Access Problems with 7.0

[Doug Hardie]

> I recently upgraded 3 of my 5 servers to 7.0.  Two of them are on  
> new hardware and one is on hardware that used to run 6.2.  Since  
> then, 2 of my thousands of users are unable to access the servers  
> running 7.0.  They can access the server running 6.2 just fine.   
> What happens is the server receives the SYN packet from the client  
> properly and then responds with the SYN packet.  Nothing more is  
> heard from the client.  The server sends a few duplicates of the SYN  
> and then drops the connection.
>
> At this point I am not able to verify that the client receives the  
> SYN.  Neither of them has a clue about tcpdump.  The packets look  
> fine on this end (included later).  Both are using Windows,  
> including XP and Vista.  I suspect they are receiving it and not  
> accepting it for some reason.  However, I don't really see anything  
> that would cause that behavior in the packets.  I can't reproduce  
> the problem here.  Every computer I can try works just fine.
>
> Here is one of the packet traces:
>
> 11:59:00.630414 00:00:0c:38:6f:e1 (oui Cisco) > 00:a0:cc:3e:87:9e  
> (oui Unknown), ethertype IPv4 (0x0800), length 66:  
> cpe-76-169-78-119.socal.res.rr.com.59025 > zool.lafn.org.8000: S  
> 2779920420:2779920420(0) win 8192 <mss 1460,nop,wscale  
> 2,nop,nop,sackOK>
>
> 11:59:00.630634 00:a0:cc:3e:87:9e (oui Unknown) > 00:00:0c:38:6f:e1  
> (oui Cisco), ethertype IPv4 (0x0800), length 66: zool.lafn.org.8000  
> > cpe-76-169-78-119.socal.res.rr.com.59025: S
> 2480373222:2480373222(0) ack 2779920421 win 65535 <mss  
> 1460,nop,wscale 3,sackOK,eol>
>
> 11:59:03.613011 00:00:0c:38:6f:e1 (oui Cisco) > 00:a0:cc:3e:87:9e  
> (oui Unknown), ethertype IPv4 (0x0800), length 66:  
> cpe-76-169-78-119.socal.res.rr.com.59025 > zool.lafn.org.8000: S  
> 2779920420:2779920420(0) win 8192 <mss 1460,nop,wscale  
> 2,nop,nop,sackOK>
>
> 11:59:03.613194 00:a0:cc:3e:87:9e (oui Unknown) > 00:00:0c:38:6f:e1  
> (oui Cisco), ethertype IPv4 (0x0800), length 66: zool.lafn.org.8000  
> > cpe-76-169-78-119.socal.res.rr.com.59025: S  
> 2480373222:2480373222(0) ack 2779920421 win 65535 <mss  
> 1460,nop,wscale 3,sackOK,eol>
>

Checking with the 6.2 server I see there are some differences in the  
TCP options.  7.0 includes wscale 3 where 6.2 does not.  Is there a  
way to disable that feature using sysctl to see if thats the issue?