Skip to main content

WAN Design

2.3 WAN Design 
2.3.1 WAN Communication
WANS are considered to be a set of data links connecting routers on LANs. User end stations and servers on LANs exchange data. Routers pass data between networks across the data links.
Because of cost and legal reasons, a communications provider or a common carrier normally owns the data links that make up a WAN. The links are made available to subscribers for a fee and are used to interconnect LANs or connect to remote networks. WAN data transfer speed (bandwidth) is considerably slower than the 100 Mbps that is common on a LAN. The charges for link provision are the major cost element of a WAN and the design must aim to provide maximum bandwidth at acceptable cost. With user pressure to provide more service access at higher speeds and management pressure to contain cost, determining the optimal WAN configuration is not an easy task.
WANs carry a variety of traffic types such as data, voice, and video. The design selected must provide adequate capacity and transit times to meet the requirements of the enterprise. Among other specifications, the design must consider the topology of the connections between the various sites, the nature of those connections, and bandwidth capacity.
Older WANs often consisted of data links directly connecting remote mainframe computers. Today’s WANs, though, connect geographically separated LANs. End-user stations, servers, and routers communicate across LANs, and the WAN data links terminate at local routers. By exchanging Layer 3 address information about directly connected LANs, routers determine the most appropriate path through the network for the required data streams. Routers can also provide quality of service (QoS) management, which allots priorities to the different traffic streams.
Because the WAN is merely a set of interconnections between LAN based routers, there are no services on the WAN. WAN technologies function at the lower three layers of the OSI reference model. Routers determine the destination of the data from the network layer headers and transfer the packets to the appropriate data link connection for delivery on the physical connection.

Comments

Post a Comment

Popular posts from this blog

OSI layers / Peer-to-peer communications / TCP/IP model

OSI layers 2.3.4 This page discusses the seven layers of the OSI model. The OSI reference model is a framework that is used to understand how information travels throughout a network. The OSI reference model explains how packets travel through the various layers to another device on a network, even if the sender and destination have different types of network media. In the OSI reference model, there are seven numbered layers, each of which illustrates a particular network function. - Dividing the network into seven layers provides the following advantages: • It breaks network communication into smaller, more manageable parts. • It standardizes network components to allow multiple vendor development and support. • It allows different types of network hardware and software to communicate with each other. • It prevents changes in one layer from affecting other layers. • It divides network communication into smaller parts to make learning it easier to understand. In the foll...
Post a Comment
Read more

PC Basic...

• Backplane – A backplane is an electronic circuit board containing circuitry and sockets into which additional electronic devices on other circuit boards or cards can be plugged; in a computer, generally synonymous with or part of the motherboard. • Network interface card (NIC) – An expansion board inserted into a computer so that the computer can be connected to a network. • Video card – A board that plugs into a PC to give it display capabilities. • Audio card – An expansion board that enables a computer to manipulate and output sounds. • Parallel port – An interface capable of transferring more than one bit simultaneously that is used to connect external devices such as printers. • Serial port – An interface that can be used for serial communication in which only one bit is transmitted at a time. • Mouse port – A port used to connect a mouse to a PC. • USB port – A Universal Serial Bus connector. A USB port connects devices such as a mouse or printer to the computer ...
Post a Comment
Read more

Advantages and disadvantages of link-state routing

Advantages and disadvantages of link-state routing 2.1.5  This page lists the advantages and disadvantages of link-state routing protocols. The following are advantages of link-state routing protocols:  Link-state protocols use cost metrics to choose paths through the network. The cost metric reflects the capacity of the links on those paths. Link-state protocols use triggered updates and LSA floods to immediately report changes in the network topology to all routers in the network. This leads to fast convergence times. Each router has a complete and synchronized picture of the network. Therefore, it is very difficult for routing loops to occur. Routers use the latest information to make the best routing decisions. The link-state database sizes can be minimized with careful network design. This leads to smaller Dijkstra calculations and faster convergence. Every router, at the very least, maps the topology of it...
Post a Comment
Read more