Papers Abstracts and references:

Authors: Dahlia Malkhi and Michael Reiter

Quorum systems are well-known tools for ensuring the consistency and
availability of replicated data despite the benign failure of data
repositories. In this paper we consider the arbitrary (Byzantine)
failure of data repositories and present the first study of quorum
system requirements and constructions that ensure data consistency and
availability despite these failures. We also consider the load
associated with our quorum systems, i.e., the minimal access
probability of the busiest server.  For certain limited types of
services we exhibit a quorum system over n servers with a load of
1/sqrt(n), thus meeting the lower bound on load for benignly
fault-tolerant quorum systems. For arbitrary services subject to
arbitrary failures, we prove a lower bound of 1/2 on quorum system
load, and demonstrate a novel construction meeting that bound.

Technical Report CS96-12, Hebrew University of Jerusalem, July 1996.

Authors: T. Anker, D. Breitgand, D. Dolev and Z. Levy

The  use of  a high  bandwidth  multicast  is becoming  widespread  in
today's network applications. Many of these applications use multicast
groups  with  dynamic  membership  such  as  multi-media conferencing,
multi-media  broadcasting  and multi-media distributed data bases. ATM
UNI 3.1 and 4.0  protocols  offer  the  point-to-multipoint connection
type that  enables  multicast  over  native  ATM.  Point-to-multipoint
connections  may be utilized for efficient implementation of multicast
groups.  In  both  ATM UNI 3.1 and 4.0, however,  explicit information
about the end-points (members of a multicast  group)  participating in
the  multicast  connection is  required at a  connection  set up time.
Unfortunately, there  is no  standard  mechanism that  facilitates the
maintenance of such group membership information.

In this document we present for the first time a CONnection-oriented
Group-address RESolution Service (CONGRESS). CONGRESS incorporates a 
protocol for efficient maintenance and propagation of group membership
information  in  connection-oriented  networks,  and  thus acts as a 
complementary  service to  the ATM  multicast mechanism and makes it 
more  usable.  CONGRESS  does not replace the ATM multicast service 
(i.e. does not actually open connections for data transmission), but 
only resolves group  addresses, leaving  freedom to the  application 
designer to use the resolved addresses as desired.

Applications that use CONGRESS may name groups arbitrarily, using
logical names (group addresses). This enables the application to
refer to multicast groups as abstract services. The membership of 
a group maintained by CONGRESS may change dynamically and is also
sensitive to current network connectivity. Groups may consist of a
large number of members and may span world-wide. In order to make 
the service efficient and scalable, CONGRESS services are maintained
using servers that are organized hierarchically. 

Technical Report CS96-23, Institute of Computer Science, The Hebrew
University of Jerusalem, Jerusalem, Israel, December 1996.

Authors: D. Dolev and D. Malki

This paper describes the design of the Transis system from the
point of view of applications prone to suffer network partitions.

Pre-print of a paper to appear in Communications of ACM, 39,
4, April 1996.

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