Ip Multicasting: Manas Ranjan Panda Roll # Cs200117174 Mr. Debananda Kanhar

NATIONAL INSTITUTE OF SCIENCE & TECHNOLOGY

Technical Seminar Presentation - 2004

IP MULTICASTING Presented by

Manas Ranjan Panda Roll # CS200117174 Under the Guidance of

Mr. Debananda Kanhar

Manas Ranjan Panda

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NATIONAL INSTITUTE OF SCIENCE & TECHNOLOGY

Technical Seminar Presentation - 2004

INTRODUCTION The TCP/IP family includes four types of distribution of a packet from a single host:  Unicast : To one host  Normal IP- traffic  The packet is seen only by the receiving host  Broadcast : To all hosts on a network  When trying to find another host  The packet is seen by all hosts on the local network

Manas Ranjan Panda

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NATIONAL INSTITUTE OF SCIENCE & TECHNOLOGY

Technical Seminar Presentation - 2004

INTRODUCTION CONTD…  Anycast: To one host of a group of hosts  To access a resource that is served by several computers  The packet is seen by one of the receiving hosts  Multicast:To a group of host  The packet is seen by all hosts in the group  The packet is only duplicated when needed

Manas Ranjan Panda

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NATIONAL INSTITUTE OF SCIENCE & TECHNOLOGY

Technical Seminar Presentation - 2004

PICTORIAL REPRESENTATION

B

C

A

A

A

D

UNICAST Manas Ranjan Panda

B

C

D

BROADCAST

B

C

D

MULTICAST 4

NATIONAL INSTITUTE OF SCIENCE & TECHNOLOGY

Technical Seminar Presentation - 2004

Flow of data in multiple unicasting B Y A

X C

Z

D E

Manas Ranjan Panda

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NATIONAL INSTITUTE OF SCIENCE & TECHNOLOGY

Technical Seminar Presentation - 2004

Flow of data in multicasting Y A

X

B

C

Z

D

E Manas Ranjan Panda

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NATIONAL INSTITUTE OF SCIENCE & TECHNOLOGY

Technical Seminar Presentation - 2004

IP MULTICAST ADDRESSES  IP multicasting uses class D addresses The first four bits are 1110 The remaining 28 bits specify a multicast group Multicast addresses: 

range is from 224.0.0.0 to 239.255.255.255



lowest address 224.0.0.0 reserved



up to 224.0.0.255 for routing /group maintenance

Manas Ranjan Panda

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NATIONAL INSTITUTE OF SCIENCE & TECHNOLOGY

Technical Seminar Presentation - 2004

IP MULTICAST ADDRESSES CONTD…  A multicast address can only be used as a destination address cannot appear in the source address field or in a source route. 4 28 bits class D 1110 Multicast Group ID Total 2^28-256=268 million addresses

Manas Ranjan Panda

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NATIONAL INSTITUTE OF SCIENCE & TECHNOLOGY

Technical Seminar Presentation - 2004

MULTICAST SCOPE  Members have scope  Members in a single network: scope is the network  Members in a single organization: scope is the organization  A host must have to join a specific group to receive the traffic in that group but can send to a group without joining.  Membership is controlled by the IGMP protocol. Manas Ranjan Panda

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NATIONAL INSTITUTE OF SCIENCE & TECHNOLOGY

Technical Seminar Presentation - 2004

INTERNET GROUP MANAGEMENT PROTOCOL(IGMP)  To participate in a multicast that spans multiple networks, the host must inform local multicast routers  Local routers pass membership information to other routers  IGMP is used to communicate group membership information  It uses IP datagrams to carry messages  It is a standard for TCP/IP and is required on all machines that receive IP multicast  IGMP is considered an integral part of IP, not separate

