SYN/FIN scanning using IP fragments is a process of scanning that was developed to avoid false positives generated by other scans because of a packet filtering device on the target system. The TCP header splits into several packets to evade the packet filter. For any transmission, every TCP header must have the source and destination port for the initial packet (8-octet, 64-bit). The initialized flags in the next packet allow the remote host to reassemble the packets upon receipt via an Internet protocol module that detects the fragmented data packets using field-equivalent values of the source, destination, protocol, and identification.

Non-repudiation is the assurance that someone cannot deny the validity of something. Non-repudiation is a legal concept that is widely used in information security and refers to a service, which provides proof of the origin of data and the integrity of the data. In other words, non-repudiation makes it very difficult to successfully deny who/where a message came from as well as the authenticity and integrity of that message.

The nbtstat command is a Windows utility that displays NetBIOS over TCP/IP (NetBT) protocol statistics, NetBIOS name tables, and the NetBIOS name cache. However, the nbtstat command does not support IPv6 addresses, which are the standard format for the Internet Protocol version 6 (IPv6). Therefore, using the nbtstat command with IPv6 addresses will result in an error message or no output. To enumerate NetBIOS names on a network that uses IPv6, you should switch to an enumeration tool that supports IPv6, such as Nmap, which is a network scanning and security auditing tool. Nmap has a scripting engine (NSE) that allows users to write and execute scripts for various network tasks, including NetBIOS enumeration. Nmap can also detect the operating system, services, and vulnerabilities of the target machines, regardless of the IP version they use. References:
* Nbtstat Command - Computer Hope
* Nbtstat CMD: Windows Network Command Line Prompt
* [Nmap Scripting Engine (NSE) Documentation]

https://en.wikipedia.org/wiki/IPsec
Internet Protocol Security (IPsec) is a secure network protocol suite that authenticates and encrypts the packets of data to provide secure encrypted communication between two computers over an Internet Protocol network.
It is used in virtual private networks (VPNs).
IPsec includes protocols for establishing mutual authentication between agents at the beginning of a session and negotiation of cryptographic keys to use during the session. IPsec can protect data flows between a pair of hosts (host-to-host), between a pair of security gateways (network-to-network), or between a security gateway and a host (network-to-host). IPsec uses cryptographic security services to protect communications over Internet Protocol (IP) networks. It supports network-level peer authentication, data-origin authentication, data integrity, data confidentiality (encryption), and replay protection.
The initial IPv4 suite was developed with few security provisions. As a part of the IPv4 enhancement, IPsec is a layer 3 OSI model or internet layer end-to-end security scheme. In contrast, while some other Internet security systems in widespread use operate above layer 3, such as Transport Layer Security (TLS) that operates at the Transport Layer and Secure Shell (SSH) that operates at the Application layer, IPsec can automatically secure applications at the IP layer.