Building-to-Building Connectivity
You need to review several key issues when selecting a bridge technology for building-to-building connectivity. As with WLANs, the first requirement is bandwidth. You must determine what overall bandwidth will be required between sites. If the bridges will be used for both wireless bridges and for WLAN access, the bridges must follow the appropriate technology for the client devices. If the bridge will be strictly for site-to-site connectivity, however, any bridge technology can be used, including proprietary systems.Bridge systems come in many flavors and sizes, with various throughputs available. 802.11b systems can provide throughputs of up to 6 Mbps per system, and ranges up to 20 miles (at 6 Mbps) in locations where high-gain antennas are permitted. Bridges based on 802.11g and 8021.11a technologies typically provide throughputs in the mid-20-Mbps range, but with reduced range. Some 802.11a-based or 802.11g-based bridges can provide maximum throughput at about 12 or 15 miles.For much higher throughput, you need to review some proprietary systems. Many different systems are available, including free-space optical bridges, through which data rates can reach 155 Mbps or higher but with very limited range.In all cases, line of sight is required for the longer distances, and usually for even short links.Most bridges will provide a link joining the two networks to the same subnet. If the sites are on separate subnets (typical), the bridges should be attached to a router port for proper segmentation between networks.Even proprietary systems are not secure (many think that you can have "security be obscurity") because traffic can be "received" by anyone owning a device from the same company. Security needs to be reviewed carefully and should be used if any type of sensitive data is to be sent over the link. Some bridges support EAP-type authentication, whereas others may only support the easily compromised WEP. An alternative is to use a VPN tunnel between the routers on each side of the link and have the bridges attached to these routers. This provides all bridge traffic a VPN security tunnel. |
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