Re: [RRG] What do we have consensus on?

[Lixia Zhang <lixia@CS.UCLA.EDU>]

On May 28, 2008, at 12:57 AM, Tony Li wrote:

> |Tony suggested 3 branches:
> |
> |- Transport:   this falls with #1 in the above
> |- Map-n-encap: this is #2 in the above
> |- Translation: I did not get exactly what this one is, if it is
> |                not the GSE rewrite.
> |
> |there was a debate between Tony and Brian at the time about whether
> |SHIM6 is translation. I dont think I fully understood Tony's argument
> |on why SHIM6 is a translation; may be Tony could try one more
> |time here.
>
> The way that I look at it, Shim6 establishes a set of 'identifiers'  
> that the
> transport protocols will use and then plays some games to determine  
> the set
> of 'locators' for network layer operations.  Since it is doing  
> wholesale
> swapping of the locators for the identifiers, I'd claim that it's  
> mostly a
> translation approach.
>
> I think that it's clear that it's not actually changing transport.   
> Further,
> it's pretty clear that while it is piggybacking some information, it  
> really
> isn't going to the full-scale extent of a real encapsulation.
>
> That said, I recall thinking that there was some validity to Brian's
> position and at the same time thinking that it wasn't yet worth  
> worrying
> about the specific details.  I am, of course, very happy to revisit  
> this if
> it becomes productive.
>
> Tony

through a phone chat with Tony, I finally got what's the above tried  
to say.
It's all due to from which angle one looks at the picture.

I take the view of scaling routing by provider-aggregatable prefixes:  
for a multihomed site, both SHIM6 and Handley proposal take the  
multiple provider-based addresses all the way *into* each host.  As  
far as routing scalability is concerned, it makes no difference  
whether these multiple PA addresses stop at a shim layer, or go to  
transport layer (of course it can make a big difference as far as  
transport functions are concerned).
This is top-level branch#1 in my earlier msg http://psg.com/lists/rrg/2008/msg01220.html

Tony's above msg took the view from transport layer and *looking  
downward*: SHIM6 has this notion of EID, and the actual IP packets  
*may* be sent using IP addresses that are different from EID, hence  
"this is a translation" view, i.e. a translation from an "EID" to an  
"IP address".
(to be more precise, SHIM6's notion, as I understand it, is really a  
binding of a set of IP addresses to one transport session, so anyone  
in the set can be used. But lets not argue this semantic detail).

Lixia


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