K-20 Education Network
K-12 Network End Site Engineering Guidelines
Version 2.0

Background

Phase 1 implementation, connecting public universities, colleges, community and technical colleges and K-12 education service districts, to the K-20 Educational Telecommunications Network was completed in December 1997. Phase 2 connects approximately 400 sites, including K-12 school district campuses, baccalaureate branch campuses, community and technical college branch campuses. In March 2000, the Federal Communications Commission granted a waiver to enable connection of 15 independent college campuses in the state. Phase 2 is complete, except for the independent colleges.

With the large number of sites connected to the network, it was imperative that engineering standards be set and followed at the end sites. This document provides engineering standards for K-20 Phase 2 end sites with a primary focus for K-12 school districts.

Objectives

1. Generate documentation describing standard installations and alternative installations and the degree of District involvement in each.
2. Address consistent, recurring questions related to transport demarc, extended wiring and District routers as discovered in site surveys performed by the K-20 Phase 2 Site Survey Team.

Scope of services

1. Document the installation of network transport at all K-20 sites to include:
• Transport demarc
• Extended wiring
2. Document issues related to K-20 Peering with District routers.
3. Provide methods of installation that may be used for actual implementation.
4. Discuss the impact of District-owned active electronics in the transport path.

Reason for K-20 design standards

A primary design criteria for the K-20 Phase 2 network design is that overall network monitoring and maintenance will be managed by the K-20 Operations Cooperative (KOCO). The K-20 Technical Working Group (TWG), therefore, has requested that end site design implementations be standard across the network. This should ensure that the KOCO can solve network problems in a timely manner and as efficiently as possible. Along these lines, the design committee is also using (wherever possible) an installation methodology that would allow K-20 to contract with U S WEST Communications for any necessary on-site cable plant installation and long-term maintenance of K-20 procured and managed cabling.

Terminology

A network as large and as complex as the K-20 Phase 2 network will have a significant number of individual designs due to variances in the end site's needs and provided services. This section attempts to document the terminology that will be used to describe those sites from the K-20 TWG and institution's perspective.

Entrance facility

The entrance facility is the location where the local telephone company's services enter a client's property for cross connections to the client's own telephone or data/video network facilities. The entrance facility includes infrastructure, such as conduit or trenches, and copper or fiber optic cable and termination blocks for cables. The terminations, typically, take place in a room called the "telephone room" by the client but what is usually known as the entrance facility by telephone and data engineers.

Carrier or telephone company demarc

The termination location of the entrance cable is called the "telephone" or "carrier"-or "phone company demarc." The phone company has ownership and responsibility to this point by tariff regulations.

K-20 transport demarc

The K-20 transport demarc is the point where the circuit from the telephone company (the "telco") interfaces with the customer's on site equipment. The physical location of the K-20 transport demarc will be a jack on the customer side of the transport demarc. Customer equipment, in this specific case, will be the K-20 owned data or video equipment. K-20 plans to dispatch a U S WEST Communications crew to install the transport demarc jack as well any necessary wiring from the building entrance facility to the transport demarc location.

Large districts will have separate transport demarcs installed for data and video. The data transport demarc will be located next to the K-20 data equipment while the video transport demarc will be located next to the K-20 video equipment. Small districts will receive a shared transport circuit carrying both data and video-they will only have one transport demarc. Small districts, therefore, will need additional wiring from the K-20 transport demarc to connect to the K-20 video equipment. This additional wiring is called "extended wiring."

Extended wiring

Extended wiring, for the district's K-20 participation, is wiring installed by the district for the specific interconnection of the add+drop CSU+DSU to the district's video equipment location. The design parameters for this extended wiring are based on the type of circuit involved. The type of circuit designated for K-20 Phase 2 is a standard DS1 circuit. A number of methods can be used to extend a DS1 circuit within a customer's premise. The K-20 Technical Working Group, however, recommends an industry standard method which includes individual sheaths shielded twisted-pair (STP) wiring for the transmit and receive functions of the DS1 circuit. Appendix A includes a detailed technical discussion on DS1 signaling specifications which have informed the TWG's decision to use this standard.

Extended Wiring Support and Maintenance

The support and maintenance of any extended wiring to K-20 provided video equipment is the district's responsibility. The KOCO's responsibility to troubleshoot wiring+pathways, therefore, is strictly limited to cable plants connecting the telco demarc to the transport demarc. The district should understand that their risk of problems is increased when they deviate from recommended industry standards for their extended wiring cable plants since vendors may refuse to provide support to systems that are attached to non-standard cable plants.

Small district vs. large district

The following discussion will focus on the differences in implementation and equipment details between a large district and a small district. This is strictly a K-20 definition and does not pertain to the geographic size or the student population in a district and is, rather, related to the number of workstations projected by the year 2000 in the district. A large district, in the K-20 world, is a district that has a separate video DS1 circuit. A small district, in K-20 nomenclature, is a district that will have data and video services share a single DS1 circuit.

