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September 2, 2009 > Update on city network

Update on city network

The Telecommunications Commission met on August 17.
Information Services (IS) Director William Marion presented an update on the City computer network to the commission.

Marion defined key terms used to describe the network.


This is the network protocol used on the City Data network. It is the Ethernet standard used for most networking today


Voice over Internet Protocol. The technical name for Internet phone calls such as Skype and others.

The same technology is used within a local area network to replace telephone switching equipment. It uses the same data network that your computer uses, so it saves on wiring and equipment.

This is the newest technology for telephone systems.

Power over Ethernet (POE)

This is a way that low voltage electrical power can be provided over a network connection. Something like USB powered device. This is important for Voice Over IP (VoIP) phone systems. Then you just plug your phone device into a network jack and then you don't need a separate power cord and outlet to power the phone.

Quality of Service (QOS)

This is a feature of data networks that is needed to do Voice over IP. It prioritizes network traffic so that voice calls get priority over data. In this way, phone conversations are not impacted by, for instance, large file downloads.

Asynchronous Transfer Mode (ATM)

This is what was planned for the City network in the original 1995 plan. Since then TCP/IP has evolved to provide the same QOS features needed for VoIP at a much lower cost.

Silicon Valley Unwired (SVU) will make a presentation at the next commission meeting on September 21. SVU provides free wireless internet access throughout the City of Milpitas.

Marion explained that the network was originally upgraded in 2000. In 1995 design was done using ATM network technology. In 2000 IS staff decided that TCP/IP was a much better alternative. So at that point they replaced the core with industry standard equipment. TCP/IP is managed at much lower cost.

In 2002, prior to opening the new city hall, staff upgraded equipment in the wiring closets. The equipment was standardized on two types of hardware, creating some redundancy. They expanded the fiber optic network and connected some of the City's remote sites: Firestation 1 by Great Mall, Community Center and other locations within the City.

Last year staff exceeded the expected life cycle of existing equipment resulting in some hardware failures. Equipment was also relocated several times. Staff was concerned that existing equipment did not support POE, which would be necessary for VOIP and other applications.

Internet security devices (protection of networks and computers) were somewhat dated. Data transfer rates were maxed out at 100 megabits per second, and staff had no QOS options. These factors would impact the City's ability to go to VOIP.

Staff noted that they had lots of fiber optic cabling running to various locations and approached a new design to take advantage of these additional connections.

In the old network each building had separate wiring closets. These would be connected to a switch within that building and, in turn, be connected to the core layer.

Through a process called "teaming," multiple pairs of fiber were combined for higher data transfer capacity. This was the design standard about seven years ago. When staff looked at installing a new network, they tried to use the existing fiber to minimize the amount of new hardware the City had to buy. "Cost was definitely a factor for us" Marion said, "Essentially what we did was collapse that down to just two layers."

The new system eliminates the use of the distribution layer in the middle. Now every switch has a connection to two core switches.

Some of the advantages of the new network configuration are more rapid (one gigabit per second) data transfer to all the servers and a 10 gigabit ethernet uplink. A redundant core means that a core switch can be lost yet the network will still operate. Also, security measures have been strengthened.

"We've got a ring around the City with fiber optic cable that runs from City Hall to the Data Center, City Hall to Fire Station 1, then down Abel Street to the Data Center. So essentially they've got a ring going around Abel and Milpitas Boulevard," Marion explained. Any one of those facilities can route in either direction. So, for instance, if the cable out on the street by City Hall were cut, all of the network traffic with City Hall would go down to Fire Station 1, and then back up Abel Street. Or, if the cable coming out of Fire Station 1 was cut, it would, in turn, route everything back to City Hall.

All are ports have POE capability, which staff believes will position them to utilize VOIP in the future. "We couldn't quite afford to do it now" Marion said.

All existing fiber as been used and plans are to replace some of it. Connections from City Hall to the data center have been cut and repaired several times. When replacement is in process, all traffic will be routed through Fire Station 1.

By moving data storage and backup into the Data Center, equipment is located in a climate controlled, protected environment with high levels of security, a halon fire suppression system and building uninterruptable power supply (UPS) and generator.

The 911 dispatch center is in the same building as the data center.

"So we really put everything in one spot. And yes, if that building gets destroyed we're in trouble. But, what we came to is the fact that we could not replicate the facilities of the 911 dispatch center. There is just no practical way to do that" Marion said. "So if we lose that building, there would be no ability to go to another building and function as a 911 dispatch center."

The Data Center has a designation as an essential facility, so it was designed under design requirements for the events of fire and earthquake. The building is made of pre-stressed concrete, and is designed to withstand a higher level of earthquake activity than a normal building.

The generator has enough fuel to last for about a week. And the entire building is run by the generator. There is a large UPS that powers the data center, the radio room, and the 911 dispatch center.

"So the building was sort of designed to be somewhat bullet-proof. If that building were to be destroyed, the police department would basically be operating out of a motor home. At that point we probably would be looking at recovery of the automated systems somewhere quite a ways down the road" Marion said.

Commission Chair Alcorn said it was not a big deal to put all of the routers in the data center, because if you lose the data center then no more servers to route to anyway. "If anything needs to survive it's that building. So basically the rest of the City can go away, that building would continue to operate" Marion said. Backup of data to magnetic media is locked away in a safe. "So if anything happens we'll have other bigger problems, but when we get around to needing to bring back up the automated systems we'll simply get the stored data and restore from there" Marion said.

Marion explained that "As far as Public Safety Communications, the City has an alternate Emergency Operations Center as well as a mobile communications van. While the computer systems would be lost, radio communications are not dependent on the data center. The motor home is a mobile 911 dispatch center in case the building that houses the data center and 911 dispatch center is lost for any reason."

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