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IKE Protocol have 2 modes, that modes have different structure. Does IKEv2 protocol have two modes like IKE.

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up vote 3 down vote accepted

No, IKEv2 has nothing analogous to 'main mode' and 'aggressive mode', and they eliminated the initial 'quick mode',

When IKEv1 was originally written, they wanted a strong separation between IKE and IPsec; they had a vision where IKE might be used for things other than IPsec (other "Domains of Interpretation"). So, they completely isolated the "negotiate IKE SAs" and "negotiate IPsec SAs" into two separate series of exchanges.

In addition, they weren't sure if it would be better to minimize the number of round trip messages, or to provide identity protection; hence they designed two different modes (which would allow implementers to select the trade-off).

When they designed IKEv2, they rethought both these options. They realized that no one really used IKE for anything other than IPsec, and that forcing implementers to support different options was the Wrong Thing. Hence, they tried to combine the IKE SA and initial IPsec SA negotiation into a single set of exchanges (reducing the number of round trips, hence getting most of the benefit of "aggressive mode"), while retaining the identity protection (and DoS resistance) of main mode.

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Thanks very much for informative answer. Can we say that in IKEv2 IKE SA and IPSec SA aren't separate? – Gev_sedrakyan Apr 15 '14 at 13:37
@Gev_sedrakyan: actually, they are separate, for example, you can rekey one without the other, and one IKEv2 SA can parent multiple IPSec SAs simultaneously. However the IKEv2 mandates that they be initially generated at the same time, and that they are related in a closer way than what IKEv1 mandated. – poncho Apr 15 '14 at 13:43
And the last question about IKEv2 phase 2. Does Phase 2 have different modes like IKEv1 (Quck Mode,...) – Gev_sedrakyan Apr 15 '14 at 13:57
@Gev_sedrakyan: I tried to cover that in my answer; during initial SA bring up, IKEv2 does not have one set of exchanges to bring up the IKE SA, and then a second set to bring up the IPSec SA; it's done with one set. Now, afterwards, there is a "Child SA" exchange; that's used both as a "non-initial Quick Mode" (both to rekey IPSec SAs, and to create new ones), and as a way to rekey an IKE SA (which IKEv1 doesn't do; it does an independent Main Mode/Aggressive Mode to "rekey" an IKE SA). – poncho Apr 15 '14 at 14:16

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