broadband strategies handbook.pdf - Khazar University

portion of the broadband supply chain can be forgotten. But building out thetwo ends of the network—backbone and last mile—will be ineffective unlesscapacity exists in the middle to tie all the pieces together. Hence policies toaddress middle-mile and backhaul problems, such as promotion of facilities-basedcompetition or open-access requirements, are just as importantas policies in other parts of the network. 20Metropolitan ring networks are a special case worth noting. In mostcountries, the majority of broadband traffic is generated in urban areas. Initiallinks are typically point-to-point, but over time this architecture canbecome increasingly complex and inefficient. The topology of a ring networkis highly practical for metropolitan areas where a significant amountof traffic is destined for other users in the area. A ring network simplifiesnetwork architecture by connecting premises in central business areastogether over fiber optic cable. Traffic flows along the ring, with each nodeexamining every data packet (figure 5.7). The standard for metropolitan ringnetworks is Institute of Electrical and Electronics Engineers (IEEE) 802.17. 21One of the dangers with ring networks is that if a node goes down or thefiber optic cable breaks, the whole ring could fail. This can be overcome bytransmitting the information in two directions (clockwise and counterclockwise)or by building in other types of redundancy. Rings have tended to useSynchronous Optical Network/Synchronous Digital Hierarchy (SONET/SDH) technology for transport. Wavelength Division Multiplexing (WDM)is emerging as a transport standard because of its efficiency and integrationwith gateways to national and international backbones.Implementation Issues for Metropolitan ConnectivityMany of the implementation issues associated with the middle mile are thesame as those involved with backbone development, namely cost and competition.However, the choices of where such links should be built (or, perhapsmore accurately, upgraded, since lower-capacity links may exist) andhow the network should be designed can be more difficult, both politicallyand technically. Government interventions are usually part of a plan toconnect rural areas and are combined with other measures to roll outnetworks to those areas as well as part of metropolitan government initiatives.Even if broadband networks reach rural areas, most countrieshave a significant gap in broadband speeds between rural and urbanareas. For instance, in Europe most of the lowest broadband downloadspeeds (256–512 kbit/s) are found in rural areas.In the context of limited funds for network build-out, choices will haveto be made that balance the government’s desire to spread the benefits ofTechnologies to Support Deployment of Broadband Infrastructure 219