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T1040 L2 Switch high RX drop count on FMAN port

Question asked by Szymon Kukliński on Jun 26, 2017
Latest reply on Jul 5, 2017 by Yiping Wang



We're working on a solution, where we hook the T1040 integrated switch to a number of different switches/processors (including the LS1021 and another T1040).


Now, whenever we start sending a sequence of 65kB IPv4|IPv6 packets (which are fragmented to 1500B Ethernet frames) from the T1040 and any other port simultaneously, we observe a significant RX drop count on the integrated switch interface connected to the T1040 FMAN (chip_port 8 on VSC9953).


The issue doesn't show up on any other of the T1040 ports (tested on chip_ports 0, 1, 2, 3). When we connect two T1040 through the switch ports and we run the ping (-f -s65000) from both sides, we experience the issue symmetrically on both (we see large RX drop increase on the internal switch port connected to the T1040 FMAN - rmon.rx_etherStatsFragments in vtss_port_counters_t struct increase on chip_ports 8 on both T1040s).


This problem occurs when we use the reference application from NXP (l2switch-util) with l2switch-uio kernel driver. It seems there is a fundamental problem in T1040 FMAN <-> integrated switch connection.


Any help would be appreciated.