Re: Preparing for DMM future steps and rechartering

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.


 

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
>