Fiber vs Copper

Unanswered Question
Jul 11th, 2007

Hopefully someone can help me and hopefully this is being posted in the right place. The company I work for has just purchased a new 7 story building and I need to design the infrastructure. My question is: why do I need fiber?

All of my IDF's are directly above one another, the building is roughly 70ft, so I'm not stretching the distance limitations of copper. Unless I'm going to shell out 50,000.00 for a 6500 series switch to get 10Gb (which im not) I'm limited to the same 1Gb that I could get over a copper cable. I plan to run 4 cables from each floor, etherchannel them together to get 4Gb up the backbone of the building. I could do the same with fiber, but the cabling would be considerably more expensive. I've had a number of people tell me I should go with fiber, but no one who can give me a solid argument as to why. Any comments/input/opinions are appreciated.

Thanks

I have this problem too.
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Your solution is most likely fine if you are looking at the near term. Maybe you don't have any robust graphics/mapping, audio/visual-streaming, or VoIP requirements.

Quite possibly your business/operational applications won't require increased bandwidth and aren't expected to change over the next 3-5 years.

You might not even use an across-the-wire backup solution for devices located across a few floors.

You might issue policies that limit all desktop/printer systems to 100mb/Full duplex NICs, they certainly are getting cheaper to buy.

You might not even project having many new employees/customer additions in the near future.

There are many variables. But be conscious of the real goal---------- scalability, reliability and maintainability.

In my experiences I have never just put in enough infrastructure to meet opening day requirements. Copper and fiber installations have always been cheaper to implement early. They won't get cheaper down the line.

You could just go with your plan, but experience will prove different when 10GB comes to the smaller/mid-range switching platforms. Or your requirements mandate faster speeds.

We already are moving to 1Gb desktop NIC connections.

Things like redundant connections to core devices require pathways. Etherchannel alone

will give you some help if individual channel member ports/links fail, but it hardly qualifies as redundancy.

If you really apply the recommended Cisco Network Architecture, and apply it to your design, you may end up looking at dozens of "copper" etherchannel groups, where a few pairs of fiber would do the trick.

It really is all about pay-me-now, or pay-me-later when it comes to infrastructure design.

With 7 floors, which I'll assume are to be home-runned down to some Core/backbone environment, you'll have 28 etherchannel ports to terminate, with no real redundancy. If you added redundacy you're looking at 8 etherchannel ports per floor across 2 etherchannel groups which will need 28 ports across 2 core switches. What about STP, VTP, VLAN requirements?

You can achieve a better solution with a minimum 14 fiber ports, split 50/50 across a redundant pair of core switches (7 ports per switch)is much more reliable, easier to maintain and upgradable via relatively simple optic equipment upgrades.

It might seem expensive for opening day, but will prove a wise investment over the life of your network.

Lastly, SMF is cheaper to install than MMF, the optics are more expensive, but do drop in costs over the life of the technology.

Hope this helps.

houstonrob Wed, 07/11/2007 - 13:52

Thanks for your input.

The current design would include two 2Gb etherchannel runs each going to one of two 3750e switches connected via stackwise. The switches in each IDF are also 3750E switches with twin gig modules (so i can upgrade to 10Gb later if I need/can afford). VOIP is a consideration; my network already has QOS in place, not only for VOIP, but for our day to day data use. The main problem is that right now, there's no way I can afford to go 10Gb right off the bat, so going with fiber would require me to use 1 Gb fiber runs, exactly what I would get with copper. I understand what you're saying, but I don't see why fiber (other than fewer total runs) is a better solution. It's more expensive and I'd get less bandwidth to each floor. I plan to run two strands of 50 micron mm fiber from each floor to the MDF because I do want to upgrade to 10Gb ethernet when it becomes more affordable, but for right now a 6500 series 8 port 10Gb ethernet module and 6504 chassy comes out at around 50 grand leaving my only real option a 3750g-12 that will only give me 1 Gb. If I'm missing something as far as my fiber options go, please let me know, perhaps I'm missing something.

Thanks for your input

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