Summary

This chapter addressed the design of the long-range data transmission part of an SAP infrastructure. Wide area networks provide the communications pathway between geographically dispersed sites in a corporate network infrastructure. In most cases, long distance connections have to be leased from telecommunication providers. Bandwidth over long distances is still a rare and therefore expensive resource, especially across national borders. The costs for transmission capacity can be a major part of the total operating cost of an enterprise-wide SAP system. Because the wide area network connection is truly a lifeline for a remote office, plant, subsidiary, or affiliate, high-availability considerations and failure-tolerant architectures are crucial for the SAP network infrastructure.

These are some basic recommendations for mission-critical SAP WAN infrastructures:

• Use leased lines when low latency is a must.

• Use Frame Relay when some latency can be tolerated.

• Use ISDN dial on demand with channel aggregation if temporary connectivity is needed.

• Use VSAT links where reliable terrestrial lines are not available.

• Set filters to prevent unnecessary traffic crossing the WAN.

• Reduce network protocol overhead with spoofing and proxy ARP.

• Use bandwidth on demand to provide additional bandwidth to overcome temporary congestion.

• Consider traffic prioritization using QoS technology.

• Ask for documentation and password to read router configurations when service providers configure routers.

• Deploy encrypted virtual private network links.

• Ensure full end-to-end redundancy for WAN hardware as well as for WAN connections.

• Supply uninterruptable power to routers.

• Deploy dial backup over the public telephone network.

• Consider VSAT links when redundancy independent of terrestrial influences is necessary.

• Monitor the status of all WAN links on a regular basis and adjust bandwidth as necessary.

• Do not forget, a WAN connection is a backdoor to your data.