Udpate 27/5/00: ip_relay version 0.71 is now out. The new version adds two command line options: -d      Daemon mode, go straight into background.
-b n   Bandwidth, where n is max bytes/sec.

(See README for more notes and examples of the new options.)

ip_relay can shape the TCP traffic forwarded through it to a specified bandwidth and allow this specified bandwidth to be changed on-the-fly. Multiple data streams to different hosts/ports may be shaped to the same total bandwidth, much like a traffic shaping router would, however this application runs in user space, and works by acting as a TCP proxy.

ip_relay sprang from the fact that I use a modem for home Internet connectivity, and once a large download has started, other Internet activities: telnet, surfing, VOIP, are largely useless. With ip_relay, you can suddenly decide to shape your downloads to 50% of your available bandwidth, and make use of the more interactive applications.

After using ip_relay for a while, it became obvious to me that it had another use: simulating bandwidth limits for other applications. Most notably was testing VNC over an ethernet connection, but at modem speeds.

I am interested in hearing about your successes with ip_relay, my email address is on the bottom of this page.

- Gavin Stewart

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