Is it possible to use half duplex on a trunk link?

TechGromit

Of course your going to say why would anyone want to do this, but imagine for a minute you had one bad fiber and no redundancy. Could you get the link up by using the one fiber link with half duplex? I know your network throughput would suck, but just to get the link up until you get someone out to replace/repair the fiber.

clarson

Sounds like you are wanting to know if you can be penny wise and pound foolish.

lets save a few pennies by not putting in a redundant line. Then pay out the ass when (and it is when not if) it breaks.

and, the fibre pair is made up of a transmitting side and a receiving side. the transmitter doesn't receive and the receiver doesn't transmit. So, couldn't be done with a fixed configuration switch. So, you'd have to have some special gbic/sfp to put into the switch. And, I don't know anyone that is making a one off sfp that allows you to run your fibre connection dog **** slow.

they spend there money on etherchannel/flexlines/stackwise/etc so you can have redundancies out the ass if you want them. So, your systems maintain there throughput due to a failure or two. There isn't anyone working on running half duplex over fibre so you can keep your system barely running till you get the fibre fixed.

let your network engineer design your network not your accountant.

Magic Johnson

You can get simplex fibre, but you need the correct SFPs to use it. You can't just go from using 2 strands of fibre to single with the same kit.

Ertaz

TechGromit wrote: »

Of course your going to say why would anyone want to do this, but imagine for a minute you had one bad fiber and no redundancy. Could you get the link up by using the one fiber link with half duplex? I know your network throughput would suck, but just to get the link up until you get someone out to replace/repair the fiber.

In this scenario there is no physical path for the return traffic on a duplex sfp. It can't transmit out the receive path. The simplex sfps use different wavelengths of light to transmit and receive simultaneously on a single strand. I am a big fan and will use them whenever possible.

*Edit, here are some examples:

https://www.fluxlight.com/transceivers/?cat=1071&bra=11&connector=Single-LC

TechGromit

clarson wrote: »

Sounds like you are wanting to know if you can be penny wise and pound foolish.
lets save a few pennies by not putting in a redundant line. Then pay out the ass when (and it is when not if) it breaks.

Most often we inherent these network, it's rare we get the opportunity to design them right to begin with. To be fair, most network segments were installed with redundant pairs, but over time they went bad. I have fiber that's over 20 years old where I work. The fiber diameter is obsolete, it's increasely difficult to find replacement connectors for them. Pretty hard to justify to management we need 200k to rerun fiber just in case it fails. Next time I go to a meeting with management over a failed fiber links, I’ll let them know, if you idiots would have designed it right to begin with, we wouldn’t be having this trouble today. I’m sure that will go over well.

Magic Johnson wrote: »

You can get simplex fiber, but you need the correct SFPs to use it. You can't just go from using 2 strands of fiber to single with the same kit.

Sounds like a good Idea when your installing new fiber, but I'm limited working what with I have. I do not currently have any failed licks, but I'm trying to think outside the box for contingency planning.

clarson

TechGromit wrote: »

Most often we inherent these network, it's rare we get the opportunity to design them right to begin with. To be fair, most network segments were installed with redundant pairs, but over time they went bad. I have fiber that's over 20 years old where I work. The fiber diameter is obsolete, it's increasely difficult to find replacement connectors for them. Pretty hard to justify to management we need 200k to rerun fiber just in case it fails. Next time I go to a meeting with management over a failed fiber links, I’ll let them know, if you idiots would have designed it right to begin with, we wouldn’t be having this trouble today. I’m sure that will go over well.

Lets see, they designed a network that cant be repaired, can't be upgraded, can't be expanded, without spending 200k. Those are some great network designers. I should never have called them idiots.

but, you do need to let them know what their options are. looks like there are just two. fix it before it fails for 200k or fix it after it fails for 200k plus business losses. The only question is when will it fail. Not easy to say. But, it looks like others already have and it seems like a concern that more will.

failure to plan for the future don't mean the future is going to wait for you.

Legacy User

TechGromit wrote: »

Of course your going to say why would anyone want to do this, but imagine for a minute you had one bad fiber and no redundancy. Could you get the link up by using the one fiber link with half duplex? I know your network throughput would suck, but just to get the link up until you get someone out to replace/repair the fiber.

Yes its possible, but the syslog on the switch will go crazy with the duplex mismatch messages and the drops would quickly go through the roof. Not to mention performance would be terrible. Whats bad about it? CRC errors? Drops? You would just have to ignore the messages until its fixed I guess.

But why would you have it set to half again?

Ertaz

dmarcisco wrote: »

Yes its possible.

No, it's not via a standard duplex fiber optic transceiver, with only a single fiber available(The situation he's posing). You'd have to have a specialized sfp, which allows full duplex over a single fiber anyway. http://www.cables-solutions.com/wp-content/uploads/2015/09/22.png

Legacy User

Oh I misunderstood the post! When I read one fiber link I read it as one bad pair. My bad! If it was stated as a bad strand within a pair it'd be crystal clear for me lol