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12 Private Networks Secure and Transport
Published in Wes Simpson, Video Over IP, 2013
Leased lines are telecommunication circuits that are usually provided by a telephone company or other carrier for exclusive use of a single customer on a long-term (monthly or yearly) basis. Popular speeds today include T1 (1.544 Mbps), E1 (2.048 Mbps), E3 (34 Mbps), DS3 (45 Mbps), and OC-3/STM-1 (155 Mbps). (Many local carriers offer direct IP connections as well; we'll cover those later in this chapter.) One of the biggest benefits of these services is that many of them are available anywhere in a carrier's service area, and pricing is often regulated. At the high end, some end users are able to lease OC-12/STM-4 (622 Mbps) and OC-48/STM-16 (2.488 Gbps) circuits when they have physical presence in major city centers where long-haul carriers have points of presence. A few adventuresome users are even leasing 2.5-Gbps or 10-Gbps wavelengths directly from optical service providers and then installing their own equipment to adapt multiple signals into a common backbone.
Substation Automation and Relay Communications
Published in Walter A. Elmore, Pilot Protective Relaying, 2018
The key to substation automation has to be communications technology. Early SCADA systems operated at 1200 bits/second (bps) or less, and required conditioned voice-grade lines for data transmission. Costs of leased lines included both a fixed monthly charge and a monthly permile charge; and could approach $1000/month. As a result, only transmission substations were equipped with RTUs because bulk power system reliability demanded information, regardless of cost. Great emphasis was placed on development of protocols with high efficiency (high percentage of “useful” information bits transmitted vs. total bits transmitted) and reasonable security.
Networks
Published in Geoff Lewis, Communications Technology Handbook, 2013
For telephone line based systems, leased lines are more secure than dial-up lines because these simply connect two specified locations. In a similar way, private packet based systems are more secure than public PTT networks. Local area networks (LANs) are the most vulnerable to attack and should be protected by the use of encryption, passwords and physical keys.
A Survey on Packet Switching Networks
Published in IETE Journal of Research, 2022
The DTEs are mainly the routers on each LAN when the carriers use frame relay for connecting to LANs. The router uses a serial connection like the T1/E1 leased line to connect with the carrier's frame relay switch at the closest point-of-presence (POP). A DCE device is a Frame Relay switch. DCEs deliver frames to other DTEs via network switches, transporting frames from one DTE across the network [12] Figure 13.