Based on Cisco Collaboration Sizing Guide for Release 14 SU1 & Release 15 (PA Sizing Methodology).
Web equivalent of CiscoSizingTool.exe & CiscoSizingTool_SME.exe · For full accuracy use the official Cisco Sizing Tool from cisco.com
Cisco Sizing Methodology (Release 15): Sizing uses BHCA (Busy Hour Call Attempts), device count, and CPU/memory linear models. OVA size determines max users and features per node. This tool implements the simplified sizing rules from the Cisco PA Sizing Guide.
User & Device Profile
Max per cluster: 80,000 users across all nodes.
Feature & Traffic Profile
SME Sizing (CiscoSizingTool_SME.exe equivalent): SME (Session Management Edition) is a specialised CUCM deployment for centralised dial plan management across multiple leaf clusters. Sizing is based on DN count, concurrent calls, and inter-cluster traffic patterns.
SME Input Parameters
SME supports up to 1,000,000 DNs in the dial plan.
SME Deployment Architecture
SME is based on a specialised CUCM deployment. It primarily handles SIP signalling (no voice media). Each SME node handles trunk traffic between leaf clusters and external gateways.
Unity Connection sizing is based on mailbox count, message storage, and concurrent voicemail sessions (VMXI + SMTP). CUC v15 supports up to 60,000 users per cluster.
CUC Input
Typically 5–10% of users simultaneously accessing VM.
CUC Options
IM&P (Cisco Unified Presence / Jabber) sizing. Maximum 25,000 users per IM&P node in sub-cluster mode. Each sub-cluster supports up to 25,000 users with publisher + subscriber.
IM&P Input
IM&P Options
Bandwidth sizing using Erlang-B / Erlang-C traffic models as per Cisco PA sizing methodology. Based on concurrent call calculations from BHCA and ACHT inputs.