Programming

I am working on a project, which has the following type of hardware setup.

A special hardware device is receiving data from an external network interface. So we can have multiple such a hardware devices. Now these hardware devices will route the captured incoming data through the external network to a software running on a single PC through LAN.

If we run a single setup of the software in the LAN on a single PC, our software works with no issue.

The problem comes when we deploy two Ethernet card within the PC where the software is running. With the aid of two Ethernet interface we simulate two setup of the same software on the same PC within two different environments. Each software maintains a different setup of the network card it has to interface with.

The final setup in this case looks something like this. The two-network cards are separately connected to two different HUB port from the PC where two setup of software are running. The hardware devices, which capture incomming data from the external network, are also connected to the same HUB to different ports. Each of these hardware devices have been configured to talk to respective network cards within the LAN.

The problem is that each software environment states that some data packet is reported to be lost and if we bring down one of the software environment the error stops occurring.

Can anyone guide me that how can I trace the incoming data via the network from the LAN? Is it really a network problem? Why is that the problem stops occurring when we only run one such a setup of the software? What should be my approach to solve such an issue?

We are running the software on an AIX Ver 5 box.

Thanks in advance.

What does your routing table look like?

# netstat -nr

So you are running AIX on a PC? I didn't know you could that. What speed is the network? And what duplex? Are there any collisions? Looking at the error statistics is a good place to start. I would put a sniffer on the network to see id the network is overloaded.

Are you even using tcp/ip? This sounds more like just ethernet. Couldn't you just cable each device to a nic card? What purpose is served by dumping all of the traffic on one lan?

"So you are running AIX on a PC? I didn't know you could that. "

The software is running on AIX Ver 5, IBM Server.

"What speed is the network?"

The hardware device is operating at a speed of 10Mbps, LAN at 100 Mbps and the Host also at 100Mbps. Please remember that the host is reporting lost of data blocks.

"And what duplex?"

Data is transmission in two directions simultaneously (Full Duplex)

"Are there any collisions?"

Each hardware device on the LAN has one Ethernet CSMA/CD adapter per cable and one individual Ethernet address per adapter.

"Looking at the error statistics is a good place to start. I would put a sniffer on the network to see id the network is overloaded."

What type of statistics? How do I write / put a sniffer on the network ? Please provide me necessary hints.

"Are you even using tcp/ip?"

We are using a proprietary based Data Link Layer protocol, a variant of IEEE 802.2. The protocol frame structure embeds into the MAC (Medium Access Control) layer frame for the Ethernet LAN communications.

"This sounds more like just ethernet. Couldn't you just cable each device to a nic card?"

No it is not possible. Each hardware device is responsible for interfacing with different protocols. For example there is a hardware device specially to deal with X.25, another could be for TCP/IP, similarly for Satellite etc. Hence there is multiple such a hardware devices based upon individual protocol for interaction with the external network.

"What purpose is served by dumping all of the traffic on one lan?"

The Host engine is running on AIX Ver 5 operating system on an IBM server and interfaces with the LAN. Each hardware devices captures incoming data from respective networks and dumps it into LAN. The Host timely monitors the LAN to trace any application specific message for itself. It captures, process and dumps it back into the LAN destined to the respective hardware device to the external network.

To add to the list of information we have taken care of common shared memory access to each individual host processes.

The way you display network statistics varies from OS to OS. On HP-UX, I use "lanadmin" in interactive mode and use the "display" command. On recent versions of SunOS, I like the kstat command. For instance something like "kstat hme::hme0". I'd be a little surprised if either of these works on AIX. But I don't work on AIX so who knows.

It's been a while since I have personally used a sniffer, we have network people who do that. And anyway, each sniffer has its own instructions. But I can at least make a few general remarks. These days, a sniffer is a very high powered laptop...fast cpu, lot of memory, and all possible network connectors. No need for fast or large disks. You connect to the network and it records the traffic. You typically program it to look at traffic between specific boxes and/or specific protocols. Then it can display every packet sent by either box. And it can format the packets and highlight packets that look like an error occurred. Go to google and look for "network sniffer". A more formal name is "protocol analyser", but no one calls them that anymore.