Veroxity Wavelengths

Diverse Protection or Protected Diversity (Part 1)

Posted by Christian Williams

This will be my first attempt to clarify a couple telecom terms that are loosely thrown around, but typically misstated and misunderstood.  I will try to separate my opinions/descriptions from the definitions.  For this discussion, the opposite of Protected is Unprotected.   The opposite of Diverse is Collapsed.  This first part will discuss Protection.  Part 2 will go into diversity.

Equipment Protection – For each Active component in a piece of equipment, a Stand-By component exists to recover in the event of a failure to the Active component.

Critical components (Processors, Matrixes, High-Speed Line Cards, etc.) in a “carrier-class” network should maintain a 1+1 protection scheme.  Meaning, for every 1 active component, 1 standby component exists.  Less critical components (Low-Speed Line Cards, etc.) in a “carrier-class” network will maintain an n+1 protection scheme.  Meaning for a number greater than 1 active components, 1 standby component exists.

Hand-Off Protection – Active and Stand-By Interfaces are utilized to establish connectivity between a Service Provider and End Customer.

Hand-Off Protection is only available for TDM based interfaces.  Hand-Off Protection Technologies do not currently exist for Ethernet based services.

Network Protection – A technology which performs pre-defined steps to maintain functionality in the event of a failure.

For SONET services, network protection is ring-based.  When an equipment or fiber outage occurs, steps are taken to re-route the traffic over standby network.  The standby network is predetermined and reserved.  Fail-over time for SONET protection schemes is sub 50 milliseconds.  I plan on going into the definitions, advantages, and disadvantages of the available SONET protection schemes in a later blog entry.

For Ethernet or IP services, network protection can come in varying flavors.  Data Networks utilize technologies (OSPF, BGP, MPLS, etc.) to re-route traffic in the event of a failure.  As the failure occurs, all nodes in the network communicate to determine the best routing for future traffic.  Because the re-routing, or convergence, is not predetermined, fail-over time can be from seconds to minutes.  Data Network equipment providers are continually striving to develop technologies to minimize the convergence time.

Circuit Protection – For each active-path across a Service Provider’s network, a protect-path exists to recover in the event of a failure.

With traditional SONET based protection-schemes, protection occurs across entire rings, with all traffic on the ring failing-over simultaneously.  The major disadvantage of ring-based schemes is that traffic has to hop across rings, frequently collaping into a single location where the rings interconnect.  Circuit Protection allows the Service Provider to create two paths from end to end.  When traffic enters the network, it is duplicated and sent across both paths.  Each path is routed so that no single location is utilized by both paths.  When both data streams are received at the last piece of equipment in the network, a selector utilizes the best signal.  Circuit Protection is sometimes called Path Protection.

Veroxity utilizes Circuit Protection for routing of all SONET and Ethernet-Over-SONET services.  By utilizing Circuit Protection, Veroxity guarantees complete circuit diversity from end to end for each circuit provisioned.  Which leads us to our diversity discussion.