Department of Electronic & Computer Engineering 
Intelligent Systems Laboratory                           Pdi2etP TECHNICAL UNIVERSITY OF CRETE 

 

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- General
- Architecture                 - Routing
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- Unicasting
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Routing / General

Since our system is a super-peer network and the topology of the servers forms a general undirected graph, we have to deal with the routing problem, because routing has no trivial solution in a general graph. We present the network functionality. Our chosen solution is to use shortest paths for unicasting and minimum spanning trees for multicasting and broadcasting in our network. Moreover, we present the way that our system handles the problem of dynamic IP addresses and the problem that a client might get disconnected while the system is in operation. Then, we continue by discussing the fault-tolerance problem and its solutions. We close this chapter with a section about socket handling, where we describe why we try to keep the socket connections open in many cases and how we do that.

Let us now describe the functionality expected from our network. Our goal is to support the general character of the system and give the maximum flexibility to each node, so that it can communicate with the rest of the nodes in various ways. Thus, each super-peer must have the ability to perform the following operations:       
        
  • Unicast, i.e., send a message only to one super-peer (neighbor or not).
  • Multicast, i.e., send a message to a subset of super-peers (neighbors or not).
  • Broadcast, i.e., send messages which will be received by all other super-peers.

The goal of a routing protocol is to establish appropriate routing paths and to use network resources as efficiently as possible loading the network with the less possible overhead. Routing in a network typically involves a rather complex collection of algorithms, that work more or less independently and yet support each other by exchanging information. The complexity of the problem is due to a number of reasons:

 
  • Routing requires coordination between all nodes of the network.

  • Routing must be able to cope with link or node failures.

  • To achieve high performance, routing algorithms may need to modify the adopted routes, when parts of the network  become congested.

It is clear that routing depends on the underlying topology of the super-peers. In the case an acyclic topology  the solution is trivial, because there are no paths to choose from. Each node is connected to all others through unique paths. On the other hand, the general peer-to-peer interconnection topology of the super-peers requires additional data structures, and rather complicated protocols to achieve routing. In the next sections we will present the techniques that we use for routing in the general graph topology that the super-peers form in the P2P-DIET network. The ideas we present have been known for a while in the area of routing for data networks [Bertsekas and Gallager, 1987]. In our case we apply these ideas to routing in the overlay network formed by the P2P-DIET super-peers.

References:

  1. Bertsekas and Gallager, 1987 D. Bertsekas and R. Gallager Data Networks, Prentice Hall, 1987.

 

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- Technical Univ. of Crete
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2003 Intelligent Systems Laboratory, TUC