NTPG: Chapter 5

Introduction

The vision of a network serving all of California's primary and secondary schools has been articulated and discussed in many forums. Many schools and a few school districts have implemented ad hoc network systems in response to their own perception of the importance of this resource. This section of the Guide presents a standard network implementation model to assist county offices of education and school districts in their planning so that all such implementations will be compatible with each other and with the California Department of Education (CDE) network plans.

The future goal of "an integrated voice, data, and video network extending to every classroom" is exciting but so far from what exists today that the investment in time and dollars required to realize such a goal will be greater than most districts can muster in the near term. Yet a great deal can be done immediately, with relatively few dollars, to provide modern communications systems in and between schools throughout the state.

Our present goal is to define a highly functional, homogeneous, and well-supported network system that could interconnect California's K-12 schools and district, county, and statewide offices and that will enable teachers and administrators to begin to use new communications tools and network-based information resources. It takes considerable time to adapt curricula and other programs to take full advantage of new technology. Through the use of standard models for implementation of current network technologies, California's schools can begin this important process now.

Many states have already developed communications services for their schools. A notable example is Texas, which provides terminal access to central information resources from every classroom over a statewide network. The functionality that we propose for California will be much greater: direct access to the Internet and the emerging information superhighway from computers in every classroom.

The Internet communication protocols, commonly known as "TCP/IP," are the "glue" that will allow all computers to communicate. [1] Software that implements Internet protocols is available for all modern computers. These protocols support a very wide variety of applications, from electronic messaging to client/server data access. The use of Internet protocols will ensure that all networked computers will have direct access to the vast range of existing information and education resources on the Internet as well as to the emerging National Information Infrastructure.

Approach

The implementation we suggest would use current proven and cost-effective technology and would be expandable and upgradeable to newer technology with minimum additional investment.

This approach requires careful, modular design to meet the following criteria:

1. Any physical infrastructure development should be general and flexible enough to be reused as technology improves. For example, a school office might have a simple terminal today which could be wired to a network adapter serving the school building. Later a Macintosh, DOS, or Windows-based PC might replace the terminal, and the type of connection to the network would change accordingly. However, the wiring between the office and the network "hub" site could remain the same if it is designed properly to begin with. This is an important consideration since wiring typically represents 20 to 40% of the cost of individual network hookups;
2. Existing computers and terminals in schools and district offices should be integrated as much as possible into the communication system. This installed base represents a large investment, albeit in many cases a somewhat dated set of equipment. Wholesale replacement of that base would be a large additional burden on funding resources.

A consequence of the above is that the user interface and the services available will vary depending on the type of equipment used to access the network. For example, DOS PC's, Macintosh computers, or Unix workstations would be connected directly to Local Area Networks (LANs) and would be provided with communications software to support a broad set of functions, many of which will have graphical user interfaces and will make use of client/server technology. Apple-II computers, "dumb" terminals, or other such devices could be connected to intelligent network hubs that would allow access to network server computers or information resources but almost certainly will not support the full range of functionality provided by a direct network connection. In the short term, this is a limitation that we must accept;

1. Network servers will be located where they can be managed and supported and also provide access paths with adequate bandwidth. A system of hierarchical servers should be created in larger school districts, with automatic transfer of common information from a central system to the secondary systems each night, or at appropriate intervals. Local servers will allow each school to provide online information particular to its programs and community. This model optimizes use of network bandwidth as well;
2. School interconnect topologies (links) must be both cost effective and manageable. Communication between schools, district offices, county offices of education, and the State Department of Education must be reliable and of sufficient capacity to support the primary applications as well as allow development of new applications.

Capacity is measured both by total data traffic volume and by response time when information is requested over the network. Reliability is measured by the percentage of time that the network is able to transport data. Reliability should be well over 99.7%. Capacity should be such that no more than 10% of the communications bandwidth is used during a typical work day. This is intended to leave adequate capacity for good response time to short term communication demands.

Many schools already have some form of communications infrastructure in place. In some cases this infrastructure can be adapted to newer technologies; in other cases it may have to be replaced over time. These issues are explored further following presentation of the basic model that serves as a guideline for future communications system development.

