VoIP Basics

Topics: Real-time Transport Protocol, Internet Protocol, User Datagram Protocol Pages: 3 (490 words) Published: February 24, 2014
Packetization is collection of digitized voice samples for the load
The following image shows typical VoIP Packet
Digitized voice becomes a payload for RTP (protocol we will study) RTP is then encapsulated into UDP
And UDP into IP
So this becomes Voice over IP
At the and of this lecture we will again show how it all fits together

Connectionless unreliable datagram service on the top of IP
Adds port concept to identify peer application
Datagrams may be lost, reordered, or duplicated
Application responsible for reliability
Includes datagram loss, duplication, delay, out-of-sequence, multiplexing, loss of connectivity

Advantages over using IP directly
Can address individual applications via well-known ports
Checksums
Minimal overhead, high performance
No setup/teardown, 1 datagram at a time
End-to-end reliable stream transport
Connection oriented - full duplex virtual circuit
Conceptually place call, two ends communicate to agree on details After agreeing application notified of connection
During transfer, ends communicate continuously to verify data received correctly When done, ends tear down the connection
Provides buffering and flow control
Takes care of lost packets, out of order, duplicates, long delays Isolates application program from network details

Uses ports to identify individual connections and applications

TCOM 590, Spring 2014
Homework #1
Due on February 25th
Delivery method: hard or soft copy (email is just fine)

1.Assume audio conferencing session with multiple participants using wideband speech (RTP streams). How would you: a.Identify deferent voice streams that belong to the same session?

SSRC (Synchronization Source) in the RTP header uniquely identifies the source in the session.

b.Differentiate between RTP and RTCP packets that belong to the same session?

RTP ha.

g.Determine the voice payload size if generic wideband PCM is used to digitize voice signal?

h.Determine...
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