Abstract

 
 
 The goal of the Resource Reservation Protocol (RSVP) is to support the provision of the Quality of Service required for emerging Internet applications (such as video conferencing) that require a level of performance not guaranteed by the Internet. RSVP attempts to provide performance guarantees by establishing resource reservations (such as the number of buffers and bandwidth allocation) within routers and host computers of the Internet. Currently, Internet protocols are not formally specified when they are developed. Instead they are described in a narrative way in documents called Request for Comments(RFCs). This is the case for RSVP. To increase confidence in RSVP we have formalised and analysed its narrative specification using Coloured Petri Nets (CPNs). This paper demonstrates how CPNs can be used for modelling and analysing RSVP. Among the several beneficial features of CPNs are: graphical facilities for specification; support for different levels of abstraction; hierarchical structuring mechanisms; and verification and validation methods, such as querying the state space to investigate properties, and language equivalence to check the consistency of different levels of abstraction. Coloured Petri Nets are supported by a number of computer tools including Design/CPN. Design/CPN supports the construction and maintenance of CPN models and their simulation and analysis using state spaces. These facilities allow us to create a model that provides a clear, unambiguous and precise definition of RSVP, and to analyse the protocol for functional correctness. The paper concentrates on the approach and the tools used in this investigation.
 
 
Highlights
The Internet Integrated Service Model (IntServ) [7] is one of the proposals for providing the desired Quality of Service (QoS) for applications operating over the Internet
We aim to provide an introduction to the way Coloured Petri Nets (CPNs) can be used to create a model of protocols with soft-state mechanisms and to analyse the model using state spaces [14] and their associated Strongly Connected Component (SCC) graphs [14]
We describe the main features of Reservation Protocol (RSVP), structured to facilitate the description of the model
Summary
The Internet Integrated Service Model (IntServ) [7] is one of the proposals for providing the desired Quality of Service (QoS) for applications operating over the Internet. RSVP is designed to be run on network routers and in end hosts to support QoS applications It reserves resources for a data flow from the sender to one or more destinations (i.e. a multicast destination). Path messages travel downstream and set up and maintain path state information (e.g. the Internet Protocol address of the previous router and the data flow’s traffic characteristics). The cleanup timer determines the maximum period of time that a node (i.e. router or host) can wait to receive a path or reservation refresh message, before it removes the associated state information. Reservation Setup: Resv messages carry reservation requests (e.g. for bandwidth and buffers) used to set up reservation state information in the nodes of the route established by the path set-up message They travel upstream from the receiver(s) to the sender(s). A ResvConf message is generated by the sender (Figure 1)
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