Passive Optical LAN

tkerber

Hello TechExams. So recently I stumbled across some people on some other forums talking about ways they were saving money and technologies they were working on. Someone said that they implemented a Passive Optical LAN at their company and it was a big money saver, etc... They also were talking about how they thought it would seemingly render all work group switches and Ethernet LANs obsolete. I was wondering if any of you have worked with this technology and if you could explain it further. I'm genuinely interested in this. I was going to look for books on Amazon as well.

Passive Optical LAN Overview

philz1982

I've worked with this a ton and designed GPON networks. I've worked with Tellabs, Zhones, AcL, and Ericcson. After I put my kids to bed I will post in more detail.

philz1982

Here's a good PON resource.http://www.lightreading.com/broadband/next-gen-pon/who-makes-what-gpon-and-wdm-pon-equipment/d/d-id/669426

philz1982

So here's the deal with PON. I've done several of these at some massive buildings multi-million square feet.

Pros:

• Reduced runs. By using ONT's and spliters you can reduce the amount of runs. You can actually use multiple spliters depending on the fiber type and whether you are using a LED or laser. If you use blown fiber you can actually run fiber without having to poke the ceiling tiles which is nice in healthcare b/c you don't need to tent everything.
• Reduced power. You don't need as much power especially with 802.3 af/at (PoE) because you are not running power over the wire but rather picking it up locally at the ONT. This allows for smaller UPS sizing and also allows for different switching solutions.
• Reduced switching. If you run fiber from an MDF or an IDF you can reduce your switching to a rolled up distro where your access layer actually ports into your distribution layer.
• Reduced FTE's. You can actually reduce staff b/c you don't need as much maintenance.
• Longer Wire Life. Theoretically, if you choose the right fiber type you simply will need to upgrade your LED/Laser for greater throughput.

Cons:

• Bandwidth. Most GPON's are 1G. We've seen problems in healthcare with the new 4k streaming imaging gear that will fill up a 10G pipe (yes, I said 10G pipe).
• Familiarity. Your gonna put what where? This is the question I get from many of the ops folks. PON is still a new technology.
• Lack of VAR/SI support. There are very few VAR/SI's out there for PON and most of them suck (I mean I wouldn't let you wire up my TV suck).
• Perceived Price. Your gonna do fiber for my whole building, that's gonna cost 5 bajillion dollars. Actually PON, can run less then a wired solution when you count on the UPS reduction, switch reduction, and install difficulty.
• Oversubscription. A badly designed PON network can really screw things up. I've seen folks split a signal so many times that 56k AOL dial-up would have been faster. This goes back to the sucky support eco-system. It's just not very mature yet.

All in all the products good for Single Owner CRE, Higher ed, Transportation, Corporate Offices. I would avoid, data centers, healthcare, manufacturing, or other high bandwidth verticals.

tkerber

Thanks for the awesome reply. This is some pretty cool stuff I'm reading. For anyone who's interested I also found this document which is a pretty good breakdown.

http://www.cisco.com/web/strategy/docs/gov/gpon_paper.pdf

philz1982

tkerber wrote: »

Thanks for the awesome reply. This is some pretty cool stuff I'm reading. For anyone who's interested I also found this document which is a pretty good breakdown.

http://www.cisco.com/web/strategy/docs/gov/gpon_paper.pdf

I would just add that on page 2 of the white paper. I would never design a PON solution with a single trunk to the core or the core with a single stack. I would do a dual stack with dual connection redundancy. Also, I know you can do 72 per OLT. I usually will have 2 OLT's one for HS so that you simply unplug and replug in the event of a failure. Of course some ONT's support dual-homed fiber connections so you can do HA in the distro as well as the core.

I should add the designs I deal with are almost always HA 5 or 6 9's.

Also, make sure you catch that on the power comparison on page 3.


5. Power over Ethernet was not factored (sneaky sneaky...) Most of my designs, per customers are 802.3 af/at out every port.

So basically, remember who is writing the article (a company who want's you to buy switches). Many of their conclusions at the end are actually created by their poor Core to Distro design and the fact that they completely neglect to factor PoE into the power equation. You can't tell me that a C3850 running 1000+Watts is more efficient then a OLT/ONT setup....

Don't get me wrong, there are a TON of places I would not use GPON and would use Switched networks in a second!

tkerber

So ideally the GPON design on the right should look similarly to the Ethernet design on the left with HA and more redundancy?

philz1982

Well it depends. My designs are 95% HA. Which dictates an SLA of 5 or 6 9's. So I build differently. In a regular office space you should be fine with a single OLT to the Core. I am very curious why they would design it that way as the case study topology is obviously a HA topology otherwise they wouldn't have the Distro/Core setup for HA N+1.