ICS manipulates packets?

[mjohn]

I've got a serious and strange problem with internet connection sharing (ICS) under Win 98SE (with all MS Updates from windowsupdate.microsoft.com), which I use with a dsl connection.

After installing (and removing and installuing ... several times) ICS the auto-"dial" connection starts up correctly on my client's demand. But - neither I can visit web pages nor I can receive my e-mail from my client computer. ping works fine (to intra- and internet).
The local windows network (with file and printer sharing on the ICS host) works fine, too!

But now the strange thing:
I capture both the packets that were sent over the dsl connection (pppoe) and the packets that were sent from/to my local client. The packets I received over pppoe are correct (e.g. those with my e-mails from my pop3-account). But those that are sent from ICS host to my local client contain only nearly the same data: some bytes are omitted or changed, and the packet is filled up with "0" bytes to the original length. About 2 .. 5 bytes are lost on this way in nearly each packet.
Of course I changed the MTUs to the preferred values (network: 1492, ICS: 512), and I tried also lower values.

What should I do? Has anyone else heard about such a problem?

John

Packet loss may be associated with poor network connection. I'd be inclined to change cables/NIC's and see if it resolves.

ICS doesn't manipulate packets AFAIK, it only forwards them. So something else is corrupting the packets, IMO.

Maybe do some testing of the connection without ICS turned on and testing packets. You might find some interesting results!

Cheers
Mick

BTW - welcome to techIMO!!

[DVNT1]

This is an interesting questions. ICS does re-write the packet while substituting IP header information when it sends it out the other interface. It is possible that the new packet isn't exactly the same, at least due to a software bug.

Unfortunately I don't have ICS installed anythere to do the same test.


When you ping from the client to an Internet Host name do you get a reply?

[mjohn]

Originally posted by DVNT1
When you ping from the client to an Internet Host name do you get a reply?

Yes, in general I get a reply. Some hosts don't reply, when I use large packet sizes (e.g. ping xxx.yy -l 1300).

So I changed the ICS MTU to very little values - just now I use an MTU of 200 bytes. Now most things work - but some DNS queries (e.g. "pop.onlinehome.de" for my mail provider) will not be answered correctly. I have to use ip numbers instead, then I can received my mail.

But the manipluated packets when I use greater MTUs (e.g. 512) might be a software fault, right?

Regards
John

[DVNT1]

That's possible but, not frequent from my experiences.



Does the ICS host computer access the Internet flawlessly?


My initial thought is the NIC drivers on ICS host LAN NIC and/or client computer NIC.

[mjohn]

Originally posted by DVNT1
Does the ICS host computer access the Internet flawlessly?


My initial thought is the NIC drivers on ICS host LAN NIC and/or client computer NIC.

The LAN NIC is a Allied Telesyn AT-2500TX, the DSL NIC has a Realtek RTL8029 Chip. I changed the roles (DSL/Home LAN), but the problems with the transmitted packets into the home LAN did not change. So the NICs or their drivers cannot be the reason.

In fact the ICS gost computers seems to access the Internet flawlessly.

John

[mjohn]

mickwish,

I have only one cross over cable, but if there were problems with the cable - would the packet sniffer ethereal than show the incorrect packets identical on both sides of the connection?

I used the connection for huge filetransfers (backups) between my laptop (=ICS client) and my desktop (=ICS host) without any errors. So I don't think that standard drivers or hardware can be responsible for the damaged packets...

John

[DVNT1]

You've done adequate troubleshooting IMO. It seems like ICS is failing.

You could try the free AnalogX proxy software. That would help confirm if ICS is the problem.

http://www.analogx.com/contents/down...work/proxy.htm