VLAN (Virtual LAN)

Most enterprises have moved toward the switched network paradigm, in which computers are  connected to dedicated ports on Ethernet switches, Gigabit Ethernet switches, ATM switches, or other types of switches. Switching devices support network designs in which the entire network is  one big flat network as opposed to many subnetworks interconnected by routers. In a flat network, all workstations are in the same broadcast domain. Any computer can directly communicate with any other computer.

Voice/Data Networks  

Voice and data networking is about the trends and technologies for merging voice and data  communication on a single network. It is part of a broader “multi service networking” concept    that combines all types of communication on to a single network. Practically speaking, the single network is a packet-based IP intranet, the Internet, or special service provider networks that provide Internet-like services. Some other methods for combining voice and data are mentioned here, but the general trend is toward IP-based voice and data networking. 

Voice over IP (VoIP) 

   In just a few years, the old circuit-switched voice-centric communications network will give   way to a data-centric, packet-oriented network that seamlessly supports data, voice, and video   with a high quality of service. The switching equipment, protocols, and links are already being  put into place. A transition network is currently in place that joins the packet data world with the circuit-switched world. Integrated access solutions are being installed that support integrated data, voice, and other media into the Internet or the PSTN.         

VoIP (Voice over IP)

See Voice over IP (VoIP); Voice/Data Networks.

VPN (Virtual Private Network)

Private networks have traditionally been built with dedicated leased

lines, dial-uplines, or  other links such as satellite or microwave. Links are established among remote sites. The links are “private” because no other traffic except the traffic of the company leasing the links crosses The links A virtual private network is the creation of private links across public networks such as the Internet. The idea is to create what appears to be a dedicated private link on a shared network using encryption and tunneling techniques .Any body can create a private connection by encrypting the contents of the traffic being sent across a network, but truly secure VPNs are better built with the cooperation of service providers that can create dedicated paths with guaranteed service levels across their networks.    

VRRP (Virtual Router Redundancy Protocol) 

Some networks are connected to other networks through a single router. But a lone router is a potential point of failure that can break the connection of the subnet from the entire network.VRRP, or Virtual Router Redundancy Protocol eliminates single points of failure by providing support for redundant router connections. An additional feature is the ability to do load sharing in which each redundant link can carry traffic.The protocol reduces downtime and delays normally associated with lost links and dynamic route configuration. Redundant routers are installed and one is "elected" as the master router. If a router fails, one of the redundant "backup" routers takes over as the master router. The master router sends a special VRRP advertisement packet to the backup routers, usually every second. If advertisements stop, the backups assume the master is down and initiate backup mode, in which the next-in-line router is elected.An important point is that VRRP provides fast failure recovery. Other dynamic routing protocols such as RIP and OSPF are time-consuming and inefficient. They must discover failed routes, alert other routers, run routing algorithms to calculate alternate routers, and then build routing tables.The VRRP is so efficient at recovering from failures that most end systems may not even notice that the switching over has occurred. In addition, routers in the configuration share a virtual IP and MAC address, so that end systems see the routers as having the same address.

VSAT (Very Small Aperture Terminal) 

 See Satellite Communication Systems.