Connecting ATM Switches to Satcoms

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A number of the major ATM vendors have validated interoperability with Metrodata ATM products, most being ATM switches (Fore ASX-200, Cisco Lightstream 1010, Cisco Stratacom BPX), though we have also undertaken solutions with routers that have ATM modules (such as the Cisco 3600 and 7500 Series Routers).

As ATM is mainly used as a means of multiplexing multiple lower data rates into a single larger "trunk" link, ATM interfaces tend to correspond to fixed rates such as DS3 (45Mbps) and OC-3 (155Mbps). These speeds are fine when the infrastructure is terrestrial, however, in satellite applications the dominant cost is that of the satellite capacity and so this must be minimised wherever possible resulting in non-standard data rates.

Flexibility of data rates (i.e. the ability to support non-terrestrial data rates) requires the use of serial satellite equipment with interfaces such as EIA530, HSSI or ASI. This conversion of fixed speed ATM interfaces to flexible satellite interfaces is one of the many solutions offered by the Access Processor range from Metrodata. For ATM conversion between Telco rates the ATM Switching DSU product range can be used.

In the diagram below an ATM switch is connected via an AP3000 Access Processor to a satellite modem which is connected via satellite to a similar network at the other end of the satellite link. The Access Processor enables native ATM cells to be transported across the ATM link.

ATM Switch connecting to another ATM Switch

Metrodata's product range provides an extremely flexible solution for connecting ATM switches to the following satellite modem interfaces:

The Access Processor range supports a variety of applications including:

  • ATM to serial satellite modem conversion
  • Convergence of multiple ATM and non-ATM applications across serial satellite modems
  • Multi-casting, e.g. an outbound channel of 110Mbps via a 36MHz transponder to several receive sites, with several lower speed satellite links in the other direction

Connecting ATM Switches to EIA530 Satellite Modems

Most EIA530 satellite modems are used because they can support flexible or non Telco data rates which match into the entire satellite capacity available based on the size and power of the antenna used, and this more efficient approach is where the Access Processor product range comes into its own. The Access Processor has an EIA530_UNI module which is an ATM cell bearing interface, allowing ATM cells to be transported across a satellite modem. This EIA530_UNI module operates as a DTE and thereby slaves to the clocking provided by the satellite modem, supporting asymmetric data rates up to a maximum operating speed of 20Mbps.

The Access Processor also supports all of the standard G.703 ATM interfaces: e.g. E1, E3, DS3 and OC-3 / STM-1, so if you already have EIA530 satellite modems, then you could use an ATM port in your router, or an ATM switch and connect into the EIA530 satellite modem using an Access Processor which would allow operation over the satellite link at well over the maximum data rate possible with an EIA530 router port.

Connecting ATM Switches to HSSI Satellite Modems

Most HSSI satellite modems are used because they can support flexible or non Telco data rates which match into the entire satellite capacity available based on the size and power of the antenna used, and this more efficient approach is where the Access Processor product range comes into its own. The Access Processor has a HSSI_UNI module which is an ATM cell bearing interface, allowing ATM cells to be transported across a satellite modem. This HSSI_UNI module operates as a DTE and thereby slaves to the clocking provided by the satellite modem, supporting asymmetric data rates up to a maximum operating speed of 100Mbps.

The Access Processor also supports all of the standard G.703 ATM interfaces: e.g. E1, E3, DS3 and OC-3 / STM-1, so if you have HSSI satellite modems, then you could use an ATM port in your router, or an ATM switch and connect into the HSSI satellite modem using an Access Processor which would allow operation over the satellite link at up to twice the maximum data rate possible with a HSSI router port.

Connecting ATM Switches to ASI Satellite Modems

ASI is mainly used in the broadcast sector as a means of distributing/broadcasting video channels where broadcasting/multi-casting is common. ASI satellite modems support transmission rates over 200Mbps, although receive rates tend to be slightly lower.

Because of the ability of ASI to operate at such high data rates, it is now being used as a means of transporting data over satellite, however typical data equipment such as routers and ATM switches do not have ASI interfaces. The Access Processor has an ASI_UNI module which is an ATM cell bearing interface, allowing ATM cells to be transported across a satellite modem. This ASI_UNI module slaves to the clocking provided by the satellite modem, supporting asymmetric data rates up to a maximum operating speed of 155Mbps.

The Access Processor also supports all of the standard G.703 ATM interfaces: e.g. E1, E3, DS3 and OC-3 / STM-1, so if you have ASI satellite modems, and want to run data over them, then you could use an ATM port in your router, or an ATM switch and connect into the ASI satellite modem using an Access Processor which would offer a high speed ATM data link over the satellite link at up 155Mbps in each direction.

Connecting ATM Switches to G.703 Satellite Modems

G.703/G.704 satellite modems support fixed Telecoms rates such as E1, E2, E3 and DS3. The ATM Switching DSU range supports ATM rate and interface adaptation allowing ATM equipment with different interface speeds to be connected together. This same technology can also be used to interface between an ATM switch and a G.703 satellite modem, allowing the ATM cells to be transported across the satellite link. Different variants of ATM Switching DSU are required for each specific conversion that is required, as follows:

  • Connecting an E3 ATM switch to an E1 2Mbps G.703 satellite modem - using the E3 to E1 ATM Switching DSU
  • Connecting an E3 ATM switch to an E2 8Mbps G.703 satellite modem - using the E3 to E2 ATM Switching DSU
  • Connecting a DS3 ATM switch to an E1 2Mbps G.703 satellite modem - using the DS3 to E1 ATM Switching DSU
  • Connecting a DS3 ATM switch to an E2 8Mbps G.703 satellite modem - using the DS3 to E2 ATM Switching DSU
  • Connecting a DS3 ATM switch to an E3 34Mbps G.703 satellite modem - using the DS3 to E3 ATM Switching DSU
  • Connecting an OC-3 ATM switch to an E1 2Mbps G.703 satellite modem - using the OC-3 to E1 ATM Switching DSU
  • Connecting an OC-3 ATM switch to an E2 8Mbps G.703 satellite modem - using the OC-3 to E2 ATM Switching DSU
  • Connecting an OC-3 ATM switch to an E3 34Mbps G.703 satellite modem - using the OC-3 to E3 ATM Switching DSU
  • Connecting an OC-3 ATM switch to a DS3 45Mbps G.703 satellite modem - using the OC-3 to DS3 ATM Switching DSU

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