NETWORK PLANNING, DESIGN AND EXPANSION

Planning a New Network - General Design Considerations

The following steps are intended as general guidelines in planning a network design. These guidelines are based on the assumption of generic network traffic loads such as "typical" file/print servers and "ideal" database servers - i.e., uniform traffic load from all clients and no "unusual" application dependencies. In the later stages of network refinement in the "real world" situation - all traffic loads should be monitored and appropriate modifications/corrections made to the network design to handle application dependent traffic loads.

Network design is based on application dependencies - the location of database servers, mail servers and file servers determine the bandwidth requirements for those particular network segments. User loading and client applications determine the dynamic traffic load that need to be supported. Supporting special applications such as multi-media will require special consideration in network planning to support large file transfers required by these applications. These loads can be estimated in initial design phase but sometimes only with rough approximation especially if custom written client/server applications are involved.

Phase One - Initial Network Planning /Layout

The LAN can be laid out initially on paper making assumptions about traffic loads and determining what category of network is to be constructed: workgroup, departmental or enterprise. These categories were established by the network vendors to provide a starting point from which to choose the network components best suited to handle the traffic loads anticipated and offer some provision for expansion. If the design is meant to support a workgroup of 10-50 workstations and several servers - the network does not require the same kind of heavy-duty hardware required by an enterprise data center.

General specifications that should be outlined include:

1. Number of LAN ports required - based on number of workstations and servers in network

2. Estimate number of switched ports - try to dedicate a switched port for each server at minimum. Switched ports can be 10 Mbps or 100 Mbps depending on application and client loading. Some heavily loaded database servers will require 100 Mbps ports, lightly loaded file servers can probably deliver satisfactory response to small file requests with 10 Mbps ports.

3. Number and type of WAN ports - estimate bandwidth requirements for each port. Estimates should be based on type of applications to be supported over the Wide Area. Mail applications do not require large bandwidth unless users are sending large multi-media files. Regular transmission of large files such as CAD drawings and database replication traffic will require large bandwidth.

4. Router choice - serial ports based on WAN bandwidth requirements, types of protocols to be routed, types of physical interfaces required, etc.

5. Server Types - number and type of server - i.e., file/print, database, NFS, mail, etc. Number of clients supported by each server.

6. Clients - type of client network communication package - i.e., Oracle SQL*Net, Microsoft Named Pipes, etc. Specify types of applications on clients which communicate with server services.

The accuracy of these estimates will determine how much correction must be applied in the last stages of network tuning.

Phase Two - Construct Network or Model the Design with Network Design/Simulation Tool

Without some kind of Design/Simulation Software to test the design, the only alternative is to build the network based on assumptions and educated quesswork. Based on the number of LAN ports - determine how many hubs and switches are required. Determine the type of router needed and specify wiring requirements for cabling, connectors and plugs.

The three categories of network design that should be considered ( my own rough approximations):

1. Workgroup - small group ( 10 - 20 ) workstations, 1-file server and branch office router (basic functions / 2-port )

2. Departmental - 50-100 workstations / several servers (file/database) / several routers to other departments or headquarters

3. Enterprise - headquarters data center / 100's of workstations / main production server / router connections to all branch offices and departments

In environmments where there is a lack of experienced network designers it is advisable to consider using Network Planning/Design software tools. These tools are also good for maintaining diagrams and documentation on network configuration. Some tools allow the use of simulations and 'what-if' analysis of proposed changes to see effects on network before implementation. The kind of documents generated are the type of specifications needed to present to a contract network designer for soliticitation of bids.

There is a product called CANE from Imagenet Ltd. which uses graphical layout to design a network and maintains documentation on the network configuration. It contains a library of common devices which can be manipulated like building block objects to create a logical network The following is a list of available design tools:

1. CANE - Imagenet Ltd. / $1000 (univ-discount) / Simulation capability / (www.image-net.com)

2. NetGuru - American Hytech / $500 / (No Web Site )

3. Netsuite Toolkit - Netsuite Development / $1000 - $2500 /(www.netsuite.com)

These tools can help in the layout of networks, provide good documentation for tracking configuration and with simulation capability they can account for application specific traffic loading of the network.

The simulation tool can be used also for checking and verification of proposed network configurations when evaluating bids for a network design.

Phase Three - Monitor Network and Fine Tune

After the network is up and running under loaded conditions - monitor key segments on the network such as server ports on LAN switch to evaluate actual traffic loads. Use segmentation to balance network traffic and re-evaluate the network design.

A new technology called VLAN - allows the re-configuration of ports on LAN switches with software utilities - without having to move cables/workstations and much easier to document. This technique allows load balancing to be accomplished quickly by shifting nodes with heavy traffic demands to segments with lighter loads.

SNMP managers such as AIX Netview, SUN Solstice and HP OpenView implement capabilities like VLAN configuration on the basis of vendor/MIB (Management Information Base) support. HP for example supports MIBS from Bay Networks (and many other vendors) by allowing that vendor's element management software (Optivity) to be closely integrated into and run concurrently with the SNMP Manager.