Re: [mif] Hybrid Access Problem

[Behcet Sarikaya <[e-mail]>]

On Mon, Nov 10, 2014 at 10:08 PM, 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;
>
> (1) There is one gateway attached to both outbound networks.  This has two
> sub-cases:
>
> (1.1) Hosts behind the single gateway have separate addresses on the two
> attached networks.  In that case, the gateway is constrained to send packets
> over the outgoing network that uses the address prefix that matches the
> source address, or the packets will be thrown away by ingress filters on the
> other side.  So, the network choice is made by the hosts.
>

This case is not valid because both attached networks belong to the
same operator. Also the hosts do not get separate addresses from the
attached networks, I think.

> (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.
>

Yes, I think this is the case.

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

This could be the case.

I want to also say here that CPE here is not a mobile router.
There might be mobile routers that are connected to two networks but
not in this case, I think.

Regards,

Behcet
> 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?
>
> Margaret
>
>
>
>
>
>
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