Paramasiviah Harshavardhana

Integrated Network Design Tools (INDT): a suite of network design tools for current and next generation networking technologies

Integrated Network Design Tools (INDT) is a suite of tools being developed at Bell Labs. This suite of tools is built on a flexible software architecture based on C++ and can provide optimal network design for a mix of private line, switched voice and switched multimedia services using a mix of circuit and ATM switches and cross connects and facilities with different bandwidth granularity. INDT also has the ability to design, in a standalone mode or in conjunction with logical designs, the core transport network using mesh and/or ring topologies and using PDH or SONET/SDH products. The transport network may be designed over existing fiber routes and capacities or the tool may be used to help decide the fiber layout. We focus on a new capability within INDT, viz., SONET ring design. We present a high level description of the various submodules in the ring network design and provide an overview of the main factors that influenced our algorithm development. We also present sample studies of our approach to intra-ring load balancing as well as our economic quantification of penalties due to dual ring interconnect (DRI) and other features of interest.

Dual (SONET) ring interworking: High penalty cases and how to avoid them

The Dual (that is, two-node) Ring Interworking (DRI) feature is required to guarantee sub-second demand restoration with multiple interconnected SONET rings. There is a capacity (and, indirectly, cost) penalty for implementing DRI, as rings with larger capacities will be required to canT the same set of demands with DRI than with single (that is, one-node) ring interworking (SRI). This paper considers in detail the DRI capacity penalty with a pair of interconnected rings. In this case, the DRI capacity penalty can range from 0% to 100%, and be higher than 1000% in a contrived example. The above observation also holds if we consider a chain of interconnected rings spanning a country and carrying primarily east-to-west or north-to-south traffic. This paper analyzes the components of this DRI penalty and outlines how this penalty can be reduced. The paper also shows that almost all of this penalty can be mitigated with Triple Ring Interworking (TRI). In TRI, the essential idea is to balance the inter-ring load across 2 links involving 3 nodes rather than a single link. Finally, in a large network of interconnected tings where each ring connects to multiple rings an extension of the TRI strategy to balance the total inter-ring load across multiple separate links involved in interworking between pairs of rings will be shown to be useful in reducing the DRI penalty.

A note on weight-based load balancing on SONET rings

In a recent paper, Cosares and Saniee [2] introduced the problem of balancing loads on SONET [1] rings. This note gives a counterexample to one of their results and then states the correct result.