Selected challenges in computer networking

J.M. Smith
1999 Computer  
T he convergence of computing and networking is nowhere more evident than in the phenomenal growth of the World Wide Web. In another sense, though, computer networking is being pulled in two opposite directions. On the one hand, the Web's popularity and growth has been fueled largely by desktop applications consuming bandwidth-intensive images and video. On the other hand, thin-client computers such as 3Com's PalmPilot are becoming more commonly used as edge-of-network devices, often connected
more » ... y wireless technology. This schism is also reflected in today's computer networking infrastructure as well. Network link throughputs are climbing on an exponential curve perhaps even steeper than that of processor performance and memory capacities. Thus, there is an increasing mismatch between fiber-optic transmission bandwidths and computer speeds, pushing computing further away from the network core. Are there ways to close, or at least manage, this growing schism-whether through novel hardware solutions or the increasing programmability of network infrastructures? Finally, can we better integrate these edge-of-network devices and make them fullfledged network participants? BANDWIDTH IS OUTPACING PROCESSING Whereas a high-end workstation today has a throughput of one gigabit per second, commercially available links operate at about 10 gigabit-per-second serial throughput. Wave division multiplexing (WDM) optical systems 1 can deliver aggregate throughputs of more than 200 gigabits per second today (80 OC-48 channels), and researchers have demonstrated extremely high performance time-domain techniques as well. Figure 1 illustrates the design space that results from this mismatch between transmission bandwidths and computer speeds. The top quadrant shows networks ranging from the 10 gigabit-per-second OC-192 transmission systems commonly found in network backbones to the approximately 50-Kbps links used by POTS (plain old telephone service) or ISDN (integrated services digital network) for networking from home to an Internet access point. The concentric rings around the core represent the communications/computation power relation, or computation over bandwidth (COB). For a fixed computation power-for example, 400 MIPS-the computation power is divided by the network bandwidth to get the COB value. Some fundamental trends can be seen moving inward or outward across the rings. For example, since the "core" is highly aggregated, mixing many types of traffic and services, it only will be cost-effective to place features needed by all aggregated services there. Further, if one views the COB ratio as the number of instructions available per bit, it becomes clear that software and computing are unlikely to be present in the core except in the so-called control plane (control software and network hardware used to manipulate the behavior of the transport system). While new all-optical packet switching techniques for transparent all-optical networks have been demonstrated-for example, Paul Prucnal's Terahertz Optical Asymmetric Demultiplexer-it is unclear whether traditional techniques relying on electronic computation will remain useful in these performance regimes. A second increasing mismatch is between events in such transmission systems (for example, frame arrival and departure) and transport protocols such as TCP/IP, which discover bandwidth and control congestion at time scales of round-trip times. An oncoming challenge is therefore in mapping Network link throughputs are fast outstripping processor performance and memory capacities. Are there ways to close, or at least manage, this growing mismatch between fiber-optic transmission bandwidth and computer speeds-whether through novel hardware solutions or the increasing programmability of network infrastructures?
doi:10.1109/2.738302 fatcat:huod2aqe2rcm3cinamxhcnwtq4