Wide Area Networks (WAN)

Correct Answer: QoS

The best WAN optimization technology for implementing VoIP (Voice over IP) across a Wide Area Network would be QoS (Quality of Service). QoS is designed to provide priority to certain types of network protocols (like VoIP), ensuring they have the necessary bandwidth and latency requirements for optimal performance. The other options, although not outright 'wrong', are not as suitable for VoIP implementation. Traffic shaping is generally used to control bandwidth usage by prioritizing certain types of network traffic, but it does not specifically enhance VoIP performance. Caching helps improve access speed for frequently used data, which is not directly related to VoIP communication. Compression indeed can reduce the bandwidth usage, however, VoIP data is already compressed so additional compression may not yield significant improvement and may increase latency, which is not desirable for VoIP.

Correct Answer: MPLS

MPLS (Multiprotocol Label Switching) is the best solution for a company that is facing connectivity issues with multiple branches connected via leased lines. MPLS labels data packets, which enables them to be forwarded along pre-determined paths in the network, providing robust, efficient, and reliable connectivity. It is highly scalable and capable of handling high-performance networks, which is crucial for businesses with multiple branches connected via leased lines. The other options - ISDN (Integrated Services Digital Network), Frame Relay, and VSAT (Very Small Aperture Terminal) - are not as effective. ISDN is an older technology and not as efficient or reliable as MPLS. Its maximum transfer speed is significantly slower compared to MPLS and it does not provide the same level of service quality. Frame Relay is another older technology that tends to suffer from performance issues when networks become congested. It also lacks the flexibility and scalability of MPLS. VSAT, which utilizes satellite communication, can be affected by weather conditions and has high latency, making it less reliable and efficient for a company with multiple branches connected via leased lines.

Correct Answer: Site-to-Site VPN

The best solution for securely and cost-effectively connecting a remote office to their headquarters is through a Site-to-Site VPN. A Virtual Private Network (VPN) creates a secure tunnel over the internet, allowing the two offices to share data as if they were directly connected over a private network. This is more cost-effective than other methods because it uses the existing internet infrastructure rather than requiring the establishment of a dedicated line. In contrast, a Leased Line, while ensuring robust connectivity and performance, is much more expensive to implement and maintain. DSL and Cable Modem, on the other hand, are standard internet connectivity methods and do not offer the same level of security and privacy as a VPN, making them less suitable for a business that needs to protect its data while transferring it between locations.