The AP3000 is one of a range of Access Processor [AP] Products that Metrodata manufacture. There are currently 3 AP Product Variants all of which are Modular - AP3000 [3 Modules], AP4000 [4 or 5 Modules] and AP8000 [8 or 9 Modules]. The AP Modules are interoperable throughout the AP range.

As well as being a fully functional ATM Switch [ATM in, ATM out], the AP Products can also Multiplex non-ATM services into a Single ATM Trunk.

ATM Interfaces supported are E1, E2, E3, DS-3 and OC-3. Non-ATM Interfaces supported are T1, E1, E2, E3, DS-3, 10/100BaseT, HSSI/ECL, ASI and EIA530. ATM Over Satellite or ATM Over Serial Modules are currently HSSI/ECL, G.703 and ASI.

The Access Processor can provide speed, interface and protocol conversion between incompatible network products. We can convert ATM to non-ATM, ATM to ATM (DS-3 to E3 etc.), ATM to fiber, ATM to serial, ATM to wan, Ethernet to wan, Ethernet to G.703, Ethernet to serial, Ethernet to fiber, serial to fiber, fiber to fiber and WAN to serial.

Our real strength and competitive advantage is in our flexible Serial Modules. In order to support a variety of different Satellite Data Rates we developed a Flexi HSSI/ECL Module for the Access Processor, which can operate at any rate between 0 and 90Mbits in 1Hz increments. We then developed a Flexi EIA530 Module, which also supports 1Hz increments, up to 20Mbits. As most competitive ATM Multiplexors, ATM Concentrators and ATM Edge Switches often only support Nx64k increments on their Serial Modules, we have the most flexible product.

From Narrowband to Broadband, from 8k to 155.52Mbits we've got your bandwidth covered. In 1Hz increments, that's 20 million clock rates for EIA530 and 90 million clock rates for HSSI [High Speed Serial Interface].

Giving Flexibility to Federal ATM Networks

Federal Networks tend to be end-to-end networks designed to transport a particular application. In one network, wireless might be used between the field unit and the terminal, then satellite to connect the terminal to the main terrestrial based network. Typically this terrestrial network would be ATM based. The application would be transported/back-hauled across the ATM Network to the end-user, where the ATM cell headers would be removed [if applicable] and the field unit services/applications connected.

One of the main reasons that US DoD Networks are ATM, is due to the ability to aggregate separate links and bandwidths onto a single Network Infrastructure. But, the majority of ATM Vendors have equipment designed to work in a fixed rate environment. Very few of these switches acknowledge the presence of satellite and wireless, and simply support fixed rates such as E1, T1, E3, DS-3 and OC-3. Those few ATM Switches that do offer Serial Interface that are "flexible" are often only offering Nx64k clock rates.

Whilst working on a federal network project, Metrodata realised that what was needed was complete flexibility of data rate. We had for some time been receiving enquiries for EIA530 and HSSI to DS-3 ATM Conversion. All of these were at very "odd" data rates. Typically they would require 1Khz or 1Hz clock increments, i.e. 9.163Mbits Inbound and 322.231Kbits Outbound.

Why such weird rates? Because that was the exact amount of bandwidth required to transport the application, its Encryption Overhead and potentially an FEC Overhead as well.

So, what we provide is the ability to tailor the ATM Network inefficiently to the Applications odd data rate, rather than forcing the Application to run at a fixed rate on the network.

Metrodata provide complete flexibility of both data rate, serial interface and ATM Interface.

Also, utilising Metrodata Products within a tactical/federal environment can ensure that data integrity is improved. This is particularly useful in Unmanned Aerial Vehicle [UAV] Networks and Rapid Deployed/Field Networks.

With improved Data, more accurate decisions can be made. Accurate decisions mean better results. Data Integrity goes hand in hand with accurate and exact clocking of each piece of network hardware. The network cannot be clocked correctly, if there is a limit of Nx64k data rates on the hardware within the end-to-end solution.

