CUCM Architecture: Call Processing Models

Single Site Call Processing Model (Single Cluster)

  • All devices in a single, campus network
  • All incoming/outgoing calls go the PSTN
  • Use G.711 Uncompressed Audio Codecs
  • Simplest model to deploy

Central Call Processing Model (Single Cluster)

  • Remote phones supported by single cluster
  • PSTN and WAN connection at each site
  • G.72 Compressed CODEC between sites
  • SRST on remote routers

Distributed Call Processing Model (Multiple Clusters)

  • WAN Primary Path for intersite calls
  • G.729 codec over WAN
  • Independant WAN bandwidth control (H.323 gatekeeper or SIP Proxy)
  • The future of networks

Clustering over the WAN

  • Single point of administration
  • Database replicated
  • Features, shared lines over WAN
  • Higher requirements
  • Round Trip Delay: 40ms
  • Bandwidth: 900Kbps per 10,000 BHCA

CUCM Architecture: Clustering and Database

1. Run-time data (Intra-cluster communication signal)

  • Actively running between CUCM servers in cluster
  • Example: phone registration
  • Example: CUCM failure results in phone relocation

2. Database Data (IDS DB Replication)

  • CUCM Database information replicated between servers
  • Example: phone extension mapping
  • Example: dial-plan changes

CUCM Architecture: IP Phone Communication and Call Flow

Key Protocols

  • Skinny (SCCP) (Signaling)
  • SIP (Signaling)
  • RTP (Audio)

Phones sends off hook status to CUCM.

All actions for the handset are actioned by the CUCM brain.

Call setup via CUCM and audio stream directly between the 2 phones via RTP. (CODECs to follow)

SCCP does digit by digit processing.

SIP almost sends a micro version of the dial plan to the phone!

Welcome to CIPT 8.0: Cisco Certification and Getting the Most from this Series

Intro to CIPT1

Nuggets are shorter. 5-30 mins maximum and broken up into smaller parts.

Take notes..

Build a lab..
CUCM in VMWare Workstation

Get some cheap IP phones – 7940 or 7960 and also analog

Cheap voice router – 2610,2611,2620,2621xm,2801,1750 etc..

Dig deeper

Fall in love