In this paper a new switching technique called virtual cut-through is proposed and its performance is analyzed. This switching system is very similar to message switching, with the difference that when a message arrives in an intermediate node and its selected outgoing channel is free (just after the reception of the header), then, in contrast to message switching, the message is sent out to the adjacent node towards its destination before it is received completely at the node; only if the message is blocked due to a busy output channel is a message buffered in an intermediate node. Therefore, the delay due to unnecessary buffering in front of an idle channel is avoided. We analyze and compare the performance of this new switching technique with that of mes-sage switching with respect to three measures: network delay, traffic gain and buffer storage requirement. Our analysis shows that cut-through switching is superior (and at worst identical) to message switching with respect to the above three performance measures.

This paper reports on a study of traffic patterns among Autonomous Systems (ASes), based on traces taken at various points in the Internet. The traces display a highly nonuniform distribution of traffic on flows between pairs of hosts, networks, and ASes. Aggregation along coarser granularities, such as networks or ASes, accentuates this nonuniform distribution. In one typical trace, for example, the top 9 % of flows between ASes accounts for 86.7 % of the packets and 90.7 % of the bytes transmitted. A highly nonuniform traffic pattern suggests that routers need to maintain only limited QoS flow state. The paper discusses the implications of this phenomenon on different proposed QoS mechanisms. 1

Modern switched networks such as ATM and Myrinet enable low-latency, high-bandwidth communication. This performance has not been realized by current applications, because of the high processing overheads imposed by existing communications software. These overheads are usually not hidden with large packets; most network traffic is small. We have developed Fast Sockets, a local-area communication layer that utilizes a high-performance protocol and exports the Berkeley Sockets programming interface. Fast Sockets realizes round-trip transfer times of 60 microseconds and maximum transfer bandwidth of 33 MB/second between two UltraSPARC 1s connected by a Myrinet network. Fast Sockets obtains performance by collapsing protocol layers, using simple buffer management strategies, and utilizing knowledge of packet destinations for direct transfer into user buffers. Using receive posting, we make the Sockets API a single-copy communications layer and enable regular Sockets programs to exploit the performance of modern networks. Fast Sockets transparently reverts to standard TCP/IP protocols for wide-area communication.

Abstract—In this paper, we study traffic demands in an IP bacbkone, identify the routes used by these demands, and evaluate traffic granularity levels that are attractive for improving the poor load balancing that our study reveals. The data used in this study was collected at a major POP in a commercial Tier-1 IP backbone. In the first part of this paper we ask two questions. What is the traffic demand between a pair of POPs in the backbone? How stable is this demand? We develop a methodology that combines packet-level traces from access links in the POP and BGP routing information to build components of POP-to-POP traffic matrices. Our analysis shows that the geographic spread of traffic across egress POPs is far from uniform. In addition, we find that the time of day behaviors for different POPs and different access links also exhibit a high degree of heterogeneity. In the second part of this work, we examine commercial routing practices to assess how these demands are routed through the backbone. We find that traffic between a pair of POPs is engineered to be restricted to a few paths and that this contributes to widely varying link utilization levels. The natural question that follows from these findings is whether or not there is a better way to spread the traffic across backbone paths. We identify traffic aggregates based on destination address prefixes and find that this set of criteria isolates a few aggregates that account for an overwhelmingly large portion of inter-POP traffic. We demonstrate that these aggregates exhibit stability throughout the day on perhour time scales, and thus form a natural basis for splitting traffic over multiple paths to improve load balancing.

Can high quality be provided economically for all transmissions on the Internet? Current work assumes that it cannot, and concentrates on providing differentiated service levels. However, an examination of patterns of use and economics of data networks suggests that providing enough bandwidth for uniformly high quality transmission may be practical. If this turns out not to be possible, only the simplest schemes that require minimal involvement by end users and network administrators are likely to be accepted. On the other hand, there are substantial inefficiencies in the current data networks, inefficiencies that can be alleviated even without complicated pricing or network engineering systems.

This paper presents the results of a measurement study of the T1 NSFNET backbone. We first discuss the measurement environment and approach to data collection. We then present measurements results for: long-term growth in traffic volume, including attribution to domains and protocols; trend in average packet size on the network, both over long and medium term intervals; most popular sources, destinations, and site pairs; traffic locality; international distribution of traffic; mean utilization statistics, both of the overall backbone as well as of specific links of interest; and delay statistics. 1 Introduction The last general overview of measured behavior of the national research and education backbone infrastructure was the landmark study by Kleinrock and Naylor [13] (also in [12]), which presented measurements on the 1973 ARPANET. Since that study, the infrastructure has undergone significant change. The U.S. Department of Defense initially established the ARPANET to enable the n...

: : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : xii 1 Introduction : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 1 1. The problem : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 1 2. Overview of thesis : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 2 3. Contribution of our work : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 3 2 Taxonomy of traffic characteristics : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 5 1. Aggregation granularity : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 5 2. Host versus network centric perspective : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 7 3. Host centric perspective : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 7 1. Delay and jitter : : : : : ...

The popular press often extolls packet networks as much more efficient than switched voice networks in utilizing transmission lines. This impression is reinforced by the delays experienced on the Internet and the famous graphs for traffic patterns through the major exchange points on the Internet, which suggest that networks are running at full capacity. This paper shows the popular impression is incorrect; data networks are very lightly utilized compared to the telephone network. Even the backbones of the Internet are run at lower fractions (10% to 15%) of their capacity than the switched voice network (which operates at over 30% of capacity on average). Private line networks are utilized far less intensively (at 3% to 5%). Further, this situation is likely to persist. The low utilization of data networks compared to voice phone networks is not a symptom of waste. It comes from different patterns of use, lumpy capacity of transmission facilities, and the high growth rate of the indust...

We study the interdomain traffic as seen by a non-transit ISP, based on a six days trace covering all the interdomain links of this ISP. Our analysis considers the relationships between the interdomain traffic and the interdomain topology. We first discuss the day-to-day stability...

Real-time traffic measurements on MAGNET II, an integrated network testbed based on Asynchronous Time Sharing, are reported. The quality of service is evaluated by monitoring the buffer occupancy distribution, the packet time delay distribution, the packet loss and the gap distribution of the consecutively lost packets. Our experiments show that both time delay and buffer occupancy distributions of multiplexed video sources display a marked bimodal behavior, which does not seem to depend on the buffer size. The reliance of the network designer on traffic sources that do not exhibit substantial correlations can lead to implementations with serious congestion problems. For ATS based networks with different traffic classes, the impact of a traffic class on the performance of the other classes tends to be diminished when compared with one class based ATM networks. March 23, 1995. Published in IEEE Journal on Selected Areas in Communications, April 1990 Real-Time Traffic Meas...