Wide Area Networks

Definition

This section discusses high availability for wide area networks (WANs).

Structure

Routers

The following graphic shows a redundant router configuration:

Using special routing protocols, routers are able to detect changes in the network structure and to dynamically adapt their routing behavior. The network hosts ought to be able to use an additional default gateway or exchange the routing information using the Routing Information Protocol (RIP). Special high availability solutions for routers are also available with the aim of enabling very rapid switching and possibly also load balancing.

Provider Connection

For the provision of services beyond an intranet, the network connections delivered by the provider must generally be used. These connections should be redundant. You might consider connections to several providers so that, if one provider fails, network access can still continue. Examine the service level agreement with your provider to make sure that a certain level of network availability is guaranteed.

Redundant Provider Connection

To avoid physical disruption, consider a separate route for the provider connection.

When choosing Internet service providers (ISP) consider the following:

·        Choose ISPs that are also used by your customers, because this increases the chances of high data throughput.

·        Choose ISPs that enable “peering” to share the load so that, in the event of ISP failure, you do not experience sudden performance problems.

SAProuter

SAProuter is often used for communication between the SAP front ends and the SAP system. It is an application gateway contained within the standard SAP System. It functions as a proxy for the SAP data stream and offers various security features. The front end decides which SAProuter is used for communication. If all traffic is directed through a SAProuter (and further access is prohibited due to security reasons), it can become a single point of failure.

Since there are no switch and load balancing mechanisms for SAProuter, you can take the following measures to increase availability:

·        Switchover solution with cluster

·        Second SAProuter path, which the front end accesses with a separate logon

Redundant SAProuter