Re: Preparing for DMM future steps and rechartering

Le 11/11/2013 16:29, Sri Gundavelli (sgundave) a écrit :
> Hi Pete,
>
> I'm not sure, I agree with this, or understand this to be precise. I
>  do not know know CP (in the form of PMIP, GTP or some other protocol
>  XYZ) can be completely eliminated. There needs to be some interface
>  between the access gateway and the mobility anchor. I assumed
> your's, Marco's and Ryuji's goal is for eliminating the tunnel,
> which I don't believe it can be achieved, but still thought we can
> discuss this. IMO, its not just about inserting a RIB route and
> redistributing it, but even there in DP there is a state transfer
> needed  from the CP and the DP. Starting point appears like a simple
> route propagation, very soon it will end up with a bunch of state
> that gets moved between the two nodes.  But, may be I don't
> understand the ideas clearly on eliminating CP and eliminating
> tunnels. I'm not going to oppose this, I don't see this converging,
> IMHO.

I think it may converge.

I am not sure whether we have reached a point where we can discuss
without assuming a particular protocol (i.e. neither MIP, nor BGP), but
I think we can discuss route update method vs tunnel-based method.

We can also discuss whether new functionality is needed on the mobile
entity, vs whether the first-hop router does much on its behalf
('proxy').  Which may bring in a question of whether a Mobile Host or a
Mobile Router is considered.

Effects of route updates may be too heavy on a network ('route churn')
or less so; it may depend, among several factors, on the topology and
the addressing architecture of the fixed network.

Routing protocols are highly distributed concepts, yet many include
particularly designated entities, which have particular roles (not all
routers are equal) - these could host what we expect to be more
controlling points.

Alex

>
>
>
>
> Regards Sri
>
>
>
> On 11/10/13 3:13 PM, "Peter McCann" <[email protected]> wrote:
>
>> Hi, Sri,
>>
>> I think you will agree that PMIP is a control protocol for setting
>>  up tunnels.  A tunnel implies that we are not using the
>> destination IP of the inner packet for routing and by definition
>> will lead to a non-optimal route and a bit of state on some box
>> that can fail and lose that state.
>>
>> I hope that DMM can consider other approaches such as injecting
>> routes from the latest L2-attachment point into the access network,
>> which is a truly Distributed Mobility Management protocol for
>> getting the packets to the mobile node.  It will lead to more
>> optimal routes and more robust fault-tolerant operation of the
>> network.
>>
>> I think we can continue to use the term MAG to apply to that
>> first-hop router which is hopefully co-located with the L2
>> termination point (it may not be so in every technology depending
>> on the extent to which that technology has evolved to support truly
>> Distributed operation).  Anything that happens below the MAG
>> (between the MAG and the L2 termination point) should be out of
>> scope and we should not define any protocol there and we should
>> discourage any separation between the two.
>>
>> However, we should not require the MAG to run any form of PMIP
>> because tunnels should not be required in the architecture.  We
>> should not require an LMA, because this would imply a central point
>> of state maintenance and possibility of failure.
>>
>> It is fine to consider a split between CP and DP but I thought we
>> had agreed that any discussion of the protocol to use on such an
>> interface would be out of scope for this WG.  IMHO we should leave
>>  that to the Wireless & Mobile Working Group of ONF.
>>
>> Now, the proponents of OpenFlow and other CP/DP splits have argued
>>  that it is better to centralize the algorithms such as routing
>> protocols on a logically centralized server or servers with a
>> synchronized global view of the network. I have no problem with
>> that, in which case this centralized controller just needs to get
>> notified about the MN's current attachment point, so it can
>> install the routes (or tunnels, if an operator wishes to use them)
>> into the DP. But, the mechanisms for doing so are out of scope for
>> the DMM WG because we are not working on a CP/DP split.  I think it
>> would be appropriate for the DMM WG (which exists in the IETF, a
>> standards body that has a long history of developing distributed
>> and fault-tolerant routing protocols) to describe a more
>> distributed alternative, building on foundational Internet
>> technologies such as I-BGP, in such a way that will bring down the
>>  costs, reduce the latency, and increase the robustness of wireless
>>  access networks.
>>
>> I actually don't think we need to define any new extensions or IEs
>>  for BGP; I would like to read more about Ryuji's proposed
>> extensions here.  All we need is for the MAG to learn what IPs have
>> been assigned to the MN, decide which of those IPs are in the scope
>> of the local AS, and inject routes for those prefixes to itself. We
>> could work on alternative mechanisms for discovering this list of
>> addresses - the fundamental requirement is that we use an
>> authenticated MN ID (probably an NAI) as an index to lookup the set
>> of IPs in a distributed database. I've proposed using DNS for this
>> but there are other alternatives.  We also need a way to make sure
>> the latest UPDATE gets used by all the BGP peers. I've proposed
>> putting a timestamp in LOCAL_PREF but there are probably other
>> alternatives.
>>
>> It would also be nice to have a well-defined fall-back mechanism in
>> case the MN moves to a different AS or just too far from the
>> original MAG, in which case the I-BGP approach wouldn't scale. For
>> these cases, I think a client MIP tunnel to an HA located in the
>> original AS for each assigned IP address would be ideal. The HA can
>> behave just like the MAGs in that domain, injecting routes when MNs
>> establish tunnels to it so as to attract the packets to themselves
>> (this would be the routing equivalent of the proxy-ARP or proxy-ND
>> mechanism that works on just a single home link in MIPv4 or MIPv6).
>> We should work on mechanisms to enable dynamic assignment of local
>> HAs to MNs and dynamic establishment of security associations that
>> don't require AAA and associated round-trips to the home network.
>> Because the HA is associated with the original MAG that assigned
>> the address, this may involve some DHCP extensions.  There is
>> already a way to assign the HA IP address but we will need new
>> extensions to carry the HA credentials to the MN (maybe just an HA
>> DNS name so the MN can use DANE to retrieve a public key).
>>
>> I think something like the path I've outlined above would make a
>> good work plan for the future of DMM.
>>
>> -Pete
>>
>
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