Developer's Guide

4-10

CTI Server Message Reference Guide (Protocol Version 15) for Cisco Unified Contact Center Enterprise

Release 8.5(1)

Chapter 4 Session Management

Session Maintenance

Compared to some other protocols, TCP/IP is relatively slow at detecting and recovering from

communication path failures. If an IP packet is dropped within the network, retransmission does not

occur until the sender notices a time-out. This time-out period is usually long enough to allow for

worst-case round-trip delays and network congestion. If you need more rapid error detection, you may

send an optional HEARTBEAT_REQ message to the CTI Server whenever no messages have been sent

for the heartbeat interval. Upon receipt of a HEARTBEAT_REQ message, the CTI Server should

immediately respond with a HEARTBEAT_CONF message. If three heartbeats go unconfirmed, the CTI

client should declare a session failure and reset the TCP connection.

You must determine the appropriate heartbeat interval for a production environment—it depends on the

application and the environment. It should represent a reasonable balance between the speed of failure

detection and the network bandwidth consumed by heartbeat messages and their corresponding

confirmations. In cases where there are very few CTI clients, such as a CTI Bridge, the minimum

heartbeat interval of 5 seconds should suffice. Workstation (desktop) clients should use a much larger

heartbeat interval (at least 90 seconds is recommended), since these clients typically number into the

hundreds and possibly thousands. A Heartbeat Interval of –1 disables heartbeats. The default and

recommended setting for application developers is –1. However, if the TCP/IP time-out period is

adequate, or if there is nothing the application can do even if it is aware that something is wrong, it may

be appropriate to disable heartbeats even in a production environment.

Figure 4-2 depicts the heartbeat message flow. Table 4-6 and Table 4-7 define the HEARTBEAT_REQ

and HEARTBEAT_CONF messages, respectively.