An application layer is an abstraction layer that specifies the shared communications protocols and interface methods used by hosts in a communications network.
The GNU General Public License (GNU GPL or GPL) is a widely used free software license, which guarantees end users the freedom to run, study, share and modify the software.
The Internet Protocol (IP) is the principal communications protocol in the Internet protocol suite for relaying datagrams across network boundaries.
Netfilter is a framework provided by Linux that allows various networking-related operations to be implemented in the form of customized handlers.
Peer-to-peer (P2P) computing or networking is a distributed application architecture that partitions tasks or workloads between peers.
Quality of service (QoS) is the description or measurement of the overall performance of a service, such as a telephony or computer network or a cloud computing service, particularly the performance seen by the users of the network.
A regular expression, regex or regexp (sometimes called a rational expression) is, in theoretical computer science and formal language theory, a sequence of characters that define a search pattern.
A modern computer operating system usually segregates virtual memory into kernel space and user space.