Hello, all
I am now debugging an issue observed in echo server/client. If nclients ==
small number, then everything goes smoothly, but if nclients is big, such as
500, 1000, echo client will hang without printing final report, and debug shows
that echo client is waiting for response from server as it is expecting server
to send bytes_to_receive to client. The problems occurs in both TCP and TLS
protocol.
if (sp->bytes_to_receive > 0)
{
delete_session = 0;
}
My assumption is that due to the big traffic, some packet is missing and
re-transmission does not work well. Below the info for normal case, where
nclients == 100.
DBGvpp# show error
Count Node Reason
600 session-queue Packets transmitted
100 tcp4-rcv-process Pure ACKs received
100 tcp4-rcv-process FINs received
600 tcp4-established Packets pushed into rx fifo
600 tcp4-established Pure ACKs received
32 ip4-glean address overflow drops
1 ip4-glean ARP requests sent
1 arp-input ARP request IP4 source
address learned
Server:
DBGvpp# show error
Count Node Reason
600 session-queue Packets transmitted
100 tcp4-listen SYNs received
200 tcp4-rcv-process Pure ACKs received
600 tcp4-established Packets pushed into rx fifo
600 tcp4-established Pure ACKs received
100 tcp4-established FINs received
1 arp-input ARP replies sent
Below is the info when nclients == 500.
Client:
DBGvpp# show error
Count Node Reason
3104 session-queue Packets transmitted
498 tcp4-rcv-process Pure ACKs received
498 tcp4-rcv-process FINs received
2998 tcp4-established Packets pushed into rx fifo
2892 tcp4-established Pure ACKs received
106 tcp4-established Duplicate ACK
Server:
DBGvpp# show error
Count Node Reason
2998 session-queue Packets transmitted
500 tcp4-listen SYNs received
998 tcp4-rcv-process Pure ACKs received
2996 tcp4-established Packets pushed into rx fifo/
2 tcp4-established OOO packets pushed into rx
fifo
2476 tcp4-established Pure ACKs received
498 tcp4-established FINs received
We can see that in clients side, packets transmission is 3104, which is bigger
than normal case 600*5, but in the server side, the recived packet is only
2996, which is below 3000, which causes only 498 FIN is sent from client, so 2
live session makes "test echo" hang until timeout.
Thanks
Ping
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