Re: SONET ring questions

["Dave Cooper" <dave_cooper () eli net>]

At 10:55 AM 10/16/98 +0100, Alex Bligh wrote:
> > 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.
>
> Don't just buy from one carrier. Even if they give you dig plans,
> and diversity warranties, they are likely to reroute things without
> telling you. Even if you get around this one, and all the other problems,
> and are satisfied you have permanent, true, diversity which will protect
> you against any one fiber break, it doesn't protect you against a
> procedure break, like someone terminating the wrong circuit on misreading
> a circuit ID.

In addition to what Alex has stated, if you are purchasing this OC-12c or 
OC-3c from a single carrier, you might want to check that the carrier has
a 'dual-entrance' into your building.  Although the "main" fiber backbone
may be truly ringed and redundant, it is common practice for RBOCs and
CLECs to spur
off the backbone and bring the fibers into the building via SINGLE sheath.
This subjects the spur to backhoes or augers that might be digging up the
sidewalks in front of your building.  Most large data centers require the
telco/clec to enter the facility (via fiber) from two diverse entry points.
 This
literally brings their main backbone "through" the facility, thereby, truly
preventing a fiber-cut that will take down your OC-12/OC-48 Sonet gear.
Good dual-entries will even land the two diverse fiber runs on two seperate
FODUs
in the event that someone is moving fibers or reterminating. (However, this
kind of fiber build usually requires a revenue commitment from the customer
since it costs three times as much as a standard spur build.)  

Might be a good thing to check out if your applications are very mission
critical.

Dave Cooper
Electric Lightwave, Inc.


> The above is certainly true in the UK, and from my experience in the US
> I'd think it's doubly or quadruply true.
>
> Also, use the lowest level routing redundancy you can find. I may get flamed
> for this, but if bandwidth is not an issue, you might consider ATM switches
> instead especially if cutover time is critical.
>
> -- 
> Alex Bligh
> GX Networks (formerly Xara Networks)