[nsp] Large Number of small packets --> timeout over frame relay, IGX, ATM

[Hans-Peter Walter HAWA]

Hello,
one of our branch offices tries to connect to a self-written application 
in our main data center. It works, but 
long response times and timeouts.
We have a E1 (1,984 kilobits) that connects via frame relay to one of our 
IGX nodes (IGX_3). The IGX is 
connected via 34 megabits ATM to our IGX (IGX_1) in the main data center. 
The connection is terminated 
on a Cisco 3640 in a firewall DMZ. All other applications works fine. No 
CPU problems, no Access-lists, 
only a little bit of NAT. I had the IGX in mind, so we changed all 
parameters (MIR, CIR, PIR,...) to the 
maximum (see config below). No success. Then we sniffered a little bit and 
found out, that the client only 
sends packets with a MTU size of 50 - 70 instead of 1500.

So I routed only the one application (-server) over an existing VPN (Cisco 
VPN Concentrator)  to our data center, 
and the connection works better, but not perfect. Response time is O.K. 
now, but
 now we have sudden connection failures  (well, it's over the Internet, I 
know)...

So the only solution is to solve the frame relay, ATM, IGX or whatever 
problem. But I don't know where 
to start. I read several newsgroups, articles and googled for it, but 
absolutely no result. The developers 
can't change the MTU, so that is not an option.

Any idea or hint is appreciated.

Thanx in advance,
H.P.

---------------------------------------------------------------------------------------------------------------------------
IGX_1        TN    :0           IGX 8410  9.2.41    Mar. 30 2004 11:16 GMT 


Conn:  6.3.419           IGX_3    7.6.419            fst      Status:OK
    MIR         CIR      VC Q Depth     PIR      Cmax   ECN QThresh QIR 
 2048/2048   2048/2048  65535/65535  2048/2048   10/10  65535/65535 
2048/2048

Ownr:LOCAL Restr:NONE COS:0                            FST: y  % Util: 
100/100
Pri: L  FST-RTD: 40 msec  Test-RTD: 0 msec
Path:   IGX_1  8.2-- 8.1 IGX2 8.4-- 6.2 IGX_3
Pref:   Not Configured

IGX_1   UFMU:   OK                   IGX_3  UFMU:   OK
          UFI:   OK                              UFI:   OK
---------------------------------------------------------------------------------------------------------------------------