[c-nsp] Downsides of combining P and PE functions into a single box

[Jared Mauch]

On Wed, Oct 19, 2011 at 12:58:41PM -0400, Keegan Holley wrote:
> The real question:
> >
> > Are you selling customer links that are near to or equal to the size of
> > your core links(s).
> >
> 
> Why would anyone do this on purpose and not upgrade the core?  I understand
> over-subscription but having your edge links the same speed as your core is
> just asking for trouble.

	Because the core link sizes are the same as the edge sizes.

	This means you have to create duplicate links to haul it through more
routers vs less.


> > Anyone doing 10GE edge or looking at 100GE for customer-facing handoffs can
> > save significant amounts of money by doing P/PE.  While there are tradeoffs,
> > not having the cumulative cost of a packet being A+B+C and perhaps can be
> > localized to a single device has value.  I'm surprised that Rolland doesn't
> > see this as an optimization as it would be something the Arbor equipment
> > could help you optimize.
> >
> 
> Not sure how you save money by buying extra routers.  That's a pretty
> aggressive discount structure.

	I'm saying buy less routers.

	If your customer is talking to a peer, place them on the
same device.  Don't have a 'peering edge' vs 'customer edge'.

	It may make sense to terminate your 'core' links on the same
device as well.  It may not.  This all depends.  The problem here is how
people think about the network.  "There must be a core", or "you must transit a P device".

> > While some may see these cost savings as inelegant, the idea of a core will
> > continue to come under these pressures.  Keep in mind the fraction of a
> > chassis you must allocate for these edge <-> core links and core <-> core
> > links.  These have real world costs.  There's a reason everyone didn't go
> > out there and load-up on OC768 hardware and just stuck with N*10G.  The
> > finances don't work out.
> >
> 
> Cards are cheaper than entire routers in most cases especially at N*10 and
> 40G speeds.  Assuming you want chassis based, with redundant control planes
> and whatever the vendor uses for fabirc blades.  I'm not saying everyone
> should throw their core P routers into a dumpster, but I don't see how
> having them saves money.  You also have to add the cost of service contacts,
> power, fingers and eyes to keep them running, etc..  I think people who need
> separate cores should have them.  However, I don't see how P routers save
> money or reduce complexity.

	They don't in many cases.  I think you misunderstood my comments.

	- Jared

-- 
Jared Mauch  | pgp key available via finger from jared at puck.nether.net
clue++;      | http://puck.nether.net/~jared/  My statements are only mine.