Utilization of the redundant ring in SONET

Frank Coluccio fcoluccio at dticonsulting.com
Tue Jul 17 21:51:54 UTC 2001

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

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