In any system where a collection of N identical devices is required for the system to operate effectively, one additional device is added to the system in case one of the N fails. N+1 Redundancy is commonly used for redundant power supplies, as well as redundant trunk links in large networks.
Network Address Translation. NAT means that IP addresses on one side of a device (usually a firewall, but the feature is available on many routers as well) are transparently rewritten as the packets are passed through to the other side. In many cases, the device rewrites other portions of the IP packet, such as TCP port numbers and sequence numbers, at the same time.
Non-Broadcast Multiple Access. Some Layer 2 network media are capable of supporting many devices simultaneously, but without having the capability to support broadcasts. This means that the broadcasts sent by one of the attached devices will not reach all of the other devices in the same media group. Such media are called NBMA.
NetBIOS Extended User Interface. This is a nonroutable Layer 2 protocol that is frequently used to carry NetBIOS packets. It is most commonly seen in workgroup products such as LAN Manager and Microsoft Windows products.
Network Basic Input/Output System. This is a simple higher-layer protocol that has frequently been used for building peer- to-peer file, print, and application-sharing services over LAN workgroups.
In IP, a binary string that is used to distinguish the network part of the address from the host part. Anywhere the bit pattern has a 1, the corresponding bit in the address is part of the network address. Conversely, the bits in the address that correspond to a 0 in the netmask are interpreted as belonging to the host part of the address.
Any device that performs basic network functions such as bridging, routing, or other gateway functions.
See NIC.
See NOS.
Network Interface Card. The physical component that allows any device to connect to the network.
Novell Link State Protocol. A dynamic routing protocol for IPX that is based on a Link State Protocol.
Network to Network Interface. In ATM networks, there are two main types of connections. At the edges of the ATM network, switches connect to user devices through UNI links. The connections from switch to switch through the ATM network use NNI links.
Network Operating System. A NOS is a system that facilitates basic network functions such as file and print sharing, although it could also include other application services.
Network Time Protocol. This is an IP protocol that allows devices to synchronize their clocks with one another. Generally, at least one of the devices taking part in NTP for a given network is a master, and it is synchronized with an atomic clock or other reliable time source.