Small district design scenarios

Standard installation of data and video

The standard design for a small district calls for a shared transport DS1 to feed the data equipment via an add+drop CSU+DSU. This CSU+DSU, in turn, will feed the video equipment which can be either a desktop or a group system. The transport and associated wiring up to the CSU+DSU will be provided by K-20. The district provides the wiring from the CSU+DSU to the video equipment. The wiring from the CSU+DSU to the video equipment will be the district's responsibility. The video equipment, video IMUX, and CODEC will be provided by and installed by K-20. The K-20 Technical Working Group has mandated that the video and data systems be in the same building for a small district installation.

Large district design scenarios

Standard data installation

In K-20 Phase 2, the standard design for data installation to a large district is very straightforward. The K-20 Phase 2 data circuit and associated data equipment will be installed by K-20 in the location specified by the district.

Video installation - video in the same building as data

The installation of video is different for a large district since the K-20 transport circuit for video will be separate from the circuit for data. The district may choose have the video equipment installed in the same building+campus as the data or in a different building+campus. K-20 will also install the video transport circuit along with the video equipment (video IMUX and CODEC). The district will still be responsible for any necessary pathway infrastructure such as conduit between the video telco demarc and the video K-20 transport demarc.

Video installation - video in separate building

A district, with separate video and data transport circuits, could elect to have the data and video delivered to separate buildings+campuses.

K-20 data network and peering with District routers

A key concept of the K-20 data network design is the requirement that the K-20 Phase 2 router be connected to a single district router. The district router then acts as the egress point for all K-20 traffic, including both Internet and intranet traffic¹. The school district router will have dual Ethernet ports-one to the district campus-wide network and another which connects to the K-20 Phase 2 router. The two devices, the K-20 router and the district router, will then be the only devices on the connection between them.

The aforementioned physical design is called a "peering" arrangement between the two routers. Peering includes both the physical and management aspects of the two routers. The separate connections of peered routers allows the two owners of the routers, in this case the KOCO and the district, to clearly define who has ownership for problem identification, troubleshooting and resolution².

The K-20 router will connect either to the existing Washington Education Network (WEdNet) router or, if the school district is not a member of WEdNet, to a router of the district's choosing. K-20 clearly understands that the districts make extensive use of the Regional Data Centers (RDC) for payroll and student records and use WEdNet for access to the RDCs. A district's routed administrative connection to their current RDC remains available at the completion of the K-20 Phase 2 network install.

The individual District has the responsibility for providing the infrastructure that connects the Ethernet port on its proposed school district-to-K-20 connection router (WEdNet or other) to the K-20 data transport demarcation point. If the two routers, K-20 router and district router, are to be co-located in the same equipment room, this is a very straightforward task. Other scenarios though, such as having the district router located in another building separate from the anticipated K-20 data router location, might require significant re-engineering of the campus to meet the K-20 requirements.

¹ A school district could elect to connect to another ISP as well as K-20, but the design is very complex and is not recommended except in special cases.
² A single building district with only a local area network is not required to have a router in place to have K-20 connected to them.
³ K-20 will provide the Ethernet 10BaseT hub to tie the two routers' Ethernet ports together but not the cable plant infrastructure.

Other implementation issues

District-owned active electronics in circuit path

The K-20 Phase 2 site survey process has identified that a number of districts wish to make use of district-owned active electronic devices in the circuit path between the telco demarc and the K-20 equipment. The districts have valid and legitimate economic reasons for using their campus electronics. K-20 has no desire to disallow alternate design scenarios. K-20, however, has several operational concerns regarding the use of institution-owned active electronics in the K-20 transport circuit path.

These district-owned active electronics could include but are not limited to:

• SONET and M13 multiplexers
• Digital microwave equipment
• Copper to fiber DS1 converters

First, the insertion of non-K-20 active electronics effectively negates the KOCO's ability to use U S WEST Communications as a resource for on site transport maintenance. The district owned equipment becomes a piece of third party equipment which U S WEST Communications will not maintain under their contract with the KOCO. The loss of U S WEST Communications support in the district would significantly increase the efforts necessary by the KOCO and district staff to troubleshoot problems in K-20.

Second, the KOCO would not be able to as efficiently troubleshoot circuit problems or manage K-20 end site equipment when district owned electronics are in the path. The problem solving in such a scenario becomes a three step process. First the KOCO would attempt to "loopback" from the K-20 electronics equipment at the K-20 transport demarc RJ48X loopback jack. Second, if this is unsuccessful, the KOCO would then attempt to loopback from the local telephone company's central office (CO) creating in affect a virtual demarc for K-20. The KOCO would coordinate repair with the telephone company if the problem is isolated at this point. Otherwise, if the problem can not yet be isolated, the KOCO would have to assume that the problem is in the district's infrastructure and then transfer responsibility of the problem to the district. Institution electronics in the K-20 pathway, therefore, could potentially increase the mean time to repair (MTTR) for institutions which choose this design alternative.

The K-20 TWG feels that by making use of standards based designs and excluding district owned active electronics from the K-20 circuit paths the districts stand to benefit the most from the KOCO's expertise and troubleshooting acumen The districts are free, however, to choose to use paths that include other active electronics if they feel they have the expertise and resources necessary to troubleshoot their own particular system.

