some further increase - perhaps around 700 ms, but disturbingly were were seeing an L2VPN service experiencing an outage of up to 11 seconds.
Looking at the log messages, it seems that the service is actually going down and then taking seconds to come back up again. The device under test is directly connected to the aggregation router (which acts as a BGP route reflector for it) and the link-fail is carried out by disabling the interface on that agg router that is facing the DUT. 10000 of the routes learned by the DUT are advertised by a Spirent test centre connected to it and also to a remote node and advertised in an MPLS VRF type L3VPN. There ar another 500 routes contributed in a separate L3VPN by 500 virtual MPLS nodes in the STC - see diagram.
The ACX 2200 platform had following limitations:
IPv4 FiB size: 20k
Ipv4 RIB size: 300k
Max number of labels: 3000
Max number of BGP-LU tunnels: 1021
Max number of BGP adjacency: 256
Max number of label stack depth: 3 labels
Max number of MPLS LSP: 2000
Please note, these limitations are expected to be working in ideal condition. In the real network, if the fast-reroute and adaptive (MBB) are enabled, more resource will be used.
The possible workaround is remove the fast-reroute settings, and check whether adaptive (MBB) can be also removed.
For L2VPN, the following knobs may be useful:
set protocols bgp group IGP family l2vpn signaling delay-route-advertisements minimum-delay routing-uptime 300
set protocols bgp group IGP family l2vpn signaling delay-route-advertisements minimum-delay inbound-convergence 10