ITIS 1210ITIS 1210Introduction to Web-Based Introduction to Web-Based

Information SystemsInformation Systems

Chapter 39Chapter 39How Multicast IP and MBone WorkHow Multicast IP and MBone Work

IntroductionIntroduction

Internet contentInternet content Originally it was just static contentOriginally it was just static content

Download it, view itDownload it, view it Branched out into other formsBranched out into other forms

SoundSound VideoVideo AnimationsAnimations 3D objects3D objects

Now interactive content is prevalentNow interactive content is prevalent

IntroductionIntroduction

Problem:Problem: Providing a richer experienceProviding a richer experience Implies correspondingly larger filesImplies correspondingly larger files That take longer to downloadThat take longer to download Causing massive congestion within the Causing massive congestion within the

Internet infrastructureInternet infrastructure Some content cannot be sent over Internet Some content cannot be sent over Internet

at all because of capacity limitationsat all because of capacity limitations

IntroductionIntroduction

Example: telecast of a concertExample: telecast of a concert Assume a file size of 50MBAssume a file size of 50MB Assume an audience of 10,000 peopleAssume an audience of 10,000 people 50MB must be sent individually to 10,000 50MB must be sent individually to 10,000

subscriberssubscribers This might not be possible without This might not be possible without

seriously degrading the ability of local seriously degrading the ability of local sections of the Internet to continue to sections of the Internet to continue to service other customersservice other customers

IntroductionIntroduction One solution is the experimental MBoneOne solution is the experimental MBone

Multicast BackboneMulticast Backbone Virtual high-capacity backboneVirtual high-capacity backbone Specifically designed to transmit broadcastsSpecifically designed to transmit broadcasts Uses the IP multicast protocolUses the IP multicast protocol

Begins as a single transmissionBegins as a single transmission Instead of 10,000Instead of 10,000

Included are all addresses of every Included are all addresses of every subscribersubscriber

IntroductionIntroduction

As the file is sent across the Internet it As the file is sent across the Internet it makes copies of itselfmakes copies of itself

Those copies are routed to individual Those copies are routed to individual subscriberssubscribers

IntroductionIntroduction Example:Example:

100 people want to see a broadcast of a 50MB file100 people want to see a broadcast of a 50MB file Under normal circumstances, 5GB of data would be Under normal circumstances, 5GB of data would be

necessarynecessary 50 are connected to the Internet via ISP X50 are connected to the Internet via ISP X 25 use ISP Y25 use ISP Y 25 are on corporate network Z25 are on corporate network Z

With multicast, the file is initially transmitted as a With multicast, the file is initially transmitted as a single filesingle file Splits into three parts to X, Y, and ZSplits into three parts to X, Y, and Z

IntroductionIntroduction

Each network delivers their copy on to Each network delivers their copy on to subscribers on that network alonesubscribers on that network alone

Instead of 5GB being necessaryInstead of 5GB being necessary Three 50MB files (150MB) are neededThree 50MB files (150MB) are needed

Normally the Internet is a Normally the Internet is a unicastunicast environmentenvironment One transmission goes to one destinationOne transmission goes to one destination

MulticastMulticast enables simultaneous enables simultaneous destinationsdestinations

IntroductionIntroduction

MBone is a virtual network of host MBone is a virtual network of host computers that use the IP Multicast for computers that use the IP Multicast for communicationscommunications

Process starts by digitizing and Process starts by digitizing and compressing a video signalcompressing a video signal

The compressed signal is sent using the The compressed signal is sent using the IP Multicast protocolIP Multicast protocol Multiple destinations simultaneouslyMultiple destinations simultaneously

IntroductionIntroduction

Major advantage is the single transmissionMajor advantage is the single transmission TCP would require a transmission to TCP would require a transmission to eacheach

recipientrecipient Information about the multiple destinations Information about the multiple destinations

goes into the packetgoes into the packet Two major problems:Two major problems:

Most networks and routers on the Internet do Most networks and routers on the Internet do not understand the multicast protocolnot understand the multicast protocol

Must still use standard Internet routesMust still use standard Internet routes

IntroductionIntroduction

Solution is called Solution is called tunnelingtunneling MBone data travels in tunnels built on top of MBone data travels in tunnels built on top of

existing Internet networks and routersexisting Internet networks and routers Ends of tunnel are workstations running a Ends of tunnel are workstations running a

multicast routing demonmulticast routing demon A demon (daemon) is a process that runs in the A demon (daemon) is a process that runs in the

background and performs some useful servicebackground and performs some useful service The demon encloses the multicast packets The demon encloses the multicast packets

inside regular TCP packetsinside regular TCP packets

IntroductionIntroduction

The now-standard TCP packets are sent The now-standard TCP packets are sent over the regular Internet to the other end over the regular Internet to the other end of the tunnelof the tunnel

There the multicast packets are extractedThere the multicast packets are extracted Sent on via an MBone network that Sent on via an MBone network that

understands the multicast protocolunderstands the multicast protocol

IntroductionIntroduction Based on destination data in the multicast Based on destination data in the multicast

packetspackets The original data is sent to a number of The original data is sent to a number of

different hostsdifferent hosts Individuals connected to these hosts can view Individuals connected to these hosts can view

the contentthe content There are teleconferencing options that There are teleconferencing options that

enable interactionenable interaction Audio and videoAudio and video

IntroductionIntroduction

Multicast will probably become obsoleteMulticast will probably become obsolete Hard to compute service charges for multicast Hard to compute service charges for multicast

traffictraffic Standard feature of IPV6Standard feature of IPV6