Why the Metrodata AP3000 is a Strategic Product

The AP3000 from Metrodata is a strong product. Its features are:

• ATM Connectivity at E1, E2, E3, DS-3 and OC-3 rates
• Fiber Connectivity at Multi Mode, Single Mode Short Haul and Long Haul
• Serial Connectivity at EIA530, HSSI/ECL and ASI Interfaces
• Serial Data Rates in 1Hz clock increments
• ATM to Serial Conversion [currently HSSI and ASI, with EIA530 planned]
• Ethernet, Voice and Video also supported

With the AP3000 we provide connectivity between:

• ATM Switches, ATM Access Devices and ATM Concentrators
• Low Speed Synchronous Serial Equipment - Cryptographic Equipment
• Any speed Serial Satellite Modems
• ATM Encrypters
• Serial Encrypters
• Fiber Optic Modems

These are the "building Blocks" of Federal Systems Networks. These are inherent in almost all tactical/military systems.

Often these "Blocks" cannot be fitted together, because of an incompatibility between their interfaces, protocols or clock/data rates. This is where Metrodata can help. Our equipment basically provides the "cement" between the Blocks, removing interface connectivity issues, optimising the use of specific protocols and resolving clocking problems.

Often these "Blocks" cannot be fitted together, because of an incompatibility between their interfaces, protocols or clock/data rates. This is where Metrodata can help. Our equipment basically provides the "cement" between the Blocks, removing interface connectivity issues, optimising the use of specific protocols and resolving clocking problems.

Federal Systems Applications

Almost all of our Federal Systems Applications are solved using one Metrodata Product, the AP3000. This is a 3 Port ATM Switch, though it can be used as simply an interface/rate/protocol converter.

We have increased the range of Modules that are available to this Access Processor Platform so that we now have a Single Product that can support a variety of rates [in 1Hz increments], a variety of physical interfaces and a variety of protocols.

Metrodata are able to offer products that can be used with rapidly deployed tactical networks [with flexible bandwidth requirements] as well as Internal Infrastructure and Planned/Project based networks [with inflexible bandwidth].

Metrodata products have been used in many diverse applications and projects. Anything from back-hauling TT&C (Telemetry Tracking & Control) Signals for NASA's Space Shuttle Program to ensuring clocking on data-links from UAV (Unmanned Aerial Vehicles).

In this document we are going to be looking simply at the interoperability of Serial Equipment With ATM Networks, ATM Switches and Fiber Links.

This will be with particular emphasis on:

• Back-haul of EIA530/TTL Serial Over ATM Networks
• Interfacing ATM Switches to HSSI, EAI530 or ASI Satellite Modems
• Connectivity of HSSI and EIA530 Serial Devices Over Optical Fiber Links

As with anything involving technology, applications can change. If you feel from this Application Note that we can help you in some way give us a call or drop us an e-mail. Contact Details are provided at the end of the document.

Back-haul of EIA530/TTL Serial Over ATM

In this application there was a requirement to convert Serial EIA530/TTL to OC-3 ATM The important requirement here was that the Metrodata AP3000 supported exact clock rates from the Satellite Demodulator. This were converted to ATM in the AP3000 and connected to the ATM Switch and into the ATM Network. At the far end of the ATM Network, a second AP3000 was used to reconstruct the exact clock rate to connect into the EIA530/TTL Serial Encrypter.

Metrodata were the only company that could provide a solution.

The reason for this is that our EIA530/TTL Module for the AP3000 supports Clock Rates in 1Hz increments up to 20Mbits. Satellite Modems and Encrypters in this instance support Serial Data Rates that are also in 1Hz increments. There had to be an exact match between the Data rates.

Other Manufacturers of similar products to the AP3000 only support 8Kbits increments or even worse, specific Clock Rates. This presents a problem when to ensure effective clocking, you need to support the exact rate coming out of the Serial Encrypter.

A simple Topology of this Back-haul Application can be seen below.

Equipment that has been tested with the AP3000 in this Application:

• Satellite Modems - SLM 8650
• ATM Switches - Fore ASX200, Fore
• Serial Encrypters - General Dynamics Taclane

Interfacing ATM Switches to HSSI, EAI530 or ASI Satellite Modems

When considering connecting an ATM Switch to a Satellite Modem there are 2 elements that need to be considered:

• Is the ATM Switch connecting to another ATM Switch at the far end of the satellite link?
• Is the ATM Switch connecting to a non-ATM Network at the far end of the satellite link?

