GEOCAST Project Work Package WP2400:


Satellite Reliable Multicast Transport Protocol (SAT-RMTP)

The SATellite Reliable Multicast Transport Protocol (SAT-RMTP) is a reliable multicast transport protocol. It has been optimised for delivery of multimedia objects (e.g., bulk data or video clips) to a large group of receivers using high speed IP multicast enabled networks. The SAT-RMTP protocol was designed and developed by University of Aberdeen (UoA). SAT-RMTP has been integrated into a Network Tool for multimedia file distribution.

GEOCAST Network Configuration

The GEOCAST project provides a platform for building a next generation broadband satellite network to support IP multicast. Based on a geostationary satellite with multiple spot beams, IP multicast packets may be delivered at high speed to any point within the satellite down-link.


Network Tool Operations

The Network Tool uses three protocols:
  • Security Protocolóclient authentication and encryption/decryption of content
  • Session Protocolóto convey information about services being offered
  • Transfer Protocolñreliable multicast transmission of multimedia content (SAT-RMTP)




SAT-RMTP Client and Server Interaction




SAT-RMTP Protocol

The SAT-RMTP Protocol is designed to provide end-to-end reliable transmission of data, from a single sender to a group of receivers (one-to-many reliability), over an IP-multicast enabled network. The protocol design has been optimised to mitigate the demands at the receiver/source end-systems over the network; and to tolerate (occasional) high packet caused by traffic congestion (at network bottlenecks) or link impairments (link fades).

Key features of the SAT-RMTP protocol include:
  • Scalable and efficient bulk data transfer over asymmetric links
  • Use of Hybrid ARQ and Packet FEC for reliability
  • Support for TCP-Friendly data transmission (based on multiple layers)
  • Supports a fully distributed multicast topology (i.e. many-to-many)
  • SAT-RMTP is extensible to support other services (i.e. BoD, CoS and QoS)
  • Design based on the framework of the IETF RMT WG

Security Protocol

The Security Protocol enables clients to establish a secure association with the security server. Application layer encryption is used, and both public key and private key encryption is supported.

Key features provided by the Security Protocol include:
  • Authentication of users (clients) - using public key algorithm
  • User Access Control (AC) for a given multimedia file or object
  • Key exchange using public key algorithm
  • Confidentiality, based on file or object encryption using secret key algorithm
  • Integrity of the downloaded file or object using HMACs
  • Detection of replay attacks using random numbers

Session Protocol

SAT-RMTP uses the Service Announcement Protocol (SAP) to distribute information about the content that will be available for down-loading. Clients use the Internet Session Directory (SDR) tool to receive the SAP messages The SDR tool also provides information describing each item of content, contact information for the content provider and specifying the multicast group destination address that will be used for the SAT-RMTP transfer.



Related Resources

  • Download SAT-RMTP C++ binaries: Server [tar, gz], Client [tar, gz]
  • [GEOC-UOA-2400-2] Techical Report: Satellite Reliable Multicast Transport Protocol (SAT-RMTP): Specification and Functionality
  • [GEOC-UOA-2400-3] Techical Report: A Network Tool for Multimedia File Distribution
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