Implementation Model

There is no one "blueprint" for a network that will drop into every school. Each school will have particular physical constraints, functional needs, an existing technology base, funding constraints, and opportunities for collaboration with vendors and support groups in its area. What is presented here is a set of general guidelines that can be followed in the planning of a school network implementation.

At present there is no statewide network "backbone" for K-12 schools. Interconnection of schools, districts, county offices of education and the California Department of Education can be accomplished by acquiring Internet connection service from any of the existing Internet service providers in California (see Appendix B). It is critical that Internet connection service meet the criteria for reliability and capacity. Connection to any Internet service provider will provide communication capability to all other Internet subscribers within California, the nation, and the world.

Internet technology is designed to allow very flexible intersite topologies, but a hierarchical topology is the simplest to engineer. Generally this will mean hierarchical connection of school facilities to district offices, in many cases further aggregated at county offices, and finally a link to an Internet service provider such as CSUNet, BARRNet, or CERFnet. Coordination of circuit services (through telephone companies) and a single point of connection to an Internet service provider serves both to minimize overall costs and increase opportunities to make use of newer technologies.

The basic school network implementation model is quite simple: create a local area network (LAN) within each school building or cluster of buildings, provide at least one network server for that LAN, interconnect that LAN with the local school district offices where a similar LAN should be installed and where centrally managed information resources should exist, and connect the district offices to the nearest Internet service provider, possibly through the county office of education.

Primary technical support for network monitoring and problem resolution and for managing network resource servers should come from the district or county offices initially to avoid unnecessary duplication at the local level. As expertise is developed at the local level, more of the responsibility for daily operation and problem resolution can be assumed by individual schools.

It is impossible to cover all conceivable scenarios for implementation of this model in specific schools. However, it is possible to state general principles that should be followed in designing school network implementations. The discussion below is organized into sections corresponding to the basic model summarized in the previous paragraph. It includes a description of the general principles that are important to each level of the implementation.

School Local Area Network Implementation

A "school" is used here to mean a building or cluster of buildings that are managed as a unit and typically are on contiguous, district-owned property. Implementation of a LAN in this setting will involve installation of a cabling system to distribute the network throughout the structure(s), installation of premise wiring to support connections of computers and terminals to the network distribution system, installation of one or more network server machines in a central location [2] and provision of a network router and telecommunications circuit or radio link to connect that school to the district offices.

The most common LAN technologies in use today are Ethernet and LocalTalk. [3] Both are inexpensive and easy to install and maintain. Ethernet is adaptable to most modern computers and is built into high performance workstations, such as Sun, Hewlett-Packard, SGI, or Digital Equipment Corporation computers. LocalTalk is built into all Macintosh computers and is adaptable to DOS PC computers as well. Ethernet is roughly 20 to 40 times faster than LocalTalk. Therefore Ethernet is recommended for all computer connections, when possible, and for the school LAN "backbone" or network distribution system.

Network Adapters and Software

Individual computers will require network or communications adapters and appropriate software. Table 5-1 gives basic recommendations for the computers most commonly found in schools. Basic communications software is available in the public domain for many personal computers at no cost. More sophisticated software is being developed by a number of vendors for applications such as electronic mail, distance learning, and multimedia database access. For example, the California Technology Project is developing very easily to use software for Macintosh and DOS or Windows PC computers that will enable access to a wide variety of information resources and services (see GINA, Appendix B). Schools should look at all the available software and base choices on required functionality and support costs as well as acquisition costs.

In locations where computers will be purchased, the choice of computer type should be driven by the availability of software for the particular application(s) to be supported. Almost all modern computers can be attached to the type of network described in this document.

Table 5-1: Network adapters and software for typical computers

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Premise Wiring

A major component of the implementation will be installation of cabling to connect individual computers or clusters of computers to the LAN. The recommended topology is a "star" where each computer is wired directly to a "hub site" within the building as shown in Figures 5-1 and 5-2. A cluster of computers, typically found in a teaching lab or library, may be interconnected within the room where they are installed, and the cluster connected to the hub site with a single cable as shown in Figures 5-3 and 5-4.

