Explanation
A SIP proxy server is a component of a SIP network that handles the setup and termination of calls between SIP devices. It also performs functions such as registration, authorization, network access control, and network security. Some of the functions of a SIP proxy server are:
Centralizes dial plans: A SIP proxy server can centralize the dial plans for a SIP network, meaning that it can translate and route calls based on a unified set of rules and policies. This simplifies the administration and management of the SIP network and ensures consistent call routing across different devices and locations.
Helps to centralize the administration and call control: A SIP proxy server can also help to centralize the administration and call control of a SIP network, meaning that it can provide a single point of contact and configuration for all the SIP devices and endpoints. This reduces the complexity and overhead of maintaining multiple SIP servers and devices and allows for easier monitoring and troubleshooting of the SIP network.
References:
1: What Is a SIP Proxy? How Does a SIP Server Work? - Nextiva
2: What is a SIP Proxy Server and How Does It Work? - ULTATEL Blog
3: What is SIP proxy? | Webopedia
4: Definition of SIP proxy | PCMag
5: All About SIP Proxy: What is a SIP Server? | TelNet Worldwide

Explanation
CUBE is a Cisco IOS software feature that provides voice and video connectivity from IP phones to the PSTN or other IP networks. CUBE supports several advanced call control and mobility services, such as:
Element Grouping: This feature allows you to group multiple CUBE elements into a single logical entity and apply common configuration and dial plan across them. This simplifies the management and scalability of CUBE deployments.
Time of Day Routing: This feature allows you to route calls based on the time of day, day of week, or date. You can define time periods and time schedules and associate them with dial peers or voice translation rules. This enables you to implement different call routing policies for different time slots, such as business hours, after hours, holidays, etc.
Call Admission Control: This feature allows you to limit the number of concurrent calls on a CUBE element or a CUBE group based on the available bandwidth or the configured maximum number of calls. This prevents oversubscription of network resources and ensures the quality of service for voice and video calls.
References:
CUBE Configuration Guide
CUBE Element Grouping Configuration Guide
Time of Day Routing Configuration Guide
Call Admission Control Configuration Guide

PROCMON, DUMPLOG, and Unified System CLI are three tools that can be used to download logs for CCE troubleshooting. PROCMON is a Windows-based tool that allows administrators to capture log files and view them in real time. DUMPLOG is a command-line tool that can be used to download log files from CCE nodes. Finally, Unified System CLI is a web-based tool that can be used to access the CCE system and download log files. Reference: https://www.cisco.com/c/en/us/td/docs/voice_ip_comm/cucce/troubleshooting

External voice DNs are sourced from the Cisco Unified Communications Manager (CUCM) in a CCE Dial Plan. The CUCM is the primary source of all external voice DNs and is used to define the dial plan rules and to manage the routing of incoming and outgoing calls. The CUCM also stores the external voice DNs, which can then be used in the CCE Dial Plan to route incoming and outgoing calls. Reference: https://www.cisco.com/c/en/us/td/docs/voice_ip_comm/cucce/dial_plan_design/10_6_1/dpdf_b_dial-plan-design-106/dpdf_b_dial-plan-design-106_chapter_01.html