TEL500-Voice Communications

Session initiation protocol improvement using inter-asterisk exchange

Devesh Mendiratta & Sameer DeshmukhMS-Telecommunication

State University of New York Institute of Technology

Introduction VOIP Network VOIP Protocols

• SIP (Session initiation protocol)• IAX (inter-asterisk exchange Protocol)

Codecs

Bandwidth Utilization over VoIP Networks

Theoretical bandwidth calculation

Comparison Practical bandwidth calculation

Introduction cont.

VOIP Protocols

Centralized Distributed

• H.323• SIP• IAX

VOIP Architecture Models

SIP Protocol

Session Layer Protocol “Request and Response” Mechanism Sessions & Video data between two endpoints File types & formats After establishing a session – responsibility of

average flow transfer is delegated to RTP i.e. Transport layer

Dynamically allocation of port (10000 to 20000)

IAX Protocol

Session layer protocol Provides control & VoIP networks Point-to-point Media & signaling protocol Multiplexing of signaling UDP port 4569 Trunked IAX

Codecs

Analog voice is converted to a digital signal

Then it is carried across the Internet. Examples based on compression level

G.711G.726

G.729AGSMiLBCSpeexMP3

Calculation : Theoretical Value

Codec bit rate = (codec sample size)/(codec sample interval)

Packets per seconds = (codec bit rate)/(voice payload size)

Total packet size = L2 + IP + UDP + L5 + voice payload size

The BW required for n conversations full duplex:

BWn = BW x n x 2

CSI = 10ms

CSS = 80 bytes

VPS = 160 bytes

BW30calls = 87.2 Kbps x 30 x 2 = 5232 Kbps

Example : SIP using codec G.711

Calculation : Theoretical ValueBW Calculation Protocol SIP – codec G.711

Input data: CSI = 10 ms,CSS = 80 bytes, VPS = 160 bytes

BW30calls = 87.2 Kbps x 30 x2 = 5232 Kbps (more than 5 Mbps)

BW Calculation Protocol SIP – GSM codec

Input data: CSI = 10 ms,CSS = 80 bytes, VPS = 160 bytes

BW30calls = 36.4 Kbps x 30 x 2 =2184 Kbps (near 2 Mbps)

IAX Protocol – G.711 codec

Input data: CSI = 10 ms,CSS = 80 bytes, VPS = 160 bytes,

CBR = 64 Kbps, VPS (ms) = 20 ms,PPS = 50

BW30calls = 84 Kbps + 65.6 Kbps x 29 =1986.4 Kbps (near 2 Mbps)

H.IAX Protocol – codec GSM

Input data: CSI = 20 ms,CSS = 33 bytes, VPS = 33 bytes,

CBR = 13.2 Kbps, VPS (ms) = 20 ms,PPS = 50

BW30calls = 33.2 Kbps + 14.8 Kbps x 29 = 462.4 Kbps (Less than 512 kbps)

Practical Value

Vyatta installation Configuring interfaces & static routs on Vyatta Installing CentOS 5.2 OS on servers Asterisk 1 & 2 Installing Asterisk PBX on servers 1 & 2 Installing Wireshark & Unsniff sniffer on the machine SIP & IAX extensions settings Dial plan configuration

BW SIP, G.711, 30 CALLS

BW SIP, GSM, 30 CALLS

Comparison Table

Conclusion

SIP & G.711 codec => very good quality of voice highest consumption of BW

IAX & GSM codec => lowest consumption of BW high traffic – distortion

IAX & G.711 codec => ideal for power traffic level is relatively high requires high bandwidth

SIP & GSM codec => ideal for plans that do not

support IAX

Resources

• ^http://ofps.oreilly.com/titles/9781449332426/asterisk-UnderstandingVoIP.html

• ^http://en.wikipedia.org/wiki/Category:VoIP_protocols

• ^http://www.cisco.com/application/pdf/en/us/guest/tech/tk587/c1506/ccmigration_09186 a008012dd36.pdf

?Thank You

Any Questions Undergrad ???