Subject: Re: [rrg] Locator

From: [email-masked]
Date: Wed, 13 May 2009 03:50:20 EDT

In einer eMail vom 13.05.2009 02:13:52 Westeuropäische Normalzeit schreibt  
[email-masked]:

Ah, no.  To quote RFC-1992:

"A locator ... identifies a location in an  internetwork.  Nodes and 
endpoint
are assigned locators.  Different nodes have necessarily different locators.
A node is  assigned only one locator. Locators identify nodes and specify
*where* a node is in the network. Locators do *not* specify a path to  the
node."
 
I perfectly agree."Nodes and endpoint are assigned locators" can also be  
read: "Nodes and endpoints are assigned attributes (eventually in addition  
?! to identifiers ) which are locators.

One also needs to be aware that in this document, "node" means  'network
region', not 'host/router', as it is commonly taken to mean in  networking:

"A node represents a region of the physical  network.  The region of the
network represented by a node  can be as large or as small as desired: a
node can represent a  continent or a process running inside a host.
Moreover .. a  region of the network can simultaneously be represented by
more than one node."
I perfectly agree. However I would like to caution not to do the same  kind 
of node aggregation once again
as known from PNNI.

(In  the next section of the document, "node" is very precisely defined to  
mean
'map element' - from the node/arc terminology of graph theory, since  maps 
are
graphs - the above is just a 'starter  definition'.)
it sounds like TARA :-)
 
Heiner

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From: Toni Stoev <[email-masked]>
Date: Thu, 14 May 2009 11:31:22 +0300

So locator may name node. And node may be host/router.

Being confident routing researchers, let us go on for the routing scalability.

Please answer the following question:
Does locator have to facilitate routing with its structure?
My answer is: yes, it must.

Toni

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From: Paul Jakma <[email-masked]>
Date: Fri, 15 May 2009 22:34:56 +0100 (BST)

> My answer is: yes, it must.

I have a question, a stupid one probably... Is the following thinking 
of mine correct?:

If we encode routing information into the locator somehow, then this 
implies the 2 are tied together, and that (at least) the initial 
top-level hierarchy of internet routing is fixed for the life-time of 
the locator. So this implies either one or more of:

- that the lifetime of locators be short, and that they are
   re-calculated/re-assigned frequently enough to have a sufficient
   level of reachability between hosts on the internet.

   (e.g. imagine a scheme that assigned locators empirically, by
    examining the structure of the internet and calculating a
    spanning-tree that approximated a power-law distribution
    as good as possible and then assigning locators in an according
    fashion, thus maximising the aggregation of routing information.

    I think there may be papers describing such things, but I'm not
    sure there are RRG proposals ???).

- fairly long-lived, indeed static locator assignments. This implies
   a quite broad and flat, top-level routing table. This is basically
   what we have today, if ASes advertised just one prefix.

   Proposals under this model generally split routing into a 2-tier
   system: the flat, top-level routing table + a secondary table of
   networks behind the top-level locators (either aggregated locators,
   or remapped/tunneled somehow)

Is this right so far?

If so, and if the prevailing proposals so far are of the static 
top-level kind, then do know if a flat top-level is sufficiently 
scalable? Is there any data/work on how fast this top-level might 
grow? To what extent is the AS growth reflective of how that 
top-level might grow? To what extent is the transit-AS growth 
reflective of it?

I ask because AS growth might not be linear:

 	http://www.potaroo.net/tools/asn32/

though transit-AS growth is unclear (it doesn't grow much in fact, so 
its perhaps impossible to get a trend from it):

 	http://www.potaroo.net/ispcol/2009-03/bgp2008.html

Basically, what I wonder is whether a static top-level 
locator->routing mapping is sufficient to meet the scaleability 
requirement?

If it is not, then facilitating routing with the locator is just a 
delaying tactic - a more dynamic system would eventually be 
necessary.

If it is sufficient, great, of course - any dynamic system would by 
definition be more complex.

(There may be ways of statically assigning locators according to some 
kind of power-law distribution - but this means impressing some kind 
of order onto ISPs, which probably isn't socio-politically 
tractable).

regards,
-- 
Paul Jakma	[email-masked]	[email-masked]	Key ID: 64A2FF6A
Fortune:
Neutrinos are into physicists.

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From: Toni Stoev <[email-masked]>
Date: Sun, 17 May 2009 13:31:54 +0300

Paul, have my regards for going deep into the matter.
See my comments inline.

On Saturday 16 May 2009 00:34:56 Paul Jakma sent:
> the locator.

This shall be backwards when using locator for intra-domain routing (and AS paths for inter-domain routing).
Then locator's tying is with its routing domain (AS). And the intra-domain location-naming/routing hierarchy needs just the AS number as its top-level.

> So this implies either one or more of: 
> 

My vision is that node reachability has to be shown by locator. Then lifetime of locators has to be relevant to that reachability.

>  	http://www.potaroo.net/ispcol/2009-03/bgp2008.html

Paul, please keep helping with AS growth revision.

> of order onto ISPs, which probably isn't socio-politically 

Reconsider,
Toni