Re: Ohta-san's draft

[Greg Maxwell <gmaxwell@martin.fl.us>]

On Wed, 11 Apr 2001, Sean Doran wrote:

> This is strictly true, since we have multihoming now.
> However, what we have now simply sux.

Thank you. The baby is ugly.
 
> Note that there are very different properties between what
> you and greg maxwell talked about while i was asleep, and
> what is in Ohta-san's draft.   The latter contains an
> important optimization.
> 
> Firstly, think of the host's take on "who" vs "where"
> separation in terms of masking out the top N bits when
> trying to figure out if a received packet is "for me" or
> "not for me".  That is, sender may choose a viable path of
> which the receiver is currently unaware, and put the path
> into the "don't care" top bits.  Routers along the way DO
> care, and forward appropriately right to the receiver,
> which masks away the for-use-by-routers part (where) and
> sanity checks against the for-use-by-hosts (who) part.
> 
> Then bear in mind that this split allows for an important
> optimization: if the hosts DO care about all the bits, and
> given that real Internet traffic is often forwarded on
> asymmetric paths, and thus (and for other reasons)
> failures may be simplex, then there are NxM combinations
> of (source,destination) that must be agreed upon to have a
> connection.  Using Ohta's method, since it cares only
> about the *sender*'s choices, there are only N or M where
> N and M are the number of addresses each host believes
> can be used to reach the other.
> 
> That is, no "who"/"what" split: NxM.  With "who"/"what" split: Nx1.
> Because we don't have to do anything special with choosing
> a working/optimal source address.

But wont this require that the host 8bytes be made globally unique if used
like this?  Not only would that cause a change to the addressing 
architecture, but it would deflate the useable address space to 64bits.

Is the benefit given (the recivever not needing to know about all of it's
paths) worth the factor of 18,446,744,073,709,551,616 loss of address
space?

Also, the host doesn't have any ability to influence it's outbound path,
which might be useful.

> Given a near future which likely includes both heavily
> multihomed popular content sites, and household
> multihoming (IP over cable, xDSL, power lines, wireless, ...),
> the reduction in power of the function which finds a
> working combination of addresses [at startup or after
> topology change] is extremely important!

Thats useful, but I think we should look at where that load was shifted
to. 

> 	 Sean. (who is sleep-typing at 0645)

I'm luckey that my Internet provider lost connectivity to me last night, I
might not have been able to get to sleep otherwise. :)