Manas Ranjan Panda

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NATIONAL INSTITUTE OF SCIENCE & TECHNOLOGY

Technical Seminar Presentation - 2004

INTERNET GROUP MANAGEMENT PROTOCOL(IGMP)  IGMP has two phases  Phase 1: A host joins a multicast group  It sends an IGMP message declaring its membership  Local multicast routers receive the message and propagate group membership information  Phase 2: Local multicast routers poll hosts to see who the remaining members are  As long as at least one host responds, the router keeps the group active  If none respond, the router stops advertising

Manas Ranjan Panda

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NATIONAL INSTITUTE OF SCIENCE & TECHNOLOGY

Technical Seminar Presentation - 2004

IGMPv1  Stands for Internet Group Management Protocol  Manages multicast group membership  Runs between hosts and their immediate neighboring router  Only two kinds of packets: query and report  Packet format 4 4 4 16 bits vers ion type

unus ed chec ks um c las s D multic as t group addres s

Manas Ranjan Panda

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NATIONAL INSTITUTE OF SCIENCE & TECHNOLOGY

Technical Seminar Presentation - 2004

IGMPv2

Adds an explicit Leave message Routers can more easily determine when a group has no interested listeners on a LAN

Manas Ranjan Panda

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NATIONAL INSTITUTE OF SCIENCE & TECHNOLOGY

Technical Seminar Presentation - 2004

Multicast Trees  Paths define a forwarding tree, or a delivery tree  The tree contains no cycles  Each multicast router corresponds to a node in the tree  A network connecting the routers is an edge in the tree  The source of a datagram is the root  The last router on the path is a leaf  A forwarding tree defines a set of paths through multicast routers from a source to all members of a multicast group (size of tables is a concern)

Manas Ranjan Panda

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NATIONAL INSTITUTE OF SCIENCE & TECHNOLOGY

Technical Seminar Presentation - 2004

The Essence of Multicast Routing  A Multicast Router must have knowledge of group membership  Group membership information must be propagated across the internet  Because membership can change rapidly, information at a given router is imperfect and routing may lag changes  Design tradeoff: routing overhead and inefficient data transmission

Manas Ranjan Panda

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NATIONAL INSTITUTE OF SCIENCE & TECHNOLOGY

Technical Seminar Presentation - 2004

Reverse Path Multicasting • Underlying assumptions – It is more important for a datagram to reach each member of the group than it is to eliminate unnecessary transmission – Multicast routers contain a routing table with correct information – Needless transmission is eliminated when possible • RPM uses a two-step process – Copies of datagrams are broadcast to the internet – Multicast routers inform each other of paths that don’t lead to group members

Manas Ranjan Panda

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NATIONAL INSTITUTE OF SCIENCE & TECHNOLOGY

Technical Seminar Presentation - 2004

Reverse Path Multicasting  Membership information is propagated bottom-up  It starts with hosts that join or leave the group  Hosts communicate with their local router using IGMP  When a router learns that no group member lie beyond a given network interface, it stops forwarding and notifies the router on the path back to the root  When a router learns that there are no members along a path, that path is pruned  The system is data-driven  A router does not send group information until datagrams arrive for this group (data arrives and we know where to send messages)

Manas Ranjan Panda

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NATIONAL INSTITUTE OF SCIENCE & TECHNOLOGY

Technical Seminar Presentation - 2004

RPF  Stands for reverse path forwarding  Simple algorithm developed to avoid duplicate packets on multi-access links  RPF algorithm takes advantage of the IP routing table to compute a multicast tree for each source.  RPF check When a multicast packet is received, note its source (S) and interface (I) If I belongs to the shortest path from S, forward to all interfaces except I If test in step 2 is false, drop the packet

 Packet is never forwarded back out the RPF interface. Manas Ranjan Panda

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NATIONAL INSTITUTE OF SCIENCE & TECHNOLOGY

Technical Seminar Presentation - 2004

IPv4 multicast routing protocols    

DVMRP (Distance Vector Multicast Routing Protocol) PIM-DM (Protocol Independent Multicast, Dense Mode) PIM-SM (Protocol Independent Multicast, Sparse Mode) CBT (Core-Based Tree)

