MIT Telecommunications Facilitities

Functional Requirements For Networking

Background

The wiring plant serving today's MIT campus network was built in 1988 as part of the 5ESS phone switch installation. Facilities were constructed from existing utility spaces. Some of these utility spaces were specifically designed for telecommunication purposes while others were inserted into electrical, mechanical or janitorial spaces. Yet other telecommunications facilities were left in corridors, offices, labs and shafts.

The goal of the 5ESS project was to provide MIT with a world class telephone system across a campus ranging from state of the art buildings to those constructed before telephones were seen as a good idea. The campus network's use of the 5ESS wiring plant was yet to be realized in 1988. Today the network has outgrown many of the facilities. As we witness increasing numbers of computer networked applications such as SAP, distance learning and the world wide web, the demands on the campus network infrastructure require greater and new technololgies, devices and wiring. The problem statement is simple. Where to put it.

Growth

The campus network infrastructure has grown in many dimensions. The number of devices located in the facilitites to serve the campus network increased sharply from the launch of the modern day network in 1991 and again with bringing the dormitories on line in 1994. However it continues to rise in response to growing numbers of connections and changing technologies.

The initial standards for networking specified 1 network connection per telephone at a time when the number of computers on campus was a small. Today, there are over twice as many active computers than telephones and the advent of more flexible computing with laptops resulted increasing amounts of port capacity in the facilities. The design studios in buildings 5 and 7 and the classrooms in building E51 have further pushed the envelope by providing each student with one or more direct network connections.

The renovation of building N42 realized the need for greater reliability. performance, and centrally managed network connectivity by increasing the number of connections in team and meeting rooms and providing each staff workstation with 3 direct network connections (half the number of electrical sockets per workstation). These projects have set new standards from which the Institute is building upon in new projects such as the classrooms in buildings 2 and 4, the studios in buildings 33 and 10, the renovation of Baker House and the dozens of smaller construction efforts in progress this summer. The demands on the infrastructure will continue to rise.

The campus network is a growing infrastructure. Like the electrical plant, we will see flexible and ubiquitous access to the network. However, the network is growing in yet another dimension.

The network must also respond to growth by meeting increasing demands of load and performance. Larger equipment with multi-gigabit backplanes and low port density are required to meet these demands.

Renewal

Periodic renewal of the network infrastructure is necessary to track growth, maintain alignment with changing technologies and operate equipment with limited life-spans. Equipment serving the campus network is replaced every 4 years on average. Equipment purchased more than 4 years ago is obsolete and because the technologies change so rapidly, we do not know what equipment we will purchase 4 years from now.

Renewal of the wiring plant is an essential part of the long term health of the campus network although not considered in the existing renewal models.

Facilities cannot be designed around specific vintages of equipment or wiring topologies. They must offer enough flexibility to allow for periodic renewal, staging and the introduction of new technologies.

Directions For Networking

In the near term, we will see increasing numbers of connections via unshielded twisted pair wiring, from classrooms wired to the seat to laboratories and large office environments with several connections per station. Some of the closets today already house 500 connections and these numbers continue to climb.

The equipment used in the early days were small and could easily be mounted on a wall alongside the wiring blocks. Today's equipment mounts in 19 inch racks requiring front, rear and side clearance for access to the wiring blocks, wiring coming from the front or the rear of the quipment and ventillation fans. Some of the equipment we see today weighs over 70 pounds and can exceed 3 feet in height, each serving 50-200 connections. The trends in larger equipment continues and the question not only becomes can a 19 inch rack be wedged into an existing facility, but how many.

The wiring itself has changed may change radically in the coming years. Traditionally, we have used a compact type of connector called an rj21 that allows 12 connections to be hubbed together on a single connector. These connectors are much rarer to find today and do not exist in today's hugh performance equipment. Moving to a modular rj45 connections in the facilities creates much more flexibility in adopting new technologies however, the space required for wiring and cable management can increase by a factor of 2.

Finally, what will likely be in the future is a move away from unshielded twisted pair wiring for desktop connections to fiber optic cables. Because of their sensitive nature, the terminations need to be carefully managed and protected, again further increasing the demands on the space.

Facility Specifications

This section is based on the Telecommunications Systems - Design Outline For Academic, Research and Residential Buildings Space Requirements for Telecommunications Facilities Document.

Facility Types

The types of spaces for a complete telecommunications infrastructure are as follows:

• Service Entrance

  this is the point where telecommunications lines and cables enter the building.

