A Cisco Unified IM and Presence version 11 .5.1 on-premises deployment of instant messaging with a capacity of 50.000 users includes the multiple device messaging feature. Each of the 30,000 users has 3 Jabber clients. The customer reports that messages are not being received on all 3 clients. What should the administrator do to resolve this issue?

When the Multiple Device Messaging (MDM) feature is enabled on a Cisco IM and Presence server, the system's capacity planning must account for every individual client device. According to official Cisco sizing guidelines, each user device is counted as a separate user. In this scenario, with 30,000 users each running 3 Jabber clients, the total number of endpoints requiring service is 90,000 (30,000 users × 3 devices/user). The current system capacity of 50,000 is insufficient, leading to message delivery failures. Therefore, the capacity must be increased to at least 90,000 to support all devices.

B. Increasing capacity to 60,000 is insufficient as it does not account for the total load of 90,000 devices, which are each treated as a user.
C. Increasing capacity to 72,000 is an arbitrary value and is also insufficient to support the required load of 90,000 devices.
D. The current capacity is 50,000; reducing it to 30,000 would only exacerbate the resource contention and message delivery failures.

1. Cisco Unified Communications Manager IM and Presence Service Release 11.5(1) Sizing Guide

Chapter: "Sizing the IM and Presence Service"

Section: "Sizing Factors"

Page 6.

The document states: "When you enable the multiple device messaging feature

each user device is counted as a separate user from a sizing perspective." This directly supports the calculation of 30

000 users 3 devices = 90

000 required capacity.

2. Deployment Guide for IM and Presence Service on Cisco Unified Communications Manager

Release 11.5(1)

Chapter: "Capacity Planning for IM and Presence Service"

Section: "User Counts"

Page 21.

This guide corroborates the sizing guide

stating: "If you enable the multiple device messaging feature

each user device is counted as a separate user from a sizing perspective." This confirms that the total number of devices dictates the required system capacity.