Cisco Systems 8600 Series manual Stand-Alone ESP, Redundant ESPs

Extended Services Processor

The ESP also provides the following application interfaces:

•SNMP to configure and monitor the ESP.

•TFTP (trivial file transfer protocol) for uploading statistics, Call Detail Records (CDRs), and downloading configuration files and new software releases and revisions.

•Telnet for accessing the ESP remotely, such as from the Cisco StrataView Plus Workstation.

Stand-Alone ESP

A single ESP controlling a WAN Service Node, such as is shown in Figure 8-5,operates in the StandAlone mode. In the StandAlone mode there is no redundancy for a failed ESP. During the initial installation of a ESP, it can be configured as either Primary or Secondary but must be configured to operate in StandAlone mode.

When a second ESP is added to a single ESP operating in StandAlone mode, you must change the operating mode of a StandAlone ESP to Active or Standby mode.

Redundant ESPs

As shown in Figure 8-6,ESPs can be installed in redundant pairs in the WAN Service Node. In a redundant pair, one ESP is active, that is it controls the switched services in the WAN Service Node, and the other ESP is standby. The redundant ESPs are known as peers. The ESPs will switch roles from active to standby and vice versa under the following conditions:

•Controlled switchover invoked from the active ESP Configuration Interface.

•The active ESP detects a major service affecting failure, such as a BPX switch polling failure or an ATM NIC card failure, and relinquishes the active role, by going Out of Service.

•The standby ESP detects that the inter-ESP paths have failed and assumes the active role.

Note During a switchover, all SVC connections will be torn down and the ATM or Frame Relay CPE will have to initiate another SVC call to reestablish them. During a switchover, all SPVC calls when be released, but when the standby ESP becomes active, it will reestablish the SPVCs.

Each ESP determines its role by means of Role Resolution protocol, which exchanges messages between the two units at startup. Both the active ESP and the standby ESP monitor its role and connectivity, and if appropriate, automatically switchover (that is, switch roles from active to Out of Service and from standby to active) with the peer ESP.

The redundant ESPs need to synchronize their database so that when the active ESP has gone out of service, the standby unit can take over and resume the service. There are two types of update mechanisms for synchronizing ESP databases. These are the bulk and real-time updates. The bulk update is used to synchronize a standby ESP with an active unit whenever it is restarted. The real-time updates are those messages that are exchanged after ESPs are synchronized and while both the active and standby ESPs are communicating.

ATM and Frame Relay SVCs, and SPVCs 8-9