The recommended premise wiring is "unshielded twisted pair" (UTP) wire that meets the Electronic Industries Association (EIA) category 5 standards for high speed data communication service. [4] While 2-pair cable may be adequate for most purposes, industry standards recommend installation of 4-pair cable. The difference in cost is minimal, so we recommend installation of the latter. One end of each cable terminates in a category 5 RJ-45 jack [5] located near the computer. The other end terminates on a standard "110 distribution block" [6] at the hub site utility closet. A labeling scheme must be chosen and strictly adhered to so that cables can be identified at both ends later, as needed.

In most cases, the hub site utility closet will be shared with telephone services. It is essential that a separate wall area be set aside within the closet for data service interconnections. Typically there will be a "field" of interconnect blocks for termination of all premise wires, another field for termination of trunk cables (used for low speed data terminals), and a third field for hub equipment ports. Interconnections between premise wiring blocks and hub or trunk blocks are installed as needed in order to provide the appropriate service to each location where communication service is required.

Installation of wiring in a building typically is performed by a qualified data wiring contractor. This is a critical aspect of the program and must be planned and installed professionally with both current and future requirements in mind. [7] To be prepared for future distribution of video signals, school network planners should consider installation of RG-59 coaxial cable to those locations where video may be required at the same time that the UTP premise wiring is being installed. The coaxial cable would terminate on a wall plate mounted "F" connector in the classroom, and would be left unterminated in the utility closet. Future technologies may support video signals over other media so the installation of RG-59 cable should be limited to near term potential requirements.

It will be cost effective to install premise wiring to as many locations as might ever serve a computer. This will include administrative offices as well as classrooms, laboratories as well as libraries. The density of network service outlet locations should reflect the types of use anticipated in a given area. For example, in office areas there should be no fewer than 2 outlet locations and at least one outlet per 150-200 square feet of floor space. In a classroom, there should be outlets near the "front" of the room for the teacher, near the "back" of the room for training and reference areas, and one or more additional outlets for other occasional use. In teaching labs where a cluster of computers may exist, a one outlet may serve a dozen or so computers. However, this method of "daisy chaining" computers off of one service connections requires that all computers have the same type of service and that they share the capacity provided. This will be an undesirable constraint as new technologies become important in the schools.

In some cases it will be cost effective to run multiple cables to the same outlet location. Terminating both cables on the same wall plate will add little to the overall wiring project costs and will add greatly to the flexibility of the system. Premise wiring that is not to be used initially will not be connected to any electronics in the hub site.

Hub sites should be utility closets or other protected, non-occupied areas. Hub sites can be created by construction of small closets or cabinets in low use areas. A hub site must be located within 300 feet of any connection. Typically, multiple hub sites are required in large or multi-story buildings.

Network Distribution System

All hub sites within a school must be interconnected to complete the school LAN. The design of this network distribution system will depend greatly on the physical layout of the school buildings. We assume that Ethernet technology will be used since higher speed technology is still quite expensive.

Figures PDF (36.8KB; 3pp.)

If all hub sites are within 300 cable feet of a central location, then 10-base-T wiring can be used from a central hub to connect each hub site, as shown in Figure 5-5. If longer distances are required, either thin-net or standard thick Ethernet or fiber optic cabling can be used. Newer, high-speed communications technologies will become important to schools in a few years and will require fiber optic cabling. It is highly desirable therefore to install a fiber optic cable plant as part of the network distribution system now if funding permits. [8] Specific design of the "backbone" network distribution system will depend on the layout of the buildings to be served.

With proper design as many as 250 computers can be connected to a single Ethernet segment. Most often the practical maximum number will be much lower than this due to the amount of data sent onto the network by each computer. For planning purposes, one can assume 100-125 computers per segment. Beyond that size the network must be subdivided using "sub networks." Design of a such a system is not difficult, but is beyond the scope of this document.

The network distribution system cabling should include unshielded multi-pair trunk cabling as well as Ethernet trunk cabling. The multi-pair trunk cable will be needed to connect terminals or older computers emulating terminals to a central "network access server" (NAS). A typical NAS can serve from 8 to 128 such connections. It is most cost effective to provide one per LAN, if needed. The NAS connects directly to the Ethernet LAN.

