Optical Design question. Ring, Star or Hybrid?

[smunzani]

Hi,

We are designing going through debate on dark fiber deployment strategy for 100 sites. All sites are within Metro.

Our current bandwidth need is at least 50Mbps per site to hub. Eventually this may grow to 100Mbps or even a gig down the road.

My questions.

1. Would you go for a ring topology or Star? If Ring how many nodes you typically put on a single ring if DWDM is desired in future?

2. Since we have 2 core data centers where these rings should route through, how many dual attached rings can we have with 4 fiber topology?

3. What's best redundancy approach if we were to initially deploy SONET architecture till DWDM need arries. 4 Fiber BLSR, 2 Fiber or PPMN?

We also have 500 other small sites that will not get dark fiber initially but may lease MPLS Ethernet transport to closest Dark Fiber site. What's best approach to handle it?

Any ideas would be greatly appreciated.

Thanks,

Sam

[Rene Frank]

Hi Sam

I recommend to design a topology with several rings. It would be best for fiber costs. Each ring goes through both core data centers. For 100 sites I think 4 or 5 rings with OC48 will be good. Because 50 to 100Mbps traffic per site is not very much. If you are using 15454 then deploy a RPR ring on each ring. Connect all RPRs in the data centers on a core router, like a 7600. So what about redundancy? On SONET you don't need protection. It's done in RPR much effective. No bandwith is lost in protection. If you still need some SONET circuits use PPMN. What about DWDM? I don't that you will go to DWDM with 100 sites. It's very expensive. It better to upgrade to OC192 and deploy several RPR rings. You can build RPR rings in parallel or split the RPR rings in smaller rings. With PPMN topology it's also much easier to extend your network. By the way this is all possible in-service. I hope this gives you some design ideas.

Cheers Rene

[smunzani]

Thanks a lot Rene for the ideas. We don't want to do DWDM for now or near term future. However when we lay fiber in ground, we want to make sure it's optimized for DWDM. 20 years from now OC-192 may not cut it and if we don't lay fiber keeping DWDM in mind, it will be hard to change later.

My question are

1. What's practical limit on DWDM spans on a ring architecture? I know SONET can have 16 modes but can DWDM have 15 SPANs?

2. How many rings can I connect to ONS15454 with ML- series DPT blade? 5 rings or more?

Thanks,

Sam