thinQmaster Virtual testing partner Adaptive practice exams that find your weak spots and drill them. Every answer explained. From $69
Enroll

thinQmaster

Find your exam

Five questions free, before you decide.

Step 1 · choose a vendor

In one of our camps? Your practice exams come with the tuition — they are on your study page already.

Collaboration, Voice & AV · Intermediate

Business-to-Business Calling (B2B)

Voice and video calls between different organizations over the internet, typically using SIP URIs routed through Expressway or SBCs.

Definition

B2B calling lets employees dial partner video systems or users by URI. Outbound calls are routed by DNS SRV lookups, and inbound calls reach the enterprise via its public SRV records and Expressway-E. Security considerations include TLS, SRTP, toll fraud prevention and restricting which internal destinations unauthenticated callers can reach.

Example

A Cisco Room Kit dials ceo@partner.com, and Expressway-E routes the call via DNS to the partner's edge.

Exam tip

Expect questions on SRV lookups for B2B and on blocking unauthenticated callers from reaching PSTN patterns.

Related terms