This is my first posting to the NANOG list. I don't think this is off-topic, but if so, please send replies (or flames) directly to me (rather than to the list) and I will issue a detailed summary. We are in the process of implementing an OC-12 SONET ring connection between two sites in New Jersey that span a distance of 15 miles. The SONET ring will be provided by Bell Atlantic and is composed of fully redundant hardware (there are no single points of within the telecom equipment) and redundant rings. We are splitting the OC-12 into pairs of OC-3's on two routers in each location (running ATM on the WAN). This interface is extremely mission critical to the point that a 99.9% uptime will not be acceptable. I have the following questions: 1) Bell Atlantic assures us that, because of the redundancy, we can expect 100% uptime from the OC-12. I would like feedback as to whether this is a realistic portrayal of the SONET environment. 2) We have the option of using either single-mode or multi-mode fiber OC-3 connections - what factors should be considered in selecting the fiber media type. 3) Which routers should be used. The options are 3com NB-II's DPE+ (dual CPU), Cisco 7200 series, or Cisco 7500 (each router will have at least two 100Base-T LAN ports). OK, I know the 3com suggestion is a loaded question for this list, but has anybody used the 3com's in this capacity? We are a 3com shop that is considering switching to Cisco - this is a significant decision because switching will require us to continue to maintain the existing 3com environment (~500 routers) and the new Cisco routers. Thanks, Peter Polasek