Re: [babel] Mirja Kühlewind's Discuss on draft-ietf-babel-hmac-08: (with DISCUSS and COMMENT)

[Mirja Kuehlewind <[e-mail]>]

Hi,

Inline.

> On 7. Aug 2019, at 17:41, Juliusz Chroboczek <[e-mail]> wrote:
> 
>>>> You can also use a different timer e.g. 300s which would also ensure
>>>> that a challenge is not send more often than 300s (expect in the case
>>>> where you got a challenge reply but in case you are not talking to an
>>>> attacker and usually not need to send another challenge request
>>>> immediately).
> 
>>> If the challenge reply is lost, then the challenge needs to be resent.  It
>>> would not be acceptable to cause a 5 min blackhole after a single packet
>>> loss.
> 
>> Why 5 mins?
> 
> You're suggesting 300s in the excerpt cited above.

Sorry I mean 300ms… (one important letter).
> 
>> If the challenge needs to be retransmitted, then the mechanism for
>> retransmitting seems to be missing in the draft or what do I miss?
> 
> A -> B: Challenge
> B -> A: Challenge reply gets lost
> 
> B -> multicast group: normal control packet

But this is usually send every 4 seconds or so…? So the important but seem that these two values fit together.

> 
> (At B, the control packet fails the index test (5th bullet point in 4.3).)
> 
> A -> B: Challenge

I wouldn’t call this a retransmission but rather a new Challenge… anyway that’s just naming…

Mirja


> 
> -- Juliusz
>