BGMP stands for border gateway multicast protocol. It is used for inter-domain multicast routing and natively supports "source-specific multicast" (SSM). In order to support "any-source multicast" (ASM), BGMP builds shared trees for active multicast groups. This allows domains to build source-specific, inter-domain, distribution branches where needed. BGMP uses TCP as its transport protocol, which helps in eliminating the need to implement message fragmentation, retransmission, acknowledgement, and sequencing.
Answer option B is incorrect. The Distance Vector Multicast Routing Protocol (DVMRP) is used to share information between routers to transport IP Multicast packets among networks. It uses a reverse path-flooding technique and is used as the basis for the Internet's multicast backbone (MBONE). In particular, DVMRP is notorious for poor network scaling, resulting from reflooding, particularly with versions that do not implement pruning. DVMRP's flat unicast routing mechanism also affects its capability to scale.
Answer option D is incorrect. EIGRP is a Cisco proprietary protocol. It is an enhanced version of IGRP. It has faster convergence due to use of triggered update and saving neighbor's routing table locally. It supports VLSM and routing summarization. As EIGRP is a distance vector protocol, it automatically summarizes routes across Class A, B, and C networks. It also supports multicast and incremental updates and provides routing for three routed protocols, i.e., IP, IPX, and AppleTalk.
Answer option C is incorrect. Open Shortest Path First (OSPF) is a routing protocol that is used in large networks. Internet Engineering Task Force (IETF) designates OSPF as one of the Interior Gateway Protocols.
A host uses OSPF to obtain a change in the routing table and to immediately multicast updated information to all the other hosts in the network.

An incremental backup is a type of data backup that copies only the files that have been created or modified since the last backup operation of any type. This method is efficient because it only backs up data that has changed, which can save on storage space and reduce the time needed to complete the backup. In Kelly's case, since he is backing up only the new or changed files since the last backup, he is using an incremental backup approach.

An extranet-based VPN uses the Internet as its main backbone network, allowing users, customers, and branch offices to access corporate network resources across various network architectures. Extranet VPNs are almost identical to intranet VPNs, except that they are intended for external business partners.
Answer option D is incorrect. An intranet-based VPN is an internal, TCP/IP-based, password-protected network usually implemented for networks within a common network infrastructure having various physical locations.
Intranet VPNs are secure VPNs that have strong encryption.
Answer option B is incorrect. A remote access VPN is one of the types of VPN that involves a single VPN gateway. It allows remote users and telecommuters to connect to their corporate LAN from various points of connections. It provides significant cost savings by reducing the burden of long distance charges associated with dial-up access. Its main security concern is authentication, rather than encryption. Answer option A is incorrect. The PPTP VPN is one of the types of VPN technology.

A Gateway NAS System is characterized by having an independent NAS head that manages file services and multiple storage arrays. This configuration allows for the NAS head to be connected to external storage arrays, providing flexibility and scalability. The NAS head serves as the gateway between the clients and the storage arrays, managing file I/O requests and directing them to the appropriate storage resources.
References: The information about Gateway NAS systems and their architecture can be found in various educational resources and is consistent with the Certified Network Defender (CND) course materials, which discuss different NAS implementations and their components12.