When MTU-Discovery is enabled, BGP conversion time is higher, than when it is disabled.
An MX304 configured for MTU Discovery:https://www.juniper.net/documentation/us/en/software/junos/cli-reference/topics/ref/statement/mtu-discovery-edit-protocols-bgp.html
MTU DISCOVERY ENABLED
Is seeing an issue with slower convergence of routes. The following tests show the disparity. With MTU Discovery set, the system processing 3 million total paths in 73 seconds:
Test 41: IPV6 - 1006k sessions, 500K prefixes, and 3M paths, sharding 8, threads 21, group-split-size 50, sriov, 21cpu, 64G Mem (1 inbound/3 outbound)
# of prefixes 500000
# of peers 1006
start - begin adv | cpu/mem 17:05:29
total active paths = 512K 17:06:38 mtu discovery on mx304
total paths = 3M 17:06:42
bgp sum pending @ 0 17:06:42
dut container cpu @ 0 17:06:42
dut OutQ @ 0 17:06:42
sync container cpu @ 0 17:06:42
*Prefixes per sec 6,849.32
*Prefixes per min 410,958.90
Convergence in Seconds 73
Total Convergence 0:01:13
*prefix per min/sec invalid for full convergence test. only applicable if measuring only mx304>cRPD
========================================================================
MTU DISCOVERY DISABLED
However, if MTU Discovery is disabled, the same route scale converges in 35 seconds:
Test 43: IPV6 - 1006k sessions, 500K prefixes, and 3M paths, sharding 8, threads 21, group-split-size 50, sriov, 21cpu, 64G Mem (Peer Groups: 1 inbound/3 outbound)
start - begin adv | cpu/mem 19:28:38
total active paths = 512K 19:28:56 mtu discovery on mx304 disabled
total paths = 3M 19:28:56
bgp sum pending @ 0
dut container cpu @ 0 19:29:13
dut OutQ @ 0 19:29:13
sync container cpu @ 0 19:29:13
*Prefixes per sec 14,285.71
*Prefixes per min 857,142.86
Convergence in Seconds 35
Total Convergence 0:00:35
Workaround:
set protocols bgp receive-buffer 64k
Set protocols bgp send-buffer 64k
PR1685934
2024-01-13: Article Created