Re: [Hipsec] Sending data on HIP packets

[Robert Moskowitz <[e-mail]>]

On 04/21/2010 12:14 PM, Laganier, Julien wrote:
> Robert Moskowitz wrote:
>    
>> Is there any experience in sending data along with I2 and R2?
>>      
> I don't.
>
>    
>> Is this easy to do or very hard even with HIP aware apps?
>>      
> Hmmm. Isn't this going to create problem with PMTUD because the PMTU on the data sent over I2 and R2 will be lower than can be expected after the HIP handshake concludes? On the other hand if the first sent is TCP SYN on I2 and TCP SYN ACK on R2 then there's no problem with PMTUD...

The Initiator would have to 'know' that the data would fit within the 
allowed frame size.

The Responder (after validating I2 and setting up the HIP Association 
state) might just pass the data up the stack and immediate send R2 
without any data, the data response following later in its own datagram.

Or if the Responder 'knows' there should be a response, it holds off on 
sending R2 until it gets the data (typically a TCP SYN/ACK). In fact if 
the higher layer rejects the connection with a quite drop, the Responder 
could not even send R2 and quitely drop the Association as well.

Lots of room for smart behaviour. Or bad programming :)