NAT (Network Address Translation) - NAT is a service in which the source and/or destination addresses of IP packets are rewritten as they pass through a router or firewall. It is most commonly used to enable multiple hosts on a private network to access the Internet using a single public IP address. NAT is typically used for security reasons.
NBTSTAT - Is used to troubleshoot connectivity problems between 2 computers communicating via NetBT, by displaying protocol statistics and current connections. NBTSTAT examines the contents of the NetBIOS name cache and gives MAC address.
NDA (Non-disclosure Agreement) - Before taking most certification exams, you will need to accept the terms of the NDA. While they vary from one certification vendor to another, the general message of these agreements is that you will not share information about the exam you have taken with others after you have taken it. Microsoft's NDA CompTIA Candidate Agreement Cisco's Certification Exam Policies
NDIS (Network Device Interface Specification) - NDIS is a Windows device driver API that enables a single network interface card (NIC) to support multiple network protocols. For example, with NDIS a single NIC can support both TCP/IP and IPX connections. The NDIS is a Logical Link Control (LLC) that forms the upper sublayer of the OSI data link layer (layer 2 of 7) and acts as an interface between layer 2 and 3 (the Network Layer). The lower sublayer is the Media Access Control (MAC) device driver. NDIS was jointly developed by Microsoft and 3Com Corporation, and is nowadays mostly used in Windows, but the open-source ndiswrapper and Project Evil driver wrapper projects allow many NDIS-compliant NICs to be used with Linux and FreeBSD, respectively. magnussoft ZETA, a derivative of BeOS, supports a number of NDIS drivers.
NetBEUI - Stands for "NetBIOS Extended User Interface". It is a transport layer protocol mainly used for small Windows 9x and NT LANs. In reference to the NetBIOS distinction, NetBIOS is the applications programming interface and NetBEUI is the transport protocol. NetBEUI is a non-routable protocol meaning it will not allow communication through a router. It is broadcast oriented which causes it to not scale well. Although it can still be installed on newer Microsoft operating systems, it has largely been replaced by TCP/IP.
NIC (Network Interface Card) - A Network Interface Card is an expansion board you insert into a computer so the computer can be connected to a network. Most NICs are designed for a particular type of network, protocol and media, although some can serve multiple networks.
NiCd (Nickel-Cadmium) - Nickel-cadmium batteries (commonly abbreviated NiCd or NiCad) are a popular type of rechargeable battery for portable electronics, cordless phones, power tools, and other devices. NiCd batteries are known for the "memory effect" that they develop if repeatedly charged without being fully discharged. They are also not environmentally friendly.
NiMH (Nickel Metal Hydride) - A type of rechargeable battery similar to a nickel-cadmium (NiCd) battery but has a hydride absorbing alloy for the anode instead of cadmium, which is an environmental hazard. A NiMH battery can have two to three times the capacity of an equivalent size NiCd and the memory effect is not as significant. However, compared to the lithium ion chemistry, the volumetric energy density is lower and self-discharge is higher. Applications of NiMH type batteries includes hybrid vehicles such as the Toyota Prius and consumer electronics. Standard NiMH batteries perform better with moderate drain devices such as digital cameras, flashlights, and other consumer electronics, but, because NiCd batteries have lower internal resistance, they still have the edge in very high current drain applications such as cordless power tools and RC cars.
NNTP (Network News Transfer Protocol) - This protocol's primary purpose is to provide a mechanism for Usenet news servers (NNTP Servers) to communicate with each other and with newsreader clients. This allows for the creation of newsgroups. A newsgroup is a discussion about a particular subject consisting of notes written to a central Internet site and redistributed through Usenet, a worldwide network of news discussion groups.
NSLOOKUP - This is a command that queries a DNS server for machine name and address information. Originally written for Unix operating systems, this command is now available on Windows and other operating systems. To use nslookup, type "nslookup" followed by an IP address, a computer name, or a domain name. NSLOOKUP will return the name, all known IP addresses and all known aliases (which are just alternate names) for the identified machine. NSLOOKUP is a useful tool for troubleshooting DNS problems.
NTFS (New Technology File System) - NTFS is the standard file system of Windows NT and its descendants Windows 2000, Windows XP and Windows Server 2003. Windows version 95, 98, 98SE and ME, cannot natively read NTFS filesystems, although utilities do exist for this purpose. NTFS offers additional features over FAT and FAT32 predecessors such as transaction logs to help recover from disk failures, the ability to set permissions for directories and/or individual files, support for large hard drives, support for long filenames, etc.