Routing algorithms for differentiated services in a heterogeneous network environment
Wan Lin · Mspace (University of Manitoba) · 2004
Difierentiated Services (DiffServ) has been proposed for the next genera- tion network.DifiServ allows the users to pay for and receive differentiated services.We realize that it is impractical to implement DifiServ in all nodes at the same time.Thus, it is reasonable to assume that the network will con- sist of both DifiServ capable nodes and DiffServ incapable nodes for quite some time.For DifiServ routing, DifiServ capable links are preferred.But a path consisting of oniy DifiServ capable nodes may not exist in the network.Even if such a path exists, it may not be the "optimal" path.In this thesis, we give routing algorithms for a DiffServ capable user to establish a route in such a network.One of the routing metrics we consider is DiffServ capability.The other metric is cost.Three routing algorithms are given.In the fir'st algorithm, cost is given higher precedence over Diff- Serv capability.In the second algorithm, DifiServ capability is given higher precedence over cost.The first two algorithms consider the metrics as inde- pendent metlics.In the third algorithm, we assign a DifiServ route selection order number to each link in the network topology.The algorithm computes the optimal path using the assigned DifiServ route selection order numbels.Simulations in ns show that the third algorithm is more powerful than the first two algorithms.Through simulations, we have proved that the algorithm calculates the correct routing paths in all netwolk topologies.a best-efiort basis and no gus.ranteesare given with respect to the packet stream's characteristics.A voice stream is more sensitive to packet delays than to packet losses.If a packet experiences a delay of more than 400 milliseconds, the voice becomes unintelligible.But it can typically tolerate packet losses of up to 20%.An application with contrasting demands is the standard ftp.ftp sessions are more concerned about throughput than delays.Many critical applications such as corporate data access applications need reliable and secure network support.So, as we can see, the Internet is filled with trafrc from applications with contrasting requirements and the current best-efio¡t style service is no longer sufficient.Quality of Service (QoS) is the ability of a network element (e.g. an application, host or router) to have some level of assurance that its traffic and service lequirements can be satisfied.There are essentially two types of QoS available [71]: ¡ Resource Reservation: On an application's QoS request, and subject to bandwidth management polic¡ network resources ale reserved for the application's exclusive use.RSVP and Integrated Services (IntServ) provides this service.¡ Prioritization: Network trafrc is classified and apportioned network lesources according to netrvork management policy criteria.An application may request special treatment of its trafrc subjecting to network management policy.Differentiated Se¡vices (DifiServ) provides this service.These QoS protocols and algorithms are not competitive or mutually 'I