Re: [Hipsec] proposed changes to RFC5206-bis

Tom Henderson <> Tue, 16 December 2014 15:18 UTC

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Date: Tue, 16 Dec 2014 07:18:12 -0800
From: Tom Henderson <>
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To: Rene Hummen <>
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Subject: Re: [Hipsec] proposed changes to RFC5206-bis
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Thanks Rene for your comments; responses inline below.

On 12/15/2014 02:19 AM, Rene Hummen wrote:
> Hi Tom, hi all,
> please find my feedback in-line.
> On 12 Dec 2014, at 02:09, Tom Henderson <> wrote:
>> Hi all, I recently published the version -07 draft of RFC5206-bis
>> (mobility support in HIP).  This was merely a refresh of -06; I'd
>> like to now start moving through and closing the remaining open
>> issues so we can get the document into shape for WGLC.
>> I made a pass through the document and plan to publish the
>> following (IMO) minor changes in version -08 next week, if there
>> are no objections.  Separately, I will start threads on remaining
>> open issues that require some discussion on the list.
>> Section 3.2  Protocol Overview ------------------------------ The
>> draft states:
>> However, some implementations may want to experiment with sending
>> LOCATOR_SET parameters also on other packets, such as R1, I2, and
>> I propose to delete this sentence since we are no longer
>> experimental;
> +1
> I would actually propose to completely remove all mentioning of the
> LOCATOR_SET parameter from any message type but UPDATE within the
> context of this document in order to simplify host mobility to a
> single procedure (UPDATE with LOCATOR_SET). If, e.g., multi-homing,
> prefers the LOCATOR_SET parameter in other messages, a separate
> document can specify this message flow.

I hadn't considered this, but it would be in keeping with the 
mobility/multihoming scope split that we have already agreed to do.

I'll look into migrating the use of additional messages from this draft 
to the multihoming draft if there are no other comments.

>> later in the document (section 5.3), it states that:
>> A host SHOULD be prepared to receive a LOCATOR_SET parameter in
>> the following HIP packets: R1, I2, UPDATE, and NOTIFY.
>> and it leaves open to the implementation (Section 5.2) when to send
>> such a packet.   More on this later.
> See comment above.
>> (also) Section 3.2: ------------------ The draft states:
>> The scenarios below at times describe addresses as being in either
>> 'VERIFIED' is a typo; it should be ‘UNVERIFIED'
> +1
>> 3.2.1  Mobility with a Single SA Pair (No Rekeying)
>> --------------------------------------------------- The draft
>> states:
>> This first example considers the case in which the mobile host has
>> only one interface, IP address, a single pair of SAs (one inbound,
>> one outbound), and no rekeying
>> I propose to clarify 'IP address' as rather 'one IP address in use
>> within the HIP session', since it is seldom the case now that hosts
>> have one IP address system-wide, and what is really intended here
>> is to talk about the case for which there is only one IP address in
>> use.
> +1
>> 3.2.3. Using LOCATOR_SETs across Addressing Realms
>> -------------------------------------------------- I propose to
>> delete this section for now; we have an open issue
>> ( to better define
>> cross-family handovers, and I'd like to later propose different
>> text based on the work published in "Secure and Efficient IPv4/IPv6
>> Handovers Using Host-based Identifier-Locator Split" by Varjonen et
>> al.
> Why don’t you simply replace this section with your text in an
> upcoming revision? I don’t see the benefit in removing this section
> right now without a proper replacement.

Partly because I hadn't come up with that replacement text yet, or 
concluded that we should keep it in this draft.

I think the use case in the current draft is not very well defined (one 
host has only a IPv6 locator, while the other host has only an IPv4 
locator, and some middlebox manages the translation), so I would propose 
to delete this case.  If so, the question is whether to try to add 
something back about mobility across addressing realms in this draft.

Another possibility would be to move this topic over to the multihoming 
draft, since it involves coordination across locator sets.  Any 
objection if we descope it from this draft and make an cross-family 
handover a use case in the multihoming draft?

