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GPL’d kernel module improves long-distance Internet communication

Jun 23, 2005 — by Henry Kingman — from the LinuxDevices Archive — views

Japan's National Institute of Advanced Industrial Science and Technology (AIST) has released a GPL-licensed Linux kernel module that can improve long-distance communications and media streaming quality over broadband Internet connections. PSPacer 1.0 suppresses traffic bursts to minimize packet loss, with a single PC able to smooth up to 100 connections.

According to AIST, PSPacer smoothes bursty traffic into equally spaced packet transmissions that fall within available bandwidth limitations. This prevents the packet loss and associated communication degradation that can occur when buffers for switches and routers in the network overflow, the organization says.

AIST says PSPacer works by transmitting “gap packets” between adjacent packets. The gap packets are discarded at the input ports of switches and routers, and do not affect the network, AIST says. The number and size of the gap packets can be controlled to adjust transmit intervals.

Previously available smoothing software for Linux uses timer interruption to regulate packets, according to AIST. However, the 1 to 10ms timer resolution of Linux and other operating systems is not accurate enough to be effective, and increasing timer resolution through software creates undue CPU utilization, the organization maintains.

AIST says PSPacer 1.0 can provide bandwidth control and smoothing for up to 100 connections, when run on an ordinary PC. On gigabit Ethernet networks, each IP connection can be allocated a transmission bandwidth of between 8 Kbps and 930 Mbps. On networks of all speeds, packet transmission interval accuracy is limited only by the amount of time required to transmit a single byte.

PSPacer 1.0 is available as a loadable kernel module for Linux. After installation, users configure the module for a specific network interface, the maximum allocated bandwidth, and individual packet allocation rules for various IP addresses and ports.

AIST notes that the TCP/IP protocol most commonly used in Internet communications applications uses roundtrip time to control the maximum volume of data to be transmitted. As a result, bursty traffic may easily occur in long-distance networks where latency is large. PSPacer makes network utilization of up to 90 percent possible even in intercontinental communications with very large latency, the organization claims. It also prevents multiple streams on the same network from bursting at the same time, improving streaming quality. A peripheral benefit is reduced risk of buffer overflow exploits, AIST claims.

AIST developed PSPacer with support from the NAREGI (National Research Grid Initiative) Project, through a grant from Japan's Ministry of Education, Sports, Culture, Science, and Technology (MEXT). The software can be freely downloaded from the GridMPI website.

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