Copyright © TIBCO Software Inc. All Rights Reserved
Copyright © TIBCO Software Inc. All Rights Reserved


Chapter 3 Redundancy & Fault Tolerance : Redundancy Model

Redundancy Model
The redundancy model for TIBCO Messaging Appliance P-7500 pairs two P-7500 machines, each of which serves as a backup for the other.
Concepts
Virtual Router
Each P-7500 has exactly two virtual router instances. Each virtual router can route messages among its clients (Rendezvous application programs), and between clients and the Rendezvous gateway.
You can configure two P-7500s so that their virtual routers complement one another to provide fault tolerance through redundancy.
Roles
Each virtual router serves one of two roles—primary or backup.
Clients
Virtual routers and redundancy roles are transparent to clients. Instead, clients connect to a fixed IP address for Rendezvous functionality. A pair of virtual routers (in primary and backup roles) distributed over two P-7500s respond to those client connection requests.
In Figure 2, clients that connect to IP address M receive Rendezvous service from virtual router A1 of P-7500 A. If P-7500 A fails, those clients reconnect to IP address M, and receive service from the redundant virtual router B2 (which serves the backup role on P-7500 B).
As in a mirror image, clients that connect to IP address N receive Rendezvous service from virtual router B1 of P-7500 B. If P-7500 B fails, those clients reconnect to IP address N, and receive service from the redundant virtual router A2 (which serves the backup role on P-7500 A).
Reconnection during failover is automatic. No explicit action is required by programmers. Rendezvous clients automatically reconnect to the same IP address, and cannot distinguish whether they are connected to the primary or the backup.
Active-Active
The arrangement in Figure 2 is called an active-active configuration, because under ordinary circumstances the two primaries are both active simultaneously—each serving its own set of clients. (Meanwhile, both backups are inactive.) In a failover situation, the virtual router in the backup role becomes active, replacing the failed primary.
Logical Ports
A logical port is a Rendezvous virtual IP interface, representing either a physical port of the network acceleration blade (NAB), or a link aggregation group (LAG) that spans several physical ports of the NAB. When configuring a virtual router, you must specify exactly one logical port:
 
Gateway
P-7500 runs two instance of the Rendezvous gateway, corresponding to the two virtual routers. The gateway bridges between NAB LANs and the GP LAN. After failover, gateways also bridge between the two virtual routers in a P-7500.
Each gateway connects to the NAB using the logical port of its corresponding virtual router.
Figure 2 Redundancy Model
Symmetric Configuration
In Figure 2, the configuration of each virtual router must be identical with its diagonal opposite (except for its virtual router ID). More generally, in each pair of P-7500s configured for redundancy, the following two conditions must both hold:
 
An identical configuration includes identical IP addresses, and logical ports that refer to identical physical ports or LAGs.
In contrast, if a redundant pair of virtual routers are associated with Rendezvous gateways (on their respective P-7500s), then those gateways must have symmetric configurations (though not identical). For details, see Redundancy and the Gateway.

Copyright © TIBCO Software Inc. All Rights Reserved
Copyright © TIBCO Software Inc. All Rights Reserved