Subject: Re: [rrg] IPv4 & IPv6 routing scaling problems

From: [email-masked]
Date: Sun, 14 Feb 2010 15:11:21 EST

In einer eMail vom 14.02.2010 17:00:37 Westeuropäische Normalzeit schreibt  
[email-masked]:

Hi,

I've only just stumbled across your TARA stuff, and am  reading 
through your mails. Re "Forget DV!", and double-plus to  that!

Well, then try to convince me while viewing the following:
I was told that an average route  contains about 20 hops. Imagine a  
chessboard like grid however with 10x10 rows and columns instead of 8x8.  Imagine 
each DFZ-router has only 4 neighboring DFZ-routers (which is  certainly less 
than in reality).Imagine the ingress at the upper left corner and  the 
egress at the lower right corner. Then there are (20 over 10) = 20x19x...x11  / 
(1x2x3....x10) = 184 758 shortest paths in-between.
 
Consider that there are more than 10,000 egress DFZ-routers ! 184 756 times 
 10 000 = 1 847 560 000 shortest routes. However there are multitudes  
thereof, if you envisioned (loopfree of course) detours as well! And if you  
envisioned that DFZ routers have more than 4 neighbor nodes (BTW, can  anyone 
provide useful valid figures so that we can discuss density issues and  
aspects?)
 
What a nonsense of algorithm !!! DV is a holy cow from the early  90's!
 
Please convince me, why provisioning and managing all these routes would be 
 reasonable? 
Particularly, when you can do it without!  
 
Heiner

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From: Christopher Morrow <[email-masked]>
Date: Sun, 14 Feb 2010 15:24:04 -0500

> provide useful valid figures so that we can discuss density issues and

a T1600 has 8 slots of 4 PIC's each, you can get 1x10G for each PIC.
a CRS1 (full-height) chassis has 16 slots, 4x10G on each I believe?

you can get this sort of info, as an approximation of connectedness of
a node from every vendor's website.

-Chris

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From: Christopher Morrow <[email-masked]>
Date: Sun, 14 Feb 2010 15:25:39 -0500

> a node from every vendor's website.

oops, keeping in mind that's physical interfaces, with some MPLS
schemes the 'dfz' router could be connected to each DFZ router in the
same ASN over a logical link (LSP), so... a single DFZ router could
have (in the case of a moderate network, with US only coverage)
something like 80+ neighbors over these logical paths.

-chris