Subject: [nemo] Route Optimization by CR

From: Ryuji Wakikawa <[email-masked]>
Date: Sat, 17 Jul 2004 09:55:04 +0900

Hello

We submitted a new draft on providing route optimization by CR titled
Optimized Route Cache Protocol (ORC).

ORC is based on the similar idea to HAHA protocol. MR uses an anchor
router (either HA or CR) for route optimization. 

ORC provides MR initiated route optimization. It includes dynamically CR
discovery and dynamic binding registration depending on NEMO
communication model.

http://www.ietf.org/internet-drafts/draft-wakikawa-nemo-orc-00.txt

BTW, CR was clearly explained in Pascal's RO Taxonomy draft.

Your comments are appreciated. Please send comments.

thanks
ryuji

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From: Ignacio Soto Campos <[email-masked]>
Date: Tue, 20 Jul 2004 22:01:01 +0200

Hi Ryuji,

Some questions about this draft.

- Section 4.1

    In addition, when a mobile network node starts communication with
    a correspondent node, a mobile router may dynamically discover a
    correspondent router for the correspondent node.  The discovery is
    triggered when a mobile router receives tunneled packets from its
    Home Agent.  The mobile router first sends a correspondent router
    Discovery Request to the correspondent router anycast address.
    The anycast address is created with the prefix address of the
    correspondent node and the well-known anycast identifier.  The
    prefix length for the anycast address is always 64.  When one of
    correspondent router receives the Correspondent Router Discovery
    Request, it replies back a Correspondent Router Discovery Reply
    including all correspondent routers of the administrative domain of
    which the correspondent node is located.

I am trying to understand the mechanism for dynamic correspondent router 
discovery. If the anycast address is created with the prefix address of 
the correspondent node, does this mean that you need a correspondent 
router in the CN subnet to be able to use dynamic discovery of 
correspondent routers? if not, how any other router can know that it 
must attend that anycast address?

- Section 4.3

    Once a mobile router registers its binding to a correspondent router,
    it forwards packets destined to an address which is in range of
    correspondent router's managed prefix.

This forwarding is done in an IP-in-IP tunnel, right?

- Appendix A

    Correspondent routers can intercept packets that are from transit
    AS. For instance, if a correspondent node in AS3 send packets to the
    mobile network, the packets are routed towards the home agent since
    there are no correspondent routers in AS3.  However, on the way to
    the home agent, a correspondent router in AS1 which is the transit AS
    of AS3, can intercept the packets and tunnels them directly to the
    mobile router.

This seems to imply that route optimization can be initiated in the 
correspondent router, but I suppose that route optimization is always 
initiated by the mobile router. But then, how a mobile router can 
discover a correspondent router that is in a different AS from the 
correspondent node?

- Appendix B

In Figure 2 and 3, If I understand correctly, the Correspondent node in 
the upper part of both figures should be a mobile router.

Best regards and thank you,

Ignacio

---

From: Ryuji Wakikawa <[email-masked]>
Date: Wed, 21 Jul 2004 09:51:40 +0900

Hello Ignacio

please find my inline comments.

On 2004/07/21, at 5:01, Ignacio Soto Campos wrote:

> I am trying to understand the mechanism for dynamic correspondent 
> router discovery. If the anycast address is created with the prefix 
> address of the correspondent node, does this mean that you need a 
> correspondent router in the CN subnet to be able to use dynamic 
> discovery of correspondent routers? if not, how any other router can 
> know that it must attend that anycast address?

In our current spec., you always need a CR in the CN subnet (which 
prefix len is 64)
The CR contain addresses of other CRs in the CR discovery reply 
messages.

MR needs prefix address and prefix length to generate the CR anycast 
address,
but MR can not retrieve the prefix length from packets originated by CN.
Thus, we make the assumption for CR discovery that a
CR is always placed in the edge network of CN.

If MR statically knows CR, no reason to place CR in edge networks.

> This forwarding is done in an IP-in-IP tunnel, right?

Yes.

> discover a correspondent router that is in a different AS from the 

MR does not attempt to discover a CR in a different AS.
Some BGP routers may have CR functions and intercept packets sent from 
another AS, while routing packets.
Since this RO is blindly occurred, we needs to investigate security 
issue and do not complete it yet.
That's why we put this into Appendix.

> - Appendix B
>
> In Figure 2 and 3, If I understand correctly, the Correspondent node 
> in the upper part of both figures should be a mobile router.

Yes, right.
Thanks.

regards,
ryuji

>> router (either HA or CR) for route optimization. ORC provides MR 
>> initiated route optimization. It includes dynamically CR