Re: Default TCP Options creating problems

Re: Default TCP Options creating problems

[Eric Dumazet]

Le vendredi 27 janvier 2012 à 19:45 +0530, Nanda Kumar a écrit :
> Hi,
> 
> I am using Ubuntu 11.10 and unable to connect to my ISP login server.
> The same is working under windows. Under linux, ISP server does not
> respond TCP SYN packet even. I did a comparison of packet capture of
> windows and linux and found, linux include TCP options by default.
> After manually disabling TCP Timestamp via sysctl, the login is
> happening fine.
> 

> 
> Is there any reason why TCP option is enabled by default? The same
> problem was happening under OpenSUSE 12.1 x86_64 also. My friend
> informed me that his android mobile is also unable to connect to ISP
> login server.

I am very sorry, but you should complain to your ISP, 20 years after RFC
1323, it should support it.

TCP options are ... options, and as such should not be denied by a
conformant TCP stack.

Re: Default TCP Options creating problems

[Nanda Kumar]

Hi Eric,

On Friday 27 January 2012 08:19 PM, Eric Dumazet wrote:
> Le vendredi 27 janvier 2012 à 19:45 +0530, Nanda Kumar a écrit :
>> Hi,
>>
>> I am using Ubuntu 11.10 and unable to connect to my ISP login server.
>> The same is working under windows. Under linux, ISP server does not
>> respond TCP SYN packet even. I did a comparison of packet capture of
>> windows and linux and found, linux include TCP options by default.
>> After manually disabling TCP Timestamp via sysctl, the login is
>> happening fine.
>>
>> Is there any reason why TCP option is enabled by default? The same
>> problem was happening under OpenSUSE 12.1 x86_64 also. My friend
>> informed me that his android mobile is also unable to connect to ISP
>> login server.
> I am very sorry, but you should complain to your ISP, 20 years after RFC
> 1323, it should support it.
>
> TCP options are ... options, and as such should not be denied by a
> conformant TCP stack.
>
>
>
>

Thank you for the reply. Yes even I feel so. I have put up this issue to 
ISP.

However this issue is happening only with TCP timestamp option. All 
other options are working fine. Any idea?

Regards,
Nandakumar

Re: Default TCP Options creating problems

[Eric Dumazet]

Le vendredi 27 janvier 2012 à 21:21 +0530, Nanda Kumar a écrit :

> Thank you for the reply. Yes even I feel so. I have put up this issue to 
> ISP.
> 
> However this issue is happening only with TCP timestamp option. All 
> other options are working fine. Any idea?
> 

If you disable all options but tcp timestamps, what happens ?

Re: Default TCP Options creating problems

[NandaKumar]

On 1/27/2012 8:50 PM, Eric Dumazet wrote:
> If you disable all options but tcp timestamps, what happens ? 

No, it doesn't work. I disabled SACK and window scaling. The connection 
gets established immediately once I disable tcp_timestamps. It may be 
problem with ISP. I am still awaiting their response. Not sure what sort 
of filtering they use for TCP Timestamps.

Thank you for your time.

Regards,
Nandakumar