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Archive      23 July 2007              #61


by William Flanagan, Publisher

You know that adding VoIP is going to make the IP network more expensive than before, but not knowing how much more expensive has been scary. Now we have some interesting cost figures on extending high availability (HA) beyond the core network, thanks to a briefing from Tad Anderson, director of service operations at Presidio Networked Solutions (www.presidio.com).

As a systems integrator that deploys and supports networks, Presidio is finding more frequent requirements for high availability that extends beyond the core infrastructure.  When voice is added to IP networks, the most typical event that triggers a demand for HA, management may realize that the levels of availability acceptable for the data network, while rising, aren't up to the level of a PBX, Centrex, or telephone service in general.  It will be a while before the old one-liner no longer applies:  "How often do you email the help desk to say your phone isn't working?"

But it might not be too long, because the extra cost for full-as-possible redundancy isn't outrageously high.  In short:

-- The cost in the core may increase slightly:  you'll want to equip every device that can accept it with a redundant control card.  You'll also want to stock complete spares.  Today, Presidio sees most core routers and switches installed with redundant power supplies (historically the first component that fails) and dual-homed links--if so, there's not much more than control cards needed here until you move to fully redundant router/switch pairs.

-- In the distribution and access portions of the network, Tad sees about 35% more spent for equipment, much of which is related to power. Some costs will be associated with staff training and new procedures/policies oriented toward HA ("Thou shalt not reboot the router just to see if that helps").

Many edge devices have been installed with a single power supply and no battery backup.  Adding those items can be a significant expense, particularly an uninterruptable power supply that is intended to carry not only the access switch but also the IP phones drawing power over the attached Ethernet cables.

Power has continuing costs, of course, in the monthly electric bill. Then you have to contend with Newton's 14th Law of Physics:  Heat that goes in must go out.  In other words, you need more air conditioning or ventilation to prevent overheating the wiring closet.

You have to take "closet" quite literally at many sites, which means space for network equipment can be very tight.  LAN racks may share the closet with office storage or the janitor's mop and supplies.  Adding a UPS might be a problem just because of its size.  A small amount of remodeling or moving a wall may be needed.

The good news:  according to Anderson, total cost of ownership for a network built for high availability out to the edge can be about 5% higher than what's standard today.  Remember that the largest cost component of a network is the labor to operate and maintain it--something that needn't change much.

This statement isn't an absolute guarantee, but we hope it removes a big chunk of the "fear of the unknown" from your network planning.

Your discussion is always welcome.


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Flanagan Consulting
W. A. Flanagan, Inc.
45472 Holiday Drive, #3
Sterling, VA 20166
Ph:  +1.703.242.8381
Fx:  +1.703.242.8391
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