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
What is SIP?
Session initiated protocol
What is RTP?
Realtime transport protocol
What is RTP used for?
- Transporting multimedia data stream
- Sending packets via UDP
What is SRTP?
Secure realtime transport protocol
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OSI model58
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Server room equipment7
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IPV4 and IPV625
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DNS13
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TCP and UDP17
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NAT9
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Firewalls18
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Wireless LAN21
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Command line18
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TCP view and Superscan16
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Wireshark18
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Encryption7
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Digital Signatures8
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VPN8
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World wide web architecture7
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URL, HTTP and HTML25
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Server and Client side scripting16
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Internet mail30
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VOIP19
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IRC7
