CCIE Collaboration Flashcards

In SIP, what is the purpose of the SDP (Session Description Protocol) body in an INVITE message?

Answer: Negotiating media parameters like codec, IP address, and port for RTP

The SDP body in a SIP INVITE describes the media capabilities (codecs, IP, ports) that the calling party can support, initiating codec negotiation.

What is Cisco's SRST (Survivable Remote Site Telephony) feature used for?

Answer: Providing basic call processing at branch offices when WAN to CUCM fails

SRST allows a Cisco router at a remote site to provide basic call processing when WAN connectivity to the central CUCM is lost.

Which transport protocol is typically used by RTP (Real-time Transport Protocol) for voice media streams?

Answer: UDP

RTP uses UDP for voice media because UDP's lower overhead and lack of retransmission is better suited to real-time media than TCP's reliable delivery.

What is the Cisco Webex Calling architecture's cloud component that handles call control for cloud-registered devices?

Answer: Webex Cloud Call Control (formerly Broadworks/BroadCloud)

Webex Calling's cloud call control (built on Broadworks) handles call routing, device registration, and features for cloud-registered IP phones and soft clients.

In Cisco UC, what is the function of a CUBE (Cisco Unified Border Element)?

Answer: Acting as a back-to-back user agent for SIP trunks between UC systems

CUBE is a SIP back-to-back user agent (B2BUA) that provides interoperability, security, and demarcation between enterprise UC systems and SIP trunks.

What mechanism does Cisco CUCM use to ensure voice path optimization between two IP phones at the same site?

Answer: Region/Location with direct media (hairpin avoidance)

Cisco CUCM uses Region/Location configurations and direct media negotiation to ensure RTP streams flow directly between endpoints, avoiding unnecessary hairpinning through the WAN.