Changes in version 8 resulting from comments in: Re: Retransmission of I2 messages

[marcelo bagnulo braun <marcelo@it.uc3m.es>]

El 11/12/2006, a las 10:02, Matthijs Mekking escribió:

> Hi,
>
> I have a question about the proto draft. In section 7.12, the draft 
> says
>  "If the initiator does not receive an R2 message after I2_TIMEOUT time
> after sending an I2 message it MAY retransmit the I2 message" and "Thus
> the initiator SHOULD fall back to retransmitting the I1 message when
> there is no R2 received after retransmitting the I2 message
> I2_RETRIES_MAX times."
>
> I am concerned about keywords MAY and SHOULD in section 7.12. If an
> implementation decides not to implement these retransmissions, then
> according to the protocol specification, the fall back to 
> retransmitting
> I1 messages would never occur (because this SHOULD happen after
> I2_RETRIES_MAX retransmissions of I2). If the I2 is not accepted by the
> responder, and no retransmissions are sent, than the context would stay
> in I2-SENT, and is never able to reach ESTABLISHED.
>
> I think the host MAY retransmit I2 messages, but MUST fall back after a
> certain amount of time, to avoid this deadlock situation. The same
> applies for retransmitting I2bis messages.

I have rephrased this section  in order to clarify this.

the section is now:

If the initiator does not receive an R2 message after I2_TIMEOUT
time after sending an I2 message it MAY retransmit the I2 message, using
binary exponential backoff and randomized timers.
The Responder Validator option might have
a limited lifetime, that is, the peer might reject Responder Validator 
options
that are older than VALIDATOR_MIN_LIFETIME to avoid replay attacks. In 
the case that
the initiator decides not to retransmit I2 messages or in the case that 
the
initiator still does not recieve an R2 message after
retransmitting I2 messages I2_RETRIES_MAX times,
the initiator SHOULD retransmit the I1 message.

Hope this clarifies this issue

Thanks for the review,

regards, marcelo



> Furthermore, last week I have sent an e-mail with questions about the
> proto6 draft (http://ops.ietf.org/lists/shim6/msg01738.html). I would 
> be
> very grateful if someone could answer them.
>
> With kind regards,
>
> Matthijs Mekking
> matthijs@NLnetLabs.nl
> NLnetLabs/Radboud University