Voice over Internet Protocol (VoIP) Fundamentals

Vocabulary flashcards covering fundamental terms, components, protocols, QoS metrics, and secure implementations related to Voice over Internet Protocol (VoIP).

Voice over Internet Protocol (VoIP)

Methodology and set of technologies that deliver voice and multimedia sessions over IP networks.

Public Switched Telephone Network (PSTN)

Worldwide circuit-switched telephone network used for traditional phone calls.

IP Network

A computer network that uses the TCP/IP protocol suite to send data as packets between devices.

IP Telephony / Internet Telephony

Alternative names for VoIP that emphasize voice transmission over IP rather than the PSTN.

Voice over Broadband (VoBB) / Broadband Telephony

VoIP services delivered over high-speed broadband connections.

Signaling Protocol

VoIP protocol type used to set up, manage, and terminate calls (no user voice data).

Transport Protocol

VoIP protocol type that carries the actual voice packets once a call is established.

Non-Proprietary Protocol

Open standard VoIP protocol available for use by any vendor without licensing fees.

Proprietary Protocol

VoIP protocol owned and controlled by a single company; usually requires licensing.

Endpoint Device

User-facing hardware or software such as an IP phone, softphone app, PC, or smart speaker.

IP Phone

Networked telephone that converts voice to IP packets; depends on a Call Manager to operate.

Softphone

Software application that provides VoIP calling capability on a computer or mobile device.

Call Processing Server (Call Manager)

Server application that registers endpoints, stores configuration, and sets up VoIP calls.

Cluster (VoIP)

Group of interconnected call processing servers acting as one logical unit for load-balancing and redundancy.

SIP Trunk

Logical IP-based link that carries phone numbers and call traffic between call managers or to service providers.

Voice Gateway

Device that interconnects VoIP networks with the PSTN, translating signaling and media formats.

Network Switch

Layer-2 device that provides physical connectivity and forwards traffic within a VLAN; supplies PoE and voice VLAN support.

Power over Ethernet (PoE)

Capability of a switch to deliver electrical power to devices like IP phones over Ethernet cabling.

Voice VLAN

Layer-2 broadcast domain dedicated to IP phones, mapped to a unique subnet for easier QoS and management.

Network Router

Layer-3 device that forwards packets between different subnets/VLANs; can apply QoS policies.

Quality of Service (QoS)

Techniques that prioritize certain traffic types (e.g., VoIP) to ensure acceptable performance.

Packet Loss

Condition where packets are dropped, often due to congestion, causing gaps in voice or video.

Packet Jitter

Variation in packet arrival times that can degrade real-time audio/video quality.

Packet Latency (Delay)

Time a packet takes to travel from source to destination; high latency causes echo/overlap.

Bandwidth

Maximum data capacity of a link; managed by QoS to allocate resources to priority traffic.

Mean Opinion Score (MOS)

Numeric rating (typically 1–5) of perceived call quality as judged by human listeners.

Differentiated Services Code Point (DSCP)

6-bit field in an IP header used to classify and prioritize packets for QoS handling.

High-Priority Queue

Router or switch buffer that expedites forwarding of marked traffic like VoIP packets.

H.323

ITU-T, non-proprietary VoIP signaling framework considered complex and less used today.

Session Initiation Protocol (SIP)

IETF, non-proprietary signaling protocol that establishes and terminates multimedia sessions; widely adopted.

Skinny Client Control Protocol (SCCP)

Cisco proprietary signaling protocol used mainly with Cisco IP phones.

Real-Time Transport Protocol (RTP)

Non-proprietary transport protocol that carries encoded voice or video over IP networks.

Secure Real-Time Transport Protocol (SRTP)

Encrypted version of RTP that protects confidentiality and integrity of media streams.

Codec

Hardware or software that encodes/decodes and compresses/decompresses voice or video signals.

VoIP Call Establishment

Process where endpoints and call manager exchange signaling (e.g., SIP) to set up the media path.

Secure VoIP (SVoIP)

Implementation where encryption is applied at the IP phone before voice is sent over an unsecure network.

Sectéra vIPer™ Phone

General Dynamics IP phone certified to encrypt voice up to Top Secret/SCI for SVoIP deployments.

Voice over Secure Internet Protocol (VoSIP)

Implementation where voice travels on a classified (secure) IP network and is encrypted by network encryptors.

Network Encryptor

Device that applies encryption at network boundaries to protect classified data traversing unsecure links.

Packet Switched vs. Circuit Switched

VoIP uses packet-switched IP networks; PSTN uses circuit-switched dedicated paths.