Consolidated Guidance: Describing the Network Design

Synopsis

The descriptions of the internetworking equipments, protocols, conventions, and guidelines allow the architects to manage the evolution of the network infrastructure and support application service changes. This document provides some initial suggestions for what to consider when creating and updating these descriptions.

Guidelines

• Consider the types of user. The following individuals may use the service descriptions:

  • System and Network Designers. These individuals refer to these descriptions to implement the networking designs.

  • Procurement Specialists. These individuals refer to these descriptions when purchasing compliant, commercially available network equipment or developing specifications for contracting the development of custom items.

  • Quality Assurance. These individuals confirm that the items used on the project conform to these descriptions.

• Consider all three usage environments .

• Generally, a top-down design strategy ( Murhammer et al. 1999 ) may work best, using a reference model such as the OSI reference model ( ISO/IEC 7498-1 1994 ). This starts with an analysis of the types of applications on each platform and their communications needs. This analysis focuses on the current as well as future applications, identifying the characteristics that should be optimized, deduced from the overall system properties . The Technical Boundaries Descriptions and the Integrated Technologies Descriptions provide the basis for understanding the application types and their networking needs, such as the settings in which they will be used. Consider:

  • Bandwidth: throughput (e.g., multimedia applications)

  • Guaranteed response times

  • Expansion: accommodating new clients, servers, or networks into the topology

  • Life expectancy of the network

  • Security

  • Cost/budget expectations

  • Network management

  • Legacy protocols and infrastructure (cabling)

  • Quality of Service and Type of Service

• The current or planned capabilities of the platforms ( Platform, Equiupment, and Solutions Reference Set ) will affect the network design, such as:

  • Network interface card support (legacy devices)

  • Graphics, text, video, voice application support

  • Basic platform performance ( CPU ), memory, or disk

  • Operating system support for the necessary API s (protocol stacks)

• Consider the operational environment characteristics that will affect the network design ( Technical Boundaries Descriptions ), such as:

  • Locations for access to the network

  • Workgroup structures

  • Access to high-speed remote connections ( DSL , cable modem)

  • Secure remote access to the network ( VPN )

  • Who will manage the distributed applications or infrastructure (e.g., network operations)

  • Number of users, expected growth rates

  • Need for mobility (e.g., wireless)

• Guidance on applying various IP networking technologies ( LAN , WAN ), protocol selection and use is available in ( Murhammer et al. 1999 )

• Detail the characteristics of networking equipment (hubs, bridges, routers, switches) in the Platform, Equipment, and Solutions Reference Set . Network-specific conventions and guidelines (addressing, naming, routing, etc.) are documented in this reference set. Consider items already in the agencies inventory, as noted in the Analyze the Situation activities.

• Identify standards that apply and note how they have been adapted. Refer to or add these descriptions to Agency Standards Reference Set , as needed. Identify proprietary protocols.

• Identify or produce reference implementations, as needed, to illustrate or study the network design decisions.

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