[Serdev] TCP problems

[Katty Xiong]

SIPp UAC ---------------SER--------------SIPp UAS
199.199.2.31	 199.199.2.50   	199.199.2.30

I abstract more info from the packet trace. It would
be great if someone already has a solution or
workaround for this.

Problem: when SIPp UAC generates high load (800 CPS),
SIPp UAC works for a while and then SIPp at UAC
reports the following error: 
Broken pipe on TCP connection, remote probably closed
the socket.

The problem is related with TCP zero window:

In the beginning, SIPp at UAC creates a new TCP
connection with SER to exchange SIP messages between
them (connection pair: 199.199.2.31:51402 and
199.199.2.50.5060). But with high load (800CPS), TCP
at both SIPp and SER publicizes zero window after some
time, and then no SIP message can be sent through this
connection. 

When timeout, SER creates another connection with SIPp
UAC (connection pair: 199.199.2.31:5060 and
199.199.2.50:59094).  And SER uses this new connection
to send SIP messages to SIPp UAC. SIPp UAC does not
use the new connection to send any packets. 

After some time, the first connection is reset (TCP
RST) by SER and the second connection is reset by
SIPp. And then SIPp at UAC reports error.

My question is: Is it possible to prevent SER from
creating a new connection? How often does SER resets
idle TCP connection? Is it tunable?

Thanks,
Joy




--- Andrei Pelinescu-Onciul <andrei at iptel.org> wrote:

> On Jan 09, 2007 at 10:33, Katty Xiong
> <cyyxiong at yahoo.com> wrote:
> > Hi, 
> > 
> > I am using SER (Ottendorf) and SIPp for some
> > performance study and get several errors when
> using
> > TCP protocol. From the packet trace, I notice when
> TCP
> > publicize zero window at SIPp or SER side, SIP
> message
> > will get truncated or several partial or whole SIP
> > message get combined in one TCP packet, which
> leads to
> > error. I haven’t checked the code yet, but if
> somebody
> > already knows this off the head, please clarify me
> of
> > the following questions.
> > 1) When SER receives a truncated SIP message, how
> does
> > it handle the partial message? 
> 
> It waits for the rest of the message (on tcp).
> 
> > 2) When SER receives a packet that has one partial
> SIP
> > message combined with another partial SIP message,
> how
> > does it handle the packet?
> 
> > 3) When SER receives several SIP messages in one
> TCP
> > packet, how does it handle the packet?
> > 4) Does SER care how TCP send one SIP message (in
> > several TCP packets, combined with other SIP
> > messages)?
> 
> 
> No, it doesn't, each message is handled separately.
> In fact on tcp ser
> just reads from the tcp stream until it gets a whole
> message, then
> processes it and then repeats the entire process.
> 
> 
> Andrei
> 


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