T1040 L2 Switch high RX drop count on FMAN port

[elszymono]

Hello

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.

[yipingwang]

Hello Szymon Kukli,

First of all, in Linux IP packet fragmentation is operated in L3(TCP/IP networking stack in Linux Kernel), the networking packet handled in L2switch is in L2(driver layer).

Port8 and Port 9 in L2switch are 2.5G SGMII ports connecting to FMAN. In l2switch-util application, the Maximum frame length is configured as 10240.

Please refer to the following in the file include/vtss_api/vtss_port_api.h of l2switch package.

#define VTSS_MAX_FRAME_LENGTH_MAX      10240

So please enlarge the variable VTSS_MAX_FRAME_LENGTH_MAX to make it support your networking environment.

Have a great day,
TIC

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