>> 4.3  UPDATE Packet with Included LOCATOR_SET
>> -------------------------------------------- There is a sentence
>> that says:
>> The sending of multiple LOCATOR_SET and/or ESP_INFO parameters is
>> for further study; receivers may wish to experiment with supporting
>> such a possibility.
>> I propose to delete this since supporting it is more complicated
>> and I am not sure of the use case.
> +1
> What about mandating a _single_ LOCATOR_SET parameter per HIP
> packet?

I'd agree with that proposal.

>> 5.1. Locator Data Structure and Status
>> -------------------------------------- The draft states:
>> In a typical implementation, each outgoing locator is represented
>> by a piece of state that contains the following data:
>> I propose to clarify this by deleting 'outgoing locator' and
>> replacing with 'locator known about the peer' since outgoing might
>> be interpreted instead as the source address.
> What about saying ‘each locator announced in a LOCATOR_SET
> parameter’?

Agree, that is even more precise.

>> I would also like to add these two sentences to the end of this
>> subsection:
>> In addition, an implementation would typically maintain similar
>> state about its own locators offered to the peer.
> I wouldn’t mind about adding this text.
>> Finally, the locators used to establish the HIP association are by
>> default assumed to be the initial preferred locators in ACTIVE
>> state, with an unbounded lifetime.
> +1
>> 5.2. Sending LOCATOR_SETs ------------------------- The lead
>> sentence states:
>> The decision of when to send LOCATOR_SETs is basically a local
>> policy issue.
>> I propose to add:  "LOCATOR_SET parameters MAY be included in HIP
>> packet types of R1, I2, R2, UPDATE, and NOTIFY."
>> We have previously not included R2 in this list, but the work
>> published in "Secure and Efficient IPv4/IPv6 Handovers Using
>> Host-based Identifier-Locator Split" by Varjonen et al. discussed
>> some benefits found by allowing the parameter also in R2.
> I admit that I didn’t read the referenced paper. Still, I think we
> should make the mobility procedure plain simple. I therefore suggest
> to only specify the use of the LOCATOR_SET parameter in UPDATE
> messages.

If we follow your proposal, this could migrate to the multihoming draft.

>> There is also a paragraph that states:
>> Note that the purpose of announcing IP addresses in a LOCATOR_SET
>> is to provide connectivity between the communicating hosts.  In
>> most cases, tunnels or virtual interfaces such as IPsec tunnel
>> interfaces or Mobile IP home addresses provide sub-optimal
>> connectivity. Furthermore, it should be possible to replace most
>> tunnels with HIP based "non-tunneling", therefore making most
>> virtual interfaces fairly unnecessary in the future.  Therefore,
>> virtual interfaces SHOULD NOT be announced in general.  On the
>> other hand, there are clearly situations where tunnels are used for
>> diagnostic and/or testing purposes.  In such and other similar
>> cases announcing the IP addresses of virtual interfaces may be
>> appropriate.
>> I'd like to reduce this to the following:
>> Locators corresponding to tunnel interfaces (e.g. IPsec tunnel
>> interfaces or Mobile IP home addresses) or other virtual interfaces
>> MAY be announced in a LOCATOR_SET, but implementations SHOULD avoid
>> announcing such locators as preferred locators if more direct paths
>> may be obtained by instead preferring locators from non-virtual
>> interfaces.
> +1 but I would replace “ more direct paths may be obtained by instead
> preferring locators from non-virtual interfaces” with “non-tunneling
> interface and their locator(s) provide more direct path to the HIP
> peer”.

I'm finewith the suggested wording change.

>> 5.3. Handling Received LOCATOR_SETs
>> ----------------------------------- The draft states:
>> A host SHOULD be prepared to receive a LOCATOR_SET parameter in
>> the following HIP packets: R1, I2, UPDATE, and NOTIFY.
>> Similar to the proposal in 5.2 above, I'd like to change to:
>> A host SHOULD be prepared to receive a LOCATOR_SET parameter in
>> the following HIP packets: R1, I2, R2, UPDATE, and NOTIFY.
> See my above comment.