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Technology Stocks : The *NEW* Frank Coluccio Technology Forum -- Ignore unavailable to you. Want to Upgrade?

To: GraceZ who wrote (3412)	7/22/2001 2:46:52 PM
From: Frank A. Coluccio	Respond to of 46821

The diagram is oversimplified in some ways. The wrap-around occurs within the node devices, themselves, on the interfaces that are closest to the break, and not on the fiber section, as loosely shown. For another view of the various types of SONET architectures, each differentiated by the number and type of strands used, see: commweb.com Don't ask me why they don't show a break in the above diagram. If I come across a more descriptive diagram I'll post it, or maybe someone else here will, first. Your observation concerning the extra time that it takes to traverse the 'elongated' ring is a design consideration that has to be taken into account in the calculus used to assure 50 ms restoration times. As does the number of nodes (not to exceed fifteen) that can reside on the same ring. The first of these parameters, distance, is a soft constraint, dependent on whether the carrier wishes to meet the popular 50 ms restoration time. Some rings, such as transoceanics and transcontinentals, have restoration times that, by design, actually exceed 50 ms, being guided by the circumference in the ring design. The second parameter (number of add-drop muxes, or ADM, nodes, which serve as on-off ramps) is bound by a hard address-ing constraint, I believe. At least it was when SONET was originally specified. There may be exceptiions to this in latter day so-called next-gen SONET ring designs, not sure.

To: GraceZ who wrote (3412)	7/25/2001 6:17:58 PM
From: Frank A. Coluccio	Read Replies (1) \| Respond to of 46821

Grace, this goes back to your question in the uplinked post. I came across a more descriptive set of diagrams in a reply from a NANOG poster who was addressing a similar question. See Figure 15 in the following white paper titled: Optical Fiber Networks: Linear and Ring Topologies, from G3M Corp: g3m.com The straight line going through the span between Nodes E and F represents the cable break. Note the dotted lines within Nodes E and F, which represent the wrap-arounds (aka loopbacks). This particular type of ring is a 4-fiber bidirectional line switched ring (4Fiber BLSR). It has the ability to restore more types of failures than the 2Fiber BLSR (hey, way a minute... it has more fibers, so by definition it would have to have the capability to restore more!) and node failures than the UPSR or 2Fiber-BLSR, as explained in the accompanying text. It is also capable of restoring the entire rated payload of the ring instead of only half, as is the case with 2Fiber Rings, which the text also touches on. HTH. FAC