srihari varada wrote:

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.

We looked into SDH/SONET for our Australia-US capacity and backhaul. The SDH/SONET products you can buy are: - protected SDH/SONET presented to customer on a single circuit. - protected SDH/SONET presented to customer on two circuits (called "interface protection"). - protected SDH/SONET with both Main and Protect circuits presented to the customer. - "extra traffic channel" which is the Protect circuit of another customer. Obviously when that other customer requires the protection, you see Alarm Indication. This can be viewed as being an unprotected SDH/SONET circuit. What you can't buy is two unprotected diversely-routed circuits. You can simulate that by purchasing a protected circuit with a single customer interface and an extra traffic channel. If your vendor has a multi-ring archiecture, you may also be able to purchase multi-drop capacity. For example, our Southern Cross Network capacity is +-STM1--- Hawaii ---STM1-+ | | Sydney Oregon | | +----------STM1----------+ We then used protected (shown by ===) and extra traffic circuits (shown by ~~~) to backhaul that three-drop ring to the PoPs. Hawaii PoP = = +-STM1--- ---STM1-+ | Hawaii | ~~~~~ ~~~~~~ Sydney PoP Sydney Oregon Washington PoP ===== ====== | | +----------STM1----------+ Other architecuters were possible, but cost more. The backhaul providers were PowerTel (Sydney), WCI (Oregon-Washington) and Verizon (Hawaii). All were more than willing to meet our rather odd backhaul requirements, although Verizon could only offer protected capacity. The engineering staff were all wonderful to deal with. We did have issues with provisioning, and I would encourage you to check that: - the round-trip time is within expectation - the bit error rate is low, as a high rate is a symptomm of configuration error - the protection works We also had additional issues where international standards vary from US practice, these mainly lead to SONET being provisioned where we intended SDH. We use MPLS to load share and to provide end-to-end protection. Note that using end-to-end protection has significantly more delay then using SDH's native segment protection on long undersea links. But the ability to load share and get 310Mbps out of 155Mbps of expensive undersea capacity swayed the decision towards MPLS. -- Glen Turner Network Engineer (08) 8303 3936 Australian Academic and Research Network glen.turner@aarnet.edu.au http://www.aarnet.edu.au/ -- The revolution will not be televised, it will be digitised