Certkiller is running CCM in a cluster over the WAN deployment. What is the maximum round-trip delay that can be present between two members in a cluster?

A.
20 ms

B.
30 ms

C.
40 ms

D.
50 ms

Explanation:
WAN Considerations
For clustering over the WAN to be successful, you must carefully plan, design, and implement various characteristics of the WAN itself. The Intra-Cluster Communication Signaling (ICCS) between
Cisco CallManager servers consists of many traffic types. The ICCS traffic types are classified as either priority or best-effort. Priority ICCS traffic is marked with IP Precedence 3 (DSCP 26 or PHB AF31 in
Cisco CallManager releases prior to 4.0 and DSCP 24 or PHB CS3 for release 4.0 and later). Best-effort
ICCS traffic is marked with IP Precedence 0 (DSCP 0 or PHB BE). The various types of ICCS traffic are described in Intra-Cluster Communications, page 2-17, which also provides further guidelines for provisioning. The following design guidelines apply to the indicated WAN characteristics:
The maximum one-way delay between any Cisco CallManager server for all priority ICCS traffic should not exceed 20 ms, or 40 ms round-trip time (RTT).Delay for other ICCS traffic should be kept reasonable to provide timely database and directory access. Measuring the delay is covered in
Delay Testing, page 2-19. Propagation delay between two sites introduces 6 microseconds per kilometer without any other network delays being considered. This equates to a theoretical maximum distance of approximately 3000 km for 20 ms delay or approximately 1860 miles. These distances are provided only as relative guidelines and in reality will be shorter due to other delay incurred within the network. Reference: Cisco IP Telephony Solution Reference Network Design (SRND), Cisco CallManager Release 4.1, April 2005.