pete@cobra.BRass.COM (Peter Polasek) writes:

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.

100% uptime meaning Bell Atlantic will pay you some small token amount when it fails? or 100% uptime meaning it will never fail? Figure out how much Bell Atlantic will pay you, and compute your risk factor. However, you are getting into the insanity region of availability vs. disaster planning, category 5 hurricane, regional firestorm, sabotage or terroist attack, etc. Yes, all have happened, and will happen again. But paying a bigger insurance premium may be cheaper for these extremes. Even a perfectly functioning SONET ring will have some delay as the APS switches to the protect circuit. So make sure your application can tolerate whatever the maximum switching delay. Most carriers consider SONET outages of less than 60ms 'normal' and an overall SONET end-user restoral of 2 seconds 'acceptable.' SONET also has its own set of hardware failures (e.g. APS controller failure), user errors (e.g. improper provisioning, improper maintenance), and the dreaded multiple failure modes (e.g. a fiber cut during a Forced Switched, double Forced Switches in the same ring at the same time, and other types of ring partitions), and software/firmware bugs. Humans are always a single point of failure in any system. In the last carrier summary report I saw the number of SONET failures was very small, but was greater than zero. The number of carriers reporting was also small, making any statistical relevance of the numbers virtually nill. On average less than 5.5 SONET outages a year were reported across 7 carriers.

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.

Distance and equipment.

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.

3com is more likely to jump when when a customer with 500 3com routers has a problem than cisco will jump for someone with only a couple of cisco routers. Assuming cisco will even agree to sell their favored products to anyone without their seal of approval. And you already know the capabilities and operation of 3com. On the other hand, cisco's SONET products have had the extensive testing and feedback from a number of noted luminaries/customers who haven't been shy about encourging cisco to rectify any apparent shortcomings. So you won't be the leading edge trailblazing customer. And since its a good bet Bell Atlantic will blame any problems you encounter on your CPE equipment, using the CPE equipment which Bell Atlantic 'related subsidaries' resells may cut short at least one round of finger-pointing. -- Sean Donelan, Data Research Associates, Inc, St. Louis, MO Affiliation given for identification not representation