Local Network Server

It is highly recommended that each school install a "network server" to support local storage of commonly used information, software, electronic mail, and other functions that may require high-speed communication to the user's computer. Since the connection to the outside network will be much slower than the school LAN, it will be most efficient to access information locally. In particular, software that is to be shared among the school's computers must be stored locally since it would be very tedious to transfer it across the slower external link. The network server will be connected directly to the Ethernet network.

The location of the server should be chosen carefully to ensure its protection from abuse and environmental damage. Traditionally the school library is the focus of information gathering and storage activities, and many school libraries have clusters of computers or terminals already installed. The library would be a very logical place to locate the network server computer. The Network Router (see below) might also be located there if a suitable utility space is not available.

The network server will be a small but powerful computer with a large amount of disk storage capacity, typically 1-4 gigabytes. It will run software capable of supporting access by a large number of users simultaneously. It could also support dial-in access from teachers' or students' homes using standard inexpensive modems. [9] The design and functionality of a typical network server is described later in this guide (see Part III, Chapter 6, Network Servers).

External Connection

A single communication circuit will connect the school LAN to the local school district offices. In the school, there will be a Network Router attached between the LAN and this circuit. On the LAN side, the connection will be a typical Ethernet cable. On the external side, the connection will depend on the type of communication circuit used, as discussed below.

Interconnection of Schools with District Offices

All schools within a district should be connected individually to the network router at the school district offices. This "star topology" will be much easier to manage and will minimize conflicting use of the rather low communication bandwidth initially available. As needs change, the capacity of each school's connection can be increased appropriately.

Several standard communication circuit services may be used to effect this connection. The least expensive will be dial-up using high speed modems. However, this type of connection is not recommended due to its very limited speed. Dedicated (permanently installed) communications circuits are strongly recommended since they will allow unattended access to and from the school network at all hours. This will be particularly important if information files are to be down-loaded during the night to local network servers. Table 5-2 shows the most common options for dedicated circuit services. The exact costs must be determined by contacting local communications service providers. The equipment needed at each location must also be taken into account in determining total costs.

Table 5-2: Short-distance point-to-point communications options

Frame Relay communication services are becoming available in many areas. Frame Relay is a shared, packet-based data transport service. A school site would contract for Frame Relay service as part of a larger service group that includes the school district office and may include the Internet service provider. All members of that group would share the communications capacity. The advantage of this service is that only one end of the circuit needs to be ordered (each member orders a connection to the common service), and the capacity offered to each member can be upgraded independently. Also, because in many areas the cost of Frame Relay service is not dependent on distance to the service provider, the service to rural schools will be much less expensive than equivalent services. Overall system costs will be minimized since the central router at the district office will need fewer connections.

If Frame Relay is chosen, the overall service group must be carefully engineered. For example, since all schools would share the connection to the district office (and possibly to the Internet service provider), that must be a high capacity connection. For the initial design, the aggregate capacity of all school links should not exceed the capacity into the district office (or the Internet service provider) by more than a factor of 3 or there may be noticeable congestion and variability in response times across the system. There are many other factors that must be considered as well, such as the virtual connection topology and how best to connect to an Internet service provider. Therefore, it is recommended that an experienced network engineer be utilized to develop an operational plan for Frame Relay if it is chosen as the school interconnection service.

Future options for interconnecting schools and district offices will include:

• Community Access Television (CATV) cable systems offering either shared or dedicated bi-directional data communication services;
• Metropolitan area fiber optic communications service providers;
• Switched Multi-megabit Digital Service (SMDS) providing data transport service at speeds up to 34 megabits per second; and
• Asynchronous transfer mode (ATM) connection services supporting voice, data, and video communications at speeds into the gigabit per second range. [10]

The costs for the last three options are unknown at this time but may be generally higher than those indicated in Table 5-2. The cost for the CATV option may be negotiable as part of the local CATV contract with the community. As of early 1994, Frame Relay has become available in California. Frame Relay may prove particularly cost-effective in rural areas since the tariff is independent of distance. School network planners should look at the total cost of any solution based on quotes from communications and equipment suppliers in their area.

