Robust network design for IP/optical backbones

Abstract

Recently, Internet service providers (ISPs) have gained increased flexibility in how they configure their in-ground optical fiber into an IP network. This greater control has been made possible by (i) the maturation of software defined networking (SDN), and (ii) improvements in optical switching technology. Whereas traditionally, at network design time, each IP link was assigned a fixed optical path and bandwidth, modern colorless and directionless Reconfigurable Optical Add/Drop Multiplexers (CD ROADMs) allow a remote SDN controller to remap the IP topology to the optical underlay on the fly. Consequently, ISPs face new opportunities and challenges in the design and operation of their backbone networks [1], [2], [3], [4].Specifically, ISPs must determine how best to design their networks to take advantage of the new capabilities; they need an automated way to generate the least expensive network design that still delivers all offered traffic, even in the presence of equipment failures. This problem is difficult because of the physical constraints governing the placement of optical regenerators, a piece of optical equipment necessary for maintaining an optical signal over long stretches of fiber. As a solution, we present an integer linear program (ILP) which (1) solves the equipmentplacement network design problem; (2) determines the optimal mapping of IP links to the optical infrastructure for any given failure scenario; and (3) determines how best to route the offered traffic over the IP topology. To scale to larger networks, we also describe an efficient heuristic that finds nearly optimal network designs in a fraction of the time. Further, in our experiments our ILP offers cost savings of up to 29% compared to traditional network design techniques.

Telecommunications network design: Technology impacts and future directions

“…As a result, network operations changed and the optical backbone layer no longer performed any failure restoration rerouting activities. Only the IP traffic layer network performed rerouting to account for network failures [35, 54]. There were several reasons for this change: For telephone traffic networks, the nodes (switches) are extremely reliable [6] and normal restoration planning does not need to account for node failures.…”

“…During the IP traffic era, network engineers concluded that it was not cost effective to perform backbone layer network restoration. In fact, some new optical network capabilities could make backbone layer restoration more attractive again [54].…”

“…Subsequent developments in optical cross‐connects [126] and SDN standards [103] enabling centralized control schemes have made this idea feasible for current fiber optic networks [93]. There is some work on this topic [34, 53, 54] but additional optimization‐based research would be useful.…”

Arrow

“…Today's service providers cope with the loss of capacity caused by fiber cut events by over-provisioning the network. In particular, to protect from massive packet loss, WAN operators preallocate extra capacity for failover paths using (𝑖) failure-aware Traffic Engineering (TE) [17,40,48,63,79] and (𝑖𝑖) optical path protection [14,19,59,68,80,81,84]. In such techniques, when fiber cuts occur, traffic is automatically shifted from failed IP links to pre-allocated backup paths.…”

Operation algorithms for energy-efficient backbone networks

“…The authors in [131] presented an ILP and designed an efficient heuristic that solves the equipment placement problem in network design, determines the optimal mapping of IP links to the optical infrastructure for any given failure scenario and determines the best route for the offered traffic over an IP topology. Experiments showed that the proposed ILP offers cost savings of up to 29% compared to traditional network design techniques.…”