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High-Fidelity Link Shaping Roman Chertov
 

Summary: High-Fidelity Link Shaping
Roman Chertov
roman@santabarbaralabs.com
Santa Barbara Labs
1. INTRODUCTION
Network testbeds are an invaluable tool for conducting experiments with real hardware and
software in a controlled and easily manageable environment. Typically, testbeds employ an
emulation component to control the delay and bandwidth of experimental links. On most
testbeds, the nodes are only a few milli-seconds away from each other and the link speed
is either 100 or 1000 Gbps. Such an arrangement is acceptable for LAN only experiments;
however, networks, which have long distance links, experience much higher delays. For
instance, networks with Geostationary Earth Orbit (GEO) satellite links can experience a
delay of 125 ms per hop. Additionally, networks with satellite links can have a significant
variation of speed between the links. Hence, providing a variable delay and bandwidth is
paramount, when conducting Wide Area Network (WAN) experiments.
Link shaping over Ethernet can be provided with three methods: rate limiting at the
network node, transparent bridging, and IEEE 802.3x flow--eontrol. In this report, we will
investigate which ofthe link shaping approaches will provide the best performance without
inducing emulation artifacts.
Transparent bridging is a popular link shaping approach. In such a case, an extra de-

  

Source: Almeroth, Kevin C. - Department of Computer Science, University of California at Santa Barbara

 

Collections: Computer Technologies and Information Sciences