Slow outbound, fast outbound cross country connection
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Slow outbound, fast outbound cross country connection
I'm having an issue where a server in CA (1000/full) and in VA (100/full) have very lopsided data transfer.
CA -> VA with iperf shows ~20Mbps
VA -> CA with iperf shows ~93Mbps
If we change the CA server to 100/FULL, transfer speed is 93Mbps both ways.
Some tuning was done to TCP window scaling parameters, but it won't correct the issue, just improve the CA -> VA numbers to what is listed above. I will say, turning TCP window scaling OFF will lower the transfer speed both ways to < 20Mbps.
The only clue I have when looking at wireshark dumps is that the window scale going OUT would never go past 10240 (scale is 8, so 2^8 x 40bytes). In the opposite direction, the window size will go above 3MB (scaled).
It is not a bandwidth problem as iperf with UDP shows 93Mbps both ways. Local transfers (CA 1000/full to CA 100/full) show full speed both ways, so I feel it is strictly related to TCP window scaling.
RedHat 5 64-bit on both sides. Any ideas why it won't scale above 10240?
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SJC_host# scp large root@VA_host:/usr/local/src/large2
large 100% 100MB 1.5MB/s 01:08
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AFTER:
-----
SJC_host# !scp
scp large root@VA_host:/usr/local/src/large2
large 100% 100MB 1.7MB/s 00:59
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The offload engine should be on :
----
# ethtool -k eth2 (interface the bond is running off of - yes, we tested w/o bonding)
Offload parameters for eth2:
Cannot get device udp large send offload settings: Operation not supported
rx-checksumming: on
tx-checksumming: on
scatter-gather: on
tcp segmentation offload: on
udp fragmentation offload: off
generic segmentation offload: off
generic-receive-offload: off
----
I played with turning off SACK as well - performance was terrible with it off.
Apologies to all. I was about 100% certain we had tested outside of the firewall. The NOC is telling me this is an issue with the Nokia CheckPoint firewall which has been escalated to the vendor.
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