In this paper we focus on Chord P2P protocol and we study the process of unexpected departures of nodes from this system.
Each of such departures may effect in losing any information and in classical versions of this protocol the probability of
losing some information is proportional to the quantity of information put into this system.
This effect can be partially solved by gathering in the protocol multiple copies (replicas) of information. The replication
mechanism was proposed by many authors. We present a detailed analysis of one variant of blind replication and show that this
solution only partially solves the problem. Next we propose two less obvious modifications of the Chord protocol. We call
the first construction a direct sums of Chords and the second - a folded Chord. We discuss the recovery mechanisms of partially lost information in each of these systems and investigate their reliability.
We show that our modification increases essentially the expected lifetime of information put into the system.
Our modifications of the Chord protocol are very soft and require only a small interference in the programming code of the
original Chord protocol.
Supported by the EU within the 6th Framework Programme under contract 001907 (DELIS) and by the grant No 331540 of the Institute
of Mathematics and Computer Science, Wrocław University of Technology, Poland.