|
BT has built and currently operates two separate networks: a) the "City Network" which is specifically
designed to serve a small number of extremely high-use sites. This network serves the City Government’s
own 35 sites and approximately 15 other sites belonging to such organizations as the State
of Vermont, Burlington Housing Authority, Community Health Care of Burlington etc; b) the "Universal Network"
which is designed to pass and serve every premise in the City. Although connected to each other, the design
and operating principles of these two networks are very different.
City Network: This is a flat network in which each site is connected directly with at least
6 fiber strands spliced through to the city hub in a "home run" configuration. The data network uses Omnitron-Systems gigabit Ethernet
transceivers in the hub and at the remote. At each city department site the links terminate at a demarcation point and then connected with
whatever internal data networks exist at the site. A Cisco 3500 level 3 switch manages the In addition, the
network distributes voice traffic using RAD technologies T1 and DS-3 transceivers into Adtran TA75-/1500 channel banks.
This traffic is connected to the voice switch via a GR303 interface using an Adtran TA4303 concentrator.
The voice switch is a 5ESS owned by TelCove to whom BT outsourced its voice switching. As of June 26, 2006,
BT has started migrating City voice traffic to BT’s own Tekelec 6000/7000 switches. Internet bandwidth is procured from
several vendors, connected through a Cisco 7206 VXR router, utilizing a Cisco PIX 515e.
Universal Network: This utilizes an ITU - T G.984.x GPON platform produced by Optical Solutions Inc, "OSI"
(which company was recently purchased by CALIX Inc., which is, in turn, partly owned by Cisco).
All transmission utilizes ATM framing. This guarantees a high QoS. Splitters are located in a small number of
secure, powered and climate controlled Local Concentration Points (LCP). Individual premises are connected with
fiber drop wire to a NAP by individual fibers via "home runs" back to the LCPs. Currently, the network is
configured using the 1.2gig/622meg GPON rate to provide 45mbs burstable to 100mps to each premise. However, the
configuration of the distribution plant has been designed to make it relatively simple to increase this to the next GPON
rate of 2.4gig/1.2gig as it become cost effective. This configuration also makes it possible, at some future date, to use
active elements in the network (instead of passive) without having to install large numbers of outside cabinets, enclosures,
pedestals etc since all the active equipment could also be accommodated in the LCP huts.
Voice telephone is provided using paired Tekelec 6000 & 7000 switches connected to the OLTs via GR303 interface(s).
Standard telephone quality of service is achieved because the GPON platform uses ATM framing. The voice network is also
E911 and CALEA compliant, which is characteristic
of "standard" telephone service (POTS). This network designed to the FITL (fiber in the loop) standards that are used by
the large RBOCs, which includes the GR-909 standard for battery back in the event of power loss at the customer premises.
However, the paired 6000 & 7000 Tekelec switches can also provide Voice Over IP (VOIP). Thus, should it ever
be desirable to offer "VOIP" instead of, or in addition to, standard telephone service, BT can do so easily.
Internet access is via two redundant Cisco Cat6500 switch and two redundant Cisco 7206 VXR routers.
Cable TV signals are received by BT’s 5-meter SimulSat dish, transmitted to the central office/headend, encoded, and
(if necessary) encrypted, and then transmitted in an IPTV Mpeg2 format. The prime contractor for this "head-end" equipment
is TUT Inc. However, individual sub-components come from other manufacturers. (Verimatrix, Entone, Motorola)
AC power to the central office/headend is provided by a dedicated 800amp 3 phase commercial entrance.
This feeds an Eltek 1200amp - 48Vdc power plant that provides power to the DC equipment and to a Pylon 30KvA inverter
for the AC gear. The -48Vdc plant is backed up by two redundant EnerSys VRLA 2000ah battery strings providing 8
hours of battery back up to essential telecommunication equipment. In addition, there is a Kohler 180kw natural gas
powered diesel generator that switches on within 30 seconds of power failure. As a last resort, the network is wired to
a plug on the outside of the building to which a portable generator could be attached. All power installations are bonded
and insulated to meet RUS 1751F-810 specifications.
BT’s Network Operations Center (NOC) uses Omnitronix alarm point devices to send SNMP alarm messages to dedicated servers
for network servalance. The NOC is manned during working hours and is monitor outside of working hours via alpha pagers and a
Call Center provide 24/7/365 coverage.
|
