Re: [mif] Hybrid Access Problem

[Michael Richardson <[e-mail]>]

Margaret Wasserman <[e-mail]> wrote:
    > Let me see if I can start a technical discussion here...

    > If you have an ISP today that has two different access networks
    > available, such as one 3GPP network and one DSL network, how do(es) the
    > gateway box(es) (connected to both networks) decide where it should
    > send each packet it receives?  I think there are several possible cases
    > here;

These scenarios are all in the homenet architecture document, btw.
Can you tell me if this is IPv4+NAPT or IPv6?  (The IPv4 case without NAPT is
mostly the same as IPv6)

    > (1.2) Hosts behind the gateway have only one address each.  This has
    > two sub-cases:

    > (1.2.1) The gateway has separate addresses on the two networks, and
    > does some sort of translation from internal to external addresses in
    > the prefix of the "right" outgoing link.

NAPT.

    > (1.2.2) The gateway has only one IP address that is somehow shared
    > across the two links.

MPPE or equivalent.

Can you tell me if in your scenarios, the operator of the two access networks
is the same? 

    > (2) There are two gateways, each attached to a single outbound network.
    > In this case, hosts will always have separate addresses for the two
    > networks, and will need to make a decision about which outbound network
    > to use.

As you say, this is a kind of MIF with multi-provisioning domains, and
if the host can decide the right choice of source address, the rest is
"solved" by homenet already.

    > Cases 1.1 and 2 are essentially the same from a host standpoint, in
    > that the host needs to make a network choice.  This is a problem we
    > have discussed in MIF -- What sort of information does/should the host
    > need to make that choice, and how is that information communicated to
    > the host?

Yes, I agree.

    > Case 1.2.1 is a typical case of how NAT (or NPTv6) can be used for
    > multi-homing.  The IETF generally prefers to avoid recommending
    > solutions that use NAT, but do we have a better answer?

    > Case 1.2.2 becomes a layer 2 problem and is probably outside the scope
    > of the IETF.

    > Are there cases that I am missing here?

I am trying to think whether embedding a second layer of the problem in the
scenario changes anything significantly.

-- 
]               Never tell me the odds!                 | ipv6 mesh networks [ 
]   Michael Richardson, Sandelman Software Works        | network architect  [ 
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