network topology for 10 GBit fiber

tubs-ffm

Active Member
Sep 1, 2013
122
39
28
Hello,

I have a question regarding advantages and disadvantages of two different network topologies I am taking in consideration. The description and illustration below are simplified and does not show each detail like VLANs.

I am upgrading my home network. Today PC 1 and Server already are connected via fiber (10GBASE-SR) and a SFP+ switch to each other. My next bottleneck is the link between left side and right side. One pair of multimode fiber OM4 would satisfy my needs. But my current plan is to install one 12 fiber MPO OM4 of about 30 m length for two reasons: to be flexible for the future and because a single 3 mm cable makes the installation easier (I must squeeze it somewhere between wall and floor). By this the question came up how to connect the devices on the right side:
  1. one or two trunks from left to right and all 4 ports on right side connected to a SFP+ switch located on right side.
  2. each of the 4 ports on right side directly connected to the SFP+/coper switch on the left side. MPO cable connected to breakout pig tail or LC box.
The advantage I see in option (2) is that I can save one switch.
- administration: I can manage all VPN and connections via single L2/(L3) switch
- power consumption: one 24/7 device less
- space: one (blinking) device less in the visible area ("WAF")

Disadvantages?

topology.png
 

Tom5051

Active Member
Jan 18, 2017
361
79
28
44
cost, 6 pair MPO trunk cable is a lot more costly than 6x OM4 runs, then the MPO breakout cassettes are $100 each end, then you need LC patch cables anyway. Tape 6 OM4's together and run them directly from switch to client, less connections. TBH you would be fine with OM3 runs if you're talking 30m. OM3 will do 100GBit to 100meters (300feet). MPO would be neater but expect to pay about 3x the cost of multiple OM3/OM4 runs
 
Last edited:

Tom5051

Active Member
Jan 18, 2017
361
79
28
44
if you need less fibers and less cost, look into OS2 and BIDI transceivers. Uses 2 different light spectrums so can send and receive on a single fiber. I didn't go this route because 40G and 100G SR don't have BIDI
 

Rand__

Well-Known Member
Mar 6, 2014
6,325
1,592
113

tubs-ffm

Active Member
Sep 1, 2013
122
39
28
cost, 6 pair MPO trunk cable is a lot more costly than 6x OM4 runs, then the MPO breakout cassettes are $100 each end, then you need LC patch cables anyway.
Thank you. For sure, the cost factor I also will take in consideration. But focus of my question in this thread is the technical aspect of the network topology.

But for price comparison I also need to take in consideration what HW already is available. For option (2) as described above I do not need new transceivers at all. I only would move "move" one end located today on the right side to the left side. Yes, 4 times OM4 are half price of one MPO. But it only is 25 to 30 meters.

Tape 6 OM4's together and run them directly from switch to client, less connections.
As mentioned above. Available space is one limiting parameter. My goal is to route the cable without construction work. So, I can use 1 MPO or 1, maybe 2, multimode cables.

if you need less fibers and less cost, look into OS2 and BIDI transceivers. Uses 2 different light spectrums so can send and receive on a single fiber. I didn't go this route because 40G and 100G SR don't have BIDI
My real technical needs in regards of bandwidth would be covered by one 10 Gbit connection + VLANs. This was my first idea. But why not prepare for future needs if it is not much more effort and does not cost much more.
 

tubs-ffm

Active Member
Sep 1, 2013
122
39
28
-Availability,
-Expandability
Than you. I will take this in consideration.

Not to be misunderstood. I am not talking about any business critical installation. It is an oversized home set-up. No cluster, no fail over HW. The "availability" point is interesting. In my mind was "two switches in line = two possible point of failures in the line to the server."

CRS305 is what I use today between Server and PC. CRS309 currently is my preferred choice if I need more ports.
 
