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LVS and reply delay

To: <lvs-users@xxxxxxxxxxxxxxxxxxxxxx>
Subject: LVS and reply delay
From: "Darek M" <darekm@xxxxxxxxxxxxxx>
Date: Thu, 20 Mar 2003 08:50:26 -0500 (EST)
Hey guys,

LVS on Slackware 8.1 operating in the NAT option.

It works very well with one exception. When making a request to the site,
the connection seems to stall for anywhere from 3 to 6 seconds before the
page is returned to the client browser.

I will paste a tcpdump log below. Is this a somewhat common occurance? I
double checked the network connectivity, and swapped around interfaces, and
NICs and their drivers with no remedy. Maybe there is a patch out for
this? I am pretty confident that I followed the install procedure
correctly but it does look to me like it is the LVS kernel module/software
deciding where to send the packets.

Also, I do not suppose keepalived that I use would have anything to do with
it. It just updates the pool.

There is a delay in the internal server's response, but telnetting to port
80 from the loadbalancer itself yields an instantaneous response and
banner.

I appreciate any feedback. And maybe other ways of trouble shooting this.

A picture is in order.
             +-----------------------------------+
(client) --> |public_server_ip (public interface)|
             |  10.6.6.1 (private interface)     |(loadbalancer)
             +-----------------------------------+
                |                      |
                |                      |
            10.6.6.10 (webserver)   10.5.5.10 (inactive)

tcpdump output

13:31:32.307982 client_browser.52993    > public_server_ip.80: P
13:31:32.308024 client_browser.52993    > 10.6.6.10.80: P
13:31:32.449464 10.6.6.10.80            > client_browser.52993: .
13:31:32.449504 public_server_ip.80     > client_browser.52993: .
pause (after this point, 2 way communication seems fast)
13:31:35.338241 10.6.6.1.34264          > 10.6.6.10.80: S
13:31:35.338378 10.6.6.10.80            > 10.6.6.1.34264: S
13:31:35.338428 10.6.6.1.34264          > 10.6.6.10.80: .
13:31:35.338643 10.6.6.1.34264          > 10.6.6.10.80: R
13:31:37.806840 10.6.6.10.80            > client_browser.52993: P
13:31:37.806864 public_server_ip.80     > client_browser.52993: P
13:31:37.807974 10.6.6.10.80            > client_browser.52993: P
13:31:37.808003 public_server_ip.80     > client_browser.52993: P
13:31:37.808098 10.6.6.10.80            > client_browser.52993: .
13:31:37.808126 public_server_ip.80     > client_browser.52993: .
13:31:37.812419 client_browser.52993    > public_server_ip.80: .
13:31:37.812441 client_browser.52993    > 10.6.6.10.80: .
13:31:37.812795 10.6.6.10.80            > client_browser.52993: .
13:31:37.812826 public_server_ip.80     > client_browser.52993: .
13:31:37.812918 10.6.6.10.80            > client_browser.52993: .
13:31:37.812947 public_server_ip.80     > client_browser.52993: .
13:31:37.813041 10.6.6.10.80            > client_browser.52993: .
13:31:37.813070 public_server_ip.80     > client_browser.52993: .
13:31:37.813165 10.6.6.10.80            > client_browser.52993: .
13:31:37.813191 public_server_ip.80     > client_browser.52993: .
13:31:37.823065 client_browser.52993    > public_server_ip.80: .
13:31:37.823087 client_browser.52993    > 10.6.6.10.80: .
13:31:37.823436 public_server_ip.80     > client_browser.52993: .
13:31:37.823408 10.6.6.10.80            > client_browser.52993: .
13:31:37.823533 10.6.6.10.80            > client_browser.52993: .


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