Ove Strandberg

Adaptive connection admission control for differentiated services access networks

In our earlier work, we have proposed some modifications for the bandwidth broker framework. With our modifications, it is possible to use measurement-based admission control in addition to the more traditional parameter-based admission control. Moreover, we have presented a new flexible admission control scheme that has proven to be very efficient in terms of bottleneck link utilization. Two problems, however, have arisen: the use of scheduling weights in admission control and bursty connection arrivals. In this paper, we present that the former one can be dealt with the use of adaptive scheduling weights, while the latter one can be fought with adaptive reservation limits. The proposed new algorithms are validated through simulations and their performance is compared against the nonadaptive basic scheme.

Packet discarding inside a SIMA network: a waste of network resources?

Simple Integrated Media Access (SIMA) is a network service based on drop preference bits in every packet. A key characteristic of SIMA is that the packet discarding decision are made locally without any knowledge about the load condition in other parts of the network. A possible problem of SIMA is that some packets could be lost in the last node after they have gone through the whole network. This seems to be a waste of network resource,s as some other packets could be transmitted in the network instead of the packets discarded in the last node. The question addressed in the paper is how much a network may profit by using perfect information about the network load condition in a way that the goodput in maximized by discarding packets only in the first node. A network with 5 nodes has been evaluated with a large number of different load conditions. The results show that the average benefit is less than 2 percent of the network capacity if the overall packet loss ratio is at most 20 percent. Only if the average packet los ratio is very high, could the benefit be significant.

Transfer delays in a SIMA network

Differentiated Services approach has been recently proposed for providing Quality of Service in Internet. Simple Integrated Media Access is a network service concept that use this approach by utilizing priority bits in packet headers. Three drop preference bits are used for making the decision about packets to be discarded when congestion arises in a core network node. A single delay indication bit marks the packet either as belonging to a realtime or non real time flow. The acceptance of packets is not directly connected with real time properties of a packet. The real time support of SIMA is based on two features. First, real time packets are placed to a short real time buffer inside a core network node. Secondly, the real time buffer is always emptied before the longer, non real time buffer. This means a shorter queuing delay for real time packets. For the successful operation of the network it is crucial to have small enough transfer delay for real time packets. On the other hand, the difference in transfer delay must be significant enough between real time and non real time service in order to justify their existence. Finally, there is also the question, whether real time packets can block non real time flows since the real time packets are always transmitted first in a SIMA node. To answer these questions this paper addresses the issues related with transfer delay of packets over a SIMA network. We present extensive simulation results about the transfer delay distributions in order to provide insight into SIMA and transfer delays.

An efficient and scalable resource monitoring approach for MPLS-enabled IP networks

This paper studies the network resource monitoring issues in MPLS enabled IP networks. First it analyzes the MPLS use cases, relevant standards and various MPLS management proposals. Some basic concepts relevant to MPLS network resource management are clarified such as 1) Label Switched Path (LSP) route selection method, 2) LSP setup method, 3) LSP computation method and 4) LSP deployment mode. It is shown that, among all the technical method alternatives, the combination of the explicit routed and control plane signaled LSP makes the resource management task more complicated and challenging. Then, the network topology discovery functionality is found to be different in MPLS networks than in the conventional IP networks. The existing IP topology discovery method can’t provide an accurate and up-to-date topology database, which is critical for the dynamic resource management. A new method named LSP feedback, which piggybacks the MPLS topology information on the reverse messaging of the label distribution protocol, is introduced. The LSP feedback method has advantages in its high accuracy, more up-to-date and low overhead. But it still has some drawback such as lack of global topology information on the routing domain. This document proposes two approaches to enhance the LSP feedback method. Finally, a bandwidth limit calculation algorithm is described in details.