On Sun, Mar 13, 2011 at 2:11 PM, Jeff Wheeler <jsw@inconcepts.biz> wrote:
On Sun, Mar 13, 2011 at 1:27 PM, Christopher Morrow <morrowc.lists@gmail.com> wrote:
there's probably a different need in TOR and BO/SOHO locations than core devices, eh?
In today's backbone, this is certainly true. Feature-driven upgrades shouldn't be much of a factor for "P boxes" today, because modern networks have the option of simply label-switching in the core (just like 1990s networks could ATM/Frame-switch) without doing much of anything else. Feature-driven upgrades should be largely confined to "PE boxes."
not everyone drinks the mpls koolaide... so it's not always 'just a label switch' and depending upon how large your PE mesh is, there are still some challenges in scaling this. MPLS also only shifts the burden to another place, if you provide ip-transit and you need a full table you'll have to put those routes somewhere. Sure the 'core' may not need that info, but the edge likely does, yes? Have 100g customers today? planning on having them in the next ~8/12/18 months?
For the same reason, upgrading a P box should be easy, not hard. After all, it's just label-switching. In today's backbones, it should
upgrades aren't hard, unless you get yourself into a SPOF situation with the 'P' router(s)... mechanically the upgrades aren't hard. Cost-wise though it could be, it depends upon your particular cost structure I imagine.
be more practical than ever to buy the most cost-effective box needed for now and the predictable near-term. Cost per gigabit continues to fall. Buying dramatically more capacity than is planned to be necessary sinks capital dollars into a box that does nothing but depreciate.
The discussion at the RAWS meeting, and which seems to hold true for larger networks, is that a box lives in the network for ~5-7 years. First, for the core-class device today, in the core, then progressively further to the edge. Some thought goes into 'today I have X requirements, I can project based on some set of metrics I'll have X+Y tomorrow.'
I realize that organizationally-painful budgeting and purchasing processes often drive networks to buy the biggest thing available. Vendors understand this, too: they love to sell you a much bigger box than you need just because upgrading is hard to get approved so you don't want to do it any more frequently than necessary, even when that behavior is detrimental to cash-flow and bottom line. The more broken your organization, the more you need to spend extra money on "too big" boxes. Sounds pretty self-defeating, doesn't it?
sometimes... sometimes it's just business. I suppose the point here is that a box doesn't live ~12 months or even 24, it lives longer. Planning that horizon today is problematic when a box today (even the largest box) tops out just north of 2m routes (v4, I forget the mix v4/6 numbers). your network design may permit you to side step that issue in places, but planning for that number is painful today. -Chris