There is so much to this question that it’s challenging to distill into a succinct answer.
First, most customers should seriously consider Webex Calling multi-tenant before reverting to CUCM on-prem or hosted by Cisco with Webex Calling Dedicated Instance (WxC-DI). The solutions Cisco competes against these days are not comparable to CUCM in functionality or complexity. CUCM/CUC have a devoted following amongst engineers that know it, myself included, but they are very intimidating to learn and are frequently perceived as out of step with where IT leadership wants to steer the organization: SaaS, simple, “good enough” (argh!), etc.
WxC-DI is the exact same core products as the on-prem suite: CUCM, IM&P, CUC, CER, and Expressway. You have admin access similar to on-prem; platform/SSH being the main exception. Cisco’s stated positioning for it is:
- Customers with a large contingency of legacy phones that cannot migrate to Webex Calling multi-tenant, eg 7900. I struggle with this point as it’s making a long-term choice based on a short-term, sunk cost, limitation.
- Customers that need corner-case features only available on CUCM. There certainly are feature gaps but the Nortel engineers felt the same way for the last 20 years. A lot of good it did them.
- Customers with an integration/add-on product that has no equivalent in the multi-tenant platform. Think AXL and CTI. This is valid but does that require the entire org use CUCM or only the subset of users that require that integration?
As for advantages, WxC-DI:
- Eliminates the cost of upgrades which most customers pay a partner to for them.
- It avoids the need to buy and refresh compute/storage for the VMs
- It has and will continue to get features not available in the on-prem stack. For example, integrated PSTN connectivity as an option. Anything forward looking requires an NDA so I can’t discuss it here. Ask your Cisco account manager.
There are drawbacks to WxC-DI, namely:
- You cannot delay upgrades forever; Cisco runs N-1 major release, currently 14 and 12.5. When 15 comes out anyone left on 12.5 must allow Cisco to upgrade their instance(s). Be sure that any 3rd-party apps you integrate are supported by their vendor and will support new version in a reasonable timeframe.
- There are connectivity costs between customer LAN/WAN and Cisco’s data centers. IPSec tunnels (Virtual Connect) are the cheapest option. Private transport options also exist. Don’t overlook this in your TCO. It’s worth mentioning that WxC multi-tenant also has private transport connectivity options, if that is a requirement. There absolutely is an advantage to private transport (eg SLA, QoS, immunity to internet disfunction/congestion) for any UCaaS solution but be careful to either saddle every solution with that cost or none of them; either it’s a requirement or it isn’t.
