Common WAN Implementation Issue

WAN Communications:
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 common LAN bandwidth. The charges for link provision are the major cost element, therefore the WAN implementation 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 connect geographically separated LANs. WAN technologies function at the lower three layers of the OSI reference model end-user stations, servers, and routers communicate across LANs, and the WAN data links terminate at local routers.
Routers determine the most appropriate path to 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. Routers can also provide quality of service (QoS) management, which allots priorities to the different traffic streams.

Steps In WAN Design:
Businesses install WAN connectivity to meet the strategic business requirement of moving data between external branches. Because WAN connectivity is important to the business and expensive, you need to design the WAN in a systematic manner. This figure shows the WAN design steps.
Each time a modification to an existing WAN is considered, these steps should be followed. However, because many WANs have evolved over time, some of the guidelines discussed here may not have been considered. WAN modifications may arise from expanding the enterprise WAN servers or accommodating new work practices and business methods.

These are the steps for designing or modifying a WAN:
Step 1. Locate LANs - Establish the source and destination endpoints that will connect through the WAN.

Step 2. Analyze traffic - Know what data traffic must be carried, its origin, and its destination. WANs carry a variety of traffic types with varying requirements for bandwidth, latency, and jitter. For each pair of endpoints and for each traffic type, information is needed on the various traffic characteristics.

Step 3. Plan the topology - The topology is influenced by geographic considerations but also by requirements such as availability. A high requirement for availability requires extra links that provide alternative data paths for redundancy and load balancing.

Step 4. Estimate the required bandwidth - Traffic on the links may have varying requirements for latency and jitter.

Step 5. Choose the WAN technology - Suitable link technologies must be selected.

Step 6. Evaluate costs - When all the requirements are established, installation and operational costs for the WAN can be determined and compared with the business need driving the WAN implementation.
As shown in the figure, the design steps describe here are not a linear process. Several iterations of these steps may be necessary before a design is finalized. To maintain optimal performance of the WAN, continued monitoring and re-evaluation is required.

WAN Traffic Considerations:
To determine traffic flow conditions and timing of a WAN link, you need to analyze the traffic characteristics specific to each LAN that is connected to the WAN. Determining traffic characteristics may involve consulting the network users and evaluating their needs.


Post a Comment


NBA Live Streaming. Copyright 2008 All Rights Reserved Revolution Two Church theme by Brian Gardner Converted into Blogger Template by Bloganol dot com | Distributed by Blogger Templates Blog