SONET ring questions

Thu Oct 15 22:31:54 UTC 1998

> 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.

Assuming the primary and backup paths are not in the same cable
anywhere (don't laugh, it happens), the chances of the OC-12 itself
failing inside Bell land are tiny. (Of course, if your local loop gets
assaulted by a backhoe, you're in trouble.) 

> 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.

Single mode goes farther. Multi-mode is cheaper. If you've got
relatively short cables, save some money and use multi-mode. If
you're dragging fiber all the way across the building, or between
buildings on a campus, use single-mode.

> 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.

If you go Cisco, I'd recommend the 7500 series. The 7200 series won't
handle two OC-3's and two fast ethers. You'll drop packets.