Subject: [homenet] Does the draft-arkko-homenet-prefix-assignment-01 block the chances for policies in multihomed networks?

From: Mattia Rossi <[email-masked]>
Date: Fri, 04 Nov 2011 15:24:53 +1100

I'm not sure if I'm missing anything here, but as far as I understood, 
the draft does not allow having multiple prefixes within a subnet 
segment. Is tht right?

So in the following case:

    subnet 1    subnet 2
       |            |
      R1           R2
       |            |
       +------------+
       |            |
      H1 - (ISP1)  H2 - (ISP2)

If I want to be able to reach the Internet from a host in subnet 1 via 
H1 or H2, depending on my policy in place, I need to use prefixes of 
both , H1's and H2's prefix pool in subnet 1. So the host can use 
addresses from both subprefixes and make sure that the return packets 
are routed back to the host properly.

draft-arkko-homenet-prefix-assignment-01 anyhow seems to allow only one 
prefix per subnet, e.g. R1 would only get to use one prefix for subnet 
1, which screws the host in subnet1 which might have a policy of using 
H1 for video and H2 for other or any of the other problems discussed in 
this list.

As said, I might miss something here, but it's not clear to me from the 
draft.

Mat

-- 
Mattia Rossi
R&D Engineer
Centre for Advanced Internet Architectures (CAIA)
Faculty of ICT
Swinburne University of Technology
Hawthorn
3122 VIC
Australia

email: [email-masked]
phone: +61 3 9214 4844

---

From: Mattia Rossi <[email-masked]>
Date: Fri, 04 Nov 2011 15:30:45 +1100

On 04/11/2011 15:24, Mattia Rossi wrote:
[..]
> both , H1's and H2's prefix pool in subnet 1.

Err.. I meant content sitting at ISP1 or ISP2 not reachable from the 
Internet (walled garden).

Mat

---

From: Acee Lindem <[email-masked]>
Date: Fri, 4 Nov 2011 09:00:11 -0400

Hi Mattia,

> the draft does not allow having multiple prefixes within a subnet 

No - what it avoids is two prefixes that are subnets of the same prefix advertised in a Usable Prefix TLV from being assigned on a network segment. 

Thanks,
Acee 

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---

From: Laurent Toutain <[email-masked]>
Date: Fri, 4 Nov 2011 15:47:07 +0100

Hi Mattia,

In our proposal, we assigned a SID for each GP prefix, and I think
draft-arkko-homenet-prefix-assignment does the same. but that does not
solve completely the problem:

If a host in subnet 1 selects a prefix from H1 and routing inside the Home
Network send packets to ISP2, in-gress filtering of ISP2 will block the
traffic. The source address must be taken into account to find the ISP.
 Since GP is flooded inside the home network, every router is aware of the
provider prefixes, so routers can be modified to take into account the
source address in the forwarding process.

In [1] you will find more information on the way we solve it. The main idea
is to add another lookup instead of using the default route. When you use
the default route it means that the prefix is outside of the home network.
In that case, we use another "routing table" to find the next hop based on
the prefix included in the source address, so packets reach the right
provider. This table is built the same way, for example a shortest path to
the provider prefix.

The second problem is to inform the host of available services from
provider H1 and  provider H2. Hosts have to be aware of the prefixes they
should used to reach a service. We need to develop a protocol for that and
modify source address selection in the host.

Laurent
---

[1] de Santerre, E.G.; Jammoul, S.; Toutain, L.; , "Solving the Ingress
Filtering Issue in an IPv6 Multihomed Home Network," *Networks (ICN), 2010
Ninth International Conference on* , vol., no., pp.272-278, 11-16 April 2010
doi: 10.1109/ICN.2010.50

On Fri, Nov 4, 2011 at 05:30, Mattia Rossi <[email-masked]> wrote:

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