There are several methods that may be employed to integrate a CUCM cluster and a VCS cluster. These methods include H.323 trunks, SIP trunks, and configuring the CUCM to register to the VCS. This latter method is reserved for older versions of CUCM. In this article, we are going to assume VCS X6 or later and CUCM 6x/7x/8x.
The following diagram provides an overview of our example design:
In our example, we have a CUCM cluster that hosts voice gateways, VoWLAN phones, and standard desk phones. The voice gateways may be leveraged to provide media path for PSTN parties that are audio-only participants in a video call or conference. Desk phones may be standard voice phones or video enabled phones such as the 9951 or 9971 IP phone.
The CUCM cluster has at least one SIP trunk to the VCS call control cluster. The VCS itself hosts SIP and H.323 registrations from video endpoints and video infrastructure devices such as Multipoint Control Units (MCUs) and ISDN gateways.
For our example,
- Assume we have a multi-node CUCM cluster with three (3) call processing nodes.
- Assume we have a multi-node VCS cluster with two (2) VCS Control systems.
- A 5-digit dial plan is used and (conveniently) we can add video to the dial plan without introducing overlap
- There are two approaches that will be discussed:
- Using static SIP trunks
- Using DNS SRV for dynamic load balancing and failover
There are several CUCM system level configurations that warrant some attention when preparing to integrate a CUCM and VCS solution. These are discussed in order of configurations.
While not required, it is a good idea to define a device pool specifically for the SIP trunks that are added for the VCS cluster. This gives administrative control over media resource group lists and region. Though, MRGLs can be added at a trunk level, I don’t typically adopt that practice.
SIP Trunk Security Profile
If you plan on leverage TLS and SRTP, then you need to have a security profile that enforces this configuration when applied to the VCS SIP trunk. In addition, you will also need to deal with security certificates, which are discussed later.