WAN Design Principles

Correct Answer: VPN

VPN (Virtual Private Network) is the best solution to securely connect multiple office locations over the public Internet. A VPN creates a secure and encrypted connection, which is similar to a tunnel, between the networks at different locations, ensuring the data is not accessible to attackers. It uses the public Internet infrastructure but adds a layer of security. The other options like Leased Line, MPLS (Multiprotocol Label Switching), and ISDN (Integrated Services Digital Network) can also be used to interconnect business locations but they are not the best options considering the requirement to use the public Internet. A Leased Line does not use the public Internet hence it's not suitable for this scenario. MPLS and ISDN are technologies used for creating WANs but they don't inherently offer the same level of security as a VPN for data transmission over the public Internet.

Correct Answer: Leased Line

The best answer is 'Leased Line'. A leased line is a dedicated, point-to-point communication line that provides a company with a guaranteed level of service. It's most appropriate when a company plans to connect a remote branch using a dedicated T1 line since this is exactly the situation leased lines are designed for. MPLS (Multiprotocol Label Switching) is a protocol for efficient network traffic flow but is not specific to T1 line usage. VPN (Virtual Private Network) is a technology that creates a safe and encrypted connection over a less secure network, such as the internet, not a dedicated T1 line. ISDN (Integrated Services Digital Network) is a set of communication standards for simultaneous digital transmission of voice, video, data, and other network services over the traditional circuits of the public switched telephone network. However, it's less suitable as it's outdated and less likely to provide the reliable, high-speed connection a T1 line offers.

Correct Answer: MPLS

MPLS (Multiprotocol Label Switching) is the best alternative WAN technology a manufacturing company should consider when deciding to replace their legacy Frame Relay network. MPLS is a protocol for speeding up and shaping network traffic flows. It's more flexible than Frame Relay, can support different types of services, and allows for quality of service (QoS). The other alternatives are not wrong per se, but they are not the best options in this scenario. Leased Line is a dedicated telecommunication line which provides a company with a guaranteed amount of bandwidth however, it may not provide the same level of efficiency and flexibility in traffic engineering as MPLS ADSL (Asymmetric Digital Subscriber Line) and ISDN (Integrated Services Digital Network), although they can be used for WAN connections, are typically used for smaller-scale, such as residential or small business connections. They may not provide the necessary bandwidth and reliability a manufacturing company may require for its operations.