Metropolitan Digital Data Services (MDDS)

What is Metropolitan DDS?

A Telecom NZ service :-(
Metropolitan Digital Data Service is a cut price version of standard DDS and is available only in several major cities in New Zealand. A Metropolitan area is generally the free dial call area in a city. Not all of the standard DDS services are available under MDDS. So far there are 2.4Kbit, 4.8Kbit, 9.6Kbit, 48Kbit, 64Kbit and 128Kbit.
An important omission from MDDS is the 19.2Kbit DDS.

MDDS services in New Zealand are currently only provided by Telecom NZ.

Initially only 9.6Kbit and 48Kbit services were available up until early 1995. 64Kbit and 128Kbit services were made available from mid 1995 and the 19.2K MDDS service was promised by the end of 1995.
As of now (April 1996) the 19K2bit service is still not available.

MDDS is available in the following areas.
Palmerston North

Telecom have said that additional areas will be provided with MDDS. A call to the nearest Telecom Business Centre will provide the most up to date MDDS coverage.

MDDS is a dependable digital service with relatively low priced (when compared to standard DDS) and is ideally suited for full time connections to the Internet in New Zealand.

What does it cost?

Installation is $410 per end of the MDDS link - $820 total Same installation cost for all speeds of MDDS.

MDDS rental consists of an access charge per end of the link There are no ongoing time related charges, no per minute rental charges or link distance charges. Thbe MDDS can be fully utilised or just move minimum data volumes and the cost is the same.

9.6Kbit is $150 per end, total rental is $300 per month
48Kbit is $275 per end, total $550/month
64Kbit is $480 per end, total $960/month
128Kbit is $720 per end, total $1470/month

MDDS prices for the faster 64K and 128K speeds are rumoured to be reducing in Mid 1996 so exact pricing should be obtained from Telecom.

Ordering an MDDS link

These can be obtained from the nearest Telecom Business Centre or Sales office and they will post original copies to you or fax them directly.

The application consists of four pages.
Page 1. General Company information and billing addresses Pages 2 and 3. The site drop information, address, contact people, location in building where MDDS is to be terminated. There is one page for each end of the MDDS link. You will have to contact your Internet Service Provider to get the exact details to complete for their end of your MDDS link. Some service providers prefer to complete the whole document as it makes sure there are no delays due to incorrect or missing answers.
Page 4. DDS interface type and control signal options. The options here for interface type depend on the DDS speed. For 9K6 and below an asynchronous v24 interface or an X21bis synchronous interface is available. 48K and above are available only as synchronous serial with either X21 or v35 interface.

After the completed application is returned to Telecom it can take anything from one day to 15 days for the MDDS to be installed. In a very few metropolitan areas there could be longer delays if some upgrading is required of the local exchange. Even longer delays are probable if new cables need to be laid.
Normal installation time is about 5 to 7 days. In any case Telecom will provide a latest date for commissioning the new link.

Equipment shortages seem to be a recurring problem that cause delays with MDDS installation. At different times there can be shortages of the NTU 2 then when these are in plentiful supply there are no control cards available to install in the exchange. Sometimes a delay may occur because a card frame needs to be installed at the exchange.

MDDS installation

Just about all MDDS installations are now carried out by Installation companies that contract to Telecom. The good news is that the actual people who do the installations are usually ex-Telecom staff and they tend to know what they are doing. The same person will often install both ends of an MDDS and will phone the contact people (as included in the application site forms) to arrange a mutually suitable time to call and do the site installation.

MDDS requires a single copper line pair. It cannot be installed on a line used for 1+1 or other multiplexing schemes for providing more than one analogue (phone) service over a copper pair.
The installation cost will include stringing an overhead cable from a Telecom street pole to the building and hence to the required NTU location. It will NOT include installing new trunking or excavating for an underground cable on the customer's property or building.

An MDDS link is terminated at each end in a modem-like box known as an Network Terminator Unit or NTU.
For 9k6 and 48K mdds installations the NTU can either be an older type made by Telettra, usually with a brown plastic case and black front panel, or the newer NTU2 in a grey plastic case.
64K and 128K MDDS use a fairly large cased NTU made by Open Technology connection using MDDSconnection using MDDS
All NTUs require a 240v AC mains power outlet. Power consumption for the older Telettra NTUs is about 40 Watts, the newer NTU2 is about 10 Watts and the Open Technology NTUs need about 20 Watts.
The lower power NTU2 can be stacked. Telettra NTUs will overheat if stacked. Both types are able to have two beside each other on a standard 19inch rack frame shelf.
The larger Open Technology type NTU cannot be stacked due to its wedge shape, nor will it fit beside other NTUs in a rack frame. It requires its own rack frame shelf and is a general pain to deal with. Telecom have no plans to provide a more rack-frame, shelf-space or desktop friendly 64k/128k MDDS NTU.

Internet connection using MDDS

MDDS is the lowest cost Digital Data link option in the main centres where MDDS is available.
Compared to DDS there are significant savings when using MDDS as the only rental for a point to point MDDS is the access fee for each end of the link. There is no transmission fee.
The most popular MDDS connection is the 48Kbit service.
Until mid 1995 there were only two MDDS options available, the 9K6 and 48K option. The 48K cost $450 per month.
In a review of prices Telecom announced overall price reductions in DDS and MDDS services in June 1995. Part of these reductions was an INCREASE in the price of 48K MDDS, from $450 to $550 per month.
The only reason Telecom had to offer for this increase was a repositioning of the prices to even out the steps between 9K6, 48K and 64Kbit MDDS links. Due to the obvious annoyance from many existing 48K MDDS users the price increase for existing users was phased in over 6 months
All new 48K MDDS were immediately charged at the higher prices.

A 48K MDDS can move about 17megs of Internet traffic per hour. Many Internet Service Providers start with a 48K link. Performance is generally good enough for a multi-line ISP with up to as many as 20 active connections. Only when several file downloads occur simultenously will response times start to get longer.

Data Compression can significantly increase the throughput over an MDDS although this requires router hardware at each end of the MDDS with sufficient grunt/memory.

Connecting MDDS to an Internet network.

The exact type of connection will depend on the interface provided (or requested) on the NTU. The slower 9k6 NTU with its async interface can be directly connected to an async port on a PC or workstation. This workstation will probably need to be running routing software, most Unix OS will include routing, and other OS such as OS/2, MacOS, Windows NT etc usually have routing capability either built in or by installing additional modules.
Synchronous MDDS links will require a router or computer interface that supports synchronous serial connections.
Usually an external ethernet (or token ring) router box is used to manage a synchronous MDDS link. This often turns out to be the single most expensive hardware required to connect an MDDS.
Such routers will totally manage an Internet connection providing the required sync serial port interface (usually X21). They also include full routing capability, provide internet routing management and may often include limited firewall capability.

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Last modified: 10 March 1997.