Framework for IP Multicast in Satellite ATM NetworksA. Roy-Chowdhury, N. Bharatula, G. Akkor, K. Chandrashekhar, M. Raissi-Dehkordi / Advisor: J. S. Baras

IP Multicast Fundamentals

• Multicast ConceptsPoint-to-multipoint or multipoint-to-multipoint data transmission.Application sends single copy of data; network replicates and sends to all

receivers – provides better bandwidth utilization, reduces host processingand traffic redundancy.

• IP MulticastingReplication at the IP layer – router sends a copy of the IP datagram per

outgoing link.Notion of multicast group composed of senders and receivers – Class D

address space (224.0.0.0 ~ 239.255.255.255).Receivers can dynamically join/leave; senders need not be group members.Applications: video-conferencing, shared workspace, distributed interactive

simulation, resource location.Protocols (fixed networks): MOSPF, DVMRP, CBT, PIM-DM, PIM-SM;

MSDP, BGMP.Example: Multicast Backbone (MBone) of the Internet.

Problem StatementTo design a framework for IP multicasting in a satellite network, where the satelliteis an ATM switch with no IP routing functionality.• Satellites are a attractive medium for group data delivery, due to wide coverage and broadcast capabilities. •IP multicast over satellites is not well-defined - no IP routing functionality in current satellites. Very high latency with routing at the NOC.• ATM for satellite transmission compounds the problem – support for multicast in ATM is minimal and orthogonal to the IP multicast paradigm.The problem hence involves selection of suitable IP multicast protocol and designing the mechanism for IP multicast over the satellite ATM network.

Network Topology

Proposed Framework

• Multiple terrestrial LANs that have one or more satellite terminals connected tothem; satellite has ATM switching functionality, no IP.

ATM Multicast• UNI 3.1 - Point-to-multipoint (p2mp) VC: cell replication at switches where branching occurs. Unidirectional multipoint distribution.

•Emulating multipoint-to-multipoint service:Centralized multicast server (MCS) – ATM switch; one group per server.Distributed VC mesh: one p2mp VC per sender; need more network

resources.

•IP multicast using UNI 3.1: Multicast Address Resolution Server (MARS) for mapping {Class D address, ATM address 1 .. N}.

• Native IP multicast in LANs using Protocol Independent Multicast –Sparse Mode (PIM-SM):

Each subnet/LAN has its own PIM-SM entities; one or more satelliteterminals act as Rendezvous Point (RP) for all multicast hosts in itssubnet.

Multiple RPs per Class D address – multicast entities see only the local subnet RP.

• ATM multicast using VC mesh across subnets over satellite links:MARS located at the NOC.RP of receiving host sends join to MARS if not part of multicast tree.RP of source creates p2mp VC to RPs of all subnets with receivers.p2mp VC branching with cell replication at the satellite.

Simulation• Simulate the satellite network in OPNET 9 – has support for PIM-SM; no ATM multicast.• PIM-SM module configured with 2 senders and 3 receivers per group in eachsubnet.• Changes to PIM-SM to allow multiple RPs per multicast address.• Addition of multicast features (p2mp VC, MARS) to ATM.• Implementation of PIM-SM-ATM interface.• Work in progress

Future Work• Develop and implement collusion-resistant key generation and distribution schemes for secure multicast communication; evaluation of such schemes forour multicast architecture.• Develop and implement efficient source authentication schemes for multicastin our architecture.• Develop multi-level security schemes for multicast applications.

References1. B. Fenner, M.Handley, H. Holbrook, I. Kouvelas, “Protocol Independent Multicast – Sparse Mode (PIM-SM): Protocol Specification (Revised)”, Internet Draft, draft-ietf-pim-sm-v2-new-05.ps, Work in Progress.2. G. Armitage, “IP Multicasting over ATM Networks”, IEEE JSAC, Vol. 15,No. 3, April 1997.3. M. Ramalho, “Intra- and Inter-domain Multicast Routing Protocols: A Survey And Taxonomy”, IEEE Communications Surveys and Tutorials, First Quarter 2000, Vol. 3 No. 1.

Satellite network architecture

NOC

p2mp VC

Overall Network

Subnet

OPNET Simulation

AcknowledgementThis work is sponsored in part by Lockheed Martin Global TelecommunicationsInc., under the grant #123456789.

• Modification to PIM-SM RP functionality for ATM multicast between subnets.• Redefinition of PIM-SM to allow active peer RPs.• Define PIM-SM over ATM multicast as a new inter-domain multicast protocol.

MCS Architecture VC Mesh MARS Cluster

IP/ATM Multicast Framework