Manas Ranjan Panda

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NATIONAL INSTITUTE OF SCIENCE & TECHNOLOGY

Technical Seminar Presentation - 2004

DVMRP  First multicast routing protocol ever deployed in the Internet  Each router maintains a ‘multicast routing table’ by exchanging distance vector information among routers Constructs a source tree for each group using reverse path forwarding  There is a “designated forwarder” in each subnet Multiple routers on the same LAN select designated forwarder by lower metric or lower IP address (discover when exchanging metric info.)  Once tree is created, it is used to forward messages from source to receivers Manas Ranjan Panda

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NATIONAL INSTITUTE OF SCIENCE & TECHNOLOGY

Technical Seminar Presentation - 2004

PIM-DM  Similar to DVMRP  Floods multicasts out of all interfaces except the source interface  Uses RPM  Prune message to eliminate unneeded branches  Protocol-independent  Needs to establish its own router-to-router dialogs

Manas Ranjan Panda

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NATIONAL INSTITUTE OF SCIENCE & TECHNOLOGY

Technical Seminar Presentation - 2004

PIM-SM  Designed to provide efficient communication between members of sparsely distributed groups  Rendezvous point (RP) are used by senders to announce their existence and by receivers to learn about new senders of a group  Requires host group members explicitly join a delivery tree by transmitting Join message  One set of RPs per sparse-mode domain, not per group.  Each group has precisely one RP at any given time.  DR sends Join/Prune messages toward the RP and maintain the active RP Manas Ranjan Panda

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NATIONAL INSTITUTE OF SCIENCE & TECHNOLOGY

Technical Seminar Presentation - 2004

CBT  Construct a single tree shared by a Group  Protocol independent  Core router equivalent to RP  CBT state bi-directional  Data flows in either direction along the branch  Advantage  Less traffic  Better scalability  Disadvantage  Bottleneck at CR  Single point failure Manas Ranjan Panda

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NATIONAL INSTITUTE OF SCIENCE & TECHNOLOGY

Technical Seminar Presentation - 2004

Protocol Independent Multicast (PIM)  PIM consists of two protocols  PIM Dense Mode (PIM-DM) Most networks have hosts that listen to each multicast group  Uses RPF to broadcast datagrams to every group  Strops sending when it receives prune requests  Assumes router also uses conventional routing protocols 

 PIM Sparse Mode (PIM-SM) Members of multicast groups occupy a small subset of possible networks  Like CBT, requires a point to which joins are sent 



Builds a forwarding tree, trees rooted at rendezvous point

Manas Ranjan Panda

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NATIONAL INSTITUTE OF SCIENCE & TECHNOLOGY

Technical Seminar Presentation - 2004

MULTICAST APPLICATIONS

Multicast Videoconferencing Multicast Newsfeeds Multicast Access to On-Demand Services Non-media Applications

Manas Ranjan Panda

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NATIONAL INSTITUTE OF SCIENCE & TECHNOLOGY

Technical Seminar Presentation - 2004

REFERENCES [1] Banikazemi, Mohammad “IP Multicasting: Concepts, Algorithms, and Protocols” http://www.cis.ohio-state.edu/~jain/cis788-97/ip_multicast/index.htm [2] Juan-Mariano de Goyeneche, “Multicast over TCP/IP HOWTO” http://www.tascnets.com/mist/doc/mcpCompare.html. [3] Williamson, Beau. “Developing IP Multicast Networks” Indianapolis: Cisco Press,2000. Multicast Quick Start Configuration Guide http://www.cisco.com/warp/customer/105/48.html [4] Dave Price, Sandy Spence, University of Wales”JANET Technical Guides” http://www.ja.net/documents/ [5] Forouzan Behrouz A. , Data Communications and Networking, 2nd edition, TATA McGRAW-HILL Edition

Manas Ranjan Panda

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NATIONAL INSTITUTE OF SCIENCE & TECHNOLOGY

Technical Seminar Presentation - 2004

Thank you ! Manas Ranjan Panda

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