Subject: Re: [DNA] RE: Review of link-information from Pekka Savola

From: "Tero Kauppinen (JO/LMF)" <[email-masked]>
Date: Sun, 01 May 2005 11:58:47 +0300

Alper Yegin wrote:
> Pekka,
> 
> I perceive this mostly as a stack configuration issue. If your IP has
> nothing to do with a given interface, it should not be getting any
> notifications from there (include the link up). [For example, you would
> not plumb IP driver on a non-IP L2 driver].

I agree.

> 
> IPv4 vs. IPv6 distinction is harder. Link up would tell "IP is enabled",
> but not necessarily which version of the IP is supported on that link.
> The DNA process that consumes the link up notification would have to
> figure that out.

Why should DNA be started on an interface that doesn't support IPv6 in 
the first place? Naturally this issue comes valid if a node roams from 
an IPv6 network to an IPv4 network (or vice versa). IMHO that's beyond 
the scope of DNA. Anyway, what will happen is that the DNA process will 
try to confirm whether it's still on the same IPv6 link or not but the 
process will fail (i.e. timeout). What the node can of course do is to 
run DHCP to get an IPv4 address (in parallel or after the timeout).

/Tero
> 
> Alper
> 
> 
> 
> 
>>>>     Node's establishment of a link-layer connection with an
>>>
>>>attachment
>>>
>>>>     point that signifies the availability of IP service (i.e.,
> 
> being
> 
>>>>able
>>>>     to send and receive IP packets) between the two is considered
> 
> a
> 
>>>>link
>>>>     up event.
>>>>
>>>> ==> a physical link is a link which can carry any media.  Maybe
>>>>you should
>>>> reword this slightly -- for example, a host does not know about
>>>>availability
>>>> of IP (or anything else).  Maybe "availability of IP service" is
>>>>specific to
>>>> some link types which can only carry IP service, not any L3
> 
> protocol?
> 
>>>Not sure if I understood this. Could you please elaborate a bit
> 
> more?
> 
>>You're making the assumption that once a lower-layer link is up, the
>>link can be used to transport IP packets.
>>
>>What if the link supported only IPX or CLNS packets?  What if the link
>>supported only IPv4 but not IPv6 packets? As an example of these,
>>consider protocol-based Ethernet VLANs.
>>
>>That said, I'm not sure how much this spec can do about this kind of
>>situation.  Maybe it could be a bit clearer that it's making a leap of
>>faith when associating "link up => IP protocol available" unless the
>>link can be known a priori to support IP protocol (e.g., I'd guess if
>>you do PPP and also IPCP, you can be pretty sure of that..).
> 
>

---

From: Alper Yegin <[email-masked]>
Date: Mon, 02 May 2005 16:52:00 -0700

> the first place? 

I meant to say, the host does not know whether there is an IPv6-enabled
router on that link or not.... So, it's not a local host configuration,
but a network configuration which can only be dynamically discovered
(but not necessarily via the link up notification).

> Naturally this issue comes valid if a node roams from

Sure.

Alper