• Building Distribution Frame (BDF)

  this is the main telecommunications signal distribution point in each building. This closet distributes to intermediary distribution frames in a building and to individual final destinations such as classrooms and offices.

• Intermediary Distribution Frame (IDF)

  this is a distribution point to end locations such as classrooms, offices and residences. There is typically one or more IDF facilitites on each floor of a building. The function of the IDF is to interface end locations with the BDF and other IDF facilitites within a building.

Common Facility Requirements

The requirements common to all of the above facilities are as follows.

Facility Location Requirements

1. Facilitites must be located in dedicated spaces. Other storage, mechanical or janitorial functions should not interfere with the facility.
2. Facilitites and cable pathways must be located away from sources of electromagnetic interference.
3. Facilities must be located in dry areas and preferably away from water sources and pipes.
4. Facilities should have access to main corridors to facilitate needed work and repairs on a 24 hour basis. Facilities should not be located in departmental alarmed areas.
5. Facilities cannot exceed 250 feet from the furthest point served as measured through the common horizontal cable path.
6. It is preferable that all facilities within a building be stacked on top of each other to minimize cable runs and help meet distance limitations.

Common Facility Interior Requirements

1. Facilities must be well lighted.
2. Facilities must contain a grounding terminal with a #6 AWG wire to approved ground.
3. Conduits, sleeves and floor penetrations must be fire stopped with ATSM E814 or UL 1479 qualified putty seal.
4. Facilities should have a minimum of 4 20A 120V duplex outlets, two on emergency power, two not on emergency power. It is preferable that multiple outlets be installed on each wall.
5. The minimum ceiling height in 90 inches. The minimum door height in 80 inches. The minimum door width in 36 inches.
6. 3/4" plywood boards should be installed along the walls, a minimum of 72 inches tall.

Requirements Specific to Facility Type

Service Entrance Requirements

Telecommunications lines and cables on the MIT campus of provided via an underground duct system. The duct system to a building is normally composed of 4" conduits. The number of conduits in a duct bank is based on the number of telecommunication lines that could potentially be provided to the building. The estimates of the number of telecommunications lines necessary are based upon the potential number of users in that building. Offices, laboratories, classrooms and residences are assumed to require 1 telecommunications outlet fed from an underground line unless more is requested during the design stage in addition to other needs such as fiber optic cabling to serve the building network.

All entrance point conduits should be galvanized steel and concrete encased.

Building Distribution Frame (BDF) Requirements

Usually, the BDF is located in the basement. 4" EMT conduits must be installed from the service entrance point to the BDF. The BDF houses outside plant cable termination, cable protection units, power supplies, optical cable light interface units, riser cable interface junctions, cable television equipment, network cabling and equipment mounted in 19" racks and end station wiring.

Intermediary Distribution Frame (IDF) Requirements

These facilitites feed end locations such as connections to offices and classrooms. These closets must be within 250 feet of the furthest point they serve and preferably stacked with floor corings and conduit sleeves connecting them. IDF's house end station termination junctions for voice, data and catv services, termination of riser cables, power supply units and netwlrking equipment mounted in 19" racks. The size of the IDF should be determined by the total potential number of connections the floor can support.

Determining Number of Connections

Each space design will influence the number of connections required but to do facility planning the total number of potential connections needs to be esitimated. A networked classroom will require more connections per square foot than an office. The table below is an estimate based on space type.

Facility Classifications

Although MIT has a wide variety of facilitites, they can be classified into 3 categories for the purpose of determining priorites for replacement. Issues such as access, security and resistance to floods, dirt, falling plaster, ladders and power outages have not been included in this classification.

• category III:

  This facility does not meet current needs. Additional space for adds and changes is not available or will not properly house equipment currently deployed. Or the environment for the equipment is hostile (overheated mechanical space, water in janitor closet, proximity of high voltage gear) resulting in service outages. Equipment renewal is not possible.

• category II:

  This facility meets current needs but not the needs of future technologies such as fiber optic cabling or low port density/high speed switches. Large network installations such as modern classrooms may not be possible. Equipment renewal requires significant construction work such as re-wiring the facility.

• category I:

  This facility meets current needs and with some or no additional construction work will meet the needs of anticipated future technologies.

Facilities

The following table lists the existing active telecommunications closets and their corresponding classifications. There are many closets not listed here that do not currently contain active network equipment although they may in the future. Data on these inactive closets is not currently available but should be considered.