Alternative DS1 extended wiring

The goal of the K-20 design is to deliver a network that is as stable and as fault tolerant as possible. The STP extended wiring for DS1 circuits is a significant element to meet those ends. However, another item, which has frequently been an issue with the districts, is the request to use something other than shielded cable for the extended wiring. A significant number of school districts have already placed TIA+EIA 568 Category 5 (CAT5) unshielded twisted-pair (UTP) cable throughout their campuses. The districts feel that they should be able to use this (existing) CAT5 cable as the physical distribution medium for their video extended wiring.

The K-20 Technical Working Group recognizes that a district can use alternate cabling strategies, such as TIA+EIA 568 CAT5 UTP to connect the K-20 video equipment to the K-20 shared or video transport demarc. The TWG, however, feels that while alternative cabling methods can be used for the extended wiring, there is a higher potential for failures with these methods since none of the K-20 vendors explicitly support UTP cabling in their equipment's specifications. Shielded cable plants for DS1 services will provide the most robust solution for the districts.

The districts must understand, as was stated earlier in this document, that they are fully responsible for supporting and maintaining extended wiring placed on their campus. They must also understand, further, that they are also responsible for the video equipment, imux and codec+desktop placed on their campus. The KOCO will attempt to help as much as possible but the educational sectors authorities, baccalaureate, community and technical colleges, and K-12 have agreed that extended wiring and video equipment are the responsibility of the institution upon which they are placed. Each sector is working to provide a suite of services that will help their individual institutions support such equipment in a timely and cost effective manner.

Conclusion

The K-20 network will provide digital services to the K-12 community at prices and capacities significantly below market rates. The scope of the project is extremely large, however, and the need for design and implementation standards across all the participants is paramount. A project as large as K-20 would not have any chance of succeeding without standards and rigidly adhering to those standards. The K-12 school districts, therefore need to understand and follow, to the best of their ability, the standards and guidelines outlined in this document. The K-20 Technical Working Group is excited about the learning and teaching opportunities that the K-20 network will provide across the state of Washington and look forward to serving the districts as the K-20 implementation team installs K-12's network piece of the K-20 network.

APPENDIX

DS1 signaling

A DS1 signal is a four-wire signal running on cable that possibly has regeneration electronics; this means there are two cable pairs in the transmission path. One pair is the transmit path from the telco to the customer. The other pair is the transmit path from the customer to the telco. A standard DS1 signal leaves a transmitting device at a 0 dB (decibel), which is a measurement of the signal level or energy in the signal. A standard DS1 receiver can read an incoming signal so long as the signal level is greater than -30 dB. The circuit path between DS1 regeneration devices, therefore, can have no more that 30 dB of loss if the circuit is to function to specification.

The end sections of any DS1 circuit, which includes the end in the telco central office as well as the customer end, are based on a modified DS1 design. This modified design is related to the occasional need to place a hard loop on the circuit for troubleshooting. This means the transmit pair is physically connected to the receive pair which results in the signal being sent back to the starting point. The K-20 Phase 2 project provides loop back at the customer end by the use of RJ48X jacks. An RJ48X jack provides for an automatic hard loop back for the DS1 signal should the line or patch cord be removed from the jack.

The cable plant must meet certain physical and electrical criteria for the loop back to be guaranteed to work in all circumstances. The loss contributed by the end sections of a DS1 circuit, for example, must be limited to one half of the typical section loss, or 15 dB. The telco design for a DS1 service, by tariff is allowed to use 11.25 dB of the 15 dB end section on the telco side of the telco demarc. This leaves 3.75 dB of loss for extension of the DS1 circuit on the customer side of the demarc to the customer's equipment.

The K-20 transport demarc, therefore, must be within 625 wire feet of the telco demarc if the circuit is based on the attenuation of shielded cable as specified by the K-20 Design Steering Committee. Any K-20 Phase 2 device connected to a K-20 DS1 circuit must, furthermore, be within this 625 foot limit from the telco demarc to be within specification. The data IMUX is this device for large districts. For small districts the DS1 circuit terminates in a dual port CSU+DSU. This CSU+DSU has a DSX port that will feed the video IMUX. The signal leaving the CSU+DSU towards the video IMUX is a standard 0 dB level DS1 signal. The design rule for the cable from the CSU+DSU to the video IMUX is a standard DS1 end section design, or 15 dB of loss.

The K-20 Phase 2 DS1 wiring, which will be installed by U S WEST Communications from the telco demarc to the K-20 transport demarc, is based on the most common and reliable standard for DS1 circuit extensions. The standard U S WEST Communications will use is referred to as a "two cable unidirectional operation," with the end termination in the RJ48X jack. This standard, based on two separate shielded cables, provides the greatest signal separation and also promotes the longest extension distance and best signal quality. This design is entirely passive as there are no electronic devices in the circuit path other than the telco "Smart Jack" or network interface unit (NIU) and the end device. This is the same standard the K-20 Design Steering Committee has requested be used for district installed extended wiring.