7.6.3 Module Quiz – WAN Concepts (Answers)

Explanation: A WAN connects multiple LANs that are in geographically separated locations. A MAN connects multiple LANs in a large campus or in a city. WLAN is a wireless LAN that covers a rather small geographic area.

Explanation: ISDN and ATM are Layer 1 and 2 technologies that are typically used on private WANs. Municipal WiFi is a wireless public WAN technology. Corporate communications over public WANs should use VPNs for security.

Explanation: Technologies such as SONET, SDH, and DWDM are designed to run over fiber optic cables.

Explanation: WANs are used to interconnect the enterprise LAN to remote branch site LANs and telecommuter sites. A WAN is owned by a service provider. Although WAN connections are typically made through serial interfaces, not all serial links are connected to a WAN. LANs, not WANs, provide end-user network connectivity in an organization.

Explanation: A wide-area network (WAN) provides network connectivity over a wide geographical area compared to a local-area network (LAN) that is usually limited to connecting devices in a room or building. A storage-area network (SAN) contains storage media such as hard drive disk arrays that provide storage for applications and servers. A wireless LAN (WLAN) provides connectivity for wireless devices in a limited space.

Explanation: For this small office, an appropriate connection to the Internet would be through a common broadband service called Digital Subscriber Line (DSL), available from their local telephone service provider. With so few employees, bandwidth is not a significant problem. If the company were bigger, with branch offices in remote sites, private lines would be more appropriate. Virtual Private Networks would be used if the company had employees who needed to connect to the company via Internet.

Explanation: WAN operations focus primarily on the physical layer and the data link layer of the OSI model.

Explanation: MPLS can use a variety of underlying technologies such as T- and E-Carriers, Carrier Ethernet, ATM, Frame Relay, and DSL, all of which support lower speeds than an Ethernet WAN. Neither a circuit-switched network, such as the public switched telephone network (PSTN) or Integrated Service Digital Network (ISDN), nor a packet-switched network, is considered high speed.

Explanation: Public cellular networks provide a highly mobile Internet connection at high data rates.

Explanation: A point-to-point topology only connects two nodes. A bus is a legacy topology for LANs. Mesh and full mesh topologies have more connectivity than needed (all or most of the branches will be connected to each other). A hub and spoke design will connect the headquarters to all its branches, as desired.

Explanation: A WAN operates beyond the geographic scope of a LAN and it is owned by a service provider. WANs are used to interconnect the enterprise LAN to remote LANs in branch sites and telecommuter sites. WAN service providers include carriers such as a telephone network, cable company, or satellite service. It is not feasible to connect LANs across a country, or around the world, with physical cables.

Explanation: The two most common types of circuit-switched WAN technologies are the public switched telephone network (PSTN) and the integrated services digital network (ISDN). Frame Relay and ATM are packet-switched WAN technologies. DSL is a WAN technology that offers broadband Internet access.

Explanation: VPNs over the Internet provide low cost, secure connections to remote users. VPNs are deployed over the Internet public infrastructure.

Explanation: For this small office, an appropriate connection to the internet would be through a common broadband service such as digital subscriber line (DSL), available from the company’s local telephone service provider, or a cable connection from the cable company. Because the company has so few employees, bandwidth is not a significant issue. If the company were bigger, with branch offices in remote sites, private lines would be more appropriate. VSATs are used to provide connectivity to remote locations and are typically used only when no other connectivity options are available.

Explanation: When traveling employees need to connect to a corporate email server through a WAN connection, the VPN creates a secure tunnel between an employee laptop and the corporate network over the WAN connection. Obtaining dynamic IP addresses through DHCP is a function of LAN communication. Sharing files among separate buildings on a corporate campus is accomplished through the LAN infrastructure. A DMZ is a protected network inside the corporate LAN infrastructure.

Explanation: Digital leased lines require a channel service unit (CSU) and a data service unit (DSU). An access server concentrates dialup modem dial-in and dial-out user communications. Dialup modems are used to temporarily enable the use of analog telephone lines for digital data communications. A Layer 2 switch is used to connect a LAN.

Explanation: A connection-oriented system predetermines the network path, creates a virtual circuit for the duration of the packet delivery, and requires that each packet carry an identifier. A connectionless packet-switched network, such as the internet, requires each data packet to carry addressing information.

Explanation: Unlike circuit-switched networks, which typically require expensive permanent connections, packet-switched networks can take alternate paths, if available, to reach the destination.

Explanation: Dense wavelength-division multiplexing (DWDM) is a newer technology that increases the data-carrying capacity of SDH and SONET by simultaneously multiplexing data using different wavelengths of light. ISDN (Integrated Services Digital Network), ATM (Asynchronous Transfer Mode), and MPLS (Multiprotocol Label Switching) are not fiber-optic technologies.

Explanation: SDH and SONET are high-bandwidth fiber-optic standards that define how to transfer data, voice, and video communications using lasers or light-emitting diodes (LEDs). ATM (Asynchronous Transfer Mode) is a Layer 2 technology. ANSI (American National Standards Institute) and ITU (International Telecommunication Union) are standards organizations.

Explanation: A leased line establishes a dedicated constant point-to-point connection between two sites. ATM is cell switched. ISDN is circuit switched. Frame Relay is packet switched.

Explanation: A private WAN solution that involves dedicated links between sites offers the best security and confidentiality. Private and public WAN solutions offer comparable connection bandwidth, depending on the technology chosen. Connecting multiple sites with private WAN connections could be very expensive. The website and file exchange service support is not relevant.

Explanation: LTE, or Long-Term Evolution, is a fourthgeneration cellular access technology that supports internet access.

Explanation: The equipment located at a cable service provider office, the cable modem termination system (CMTS), sends and receives digital cable modem signals on a cable network to provide internet services to cable subscribers. A DSLAM performs a similar function for DSL service providers. A CSU/DSU is used in leased-line connections. Access servers are needed to process multiple simultaneous dialup connections to a central office (CO).