VOIP Flashcards
What is VOIP?
Transmission of voice data over a traditional packet switched IP network
What are the main parts of VOIP?
- IP network
- IP PBX/call processing server
- End user devices (soft phones)
- VOIP gateway
What does an IP network for VOIP need to be able to do?
Able to distinguish between voice and data traffic and give a higher priority to voice
What does a VOIP gateway do?
Provides a bridge between VOIP network and standard phone system
What tasks can a VOIP gateway perform
- Voice compression
- Echo cancellation
- Silence compression
How is a called made from PSTN to VOIP?
- Call made, goes through local exchange
- Directed to VOIP gateway
- Gateway uses DNS to look up IP number
- Gateway connects to IP PBX to ring phone, move voice data etc
What are some VOIP signalling protocols?
- H.323
- SIP
- Skinny
- MGCP
What are some VOIP transport protocols?
- RTP
- RTCP
- SCTP
What are some of the quality of service issues related to VOIP?
- Delay
- Packet loss
- Bandwidth
- Security
- Jitter
- Echo
- Reliability
What does jitter related to?
Variation in packet time arrival
What are two methods to secure VOIP from DOS attacks?
- Use private addressing for all VOIP processing systems
- Use firewalls
What are some security functionalities in relation to SRTP?
- Encryption of VOIP
- Authentication of sender
- Integrity checks to avoid any unauthorised changes
- Anti relay functionality to avoid unauthorised access
What is z-fone?
Not a VOIP client but an add on
What is Asterisk?
An open source engine for building communications applications
What can Asterisk handle?
- PBX switching
- Application launching
- Codec translation
- Scheduling and I/O management
