s/ware application worked before ADSL changeover

[casperl]

Hi Ladies & Gents,

I have a friend who runs a pharmacy. He connects through a local ISP in his town to the internet. The pharmacy runs a vertical market application on a linux box (Suse 7) that connects to a medical-aid database (in South Africa). At the beginning of July the ISP changed their diginet lines for Telkom ADSL lines to a 1st tier ISP in Johannesburg.

Since then the connection to the medical aid co has been intermittent and lately the software cannot connect at all to one specific medical aid.

I have tried various options - the distant IP is accessible, all local machines can connect to the internet. The same application, same linux box works over an M-Web modem, but not ADSL. There appears to be multiple hops between the local box and the destination ISP (> 30 hops).

I have spent days with the support people of the ISP's as well as the medical application. Apparently warnings were given against running that specific app over ADSL.

It appears to be a latency / timing problem. There are (multiple) firewalls and NAT routing between the local box and the distant IP. All relevant IP addresses as well as ports are accessible. Unfortunately due to virus threats ICMP (ping) has been disabled by the ISPs involved. I can telnet to the distant box over the relevant ports etc. Many other ports (used for DC+ / IRC / DCC etc transfers) have also been disabled by the ISP(s) concerned. Web browsing and FTP to remote sites works better than ever. Retreiving POP3 mail from remote accounts (on distant web hosting co's) give intermittent errors from other machines on the same subnet.

My question is firstly: 1) Why does such a problem exist over ADSL and 2) What can be tweaked / changed / done to try and bypass this issue.

Thanks in advance for any help

 

[stoke]

My Guesses ---

1) It exists cos SAIX based ADSL runs into the big slowdown just before leaving the country to New York. You can see the slowdown by running a tracert to any USA ip address. The slowdown is never less than 300 ms. I have heard counltess arguments indicating that the slowdown is actually the distance the data is travelling, but I have also seen international people accessing our local servers coming in with 70ms lag (Not Sattelite). This slowdown MUST be part of the port shaping priority thing that SAIX enforce.

2) A - Setup a VPN on port 25 between your network and the remote network. Establish the VPN connection, and then try to do the connect. The port 25 will "skip" the port shaping problem, and the VPN will eliminate any hop-count issues.

2) B - Ask teklom to lend you a 4GB Unshaped account to try. They OWE you this.