Chris Stegh / /

Microsoft + Cisco Break the Ice: CUBE Media Bypass

Microsoft and Cisco announced the completion and release of Media Bypass for Direct Routing. Organizations who own Cisco UC Manager CUBE border controllers now have one less barrier as they move to Microsoft Teams for voice service. Newer CUBE border controllers can be reused as certified Session Border Controllers for Teams, and use media bypass for traffic optimization.

Direct routing is one of the two methods of connecting Teams phones and PCs to the Public Switched Telephone Network. Cisco has supported direct routing with CUBE for some time. With Direct Routing, calls come in and out of the organization through a SIP trunk of their choice, rather than using Calling Plans through Microsoft’s data center. Our previous blog takes a deeper dive into the pros, cons, and call flows of direct routing versus Microsoft’s calling plans.

Without media bypass, the call would’ve traversed from the user, all the way to Microsoft’s Teams data center (1), back to the SBC (2), and finally out to the SIP trunk (3, in the figure below).

WIthout Direct Routing (2)

Now, Cisco also supports media bypass. Media bypass allows a call to/from a user to pass directly through the CUBE and directly connected SIP trunk. This more efficient call flow is shown below at right.

Note: CUBE version 14.1 [IOSWith Media Bypass (2)-XE 17.3.2] or later is required to enable Media Bypass. CUBE is software that can be deployed on many of Cisco’s hardware platforms (including the popular 2900/3900 Integrated Services Routers and larger data center Aggregation Services Routers).

What’s the significance?

Eliminating the hairpin provides far less latency and to some users, an audible difference in the quality of the call. Improvements would be especially noticeable for callers who are far from the Microsoft data center, because of the distance voice traffic would save in transit.

Another benefit is less traffic to/from the ISP and Microsoft data center. The ‘hairpin’ that was once doubling the traffic to Microsoft is now clipped as traffic is kept locally.

Finally, this can save existing CUBE owners a bunch of capital expense in new SBC technology. The hardware (and especially) licenses are worth a significant amount. Extending the life of already depreciated hardware makes the overall TCO of Teams more attractive.

Other considerations for Direct Routing:

Microsoft-friendly SBC partners, like Audiocodes and Ribbon, have been in the business of interconnecting various telephony systems for 20+ years. Therefore, they will provide a richer set of features than Cisco.

  • They allow other devices and systems (besides Cisco PBXs), to connect, such as analog devices like security alarms and door buzzers.
  • They also support Survivable Branch Appliances, which can keep calls active even if the ISP connection to Office 365, or the Teams service itself, is unavailable. The SBA keeps active calls alive by running enough code in them to maintain the session for the phone and the SIP trunk to the telco.
  • They have monitoring tools that interoperate with Teams, and in the case of Audiocodes, have intelligence on the call quality of their handset devices.
  • They can be deployed on general purpose Virtual Machines, including on premises, in AWS, and Azure. CUBE is mainly to be deployed on Cisco hardware or VMWare Esxi environments, and is available in the AWS marketplace. It wouldn’t be surprising to see Cisco add CUBE to the Azure Marketplace, where it would join many existing Cisco security products.


It’s also notable that Cisco tested and supports e911 for Teams calls, through Intrado/West. For additional information about how Teams handles 911, see a blog that outlines how e911 with direct routing is supported by three service providers, RedSky, West / Intrado, and Bandwidth. These carriers provide trunks into local SBCs which are specifically provisioned to carry 911 calls (in parallel from day to day in/outbound calls) and add value add services such as mobile PC and mobile apps which force a user to put in their correct IP address if at home or another location whose IP address isn’t associated with the brick and mortar subnets of the of the organization.

This is another leg up for Cisco on its main IP PBX competitor, Avaya, whose Session Border Controllers don’t have media bypass or 911 support.

Big Picture Significance

Continued interoperability between the two tech giants is a good sign, but the partnership has limited expectations. Cisco and Microsoft compete vehemently in the meetings and voice services markets. Microsoft is giving free audioconferencing services to many Teams subscribers to take a swing at WebEx and Zoom.

The other groundbreaker of late was September's announcement of native interop of WebEx rooms with Teams

meetings. Once office workers return, the interop of existing rooms to Teams will be a focus. 

There have been rumors for many years about using Cisco phones with Avaya PBXs or using Cisco phones with Lync/Skype4Bus/Teams, but the interoperability is so limited, few if any customers have done more than experiment with that option.

It's encouraging that Cisco’s making investments so that customers can maintain theirs. It was probably a lively debate in San Jose. While opening their door for Microsoft to grab the call control licensing, Cisco maintains a new way to maintain software session management relevance even as clients migrate to Teams. They certainly have come a long way from being a hardware focused company.

We're looking forward to the efficiencies Cisco and Microsoft customers can gain from using this new option.


Microsoft’s updated list of certified SBC providers

Cisco’s new interop note for Teams with CUBE

Executive's Guidance for Moving to Teams (

Deciding Between Direct Routing and Calling Plans (

Microsoft Teams Answers the 9-1-1 Call (

Cloud-Based Phone System, Voice Calling, Video Phone System (

Work with our team of Cloud Computing Consultants who have done this so many times they know all of the “minefields” to prevent missteps.