As demands for network speed develop due to heavy use of multimedia or other bandwidth intensive application, higher-speed communications circuits can replace the initial circuits with little or no change in the equipment or LAN. This gives great flexibility in tailoring service to funding levels and application needs.

School District Office LAN and Support Systems

The school district offices should form the focal point for interconnection of all schools in the district. Within the district offices, network operations can be monitored and problem resolution managed. One or more network servers can provide essential network support as well as central archiving of common information and software.

A critical role of the district office will be to manage Internet "Domain Name Service" [11] (DNS) for the district's schools. DNS is required of all Internet networks. It defines the basic network level identity of each computer, workstation, server, and active network component. This function is described more fully below under Network Management and Operational Monitoring.The district offices should be wired in a manner similar to a typical school, as shown above. This will allow teachers, superintendents, principals and all school personnel to communicate and share information easily. In addition, a NAS connected to a central pool of modems could provide dial-in access to the district network.

Figures PDF (36.8KB; 3pp.)

Interconnection of the School District with the Internet

Connection of the entire school district to the Internet will take place through the district office interconnect site, as shown in Figure 5-6. This hierarchical model can be extended another level to interconnection of the school district offices through the county office of education facilities. Many administrative information resources could be located at the county level, and there might be cost savings if the entire county connects to an Internet service provider through a single point. The bandwidth required for this single connection, however, will be much greater than that required for each school district since traffic will be aggregated.

This hierarchical topology also provides a logical model for network support and information resource management. The school district or county offices can provide continuous monitoring of the network and provide high level technical expertise for problem resolution, relieving the individual schools of this burden. Interactions with communications circuit providers and Internet service providers will be more effective if handled through a central liaison. Similarly, it is highly desirable that network users have a single well-known point of contact in case they encounter problems or questions (see Part III, Chapter 8: Technical Support).

Internet service should be acquired from the most cost-effective, reliable Internet service provider (see Appendix C). Circuit services can be similar to those shown in Table 5-1. The higher speed services should be considered if traffic demands increase and funding permits. Circuit costs usually will be lowest when connecting to the provider with the nearest "point of presence" (POP), but newer technologies such as Frame Relay and SMDS [12] make circuit costs less dependent on distance. The Internet connection will require a high-quality router that can be configured to interact correctly with the service provider's routers. In most cases, this can be the same router used to support the local school connections.

Integration of Existing School Networks

Many schools have developed LAN systems in support of particular classroom activities or administrativefunctions. In some cases the technologies used are not those recommended for new installations. If these older LAN systems are capable of transporting Internet protocols they may be integrated into a new LAN system and replaced later as funding permits.

For example, IEEE 802.5 Token Ring is often used to interconnect DOS PC-type computers and IBM minicomputer servers. Token Ring networks can transport Internet protocols, and software is available for DOS computers to support basic Internet functions. Many Internet routers support optional Token Ring adapters. This is the recommended way that existing Token Ring LANs can be integrated into a wider school LAN system in order to extend Internet information resources to those PC users.

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Another example is a Novell Network system using Ethernet as a LAN. The Ethernet LAN, if implemented well, is perfectly capable of transporting Internet protocols as well as Novell protocols simultaneously. Each PC or Macintosh can be given software that will allow both Novell and Internet services to be used as needed. This coexistence is important so that, for example, a person using a PC that depends on the Novell server for disk file space can transfer a large file from a remote Internet server to the PC's pseudo-disk. It also permits each user to run client software such as Eudora (electronic mail), Gopher (information services), and Mosaic (World Wide Web information services), which require direct Internet access. To integrate the Novell Ethernet LAN into the wider school LAN system, a simple Ethernet repeater can be used in a manner similar to Figure 5-3.

An alternative to supporting both protocols that is sometimes suggested in cases such as the one cited above, in which a network server already exists, is to use the server as a "network application gateway." This approach is strongly discouraged. It is essential that each computer and workstation support Internet protocol data communication directly so that modern client/server applications can be supported where the server or servers may be located anywhere on the Internet. The "gateway" approach severely restricts the work-station's potential ability to access multimedia and other important information resources.

