Re: [Hipsec] Comments on 5201-bis-02

Miika Komu <> Mon, 05 July 2010 06:49 UTC

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Subject: Re: [Hipsec] Comments on 5201-bis-02
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On 07/05/2010 07:07 AM, Henderson, Thomas R wrote:

Hi Tom,

>> -----Original Message-----
>> From:
>> [] On Behalf Of Pekka Nikander
>> Sent: Sunday, July 04, 2010 12:15 AM
>> To: René Hummen
>> Cc: HIP WG
>> Subject: Re: [Hipsec] Comments on 5201-bis-02
>>> - 5.3.5 UPDATE
>>> Since working on HIPL I am wondering why HIP only defines a
>> single UPDATE packet. From the perspective of 5201, I can see
>> a conceptually compelling argument behind this approach, as
>> it allows for a general purpose packet for the transmission
>> of maintenance information. However, most extensions using
>> UPDATE that I know of (most noteworthy, ESP rekeying and
>> mobility and multi-homing) require a 3-way message exchange
>> to complete their corresponding task. The packets thereby
>> have a specific order and each of them has specific
>> semantics. Let's take mobility as an example:
>>>      (1) notify the peer of an address change,
>>>      (2) challenge the peer to confirm his new address, and
>>>      (3) satisfy the challenge.
>>> Still, with the current specifications protocol developers
>> are forced to distinguish between these 3 packets by checking
>> the contained parameter combinations. This is, in my opinion,
>> more complex than necessary and error-prone, especially, with
>> respect to the extensibility of the HIP parameters that can
>> be included in UPDATE packets. So, is there a reason that
>> prevents us from specifying different maintenance packet
>> types instead of a single one?
>> The original idea was that UPDATEs would just be a "carrier"
>> for upper level protocols, allowing upper level protocols to
>> be mixed and matched on individual packets.  E.g. so that you
>> could run a mobility exchange and ESP rekeying at the same
>> time, with the same packets.  E.g.
>>      A->B:  Notify address change
>>      B->A:  Challenge address; Initiate ESP rekeying
>>      A->B:  Send the challenge response; Continue ESP rekeying
>>             etc.
>> But since I haven't been involved in implementation efforts
>> for the last N years, I don't know if the current
>> implementations support such behaviour
> I tend to agree with Rene's observations and think it would be worthwhile to examine his proposal in the new protocol version.  I am curious how often the implementations actually couple the rekeying with address change notifications in practice.

this hasn't been the case at least in HIPL.