APPLICATION NOTE. Product Application Note: APN032

Transcription

1 APPLICATION NOTE Maximise port density and increase data rates when routing asymmetric Ethernet links via satellite modems. The Application Summary With the explosive worldwide growth of the Internet, satellites are increasingly being used to provide service to the more remote regions of the world. The very high costs of satellite bandwidth call for very efficient network implementations. For example, a typical Internet connection requires far more downstream traffic than upstream, typically a ratio of four to one. This means that for an efficient implementation, an asymmetric network is required. The current solution for provision of asymmetric circuits is to use interfaces and a Router. For example, CISCO 7505 router can support up to 8 ports at rates of up to 52Mbps. Using with the same satellite modems allows for up to 16 asymmetric services to be supported using Fast Ethernet Router Ports, at rates of up to 65Mbps. The use of offers the service provider greater utilisation and therefore maximum cost benefit from the deployed capital investment. offers maximum flexibility in choice of Modem. For high speed circuits, allows for up to 65MBps. For lower speeds, EIA-530 supports up to 20Mbps. The allows for independent transmit and receive interface selection allowing for the lowest cost modems to be chosen.

2 Ethernet over a satellite solution Before Metrodata brought out the the only way to pass Ethernet over a satellite link was to use a router. This created a number of problems and compromises: interfaces supported asymmetric data rates upto 52Mbps, Serial Ports only supported rates upto 8Mbps. Low port Density, 8 ports in a CISCO 7505 Router High cost due to performance of the Router required. Now the Metrodata provides a more efficient and cost effective solution to this requirement. Subject to available satellite bandwidth The has 25% performance gain on a Cisco Router solution (65Mbps versus 52Mbps). The can make better use of available satellite bandwidth, especially when working asymmetrically. Much greater port density, 16 Fast Ethernet Ports in a CISCO 7505 Router. Even greater port density when using L2/L3 switches and. About the The is a 10/100BaseT Ethernet Converter that can interface to a satellite system at any speed up to 65Mbps using the interface or 20Mbps using the multi-standard interface. The has an efficient HDLC packet handler capable of forwarding up to packets at 65Mbps. Key Features of the Auto-sensing 10/100BaseT. Auto MDI/MDIX switching. Wire speed filtering of local packets. Asymmetric and mixed Tx and Rx interface operation, o 30Mbps Tx. on the and 4Mbps Rx. on the multi-standard ports. o 34Mbps Rx on and 8Mbps Tx on or the multi-standard port. The multi-standard interface will connect to RS-232, X.21, EIA-530, V.35 & V.36 at up to 20 Mbps, subject only to the capabilities of the equipment connected to the. The port will run at any speed up to 65 Mbps. Both ports are DTE and take their clocking from the modems. The is only compatible with another or a member of the WAN-in-a-CAN family from Metrodata if the speed of the is fixed to the speed of the remote WC unit. Product WC n*64 WC1000 WC3445 Speed Upto 20Mbps 2048 kbps Mbps & Mbps

3 Interfacing to the Modems equipment manufacturers build the satellite modulators and demodulators in separate boxes. This means a Y cable is needed to split the bi-directional signal from the port. The and multi-standard ports are DTE whilst the satellite mod/demod present DCE interfaces. In a mixed interface system, simple straight through and EIA-530 cables may be used to connect the to the mod/demod system. Figure 1 shows an example of an asymmetrical application of the, where the link in 1 direction is E3(34.368Mbps ) and the return path is E2 (8.448Mbps). Figure 2 shows a high-speed application. Where a interfaces to a satellite system using at any speed up to 65Mbps. The table on page 4 shows how to make a Y cable for the. Figure 1 - An asymmetrical example of "Y" Cable (DCE to DTE) "Y" Cable (DCE to DTE) Figure 2 high-speed example of the The table on the following page shows the connection details of a Y cable (DCE to DTE), the other Y cable for the other interfaces are similar in concept.

4 Y Cable Function Direction Tx Modulator Rx Demodulator SG SG RT RT CA CA RD RD LC LC ST ST SG SG TA TA TT TT LA LA SD SD LB LB SG SG Reserved Reserved SG SG Reserved Reserved SG SG The Signal Definitions: RT Receive Timing RD Receive Data SD Send Data ST Signal Timing TT Terminal Timing TA data Terminal equipment Available CA data Communications equipment Available LA Loop back Circuit A LB Loop back Circuit B LC Loop back TM Test Mode SG Signal Ground SH Shield Direction

5 Metrodata Overview a technically excellent British communications company You think you have an issue connecting communications equipment and network services together? Not any more - Metrodata will have developed the solution to your current need, and we are already developing the solutions for your future needs! The communications world is full of techno-terminology and mystique. Convergence, fibre, SDH, STM1, ATM, integration, copper, interface conversion, interface extension, coaxial, dsu, satellite, broadband, connectivity, access, standards and so on. Carriers and Service Providers are coming under increasing pressure from the market to provide more than just leased lines. End to end management of their services, fast service provision, flexible bandwidth and tariffing, remote management and diagnostic tools are some examples. Be assured, the Metrodata Division is working closely with users and satellite SP s to create innovative solutions and services. Metrodata are the experts to guide you to your network solution. Contact Us Product Manager Mike Holdsworth mike.holdsworth@metrodata.co.uk Tel: +44 (0) Fax: +44 (0) Or visit the website at Ordering Information Power Supply VAC -48V DC part numbers