Last edited:

Mithril

Active Member
Sep 13, 2019
317
96
28
So, in regards to multiple LC vs MPO:

When pulling fiber the issue for both isn't cable size (unless you intend to field terminate of course), but connector size. An MPO end with cover is easier to pull than an LC-LC end with cover, much less 6 LC-LC ends! (Even staggered).

Depending on how much you value your *time*, running a second MPO at the same time makes sense, on ebay you should be able to find 30M of OM3 for under 100 each, I've seen them down around $50, or less. Make sure to also search for MTP as some people don't put both names in listings.

For under 100M (and almost certainly over to some degree) OM3 will do 40G(as BiDi)/100G no issue, and 10G to 300M. If you find OM4 cable at a price you like, go for it, there is NO harm in mixing OM3 and OM4 (or even OM2), you will get the distance rating of the lowest type (or more) but that's it. Don't mix OM1 and any others, if it works at all it will work poorly.

MPO to LC boxes are cheap as chips on ebay. I picked up 6 OM3 12 fiber MPO to 6 pair LC boxes for about 7 bucks each. Price is a little higher but here is a listing: Corning ECM-UM12-05-93T 12 Fiber LC Duplex to MTP Connector Module 4042673254508 | eBay

In regards to topology:

What problem are you hoping to solve with a 2nd switch? If you are unsure, it may be wise to go with option 2 for now and identify what you want/need a second switch to do, and if having another one in that configuration will do it for you.

As far as reducency goes, you'd need each switch to be able to reach machines and your router, which more than likely would mean a pair of stacked switches on both sides of your MPO cable(s).

My 2 cents: Go with option 2, if you need redundancy do that at your "core". If you go with something stackable then you could use LACP and provide some machines or a switch in that room (that has LACP, I've made that mistake once!) with redundant paths. Go with MPO/MTP, and run 2 of them to avoid needing to run more down the line. OM3 is fine, if OM4 is the right price on ebay go for that. Don't worry about the "out of wall" stuff, OM3 is fine and it's 10000% easier to replace than stuff you put in the wall anyways.
 

tubs-ffm

Active Member
Sep 1, 2013
122
39
28
on ebay you should be able to find 30M of OM3 for under 100 each, I've seen them down around $50, or less.
That is one point of my idea. Cost isn't an issue as I am not wiring a complete corporate building. I am connecting two rooms in a family home to each other.

MPO to LC boxes are cheap as chips on ebay. I picked up 6 OM3 12 fiber MPO to 6 pair LC boxes for about 7 bucks each. Price is a little higher but here is a listing: Corning ECM-UM12-05-93T 12 Fiber LC Duplex to MTP Connector Module 4042673254508 | eBay
Thanks a lot. So far, I only was looking for FHD cassettes. These are more expensive. Are there also small wall mount boxes available fitting one of these adaptors? For robustness against damages I do not want to have an open wire end on the floor. At least one of my ends needs to look "clean" and small. The other side also could be a pig tail or an oversized wall mount box like this:

Wall Mount Fiber Enclosure 2-Door 2-Adapter Panel - FS

What problem are you hoping to solve with a 2nd switch? If you are unsure, it may be wise to go with option 2 for now and identify what you want/need a second switch to do, and if having another one in that configuration will do it for you.
OK. Looks like my explanation was not so clear. Today I am running one copper line what even isn't real network cable but fixed installed in the wall. But I can get a GBit link and a throughput that is close to GBit. Today I also use a switch on both sides to handle the VLANs and connect all devise on both sides. So my goal and plan is to replace the "shitty" coper cable by a 10 GBit fiber link that I want to install without construction work. One 10 GBit link with VLANs would satisfy my needs. This set-up would require a switch on both sides.

But why not make it different or better or ore future ready if possible with only a little bit more more costs? So, MPO was my first idea. By this I got the idea why not connect each device individually and skip the switch on the right side.

My 2 cents: Go with option 2
Thanks a lot. So, it looks like the MPO route will not give me real benefits I need today. But it will give me redundancy and possibilities for future extensions without significant more costs or effort today.