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In the IP over DWDM Wikipedia page, we see this sentence: (this link) "A true IPoDWDM solution is implemented only when the IP Routers and Switches support ITU-T G.709. In this way, IP devices can monitor the optical path and implement the transport functionality as FEC (Forward Error Correction) specified by ITU-T G.709/Y.1331".

My question is, by which actions, the abovementioned router support ITU-T G.709? As the Wikipedia page implies, we can say the OSPF on the router couldn't see the optical links' connectivity and, they are transparent to the router, ya?

And if so, Doesn't the optical layer protection and restoration mechanism (OTN or SDH/SONET protection) intervene in IP layer protocols convergence like OSPF or even STP?

What happens if a router doesn't have an OTN interface and doesn't know anything about the optical layer?

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by which actions, the abovementioned router support ITU-T G.709?

G.709 defines the interfaces for OTN. So, a supporting router would have one or more of those interfaces.

we can say the OSPF on the router couldn't see the optical links' connectivity and, they are transparent to the router, ya?

OSPF sees "IP interfaces" and their routes. The underlying data link layer (L2) and the physical interfaces (L1) don't matter.

Doesn't the optical layer protection and restoration mechanism (OTN or SDH/SONET protection) intervene in IP layer protocols convergence like OSPF or even STP?

That's all happening in L2 and L1, invisible to OSPF. OSPF only cares about link state (up/down) and speed. STP refers to a Spanning Tree Protocol? That's L2 with IEEE 802 networks.

What happens if a router doesn't have an OTN interface and doesn't know anything about the optical layer?

Without an appropriate interface, a router can't connect to such a network.

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  • I think the OTN-layer failover recovery time affects the OSPF shortest path algorithm rerun. If it is so small, perhaps the OSPF daemon doesn't notice anything, but if the OTN layer recovery takes too much time, the OSPF daemon can notice a problem. So, it runs its shortest-path algorithm. I think that affects the overall recovery time. – A.A Jan 20 at 9:01
  • And about the spanning tree protocol: Is it possible to have an L2 network whose nodes are connected through the OTN layer? So, If we accept the transparency, the OTN layer should be transparent to both L2 and L3 protocols and STP should work on this scenario, ya? – A.A Jan 20 at 9:04
  • And I should mention that I consider there is a module or card or whatever which converts ethernet frames into OTN frame for L2 switches. @Zac67 – A.A Jan 20 at 9:09
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    @A.A You should note that a router "just" routes between its interfaces. Those interfaces may require some infrastructure (layer-2 instances) but the router doesn't care much about the actual technology and logic behind an interface it uses. xSTP isn't necessarily available on each L2 instance, it's generally available on many IEEE 802 data link layers, most prominently on 802.3 Ethernet. – Zac67 Jan 20 at 11:34

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