Docsity
Docsity

Prepare for your exams
Prepare for your exams

Study with the several resources on Docsity


Earn points to download
Earn points to download

Earn points by helping other students or get them with a premium plan


Guidelines and tips
Guidelines and tips

Computer Networking: A Top Down Approach lecture notes, Lecture notes of Computer Networks

Computer Networking: A Top Down Approach lecture notes

Typology: Lecture notes

2024/2025

Available from 07/04/2025

Grace_Alesy
Grace_Alesy 🇺🇸

17 documents

1 / 51

Toggle sidebar

This page cannot be seen from the preview

Don't miss anything!

bg1
Chapter 7 Part II
Multimedia Networking
Computer
Networking: A Top
Down Approach
6th edition
Jim Kurose, Keith Ross
Addison-Wesley
March 2012
Multimedia Networking 7-1
7.1 multimedia networking
applications
7.2 streaming stored video
7.3 voice-over-IP
7.4 protocols for real-time
conversational
applications
pf3
pf4
pf5
pf8
pf9
pfa
pfd
pfe
pff
pf12
pf13
pf14
pf15
pf16
pf17
pf18
pf19
pf1a
pf1b
pf1c
pf1d
pf1e
pf1f
pf20
pf21
pf22
pf23
pf24
pf25
pf26
pf27
pf28
pf29
pf2a
pf2b
pf2c
pf2d
pf2e
pf2f
pf30
pf31
pf32
pf33

Partial preview of the text

Download Computer Networking: A Top Down Approach lecture notes and more Lecture notes Computer Networks in PDF only on Docsity!

Chapter 7 – Part II

Multimedia Networking

Computer Networking: A Top Down Approach 6 th edition Jim Kurose, Keith Ross Addison-Wesley March 2012

7.1 multimedia networking

applications

7.2 streaming stored video

7.3 voice-over-IP

7.4 protocols for real-time

conversational

applications

 Voice over Internet Protocol

 Introduction of VoIP in 1995 by

Vocaltec Inc.

 VoIP could be applied to almost any voice

communications requirement,

ranging from a simple inter-office intercom to complex multi-point teleconferencing / shared screen environments.

VoIP – What is it?

IP Network Multimedia PC Multimedia PC Initially, PC to PC voice calls over the Internet PSTN (DC) Gateway PSTN (NY) Gateway Public Switched Telephone Network Gateways allow PCs to reach phones …or phones to reach phones

Complex multi-point teleconferencing Shared screen environments

Cisco IP Phone (Extra for Information)

 Model 7960  Executive set:  6 programmable line /feature  4 interactive soft keys:

  • Messages
  • Directory
  • Help
  • Settings
  • Services  graphic capability

Campus Example (Simplified for Information)

MCS-7835 Call Mgr. Telecomm MCS-7835 Call Mgr. NERDC MCS-7835 Call Mgr. OIR 7960 7960 DDF/CETS 7960 7960 C3524-PWR C3524-PWR C3524-PWR C3524-PWR PSTN Service CI SCO V G V OICE GATEW (^200) AY P OWE R RP S ACTI VIT Y VG Analog Gtwy - Analog Gtwy - UF Campus Core UF AVVID Campus Pilot PRI (future) Cisco Architecture for Voice, Video and Integrated Data (AVVID) (Simplified for Information)

Voice-over-IP (VoIP)

VoIP end-end-delay requirement : needed to maintain “conversational” aspect  higher delays noticeable, impair interactivity  < 150 msec: good  > 400 msec bad  includes application-level (packetization, playout), network delays  session initialization: how does callee advertise IP address, port number, encoding algorithms?  value-added services: call forwarding, screening, recording  emergency services: 999

VoIP characteristics

 Speaker’s audio: alternating talk spurts, silent periods.  64 kbps during talk spurtPkt’s generated only during talk spurts20 msec chunks at 8 Kbytes/sec:

  • 160 bytes of data (20 msec * 8 Kbytes/sec)  application-layer header added to each chunk  Chunk + Header encapsulated into UDP or TCP segment  application sends segment into socket every 20 msec during talkspurt

VoIP: fixed playout delay

 receiver attempts to playout each chunk exactly q msecs after chunk was generated (received!).  chunk has time stamp t: play out chunk at t+q  chunk arrives after t+q : data arrives too late for playout: data “lost”  tradeoff in choosing q :  large q: less packet losssmall q: better interactive experience

 It’s a tradeoff!

 sender generates packets every 20 msec during talk spurt.  first packet received at time r  first playout schedule: begins at p  second playout schedule: begins at p ’ Multimedia Networking 7 - 20

VoIP: fixed playout delay

packets time packets generated packets received loss r p p' playout schedule p' - r playout schedule p - r P - r P’ - r