Some technologies, such as "arc net" (older network technology), may not be capable of supporting Internet protocols but may offer "terminal emulation" shared access to a type of "modem pool." The modem adapter might be rewired to connect to ports on a network access server instead. This would provide simple access to information resources for the arc net users.

In any case, older LAN technologies should not be expanded and should be phased out as funding permits. It is critical that there be a relatively homogeneous installed base of technology in order that new applications of information resources can be provided to the entire school community.

Network Management and Operational Monitoring

All networks require some level of network management in order to ensure reliable service. Monitoring of the health of the network can help identify problems before they become detrimental to network users. It also can help predict trends in traffic patterns and volume.

Internet technology network management consists primarily of determining the proper routing parameters for optimal and reliable network operation, assignment of network Internet Protocol (IP) addresses and maintenance of a network-accessible database of node names corresponding to each address, [13] and monitoring the daily operation of the network. The Domain Name Service (DNS) database must be centrally managed although the database itself can be physically distributed through the use of sub domains. The primary component of the DNS database for each school district should be located at the school district interconnect site. DNS is discussed more fully under Network Servers in Part III, Chapter 6 of this Guide.

Internet network monitoring serves three primary purposes:

1. Constant observation of the "health" of the network, network components, and external network connectivity. Standard Simple Network Management Protocol (SNMP) support is built-in to most active components today. Even network servers and workstations can be monitored in this way. Operations staff can be provided with network monitoring stations that will display alerts immediately upon detecting a wide variety of problems or anomalies;
2. Collection of statistics on the performance of the network and patterns of traffic in order to identify needed enhancements or re-engineering. Using the same SNMP capabilities mentioned above, data on packet forwarding and total traffic volume can be collected and used to generate periodic reports on network utilization;
3. More rapid problem resolution. When problems do occur, SNMP tools can help to pinpoint the source of the problem(s). Such problems include transient routing anomalies, DNS query failures, or even attempts at breaking into network accessible host computers.

Since network management and monitoring is a technically demanding task and requires special equipment and software, it should be a centralized function in the initial design of school network systems, as discussed above. (See also Part III, Chapter 8: Technical Support.)

Summary

The model for school network implementation described above is based on broad experience with this technology in higher education and administrative environments. Many California schools have already installed networks very similar to this model. We believe that it is a practical first step towards bringing a powerful resource to bear for enriching all of California's school programs.

None of the suggestions above preclude or postpone in any way future development of an integrated voice, data, and video network for California's schools. Use of existing Internet carriers does not in any way preclude future development of a separate "backbone" for California's K-12 community if such a "backbone" is determined to be cost effective or required for enhanced functionality. Rather, the infrastructure recommended above can be the foundation at the local level in preparation for future high capacity networks.

[1] See RFC1432 for a bibliography of books on Internet technology.

[2] Other protocols, such as AppleTalk or Novell's IPX, may be supported on a school's local area network (LAN) as needed for local functions, such as printer sharing or local resource servers.

[3] IEEE 802.5 Token Ring is not recommended for new installations. It is more expensive, and it is not available for as wide a range of computers.

[4] See EIA/TIA-568 "Commercial Building Telecommunications Wiring Standard."

[5] A standard RJ45 jack can be used for Ethernet or lower speeds if initial cost is a major factor. Such jacks can be replaced with category 5 versions later as needed.

[6] In older sites, M66 distribution blocks may already be installed. These can be used for the time being but will not support newer higher speed technologies.

[7] See "Virtual Schoolhouse-A Report to the Legislature on Distribution Infrastructures for Advanced Technologies in the Construction of New Schools, K through 12" (Department of General Services, State of California, Feb 1993) for example conduit and utility closet plans.

[8] If fiber optic cable is installed, consideration should be given to including both multimode fiver for current and future data requirements and single mode fiber for video and future very high speed data systems.

[9] For large number of modems, a NAS might prove more cost effective. Also, access control with user authentication is required for this type of service.

[10] Many more options will become available as new technologies come to market.

[11] See RFCs 1034 and 1035 for a full explanation of Domain Name Service.

[12] At this time, SMDS services are not widely available.

[13] See RFC 1480 for a discussion of Internet naming conventions for school networks.

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