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Chat => Tech Chat => Topic started by: burakkucat on April 08, 2022, 01:02:43 AM
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(https://c1.neweggimages.com/ProductImageCompressAll300/230-0001-00007-V01.jpg)
For the experiment, let us use three Planet GT-802S media converters (as in the above image) and three 1 metre lengths of single-mode optical fibre with SC/PC connectors at each end.
Lay out the media converters to form an equilateral triangle and label them MC-1, MC-2 & MC-3. Now connect the TX port of MC-1 to the RX port of MC-2, the TX port of MC-2 to the RX port of MC-3 and the TX port of MC-3 to the RX port of MC-1.
Power on the media converters. What happens? Is there a manic storm through the fibre links? Or does calm sanity prevail? :-\
If calm sanity prevails we then proceed with the second part of the experiment. Let us connect a CPE (which will be providing Internet access) and two computers to the three media converters. The CPE does not have a DHCP server enabled on its LAN ports. For simplicity, the CPE has been assigned the 10.10.10.10 IPv4 address. Connect the LAN1 port of the CPE to MC-1 with a standard Ethernet patch cable. With similar length Ethernet patch cables, connect computer one to MC-2 and computer two to MC-3. Computer one has been assigned the 10.10.10.20 IPv4 address and computer two has been assigned the 10.10.10.30 IPv4 address. (Both computers are configured with a gateway at the 10.10.10.10 IPv4 address.)
Are the two computers able to access the Internet? Are the two computers able to access each other? :-\
The idea of this thought experiment just "appeared", a couple of nights ago, whilst I was inspecting the insides of my eyelids. Isn't it strange how the mind operates when it is just idling!
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My own thought experiment recently was, what's to stop two people on the same PON rigging some sort of optical network over that fibre, so long as they are using different light frequencies to the PON itself?
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Hi Burakkucat
SOrry it's early and I'm rushing, but have you not just created a switch for want of a better description.
I would expect optical links not to go into a storm as no data is been passed
I would expect both computers to be able to access internet and each other, if computers network set correctly
I could be wrong though sorry
Many thanks
John
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@burakkucat, I would guess nothing will work as there is no return path.
ie device A sends a packet, but the reply goes to B, device B sends a packet, reply goes to C
@Alex, another educated guess the splitters/prisms wont pass the light between properties, only to/from OLT.
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what operating systems are the computers running?
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@Alex, another educated guess the splitters/prisms wont pass the light between properties, only to/from OLT.
That's what I assumed, but I wasn't sure it would necessarily work that way.
Its obviously not something you could test without the risk of getting into a lot of trouble, plus getting anything compatible would likely be tricky to begin with. Not to mention needing to split the signal at each end so you could continue to use the normal service so it wouldn't look suspicious. ;)
Reason my mind was on that is I was thinking how its such a shame I can't run fibre across the road instead of using a wireless link, as its going to suck once I have Gigabit when the wireless link can only do 100Mbit due to the person the other side not wanting to put the dish outside. But then paying for a second FTTP there would be WAY cheaper than leasing space in an OR duct.
As for the initial thought experiment here, I'd assume it wouldn't work as these effectively are bridges so anything coming into the optical RX is sent out the wired TX, vice versa. Its not going to send something coming from the optical RX back out the optical TX as that would make no sense in their design.
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If Computer 1 (on MC-2) sends an internet ping it will be transmitted to MC-3 which will pass it to Computer 2. Computer 2 won't know what to do with it and the ping will fail.
If Computer 2 (on MC-3) sends an internet ping it will be transmitted to MC-1 which will pass it to the CPE and I assume then onwards to the Internet. However the reply will end up at Computer 1 which won't know what to do with it.
So, I suppose it's pretty much what @craigski said - there is no return path and nothing will work.... maybe... ???
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If Computer 1 (on MC-2) sends an internet ping it will be transmitted to MC-3 which will pass it to Computer 2. Computer 2 won't know what to do with it and the ping will fail.
If Computer 2 (on MC-3) sends an internet ping it will be transmitted to MC-1 which will pass it to the CPE and I assume then onwards to the Internet. However the reply will end up at Computer 1 which won't know what to do with it.
So, I suppose it's pretty much what @craigski said - there is no return path and nothing will work.... maybe... ???
Surely if computer 1 tries to send a ping via MC1 it will get sent out and passed to MC2, which will forward it to the computer plugged into it. If its destined for that computer on MC2 then the response would go to MC3 where it would be ignored by the computer connected to it. If its destined for the computer on MC3 then it will be ignored by the computer on MC2 so again wont go anywhere.
The computers would have to know to re-broadcast all traffic not destined for themselves onwards. We're pretty much creating a kind of hub so would need some way to prevent traffic looping around infinitely if its not destined for a specific client.
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Surely if computer 1 tries to send a ping via MC1 it will get sent out and passed to MC2, ...
Computer 1 is connected to MC-2, which passes any packets received on its Ethernet connection to MC-3. MC-3 will then pass said packets to Computer 2 via its Ethernet connection.
At least I think that's how it works.
:)
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Alan asks Bill a question. Bill can not reply to Alan, he can only reply to Charlie. Charlie has no idea what Bill is on about so ignores him.
Alan doesn't get a reply.
:)
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Alan asks Bill a question. Bill can not reply to Alan, he can only reply to Charlie. Charlie has no idea what Bill is on about so ignores him.
Alan doesn't get a reply.
Yes, I agree. That is exactly the situation. So my two part thought experiment ends in failure. :)
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My own thought experiment recently was, what's to stop two people on the same PON rigging some sort of optical network over that fibre, so long as they are using different light frequencies to the PON itself?
The optical splitter. Each customer's transmissions will only go to the OLT. It splits downstream and combines upstream as a funnel.
Reason my mind was on that is I was thinking how its such a shame I can't run fibre across the road instead of using a wireless link, as its going to suck once I have Gigabit when the wireless link can only do 100Mbit due to the person the other side not wanting to put the dish outside. But then paying for a second FTTP there would be WAY cheaper than leasing space in an OR duct.
Unless you've permission from the ISP that's a big no-no.
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The optical splitter. Each customer's transmissions will only go to the OLT. It splits downstream and combines upstream as a funnel.
That makes sense, I'd expect that means the ONT doesn't need to transmit as powerful as an OLT does for downstream which goes to everyone?
Unless you've permission from the ISP that's a big no-no.
The latter I meant just using a VPN to connect the sites rather than trying to do something likely illegal, at the very least against Openreach terms. Again, thought experiments.
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I'm not going to pursue this one. For all you know I work for Zen and between your massive torrent use and wanting a VPN across the road I'll live in blissful ignorance. ;D
Loss is intentionally the same in both directions. Without that loss the OLT transceiver would get nuked by upstream bursts.