Some WAN Carriers make their 'protection' bandwidth available to ISPs and other takers on a preemtable basis. That is, when a ring failure occurs the protection bandwidth is reclaimed, or preempted, by the carrier for restoration purposes, thus "bumping" the original occumpant (you) into the ditch. Since this type of bandwidth comes at a discount, one has to weigh the operational risks (SLAs?) against the financial tradeoffs, which is what I suspect you are doing. It isn't all that bad if used in a straightforward mesh topology, or one where one for one link protection is used, because the ISP will normally design to recover their mesh through regular Layer 3 routing routines, anyway. It can get out of hand, however, if the particular ring in question is having intermittent troubles, causing the ISP to encounter an undesirable number of convergences per unit of time (hours, day, week, etc).

Hello:

I would like to know how typical it is to have the redundant ring in SONET used for the transport of data while still providing protection switching features. Also, could any one give me insight into a few vendors that does it. I would appreciate, if some one could provide input on the above.

Regards,

Srihari Varada