Re: [DMM] Questions on draft-matsushima-stateless-uplane-vepc-02

[Satoru Matsushima <[e-mail]>]

Hi Behcet,


On Sat, May 24, 2014 at 1:23 AM, Behcet Sarikaya <[e-mail]>wrote:
-- snip --

> >
> > In the draft, as long as an UE keeps same prefix during hand-over among
> > EPC-E routers, those routers belong to a same group that is expected to
> > preserve same prefix for the UE. It should be initial attach when the UE
> is
> > attached to different EPC-E and assigned different prefix from previous
> one.
> > Please read section 3.3 and 3.4 of the draft.
> >
>
> Attach is OK but I am talking about handover. In Section 3.4 you say:
> Thus, UE's address
>    is unchanged even after handover.
>
> I don't understand your statement
> those routers belong to a same group that is expected to
>  preserve same prefix for the UE.
>
> I think you mentioned this before in another conversation that EPC-E's
> will be assigned prefixes based on geographical division. If a UE
> moves to a different region, how could the routers preserve the same
> prefix for the UE without host routes or host prefixes?
>
>
That's true geographical prefix could be a type of operation policy, but it
doesn't mean connectivity within the access and core network are also
divided geographically. If connectivity is also divided by the area, the UE
prefix must be re-assinged when the handover across the area. But that's an
operation matter.

If it's not, which is my thought, the EPC-E routers that belong to one
group can be reachable from eNBs during UE handover,  the control-plane
doesn't need to change the tunnel endpoint address. Since that address is
an anycast address shared among the EPC-Es, all packets come from UE are
continuously forwarded to same EPC-E group. So the UE can keep same prefix.

cheers,
--satoru