Deployment Considerations

  The choice of choosing the optimal architecture should be based on the scope and complexity of a project, the time available for completion, and the expected enhancement or obsolescence of the system. With n-tiered architectures, the network manager must do three key things:

• Co-ordinate closely with application developers

• Design the infrastructure supporting the server farm for maximum performance

• Understand application users and their access and performance requirements

Researchers believe that by the year 2040, client/server technology will have evolved from the current rigid definition applied to using specified computers to an intelligent network or to what some call a single system image. This intelligent network will have "smart hubs" or general call points to access multiple requests and assign the processing in the most efficient manner. Whether this becomes a reality or a commercial dream is beyond our vision, but in time, client/server technology will surely continue to unfold and prove its true worth.

  The major characteristics of client/server architecture include the logical separation of client and server processes, the ability to change the server without affecting the clients, and the capacity to change a client without affecting the server or other clients. Other characteristics of client/server are:

• User friendly applications

• Gives user great deal of control

• Department level managers are given the ability to be responsive to their local needs

• Network Security

• New technical approach to distributed computing

  A server is passive. It does not initiate conversations with clients although it can act as a client of other servers. Characteristically, a server:

• Waits for and accepts clients

• Presents a defined abstract interface to client

• Maintains the location independence and transparency of client interface

  The client is the networked information requestor. Typical client functions are to:

• Display the user interface

• Perform basic input editing

• Format queries to be forwarded to the server processor

• Communicate with the server

• Format server responses for presentation

  In general, client/server technology centralizes applications and information, making them available to the data owners via network terminals. Consequently, client/server technology offers many benefits over mainframe computing:

• Reduced cost of operation

• Reduced lead time for system enhancements

• Ad-hoc reporting tools that do not require programmer assistance

• Increased end-user control of the system

• Graphical user interfaces (GUIs)

Business Impact

  Client/server technology has the following features and benefits:

 Key Applications

• The key applications for client/server technology are:

• price/performance ratios

• shared processing

• application control

• speed

• data integrity via centralized data

• functionality

• GUI, highly interactive end-user interface

Measuring the Technology's Performance

The performance of client/server technology is measured in two ways:

•  cost savings - this is compared to mainframe costs in hardware and development

•  flexibility - robust development environment with sufficient analysis, design and development tools that can integrate the necessary management tools

Co-ordinate closely with the application developers

 Some applications lend themselves to WAN links between the application servers and the data servers, but the majority do not. Understanding the application's network behavior is critical to determining where to deploy the various layers of the architecture as well as the network characteristics--performance, security, and redundancy--required between each layer. Application data flow should be characterized prior to deployment. However, once in service, both the design and the operation of the application may change. Therefore, application behavior must be monitored regularly to identify bottlenecks.

Design the infrastructure supporting the server farm for maximum performance

Technologies such as server load balancing, high-speed LAN switching; Gigabit Ethernet; multipoint link aggregation (MPLA); high-performance server network interface cards (NICs), which offload low-level networking functions from the CPU; and Fibre Channel storage access can be leveraged to ensure a high-performance server farm.

Understand application users and their access and performance requirements

 The increased scale of the application architecture means that more users from more locations can use the application. To provide these users the best possible service, the network manager must understand who the users are, where they are, and what information they need to access. Optimizing the network pathways between users and the application tier with which they interact usually implies more attention to network latency, bandwidth, and traffic management, especially in the WAN.

 If the level of traffic associated with business-critical applications is projected to approach the capacity of the WAN links, more WAN bandwidth is needed. More likely, the total traffic--including both business-critical traffic and non-time-critical applications--approaches the WAN capacity limit at peak periods. In this case, WAN traffic management can ensure that the critical application traffic is given priority during periods of congestion. For example, one could guarantee that access to business-critical enterprise resource planning (ERP) tools is given priority over e-mail and stock quote updates when monthly reports are being generated and analyzed. The network manager's role should be to interpret business objectives and goals as well as to establish traffic management policies that support those goals.