In the first instance, the Satellite Link would have to carry ATM point-to-point between the ATM Switches. This requires that the Serial Module on the AP3000 can support ATM cells. This Serial ATM Module would then connect to the Serial Satellite Modem to enable a seamless connection end-to-end. At the far end of the Satellite link a second AP3000 would be required to reconvert Serial back to ATM This Can be seen in the diagram below.

In the second instance, it is more than likely that the ATM Switch is providing back-haul across an ATM network. As such, the Serial Module on the AP3000 does not need to support ATM cells, as the data it is receiving is not ATM It might be encrypted though, but as the Serial Module transports a bitstream of data it doesn't matter to Metrodata if the data is encrypted or not. This can be seen in the diagram below.

Interestingly enough, there are only a finite number of ways of connecting an ATM Switch to a Serial Satellite Modem. Which Satellite Modem interface is used, tends to depend upon the intended data rate of the link.

Standard operations are:

• EIA530/TTL would be used at speeds up to 10Mbits
• HSSI would be used at speeds up to 52Mbits
• ASI would be used above 52Mbits

But, EIA530 on a Satellite Modem can go to 20Mbits, HSSI to 90Mbits and ASI over 155.5Mbits.

Metrodata support the following standard ATM interfaces:

• E1 - 2.048Mbits
• E2 - 8.448Mbits
• E3 - 34.368Mbits
• DS-3 - 44.736Mbits
• OC-3 - 155.52Mbits

We also have the following AP Modules available that support ATM cells. These can be used to connect ATM Switches together over a satellite link:

• HSSI ATM UNI Module
• ASI ATM UNI Module

If you have a requirement to use EIA530 Satellite Modems to connect ATM Switches together, please let us know. The only reason we haven't made this yet is that no one has asked us for it.

If you simply want to connect a Serial Satellite Modem into an ATM Network, then we have several NON-ATM Serial Interface Modules. These are:

• Flexi HSSI Module
• Flexi EIA530 Module
• ASI Module

These have been tested with a variety of different Satellite Modem Vendors Equipment including Newtec, Comtech EFDATA and Radyne Comstream.

A more complete Application Note is available on this specific subject. It is available from the Metrodata Website.

Connectivity of HSSI and EIA530 Serial Devices Over Optical Fiber Links

Typically, HSSI and EIA530 devices have one drawback, their line driving capability. The drive distance of both interfaces comes down dramatically the faster you try and run the data. There is an installed base of fiber optic modems and fiber optic links in use today within Federal/Military Networks. Using the Metrodata AP3000 you can connect Serial Devices to Fiber Optic Cables in a variety of ways:

• Simplex/Full Duplex/Asymmetric Serial Data to Single Pair of Fibers
• Asymmetric Serial Data with separate EIA530/HSSI to Single Pair of Fibers
• Multiple HSSI Over Single Pair Of Fibers
• Multiple HSSI Over Single Fiber

What we are doing in the first application is simply the job of a Fiber Optic Modem [FOM]. The Metrodata AP3000 can be used therefore as a serial to fiber converter. An example of EIA530 Serial Over a Fiber Optic Link is shown in the Diagram below. The "OC-3 Fiber" reference is nothing to do with the speed of the link, it is simply in reference to the AP Module that we would use [All our Fiber Modules are OC-3].

In the second application we are providing slightly more functionality by providing the ability to support 2 separate serial interfaces, operating at different rates. This is particularly useful in medium data rate asymmetric satellite applications. Where you might have a HSSI satellite modem operating at 29.123Mbits and an EIA530 Modem operating at 187.321Kbits. You cannot use an EIA530 Modem in both directions as EIA530 has a maximum speed of 20Mbits [and this link is running at 29.123Mbits]. It is not cost effective to use a pair of HSSI Modems, as they are much more expensive than 1 x EIA530 Modem and 1 x HSSI Modem.

In the third application we are using the Access Processor almost as an HSSI Aggregation Switch. The maximum data rate we support on HSSI is 90Mbits. Generally speaking, the only equipment that runs HSSI at such rates is a Satellite Modem. Typically the maximum rate of most other HSSI devices is STS-1 or 51.84Mbits.

In the fourth application we are looking at much the same functionality as the previous app. The ability to transport Tx and Rx on the same fiber is provided by using a WDM Modification to our existing STM-1 Single Mode Fiber Module.