>> Is there a conflict between the guidance given in NAT Considerations
> Case 2 (Section 11, paragraph 2, last sentence) and the guidance in
> section 12.2 "Session ID Security"?
>>
>> From section 11:
>>
>> The CAPWAP Data Check state,
>> which
>> establishes the data plane connection and communicates the CAPWAP
>> Data Channel Keepalive, includes the Session Identifier message
>> element, which is used to bind the control and data plane. Use of
>> the Session Identifier message element enables the AC to match the
>> control and data plane flows from multiple WTPs behind the same
>> NAT
>> system (multiple WTPs sharing the same IP address).
>>
>> From section 12:
>>
>> For example, an AC MUST NOT associate decrypted
> DTLS
>> control packets with a particular WTP session based solely on the
>> Session ID in the packet header. Instead, identification should
>> be
>> done based on which DTLS session decrypted the packet. Otherwise
> one
>> authenticated WTP could spoof another authenticated WTP by
>> altering
>> the Session ID in the encrypted CAPWAP header.
>
> I see. Well, both of these sections are covering different cases. The
> first is to cover the correlation of the control and data plane -
> which is why the Session Identifier exists. The second one is
> different, which is to differentiate different control plane packets.
> That said, it does make sense to ensure that we have some consistency
> in the use of the Session ID field. The text would look like:
>
> <proposed text>
> 11. NAT Considerations
> [...]
> The CAPWAP Data
> Check state, which establishes the data plane connection and
> communicates the CAPWAP Data Channel Keepalive, includes the
> Session
> Identifier message element, which is used to bind the control and
> data plane. Use of the Session Identifier message element enables
> the AC to match the control and data plane flows from multiple WTPs
> behind the same NAT system (multiple WTPs sharing the same IP
> address). CAPWAP implementations MUST also use DTLS session
> information on any encrypted CAPWAP channel to validate the source
> of
> both the control and data plane, as described in Section 12.2.
> </proposed text> |