Configuring ATM Networks
Once the Classical IP setup is complete, all of the standard network tests can be performed. The simplest test is done by using the ping command to test the connection. One difference between SVC and PVC connections is a large latency for the first ping response when using SVCs. The reason for the latency is the setup time needed to establish the SVC. After the SVC is established, the latency for SVC and PVC connections should be the same.
After verifying the basic connectivity, you can run some network performance tests over the ATM connection. I have used the Netperf tool (see Resources) as well as some benchmarks developed locally. The maximum throughput performance is very good, around 132Mbps. This number is close to the maximum payload data rate for an OC-3 ATM network.
I have given instructions needed to set up the switch and hosts on an ATM network with Linux. The configuration steps given are specific to IP over ATM connections using the Classical IP standard. In addition to Classical IP, LAN Emulation (LANE) can be used to carry IP over ATM. LANE is supported by the Linux-ATM software as well, but configuration of LANE is beyond the scope of this article. For more information, refer to the documentation in the Linux-ATM distribution.
Hosts can communicate in several other ways using an ATM interface without relying on Classical IP. The ATM software supports “native” ATM sockets, where applications can communicate directly over an ATM connection, bypassing the IP software completely.
If you are interested in learning about ATM technology but don't have ATM hardware, the Linux-ATM software can be of help. The software has the capability to emulate an ATM device using TCP/IP to make the actual connection. By taking advantage of this support, you can get a head start on configuring ATM for Linux and learning the ATM programming interface.
Wayne J. Salamon is a Computer Scientist in the High Performance Systems and Services Division at the National Institute of Standards and Technology in Gaithersburg, MD. He has worked on system software for PCs, UNIX workstations and IBM mainframes for the past 12 years. When not doing computer stuff, he appears to play guitar, though only when connected to vacuum tube amplifiers. Wayne can be reached at firstname.lastname@example.org.
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