Re: [IPsec] clariciations for draft-sathyanarayan-ipsecme-advpn-03

[Daniel Migault <[e-mail]>]

Hi Timo,

Thanks for the feed back.

We are happy you provide requirements over "dynamically routing
subnets" as a MUST. ADVPN responds to the requirements listed in
RFC7018. If there is a requirement that does not match you opinion,
can you please point it out?

Just to make it clear this 1 day time has never been mentioned in the
draft and is your assumption. The use of TTL does not impose a 1 day
and ADVPN can take advantage of the Redirect Mechanism or MOBIKE for
multihoming. As you can see the ADVPN solution can take advantage of
all previous and future featured designed for IKEv2. As you point out
the key characteristic of our design is its flexibility.

RFC5685 is not limited to client-gateway, the second line of the
section 10 you pointed out says: [...] the mechanism can also be used
between any two IKEv2 peers. " So no additional specification are
required.

You mention load balancing may be an issue. Can you please specify the
issue you see?

One last point to clarify. it seems that you are trying to say ADVPN
misses some features provided by routing protocols. In fact ADVPN can
take advanatge of ALL of these features as ANY routing protocol can
run on the top of ADVPN. This was a MUST requirement of RFC5685. If
you see a scenrio that you think does not fit ADVPN, please document
it so we can address your specific issue.


Best Regards
Daniel

On Wed, Feb 5, 2014 at 12:50 PM, Timo Teras <[e-mail]> wrote:
> On Mon, 20 Jan 2014 18:14:58 +0000
> Praveen Sathyanarayan <[e-mail]> wrote:
>
>>   1.2 What happens when a prefix administratively changes from behind
>> one branch to another ? How do servers get notified about that ?
>>
>> [PRAVEEN] That's an interesting point Fred, and thanks for bringing
>> it up. First, please refer the ADVPN_INFO Payload and
>> PROTECTED_DOMAIN sections (3.6 and 3.9, respectively) of
>> http://tools.ietf.org/html/draft-sathyanarayan-ipsecme-advpn-03. As a
>> general rule, each spoke can download updated PROTECTED_DOMAIN
>> information periodically, which advertises everything behind the hub
>> and all other spokes combined. Of course, this does not change if
>> some subnet has moved from behind spoke A to behind another spoke, B.
>> However, the Lifetime attribute of the ADVPN_INFO payload is key
>> here. We could see this being employed in a straightforward manner to
>> allow for this transition: a) the subnet can "disappear" and be
>> unreachable for one Lifetime, or b) the original spoke can redirect
>> to the new spoke.
>>
>> We don't think this matters much in the real world, because people
>> don't just move entire subnets instantaneously. Typically, folks stop
>> using a subnet in one place, then begin using it in another. This
>> makes a lot of sense for several operational reasons, as you would
>> imagine. In fact, experience shows that since routing doesn't update
>> across the world immediately, best practice would, for instance,
>> indicate that it's best to wait a day between stopping using the
>> subnet in one place and starting to use it in another place. In this
>> case, a Lifetime of one day or less should be just fine (and we're
>> thinking that, in fact, an hour would be a reasonable Lifetime value
>> in practice).
>>
>> We would indeed argue that using Lifetime allows us to make the basic
>> implementation of ADVPN handle a transition from one administrative
>> domain to another in a straightforward manner. A redirection based on
>> RFC5685 re-uses an already defined mechanism and makes the transition
>> immediate, if/when necessary. This is one more argument for
>> draft-sathyanarayan-ipsecme-advpn as it illustrates the modularity of
>> our ADVPN proposal _and_ keeps the implementation simple.
>
> I disagree. IMGO, dynamically routing subnets is a MUST.
>
> Multiple scenarios exist. But to name one:
>
> I have complex site with multiple internal links and dynamic internal
> routing connected to ADVPN via two or more spokes (connected via
> different ISP lines).
>
> All the spokes can route to all subnets inside that site to provide
> redundancy, and in some cases load balancing.
>
> If one spoke's ISP line dies, or if the internal routing protocol
> decides other wise (e.g. intra-site link fails), the spokes should
> dynamically move the subnet from one to another.
>
> Having a failover time of _a day_ is unacceptable.
>
> The redirect mechanism seems to be limited to client-gateway
> connections, and only the gateway can send it (rfc5685 point 10). This
> is not true in advpn context as any spoke may want to later on redirect
> the SA of subnet it originally initiated. Using redirect would need
> additional specifications to be usable.
>
> Then there is also the case of load balancing... etc.
>
> I do agree that subnets should be authorized to be routed. I do that in
> existing dmvpn install, by means of automatically filtering the
> announced routes based on the presented certificate. That is, the
> certificate tells which subnets it can announce.
>
> - Timo
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-- 
Daniel Migault
Orange Labs -- Security
[phone]