Re: Questions on draft-matsushima-stateless-uplane-vepc-02

Hi Satoru,

Thanks again.

Please see my replies inline.

Regards,

Behcet

On Tue, May 20, 2014 at 8:47 PM, Satoru Matsushima
<[email protected]> wrote:
> Hi Behcet,
>
>
> On Wed, May 21, 2014 at 1:17 AM, Behcet Sarikaya <[email protected]>
> wrote:
> -- snip --
>
>>
>> >
>> >> Referring to Steps 14 and 15 in Figure 4, in Step 14, Route Update (I
>> >> guess BGP Route Update) is initiated by
>> >> which node and is going to which node?
>> >
>> > As you see step 14 in the sequence, any specific node aren't assumed to
>> > initiate routing update on vEPC side, due to the scope of the draft,
>> > EPC-E
>> > router is the receiving node of routing update
>>
>> You mean more than one node can initiate it, my question was which
>> node(s)?
>>
>
> I meant that the draft doesn't mention exactly which node advertise that, it
> could be expected to exist in the vEPC side. But I find that in terms of
> usual BGP operation, that node could be Route-Reflector(RR), or
> Route-Server(RS).
> Just one case would be expected that a set of information which includes an
> endpoint information of tunnel and an UE assigned prefix is informed from a
> mobility management node in the vEPC to RR or RS.
>

Are you sure?
How would RR or RS know about UE mobility?

I was expecting you to say MME?

>
>>
>> >
>> >> In Step 15 you have EPC-E initiating this and it is going towards RTR.
>> >> Why
>> >> is this not sufficient? i.e. since EPC-E
>> >> can detect mobility?
>> >> Why do you need Step 14?
>> >
>> > The reason of the EPC-E advertise route toward RTR is that EPC-E can
>> > aggregate multiple UE's prefixes into less BGP routes as a part of
>> > normal
>> > routing operation within operator's network.
>>
>> You mean host routes are not needed in the upstream BGP routers? How
>> does that work?
>
>
> Yes, host routes are not needed in the upstream routers because aggregated
> routes EPC-E router advertised work well for the upstream routers to send
> out packets toward advertising EPC-E routers.
>

Isn't it kind of host routes? Maybe host prefixes? Otherwise I can not
image how you would route to UEs that are topologically incorrect?

>
>>
>>
>> >Step 14 makes EPC-E not to
>> > detect mobility directly.
>>
>> I understand that.
>>
>> >
>> >> For the uplink traffic from UE, you seem to assume that it is always
>> >> towards RTR. Could it not be directed to
>> >> another UE? What happens in that case?
>> >
>> > When an EPC-E router has a route for destination of the packet from UE,
>> > the
>> > EPC-E router forward the packet to the destination.
>>
>> You mean to another EPC-E?
>>
>
> I just meant that the packets are always forwarded along with the routing
> table of each node.
>

Yes, I think that the packet to another UE would be routed downstream
before reaching the RTR.

> cheers,
> --satoru