Size a Cisco CUBE (Unified Border Element) for SIP trunking: platform (ISR/Catalyst), DSP (PVDM4), concurrent calls, and license planning for Enterprise or Service Provider deployment.
CUBE terminates SIP trunks from carriers and bridges them to your CUCM/CCE/Webex. Choose wrong and you either overspend (5x overprovisioned) or hit a capacity wall (resource exhaustion under 3 months). This tool computes the right platform, DSP density, and licenses based on your call profile.
Set inputs, click Size CUBE.
Router model for CCS target.
PVDM4 module for transcoding.
CUBE SRST / TR / SRTP count.
Redundancy topology.
CUBE runs on IOS-XE routers — historically ISR 4000 series, now pivoting to Catalyst 8000. The rule of thumb for Enterprise CUBE: ISR 4431 up to 40 CCS, ISR 4461 up to 125 CCS, CAT 8300 up to 300 CCS, CAT 8500L up to 600 CCS. For Service Provider CUBE (much higher density, no DSP): CAT 8500 with dual RP up to 4000 CCS, ASR 1000-series up to 16000 CCS. Don't buy SP CUBE for Enterprise — it's overkill and missing features (no DSP transcoding).
DSP sizing: only needed if you transcode (e.g., G.711 ↔ G.729, or G.711 ↔ Opus). One PVDM4-32 = 32 sessions of G.711↔G.729. Medium-complexity transcodes (Opus, iLBC) halve that. For pure SIP-SIP pass-through with matching codec both sides, no DSP is needed at all. If CUCM and carrier both negotiate G.711, skip DSP. If carrier forces G.729 and your phones use G.711, size DSP = peak transcoded calls.
SRTP (media encryption) doubles CPU load. A CAT 8300 sized for 300 CCS of RTP handles only ~150 CCS of SRTP-SRTP (encrypt both legs). Pass-through SRTP (no crypto manipulation) is fine — only crypto rewrite is expensive. Plan encrypted deployments at half rated capacity. Always apply +25-50% growth factor on top.
Yes. CUBE Standard/Redundant Trunk licenses are purchased per CCS.
Enterprise up to ~1000 CCS or if you need DSP transcoding. SP above 1000 CCS for density.
Yes — CSR 1000v / Catalyst 8000v run CUBE in VM. Reduced capacity vs hardware.
C8000v AMI available. Sized smaller than on-prem; useful for cloud-to-carrier trunks.
Only as a Local Gateway. Webex Calling's LGW role uses CUBE, but smaller deployment.
Single SIP trunk, 15 CCS.
2500 users, 250 CCS, G.729 carrier.
500 agents, 400 CCS, SRTP both sides.
Our UC Modernization Sprint delivers CUBE bring-up with carrier SIP trunk, CUCM wiring, HA, and documentation.