Re: Architecture [Re: Agenda for Vienna]

[Iljitsch van Beijnum <iljitsch@muada.com>]

On donderdag, mei 15, 2003, at 12:15 Europe/Amsterdam, Masataka Ohta 
wrote:

> My draft draft-ohta-e2e-multihoming-03.txt:
>                The Architecture of End to End Multihoming
> discusses, as is obvious from its title, architectural issue on
> host based approach. It, of course, mention loc/id separation.
In this draft you say TCP (and other protocols, leaving those alone for 
a moment) should get multiple addresses from the application. This is 
what SCTP already does. I don't see how this is separating the locator 
and identifier functions, it's just more instances of the combined 
locator/identifier we're used to.

I feel this approach isn't a good one both for architectural reasons 
and for deployment reasons (this simply needs too many changes to too 
many things). The current architecture doesn't differentiate between 
identifiers and locators so it imposes limits on one because of the 
requirements for the other. This is messy. Having more of those 
combined locator/identifier addresses just increases the mess linearly. 
On the other hand, separating the identifier and locator functions 
makes it possible to have both the advantages of a stable identifier 
and the advantages of flexible locators.

However, I do agree that TCP knows much more about reachability than IP 
so in practice we'll want to take advantage of that. But there are 
other ways to skin this particular cat than selecting layer 4 as the 
place to solve the multihoming problem.