Re: [802.21] Comments on 21-06-0698-01-0000_IP_configuration_methods_IE.doc
Hi Yoshi,
>> >First, it is not clear whether it is allowed to run DHCPv6 before
>> >running router discovery.
>>
>> I don't think we need a deep implication regarding the proposed IE
>> since it is a simple hint to support more efficient mobility than now.
>
> I agree that the information should be just a hint, but I need several
> compelling use cases to agree.
>
>> Anyway, it is most likely L2 trigger concept (especially Link UP) that
>> can trigger upper layer (IP layer) operation before completing its own
>> L2 operation. This benefit is an explicit consensus in IETF and
>> world-wide deployment now in mobile environment. That can reduce
>> reduncent delays sort of caused by hierarchical host operations
>> (L1->L2->L3->upper layers). Given this utility, the mobile station can
>> run its IP operation in parallel while L2 attachment. Likewise, 802.21
>> can trigger DHCPv6 before runing router discovery based on 802.21
>> conceptual model (especially Event Service).
>
> How can 802.21 trigger DHCPv6 before runing router discovery, while
> your comment below indicates that router discovery is needed before
> running DHCPv6?
Look at the Figure 1 of 21 specification. MIH Function
can trigger upper layers using Event Service and DHCP
belongs to upper layers. Once detecting a link, this
hint goes to the upper layer via MIH Function. Then,
DHCP Solicit message is sent by a mobile station before
runing RS/RA procedure.
>>
>> >
>> >Second, if it is allowed to run DHCPv6 before running router
>> >discovery, then it should be possible to run DHCPv6 and router
>> >discovery in parallel regardless of the use of proposed IE or even
>> >regardless of the use of 802.21.
>>
>> No, To run DHCPv6 on the host, it should get a related information
>> from router (Router Advertisement [Managed flag] = set), then the
>> mobile station can start sending DHCPv6 Solicit message. If no RA
>> (host timeout), the mobile station can also start initiating DHCPv6
>> operation. From the real experience, it spends at lease a couple of
>> seconds or more. Yes, it is an existing limitation from the IETF
>> perspective, but we can live with 802.21, and I don't see any trouble
>> to make use of the facilities of 802.21 to resolve those limitations.
>
> If IETF does not allow parallel runs of DHCPv6 and router discovery
> how can 802.21 resolve the limitations without violating IETF
> protocols?
Well, what I tried to explain above was for IPv6 address
configuration procedure without 21 support. In that case,
we can't run them in parallel. But, MIH Function can toss
a relevant hint generated by lower layer to the upper layer.
and DHCP works accordingly.
There is no violation against IETF standard. If a link has
no routers (RA support), host use the DHCPv6 to obtain
addresses after having sent a small number of RS as
described in RFC2461. IP_Configuration_Method IE aims to
reduce the delay caused by *a small number of RA*.
Does it makes sense ?
Regards,
Daniel