Network Components PDF

Chapter 14: Network Components 675 that they are secure, in good condition, properly configured, and well supported by appropriate third parties? The two classes of threat actors with which we should...

Chapter 14: Network Components 675 that they are secure, in good condition, properly configured, and well supported by appropriate third parties? The two classes of threat actors with which we should concern ourselves in this context are attackers and nature. We take care of the first by applying the principles of secure design we’ve discussed throughout the book and, particularly, by physically securing these cables and devices as discussed in Chapter 10. As far as natural threats, we need to be on the lookout for the wear and tear that is natural over time and that can exacerbate small product defects that may not have been apparent during our initial inspections of new products. This boils down to having qualified staff that is aug- mented, as necessary, by third parties that provide warranty and support services. Quick Review Analog signals represent data as continuously changing wave values, while digital signals encode data in discrete voltage values. Digital signals are more reliable than analog signals over a long distance and provide a clear-cut and efficient signaling method because the voltage is either on (1) or not on (0), compared to interpreting the waves of an analog signal. Synchronous communications require a timing component but ensure reliability and higher speeds; asynchronous communications require no timing component PART IV and are simpler to implement. A baseband technology uses the entire communication channel for its transmission, whereas a broadband technology divides the communication channel into individual and independent subchannels so that different types of data can be transmitted simultaneously. Coaxial cable has a copper core that is surrounded by a shielding layer and grounding wire, which makes it more resistant to electromagnetic interference (EMI), provides a higher bandwidth, and supports the use of longer cable lengths. With twisted-pair cable, the twisting of the wires, the type of insulation used, the quality of the conductive material, and the shielding of the wire determine the rate at which data can be transmitted. Fiber-optic cabling carries data as light waves, is expensive, can transmit data at high speeds, is difficult to tap into, and is resistant to EMI and RFI. If security is extremely important, fiber-optic cabling should be used. Because it uses glass, fiber-optic cabling has higher transmission speeds that allow signals to travel over longer distances. Depending on the material used, network cables may be susceptible to noise, attenuation, and crosstalk. Line noise refers to random fluctuations in electrical-magnetic impulses that are carried along a physical medium. Attenuation is the loss of signal strength as it travels. Crosstalk is a phenomenon that occurs when electrical signals of one wire spill over to the signals of another wire. CISSP All-in-One Exam Guide 676 Bandwidth is the amount of information that can theoretically be transmitted over a link within a second. Data throughput is the actual amount of data that can actually be carried over a real link. A repeater provides the simplest type of connectivity because it only repeats electrical signals between cable segments, which enables it to extend a network. A bridge is a LAN device used to connect LAN segments (or VLAN segments) and thus extends the range of a LAN. A transparent bridge starts to learn about the network’s environment as soon as it is powered on and continues to learn as the network changes by examining frames and making entries in its forwarding tables. Spanning Tree Protocol (STP) ensures that forwarded frames do not circle networks forever, provides redundant paths in case a bridge goes down, assigns unique identifiers to each bridge, assigns priority values to these bridges, and calculates path costs. The Shortest Path Bridging (SPB) protocol is defined in IEEE 802.1aq and is more efficient and scalable than STP; it is used in newer bridges. Switches are multiport bridges that typically have additional management features. Routers are layer 3, or network layer, devices that are used to connect similar or different networks. Routers link two or more network segments, where each segment can function as an independent network. A router works at the network layer, works with IP addresses, and has more network knowledge than bridges, switches, or repeaters. Gateway is a general term for software running on a device that connects two different environments and that many times acts as a translator for them or somehow restricts their interactions. A Private Branch Exchange (PBX) is a private telephone switch that is located on an organization’s property and performs some of the same switching tasks that take place at the telephone company’s central office. Proxy servers act as an intermediary between the clients that want access to certain services and the servers that provide those services. Network access control (NAC) is any set of policies and controls that restrict access to our networks. An endpoint is any computing device that communicates through a network and whose principal function is not to mediate communications for other devices on that network. A content distribution network (CDN) consists of multiple servers distributed across a large region, each of which provides content that is optimized for users closest to it.