Reviewing an application against the LAN and WAN
Daniel J. Nasser
Networking and connectivity do not only apply to email and file sharing. In many business environments applications must be available over large multi-site networks. Here are some things to think about, from Network Performance Baselining by Daniel J. Nasser, New Riders, 2000, if you are rolling out an application over a LAN or WAN.
Many factors are involved when deploying an application against a large LAN or WAN design.
The network must be baselined and examined for peak utilization levels, such as average and peak transition and historical views. It is very important to identify busy traffic periods and how they may affect the application deployment. Certain user groups have to be identified and user profiles have to be established. It is important to understand when an application is going to be engaged and how the different transactions affect different periods of the business day. It is important to know what types of clients are deployed and how dense the clients are in certain user or server areas, and how this will affect the deployment of the application.
Placement of file servers is also critical. It is important that file servers be reviewed for proper placement (either a remote decentralized design or a centralized architecture). It is important that all the clients that access servers have a low-latency channel and balanced channel to allow the application to operate smoothly.
In certain cases, it is positive for an application server to be placed in a centralized location so that all clients in a localized LAN can access the server without failure.
If the server is remote and an application blueprint model reveals that high latency is present even though no symptoms are exhibited, however, this serves as a warning flag not to place more clients across the WAN circuit; doing so would just introduce additional latency.
These are examples of the circumstances that should be taken into consideration when deploying an application. As can be seen from these examples, it is important when initially deploying an application to consider what its rollout effects will be on multiple users against this application profile.
An MIS department should prepare for application rollouts by predetermining what the rollout level count will be and where users will have to be placed. It is critical to understand how users should be placed against the internetwork infrastructure to access the application. Based on this determination, it may be necessary to place several servers on the internetwork to synchronize or transfer information to prevent stations from traveling long routes to access key file server centralized database or server resources. In the case of flat internetwork architecture or larger Ethernet LANs, this may not be a factor.
When introducing WAN architectures against the scheme, however, many considerations must be taken into account.
If multiple users are going to be placed across the other side of a WAN and they require access to a centralized server environment that already has a high level of LAN access from its local user-node standpoint, it may be necessary to place a remote server at the remote LAN site that will hold the key information for the application at the remote site. It may also be possible to design and provide database synchronization so that all information is updated on a consistent basis from the remote site to the headquarters site for all the key server central architectures related to the application flow.
These are just some of the elements that should be considered upon deployment of an application across a large internetwork. Another factor to consider is how the links are utilized on large internetworks or LAN links. It is important to determine the overall load and latency factors on certain areas of the internetwork prior to application deployment. This prevents problematic circumstances from occurring after deployment.
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